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GHA Monitoring Programme 2011-13: Technical Report

Old Apple Store

Results from Phase 2: Post-occupation testing of sustainable new homes

Acknowledgements

The Good Homes Alliance would like to thank those who assisted in helping to

produce this project report and who have made this project possible. This includes

the house builders at the test property.

Particular thanks are extended to the testing team from Oxford Brookes University

and the developer Ecos Homes.

The Good Homes Alliance would also like to thank the Department for Communities

and Local Government, (CLG) and the Energy Saving Trust, (EST) for providing funding

to help support the Good Homes Alliance Monitoring Programme.

This report was prepared by Professor Rajat Gupta, Chris Kendrick and Rohini Cherian

from Oxford Brookes University and Christopher Eaton of the Good Homes Alliance.

© Good Homes Alliance 2014

Front cover image:

Old Apple Store

Good Homes Alliance Monitoring Programme 2011-13:

Technical report: Old Apple Store

Results from Phase 2: Post-Occupation Evaluation

Table of Contents

1 Introduction .................................................................................................................. 1

1.1 Conclusions ........................................................................................................................ 3

2 Building Construction ................................................................................................ 5

2.1 Building Fabric ................................................................................................................. 5

2.2 Building services ............................................................................................................. 6

3 Occupant surveys (BUS) and interviews ............................................................. 9

3.1 Methodology...................................................................................................................... 9

3.2 BUS survey – March 2011 ............................................................................................. 9

3.3 BUS survey – July 2012 ................................................................................................ 10

3.4 Comparing the two BUS surveys .............................................................................. 12

3.5 Interview and walkthrough ....................................................................................... 13

3.6 Key findings ..................................................................................................................... 19

4 In-use Monitoring results ...................................................................................... 21

4.1 Total energy consumption ......................................................................................... 21

4.2 Total energy by end use .............................................................................................. 22

4.3 Total metered electricity by end use ...................................................................... 25

4.4 Electricity use: average daily profiles .................................................................... 29

4.5 Electricity use: baseload ............................................................................................. 32

4.6 System Performance .................................................................................................... 33

4.7 Indoor environmental conditions ........................................................................... 39

4.8 Key findings ..................................................................................................................... 50

5 Conclusions and recommendations ................................................................... 52

5.1 Key findings ..................................................................................................................... 52

5.2 Improving pre and post-handover processes ..................................................... 53

5.3 What worked well ......................................................................................................... 54

5.4 What did not work well ............................................................................................... 54

5.5 Areas for future work .................................................................................................. 55

5.6 Comparing with SAP predictions ............................................................................. 56

1

1 Introduction

The project is part of a larger brief to examine the as-built performance of a new-

build energy efficient house (co-heating test, reported elsewhere) followed up by

building performance monitoring of the occupied house using sensors combined with

post occupancy evaluation (POE) questionnaires. This report details the findings from

the monitoring and POE, and aims to extract enhanced meaning from each as a

consequence of the two programmes running in parallel.

The project team comprises staff from the School of Architecture at Oxford Brookes

University led by Professor Rajat Gupta. The in-use monitoring was undertaken by

Chris Kendrick of the Oxford Institute for Sustainable Design (OISD) Technology) and

the POE by Professor Rajat Gupta and Rohini Cherian of OISD Low Carbon Buildings.

The monitored house is part of a small development in a village to the east of

Bridgwater in Somerset. There are two detached family houses, of which this is one,

fronted by three houses forming a terrace on the village high street. See Figures 1 and

2. It is a four bedroom 139m2, detached house built in 2009 to Code for Sustainable

Homes Level 5 (zero net carbon emissions from heating, hot water, ventilation and

lighting).

Figure 1 Small housing development layout and orientation

2

Figure 2 West elevation of monitored house

The house is fitted with solar hot water (SHW) heating panels, and photovoltaic (PV)

panels on the roof. Water use is supplemented by rainwater harvesting (RHW) for

toilet flushing. It is heated by a wood pellet burner in the living room with a back

boiler feeding small radiators in each room.

Two houses of the same design were built, one house with rear aspect facing south as

intended in the design, and the other with the rear aspect facing west. The former

house was used for the co-heating test before sale in March 2010 but the subsequent

buyers were unwilling for full post occupancy monitoring and evaluation to be carried

out. The latter house was instead used. Monitoring kit was installed in

February/March 2011 and monitoring continued until June 2012.

The occupiers are a semi-retired couple (one of the occupants is a part-time GP) with

an interest in green issues who use the extra bedrooms as either spare rooms (for

visiting sons and their families) or as a study. Their occupancy patterns are fairly

constant, with occupancy both daytimes and evenings, punctuated by holidays

outside school holiday periods mainly, and family visiting.

The monitoring was detailed, and consisted of: sub-metering of electricity use

(pumps, fan, , and immersion heater); energy meters for central heating and hot

water; external conditions; temperature and relative humidity in four rooms including

living room and master bedroom; and carbon dioxide levels in the living room.

3

1.1 Conclusions

• The overall energy use is broadly in line with expectations from previous studies

given the nature of the house and the occupancy levels. However, measured

heating energy use is lower than expected and perhaps reflects the problems

experienced with the central heating system.

• The concept of MEV in a house with an air permeability of 2.82m3h-1m-2 @ 50 Pa

is questionable as the house is borderline in terms of air leakage, and the air

infiltration is considered adequate for maintaining air quality without the use of

additional ventilation. The resulting baseload of 194kW is considered high and an

unnecessary carbon penalty.

• The rainwater system was found to supply approximately 69.6m3 of non-potable

water for toilet flushing and washing machine. This equates to about half of

typical usage for two occupants in a UK house, and is worth the negligible carbon

penalty given the UK water shortages both recent and predicted.

• All pumps and fan electricity consumption is more than covered by the PV. The

SHW system provides nearly half the hot water requirements of the house hold

(48% through the year). This is completely carbon neutral as the pump will always

be powered by the PV. Overall, the house meets the Code for Sustainable Homes

Level 5 requirement regarding carbon neutral water heating, pumps and fan

energy.

• The house is experienced as being cool and hard to heat. The solar façade is west-

facing rather than the optimal south orientation, and thus lacks the expected

beneficial solar gains in the spring and winter. The wood pellet heating system

with manual refuelling is not used as much as it might be if refuelling was

automatic.

Feedback from occupants through semi-structured interviews and walkthrough has

revealed the following findings:

4

1.1.1 Things that worked well

• Solar Panels and PV have worked without issues despite their sub-optimal

orientation.

• Photovoltaic panels: 40% of overall PV generation was during the months of June,

July and August.

• Solar Thermal: Solar supplied 48% of overall hot water requirements of the whole

year (predominantly from May to September), which is slightly less than the 50-

60% often claimed.

1.1.2 Things that did not work well

• The full design intent was not met since the house was designed to be south

facing while in reality it is west facing.

1.1.3 Occupant’s perspective

• The open plan layout with large windows and balconies has been a success in

creating a light internal environment.

• The rainwater harvesting system had initial fitting problems but proceeded to

work effectively, supplying almost 50% of typical UK household requirement.

• While overall summer temperature is satisfactory, overall winter temperature is

rated as very unsatisfactory in the BUS survey. Boiler temperature setting can

easily be adjusted to provide 30-40% higher heat output from the radiators.

• The need to manually feed the wood boiler made the system labour intensive and

less likely to be used in the shoulder months (autumn and spring). Lack of

designed storage for the wood pellets has been a major issue.

• The poor quality of the material finishes and inadequate supervision during the

construction process has had a large impact on the satisfaction of the occupants.

• Access paths to individual houses from the car parking space are not smooth

enough for wheelchair and pram access.

5

2 Building Construction

2.1 Building Fabric

The building is timber frame construction with wood fibre board outer insulation,

recycled newspaper inner insulation, OSB internal lining as primary air barrier, and

either rendered or timber-clad depending upon façade. See Figure 3 for a typical

detail.

Figure 3 Wall detail

The house is well-insulated and quite airtight, with an air permeability of 2.82m3h-1m-

2 @ 50 Pa. It is fitted with simple central mechanical extract ventilation (MEV) to draw

air continuously out of the house at a controlled rate. A passive solar strategy is used,

with extensive glazing to the rear elevation protected from high summer sun angles

6

by a large roof overhang and a first floor balcony. This glazing gives onto the living

room/dining room and a small ‘snug’, both of which have hard tiled concrete floors to

provide thermal mass storage and smooth passive solar gain to these spaces.

2.2 Building services

2.2.1 Ventilation

The house is fitted with a whole house mechanical extract system, taking air from the

kitchen, ensuite and bathroom via ceiling mounted plastic grilles and extracting it to

the outside via a vent in the south side wall. The Passivent A151DC fan unit is

mounted above a built-in wardrobe in the master bedroom. Control consists of an

isolator switch placed at high level in the wardrobe. The householders were unaware

of the switch, and were also under the impression that it was mechanical ventilation

with heat recovery (MVHR) unit. The unit uses a variable speed 65W DC motor with

an electronic control system and responds to humidity levels within the house as

detected in the ‘wet rooms’. The rated specific fan power is 0.29W/l/s according to

SAP Appendix Q. This would give a maximum air extract rate of 18.9l/s or 0.18 air

changes per hour for the house volume of 368m3.

2.2.2 Rainwater harvesting

A Freerain 2400 litre submerged rainwater tank was installed using a 600W

submersible pump to supply toilet cisterns and washing machine. The system is

topped up by mains water when running low. There is no water treatment apart from

mechanical filtration at the inlet to the tank and a strainer on the feed to the house.

2.2.3 Photovoltaics

The photovoltaic array is able to supply over 50% of projected electricity usage, and

over-sized to supply immersion, pumps and ventilation use as required by a Code

Level 5 house.

Specification:

7

• 2.52kWp

• 14 x Sharp NU180-E1: 180Wp Monocrystalline Silicon Solar Module

• Fronius inverter Top of Form

• Dimensions: 1318 x 994 x 46mm

• Total area: 18.34m2

Figure 2 Photovoltaic panels

The panels are mounted on plastic pods to tilt them by approximately ten degrees, or

twenty five degrees less than the optimal inclination in the UK.

2.2.4 Domestic hot water

The hot water system uses a twin coil cylinder with a single, standard 3kW, 40-70˚C

immersion heater. The larger lower coil is for solar input, and the top smaller coil is

for the pellet boiler flow. The tank includes an integral pressure vessel to allow for

expansion. Control of the high temperature boiler water flow is via the pellet boiler

timer. The SHW system is entirely automatic but the immersion heater is manually

switched as required.

The solar pump starts when the collector/top tank temperature differential is 6°C. It

runs at full flow for ten seconds then reverts to 30% flow. When the differential is

10°C it increases by one step (10%), and a further one step (10%) for every 2°C rise

after that until 100% flow is reached.

The solar hot water system is sized to supply solar heated water for a family of four.

As such, it is oversized for the current occupancy, and consequently likely to be

underutilised.

8

Specification:

• 1 x 250l OSO Unvented Twin Coil cylinder

• SHW – 4m2

• 2 x Filsol IR20H pressurised flat plate panels

• Resol Flowcon A with Deltasol BS

The panels are sub-optimally orientated and sloped, being West-facing, at an angle of

twenty degrees.

Figure 3 SHW on balcony canopy

2.2.5 Heating system

There is an Amalfi EcoTeck 8.4kW wood pellet burning stove in the living room. This

stove feeds small radiators with thermostatic radiator valves from a back boiler in a

conventional wet central heating system with a 50W pump. Flow temperature and

heating times are set using the electronic system controller mounted on top of the

stove.

Figure 4 Wood pellet stove in living room and bedroom radiator

9

3 Occupant surveys (BUS) and interviews

3.1 Methodology

The following occupant evaluation techniques were used in Plot 5, Old Apple Store:

• Two BUS surveys –Initial in March 2011, Final in July 2012

• Semi-structured interview – March 2011 with additional feedback in July 2012

• Walkthrough survey – July 2012

The results from these evaluation techniques were triangulated with monitoring and

spot check measurements to produce a balanced view of occupant satisfaction and

concerns.

3.2 BUS survey – March 2011

Two BUS questionnaire surveys were conducted at the Old Apple store

developments. The detailed reports on both surveys are available in Appendix A. The

first BUS survey was carried out in March 2011. It included 2 different dwelling types

(two detached and one end terrace) and had 3 respondents, including the occupants

of Plot 5.

Figure 5 BUS March 2011 survey -Slider graphs of overall temperature in summer (above) and winter (below)

The key findings of the first survey were:

• Positive aspects of the development are its consideration by the occupants as

generally comfortable (less so in one of the detached dwellings) and the detached

dwellings are perceived to have a positive effect on health.

10

• There were mixed feelings about layout, appearance and location with comments

about the lack of nearby amenities.

• Storage provision seems worse in the detached dwellings and concerns on both

building types on the lack of planned storage space for the wood pellets.

• Temperature conditions in the terrace are reported as variable and hot in summer

and one of the detached dwellings complains of cold winter temperatures which

may be due to problems in operating the wood pellet boiler to their satisfaction

and/or the use of continuous mechanical ventilation without heat recovery.

• The terrace dwelling has reported air quality to be ‘dry’, ‘stuffy’ and ‘smelly’,

which reflect problems with effective ventilation. Another dwelling also reported

air quality to be smelly.

• Noise was perceived as not satisfactory with noise concerns reported between

rooms within the dwelling and from outside. Ventilation ducting may help

transmit noise between upstairs/downstairs. The acoustic performance of internal

partitions and floors need testing and reviewing to ensure as constructed, they

perform as expected.

• Lighting overall seems satisfactory but tending to excess provision of both natural

and artificial lighting.

• The occupants feel little in control of the different heating and ventilation

technologies installed – with poor access to the controls (some items are installed

in the loft) and they feel the induction process and the handbook were not

adequate to explain the technologies in detail.

• The BUS comfort index is -0.23, within the 32% percentile range; satisfaction index

is -0.26, within the 43% percentile range; and summary index is -0.24, within the

32% percentile range.

3.3 BUS survey – July 2012

The more recent analysis in June 2012 focussed only on the detached dwelling in Plot

5 and had 2 respondents.

11

Figure 6 BUS July 2012 survey -Slider graphs of overall temperature in summer (above) and winter (below)

The key findings of the second survey were:

• Positive aspects of the development are the quality of natural light and air. The

occupants enjoy the privacy, views and the balcony. The solar panels are reported

to function well.

• Average ratings for location, space and meeting needs; the layout is perceived as

poor, while the external appearance is good.

• Transport and storage provision for the wood pellets seem to be the largest

storage concern.

• Temperature conditions are reported as highly variable in both summer and

winter with complaints of slightly hot summers and cold winters. The latter may

be due to problems in operating the wood pellet boiler to their satisfaction and/or

the use of continuous mechanical ventilation without heat recovery.

• Air quality is reported to be ‘dry’, very ‘fresh’, ‘odourless’ and ‘still’ with overall

satisfaction with summer air quality and extreme dissatisfaction with winter air

quality. The description of ‘dry’ air is contrary to spot check and monitoring

results which indicate good humidity levels between 40% and 70%. The

dissatisfaction with winter air quality is more likely to be related to the low winter

temperatures than bad quality of air.

• Noise levels were perceived as very satisfactory with no noise concerns except for

noise from the downstairs WC and noise transmitted from the outside through

the chimney. Both can be resolved with proper sound insulation around pipework

and in internal walls.

• Lighting overall seems satisfactory but tending to excess provision of natural light

and dearth of artificial lighting of sufficient brightness. Energy efficient low level

12

lighting should have zones of higher light levels for reading. Newer fittings have a

faster response rate.

• The occupants feel they have almost full control of cooling, noise, ventilation and

average control of lighting. They reported almost no control over heating, since

the winter internal temperatures were found to be low caused by either the

heating provisions being inadequately sized for the spaces and or the heating

system not producing the expected levels of heating. The occupants also felt that

the induction process and the handbook were not adequate to explain the

technologies in detail.

• The forgiveness factor is very low at 0.5, this is probably due to the various issues

faced throughout the handover and for the first 2 years fuelled by the contractor’s

refusal to replace faulty fittings or repair defects.

• The BUS comfort index is -3.94, within the 9% percentile range; satisfaction index

-3.23, within the 9% percentile range; and summary index – 3.58, within the 9%

percentile range.

3.4 Comparing the two BUS surveys

Comparison between the results of the two surveys gives a clearer picture of issues

which are more specific to certain dwellings/ dwelling types and changes as a result of

adaptation of occupants over time. However it must be noted that the surveys were

administered at different times of the year (March 2011, July 2012).

Comparing variables resulted in differences being grouped into 3 main categories:

3.4.1 Changes for the worse

• Temperature in winter is perceived as more uncomfortable in the recent survey.

• Overall internal environmental conditions were perceived to be more

unsatisfactory in the recent survey.

• The artificial lighting levels perceived as too high in the previous analysis are

reported as too low in the current survey.

13

• Contrary to the current analysis, the respondents in the previous survey who felt

the dwelling had some impact on health, perceived a positive impact. Overall

design is currently rated worse than previous scores.

• Overall comfort and satisfaction indexes are much lower in the second survey,

probably as a result of the problems faced in maintenance and repair, especially in

Plot 5.

3.4.2 No change

• Average ratings for meeting occupant needs

• Positive impact on utility costs (reduction in fuel costs).

3.4.3 Changes for the better

• Storage issues are less prominent in the more recent analysis although storage for

wood pellets is still a major concern.

• Air quality is not perceived as ‘smelly’ unlike the previous survey.

• Noise concerns are less in the recent survey since the current dwelling is away

from the main road.

3.5 Interview and walkthrough

The primary occupant interview with both occupants of Plot 5 was held on the 22nd of

March 2011. A subsequent interview and walkthrough was held in June 2012 to note

any changes, although most findings were similar to the first interview. The key

findings of the interviews were as follows:

3.5.1 General comments

• Since completion of development was late by 6 months, the work was done in a

hurry, resulting in low quality of finish throughout.

• Developers have “a great vision but, they don’t have a strategy for putting that in

place”.

14

3.5.2 Satisfaction

• “Very bright and light this makes it easy to live in.”

• Access path is not smooth enough for wheelchair/pram access.

3.5.3 Handover

• Timing of the handover was inconvenient as it occurred on the first afternoon of

the shift, while some construction was still ongoing.

• Information provided is perceived as minimal with little information about the

role of different equipment.

3.5.4 Home owners Guide and Manuals

• Contains all relevant section headings but the information conveyed is mostly for

installers and not for end users. Some parts of the manual are in a foreign

language.

• It would be useful for the guide to contain information on where to buy and fit

spares (e.g. lighting), common problems, trouble shooting and maintenance

instructions in clear, simple language.

3.5.5 Size

• Sizes are good, although the narrow steps with the sharp bend are perceived to

pose a problem in later years.

3.5.6 Privacy

• Occupant request for privacy via a higher fence was overruled by the project

manager; the occupants erected a willow fence in compensation.

3.5.7 Wood Boiler

• The lack of storage or security for the fuel (wood pellets) has been a major

problem. The wood boiler needs a separate vacuum cleaner and requires cleaning

almost every other day in the winter.

15

• Commissioning of the boiler by the supplier was too quick and conveyed very little

useful information. Teething problems subsequently encountered had to be

sorted with a private plumber.

3.5.8 Hot water system

• Learning to use this system was complicated. It involves daily integration with

expected usage, weather and season. The towel rail heater in the airing cupboard

cannot be switched off.

3.5.9 PV & Solar Panel

• Both systems work well although information on maintenance was not provided.

There are two solar readouts; one in the difficult-to-access loft, the other in the

lobby - but neither has indicators which highlight any problems with the output or

the current temperature of the water in the tank. Error indicators would help to

determine when to switch on the immersion heater or call for service.

3.5.10 Rainwater harvester

• The drain which collects rain water from the garage roof was fitted incorrectly and

had to be refitted by the occupants.

• The occupants were not informed about the yearly service required for the

rainwater tank. Initial problems needed to be sorted with the help of the local

plumber. The pamphlet provided as part of the handover does not correspond

with the installed model. Manufacturers were not helpful in sorting any problems.

3.5.11 Passivent System

• The occupants were initially led to believe that they had a Mechanical Ventilation

Heat Recovery (MVHR) system. The installed mechanical ventilation system (MEV)

is perceived as weak, noisy and inflexible. Cooking odours are not sufficiently

removed but are transmitted to the upper floors. The inability to adjust the

ventilation speeds on the fan without manually rewiring the system is also a major

16

issue. The occupants were interested in upgrading the existing system to an

MVHR system.

3.5.12 Shower fittings

• The quality of fittings in the Eco range sanitary ware caused some initial leaking in

the WC which was resolved when better quality valves were installed by the

occupants.

• Some of the ‘super-modern’ shower fittings are difficult to understand. Layout of

fittings within the bathrooms is badly designed, causing reduced wall space,

inoperable windows (which could be a fire risk) and no window above the sink.

3.5.13 Noise

• The insulation for noise between floors in very good.

• Conversations from outside the house are sometimes heard in the living space,

transmitted through the flue for the wood burner. This is more noticeable in

certain weather conditions and when it’s quiet.

3.5.14 Windows

• Windows are triple glazed and very effective.

• The absence of seals around the windows caused some leaking initially. Windows

in the ground floor living space were fitted inside out with the sloped sill on the

inside.

3.5.15 Lighting

• The daylight levels are adequate except in the ground floor study and WC.

Artificial lighting levels are too low and have long response times.

• Artificial light switches are not clearly marked, products cannot be bought locally

and are difficult to fit without prior experience/ training.

3.5.16 Best Aspects

• “A very easy space to inhabit, it is comfortable, light, spacious and warm”.

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• The quality of natural light, the allotment, the privacy, views from the balcony,

large windows and the reduced fuel bills were reported as the best aspects of the

house. The occupants were also motivated by their contribution to sustainability

through energy efficiency.

3.5.17 Worst Aspects

• The noise from the equipment (along with the low winter temperatures) was

reported as the worst aspects of the house. This is perhaps increased by the

location of the mechanical extract system in the loft space above the master

bedroom. The open plan layout along with the mechanical extract system spreads

kitchen odours throughout the house.

Figure 7 Sink fitting hinders the opening of this bathroom window on the first floor

Figure 8 West facing sloping façade with large glazed openings and wide balconies

18

Figure 9 Front façade showing uneven access path

19

3.6 Key findings

• The design concept is understood and valued by the occupants. The house was

described as “light, spacious” although the BUS comfort and satisfaction index

were both very low. Most of the dissatisfaction arises with issues of construction,

commissioning of service systems and maintenance. Monitoring revealed that the

house meets the overall Code for Sustainable Homes Level 5 requirement for

carbon neutrality.


facing, while in reality it is west facing (Figure 7). Consequently the anticipated

solar gains are not received. Solar design is site specific; orientation and access

arrangements need to be determined at the briefing stage of design.

• Major misunderstandings like the purpose and type of ventilation system installed

indicate large gaps in the handover process. The handover document, although

containing relevant section headings, lacked user focussed information on trouble

shooting and maintenance. The impacts of the hasty handover conducted at a

stressful time suggests that handover should be in 2 stages, one initial just after

move in, one later when the occupants are less stressed and have more questions

after trying out the systems themselves.



Occupants feel that they have had to work out the operation of various systems

themselves and correct defects with the help of local tradesmen. The developers

have not been willing to pay for the repair of defects caused by faulty installation,

thereby increasing the dissatisfaction above that of the initial distress to the

occupants caused by the defects. On a positive note, local tradesmen have rapidly

learnt to repair and service the relatively different service systems (rainwater

harvester, wood boiler etc.). Advanced houses with exemplar targets need close

supervision and defect liabilities periods, with periodic visits from contractor to

correct any issues.

20

• The occupants are pleased with the high ceilings on the upper floor and the extent

of daylight received in most areas. The artificial lighting is perceived as inadequate

for reading.

• Paths to individual houses are not smooth enough for comfortable access by

prams and wheelchairs (Figure 8). Accessibility concerns must include material

choice for flooring at the site and building level.

• One of the main concerns expressed by the occupant has been the need to check

if the immersion heater needs to be switched on; if this could be done

automatically it would save them anxiety and perhaps reduce the use of the

immersion heater.

• The provision for the transport, storage and access to the wood pellets is

inadequate. Currently trucks cannot enter the site and have to park on the road,

and pellets are stored in the car port. The manual feed system for the boiler

makes it labour intensive and less likely to be used in the shoulder seasons.

Movement and storage of 1 ton of pellets per house should have been resolved

and integrated in the early stages of site and building level planning.


rated as very unsatisfactory. This has been confirmed by monitoring results which

show that the average temperature from October to March is mostly between 15

and 20 °C (Figure 42). The low temperatures are most likely a result of the low

boiler temperature, constant mechanical ventilation without heat-recovery and

the inadequately sized radiators. Using the SAP assessment as a guide, the

additional ventilation due to the MEV system is approximately one third of the

total, resulting in losses equivalent to 22% of the total fabric losses, or 13% of

total heat loss. The radiators are run from a timer on the pellet stove. This has

resulted in occupants feeling a lack of control over the heating system and the

compensatory use of carbon intensive Dyson fan heaters.

21

4 In-use Monitoring results

The house was monitored over a period of one year from June 2011 to the end of

May 2012 using Radiotech wireless logging equipment supplied by BSRIA. This has

been developed specifically for discreet, whole house monitoring, particularly for TSB

Retrofit projects.

4.1 Total energy consumption

It should be noted that exported electricity from the rooftop PV array was not

monitored as the electricity provider was unwilling to change the main meter for a

model that would allow pulse enabled metering of exported power. PV generation

was measured and recorded using a pulse output meter. Hence daytime usage, when

PV is generating more than required and exporting the surplus, was not measured by

the main meter. The electricity usage reported in the following section is the total

mains electrical energy that has been imported into the house, NOT the total

electrical consumption of all devices within the house (some of which will have been

provided by the PV). For consistency, the unknown usage during the day has been

assumed to be used for lighting and appliances.

Figure 10 Utility room cupboard showing sub-meters and energy meters (lower LH)

22

Figure 11 Total energy use: biomass and mains electricity

From Figure 13, a total of 6553kWh of energy was consumed in the year, 3082kWh

(47%) being electricity. From an average electricity supplier, this would equate to a

total of 1.59 tonnes of carbon dioxide emitted (electricity at 0.517kgCO2/kWh, wood

pellets carbon neutral). However, the electricity is from renewable sources (Good

Energy). The wood pellet stove was used slightly more than expected into the spring

months of 2012 because of the cool weather experienced. The stove was not used in

April and May 2011.

4.2 Total energy by end use

Figure 12 Total energy use by month (wood pellets and mains electricity)

4 Bedroom detached house, Somerset: Electricity and wood pellet consumption

0.00

100.00

200.00

300.00

400.00

500.00

600.00

700.00

800.00

900.00

1000.00

1100.00

1200.00

1300.00

Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 Mar-12 Apr-12 May-12

Month

kWh

Electricity 198.300 158.410 160.000 168.900 272.045 236.900 436.639 344.500 334.890 305.078 258.452 207.354

Wood pellet 0.00 0.00 0.00 0.00 152.60 228.90 801.15 858.38 801.15 228.90 343.35 57.23


4 bedroom detached house, Somerset: Total annual energy by end use (6783kWh)

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

900.0

1000.0

1100.0

1200.0

1300.0


kWh

Ventilation 20.6 20.9 21.6 21.1 21.3 21.0 18.9 19.6 18.1 19.3 18.2 18.9

Heating 0.0 0.0 0.0 0.0 152.6 228.9 801.2 858.4 801.2 228.9 343.4 57.2

DHW total 11.9 4.0 23.7 19.1 87.5 71.0 134.6 94.8 114.7 110.7 82.0 66.0

Pumps 40.2 41.7 41.1 37.9 39.2 36.8 39.1 38.3 36.7 40.2 38.6 41.5

Lights/appliances 125.6 91.8 73.6 90.8 128.4 121.9 292.5 240.1 216.6 149.2 133.9 84.8


23

Total energy consumption (electricity and wood pellets) by end use is shown in Figure

14. Note that the heating season is from October until May, with the heat being

provided by the wood pellet stove in the living room. Any supplementary electrical

heating from electric fan heaters is not separately monitored, and would be in the

lights/appliances category.

The ventilation fan (MEV) is on constantly, resulting in a monthly usage to be

expected from the variable speed 65W fan. Hot water is provided by both the wood

pellet stove and the immersion heater when insufficient solar heated water is

available. As expected, the SHW supplies the majority of the hot water from June to

September inclusive.

The central heating, solar and rainwater pumps also show a regular monthly usage.

The central heating pump (50W) runs continuously, and is responsible for the

majority of the pump electricity consumption. This is a fault in the installation, and

the householder has been made aware of the fact. The rainwater pump runs more

outside the summer months to refill the cisterns, whilst the solar pump runs most

from April through to September when most solar heated water is being produced.

The rise in lights/appliances usage in the winter months reflects the lack of PV

generation, the shorter days, and the use of electrical heaters.

The following pie charts provide some more detail of total energy use.

4 bedroom house, Somerset: Summer total energy use (kWh), Jun-Aug 2011

Ventilation, 63.1, 12%

Lights/appliances, 290.9, 56%

Pumps, 123.0, 24%

DHW total, 39.7, 8%Heating, 0.0, 0%

24

Figure 13 summer total energy use

Pumps and ventilation account for 36% of the total energy use in this period. Most

hot water is provided by the SHW but the immersion is used occasionally also. The

pellet stove is not used at all during the summer months.

Figure 14 autumn total energy use

From Figure 16 it can be seen that the wood pellet stove is lit in October and

constitutes over a third of the energy consumed during the autumn period.

Figure 15 winter total energy use

4 bedroom detached house, Somerset: Autumn total energy use (kWh) Sept - Nov 2011



Pumps, 113.9, 11%DHW total, 177.6, 16%

Heating, 381.5, 35%

4 bedroom detached house, Somerset: Winter total energy use (kWh) Dec 2011 - Feb 2012



Pumps, 114.0, 3%

DHW total, 344.1, 9%

Heating, 2460.7, 66%

25

From Figure 17, carbon neutral heating from the wood pellet stove accounts for over

two thirds of the total energy consumed in the house over the winter period.

Figure 16 spring total energy use

4.3 Total metered electricity by end use

Electricity use was monitored using pulse enabled electricity meters wired in via

junction boxes to individual items of interest. These gave a pulse every Watt-hour

(Wh) of energy use, transmitted wirelessly via pulse transmitters to the datalogger

upstairs.

4 bedroom detached house, Somerset: Spring total energy use (kWh) Mar - May 2012



Pumps, 120.4, 8%

DHW total, 258.7, 18%

Heating, 629.5, 44%

26

Figure 17 Total metered electricity use, Summer

From Figure 19, the main surprise is that the central heating (CH) pump remains on

throughout these months, although there is no heat being supplied to the hot water

tank or radiators through this circuit. This is a wiring or control issue that needs to be

addressed. It should also be questioned why the MEV is permanently on, when

windows could be, and indeed are, opened during the summer. Addressing these two

issues could reduce metered electricity consumption by a third in this period.

Figure 18 Total metered electricity use, Autumn

Electricity use June-August 2011 (total: 517kWh)

RW pump2%

Solar pump1%

MV fan12%

Immersion8%

CH pump21%

Lights/appliances56%

Electricity use September-November 2011 (total: 678kWh)RW pump

1%

Solar pump0%

MV fan9%

Immersion24%

CH pump16%


27

From Figure 20, it can be seen that the use of the immersion heater increases as the

solar water heating decreases, and before the pellet stove is regularly in use. It is

evident that in the ‘shoulder’ seasons the highest carbon water heating method is

employed for convenience.

Figure 19 Total metered electricity use, Winter

From Figure 21 it can be seen that with the wood pellet stove in use, the immersion is

used slightly less than before. Light/appliance use has increased as the days are

shorter, there is less PV output, and electric heaters are used in the house for spot

heating (upstairs).

Electricity use December 2011-February 2012 (total: 1119kWh)RW pump

1%

Solar pump0%

MV fan5%

Immersion18%

CH pump9%


Electricity use March-May 2012 (total: 752kWh)RW pump

1%

Solar pump1%

MV fan7%

Immersion29%

CH pump14%


28

Figure 20 Total metered electricity use, Spring

From Figure 22 it can be seen that again the immersion heater is used as the pellet

stove is not in regular use, and solar hot water is intermittent.

Figure 21 Total metered electricity use by month

From Figure 23, as expected, the metered electricity usage is much higher in the

winter months for the reasons mentioned earlier. December is particularly high

because of family visiting during Christmas/New Year. A Dyson electrical heater was

purchased in this month for heating the bedroom.

Figure 22 Total metered electricity use by season

4 bedroom detached house, Somerset: Total annual electricity by end use (3082kWh)

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0


kWh

CH pump 35.1 36.1 36.1 35.5 35.3 34.8 34.8 34.8 32.7 35.6 34.6 36.2

Immersion 11.9 4.0 23.7 19.1 83.1 57.1 86.1 46.5 63.6 96.3 67.7 62.2

Ventilation 20.6 20.9 21.6 21.1 21.3 21.0 18.9 19.6 18.1 19.3 18.2 18.9

Solar pump 2.6 2.5 2.1 0.9 0.7 0.1 0.1 0.1 0.9 1.5 1.3 2.1

RW pump 2.5 3.1 2.9 1.5 3.2 1.9 4.2 3.3 3.1 3.1 2.6 3.3

Lights/appliances 125.6 91.8 73.6 90.8 128.4 121.9 292.5 240.1 216.6 149.2 133.9 84.8


4 bedroom house in Somerset: Metered electricity use by Season

Summer17%

Autumn22%

Winter36%

Spring25%

29

From Figure 24 it can be seen that twice as much mains electricity is imported in the

Winter as in the Summer.

Figure 23 Total metered electricity use

Overall for the year, the biggest single use of electricity is the immersion heater, with

20% of total demand. This occurred during the evening to top up hot water reserves.

4.4 Electricity use: average daily profiles

Average daily profiles were produced from the monitored data for the key monitored

uses.

4 bedroom house, Somerset: total metered electricity use June 2011- May 2012

RW pump1%

Solar pump0%

MV fan8%

Immersion20%

CH pump14%

Light/appliances57%

30

4.4.1 Immersion heater

Figure 24 Hourly profile by month: Immersion heater

Main usage is in the evening in the winter months, although there are peaks around

mid-day, especially for December and January. The highest use is in October, when

solar thermal availability is low and the pellet stove is not lit regularly. This bears out

earlier observations.

4.4.2 Rainwater pump

Figure 25 Hourly profile by month: Rainwater (RW) pump

4 bedroom detached house, Somerset: Averaged daily immersion heater use, by month and hour

0.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

0.450

0.500

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

kWh

JuneJulyAugustSeptemberOctoberNovemberDecemberJanuaryFebruaryMarchAprilMay

4 bedroom detached house, Somerset: Averaged daily rainwater pump use, by month and hour

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

kWh


31

Usage is random and sporadic, and minimal during the night-time. The December

peak corresponds to the family staying over Christmas/New Year.

4.4.3 Solar thermal pump

Figure 26 Hourly profile by month: solar pump

Maximum usage is in the summer months, in line with solar radiation availability and

peaks. The overnight running in February is unexplained.

4.4.4 Central heating pump

Figure 27 Hourly profile by month: central heating (CH) pump

4 bedroom detached house, Somerset: Averaged daily solar thermal pump use, by month and hour

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

kWh


4 bedroom detached house, Somerset: Averaged daily central heating pump use, by month and hour

0.000

0.010

0.020

0.030

0.040

0.050

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

kWh


32

The pump is running continuously as noted previously. The slight variability in the

winter months relates to thermostatic radiator valve operation.

4.4.5 MEV

Figure 28 Hourly profile by month: mechanical extract ventilation (MEV) fan

The mechanical extract fan is on continuously throughout the day and night.

4.5 Electricity use: baseload

Baseload is defined in this study as the average running load of the house when

unoccupied, i.e. with no additional appliances except those on standby, those

required to be running continuously (e.g. refrigerator) and pumps/fans. This was

found by averaging the night-time electricity usage for each month. It was found to

be 194W (see Table 1 below) and adds up to 1699kWh per year. This is 55% of total

metered electricity consumption (neglecting PV generated electricity).

Table 1 Baseload data

Total kWh CH pump kWh MEV kWh Appliances kWh

Nov-11 0.205 0.045 0.027 0.132

4 bedroom detached house, Somerset: Averaged daily ventilation fan (MEV) use, by month and hour

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

kWh


33

Dec-11 0.173 0.044 0.024 0.105

Jan-12 0.211 0.043 0.024 0.144

Feb-12 0.198 0.042 0.024 0.132

Mar-12 0.205 0.045 0.027 0.133

Apr-12 0.183 0.045 0.027 0.111

May-12 0.184 0.045 0.024 0.115

Average 0.194 0.044 0.025 0.124

4.6 System Performance

4.6.1 Photovoltaics (PV) performance

The PV generated 2276kWh in total, a figure consistent with the rule of thumb of 850-

900kWh per kWp installed in the southern UK. 40% of the PV generation was in June,

July and August. The measured efficiency, including inverter losses was 12.99% for

the whole year, slightly below the expected efficiency of 13.25% (14.1% quoted for

Sharp monochrystaline PV output and 94.2% for the Fronius inverter).

4 bedroom detached house: Photovoltaic generation (kWh) Jun 2011 - May 2012

0.000

50.000

100.000

150.000

200.000

250.000

300.000

350.000


Elec

trici

ty k

Wh

0.000

500.000

1000.000

1500.000

2000.000

2500.000

3000.000

Sola

r rad

iatio

n kW

h

PV out 316.901 322.831 252.005 203.970 132.210 61.950 37.233 60.174 98.730 213.797 245.630 330.967

Solar on PV 2664.07 2677.76 1995.43 1589.58 953.770 429.750 301.540 451.010 718.140 1565.23 1842.14 2804.68


34

Figure 29 PV generation and metered electricity consumption

Total annual electricity usage for immersion, pumps and fan was 1332kWh (59% of

total PV generation), showing that the Code Level 5 requirements have been

comfortably met (heating is carbon neutral wood pellets) if lighting is under 2.5kWh

per day on average through the year. As lighting was not metered separately, this

cannot be proven however.

Figure 30 PV generation and imported electricity by month

From Figure 32, monthly PV generation was more than sufficient to cover electricity

requirements for pumps and fan for every month except December.

4 bedroom detached house, Somerset: PV generated (total 2276kWh) and metered electricity imported (total 3081kWh)

0.000

50.000

100.000

150.000

200.000

250.000

300.000

350.000

400.000

450.000

500.000


kWh

PV generated 316.901 322.831 252.005 203.970 132.210 61.950 37.233 60.174 98.730 213.797 245.630 330.967

Metered 198.300 158.410 160.000 168.900 272.045 236.900 436.639 344.500 334.890 305.078 258.452 207.354


4 bedroom detached house, Somerset: Averaged daily photovoltaic generation, by month and hour

0.000

0.250

0.500

0.750

1.000

1.250

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

kWh


35

Figure 31 Average hourly PV generation by month

On average, the PV panels operated at about half the peak output in the summer

months.

4.6.2 Hot water (DHW) production performance

The hot water is supplied by a combination of wood pellet boiler, electric immersion

heater, and solar thermal panels (SHW). The SHW specifications are given in Section

2. The intended heat meter on the SHW could not be used as the installer pointed out

that this would invalidate the warranty. Instead, a DeltaSol kWh output meter

(manual reading) was fitted by the installer, a type often fitted by them as an option,

requiring regular reading and recording of data by the householders. For this reason,

the data is only to the nearest kWh, and cannot be broken down daily. Pulsed energy

metering (flow rate and temperature of flow and return, with digital integrator) was

used on the lower (solar) DHW cylinder coil. Hot water usage (litres) could not be

recorded as usage times and flows were too low to register (as stated by BSRIA). The

immersion heater had its own pulse enabled sub-meter fitted.

Figure 32 DHW by month and source

Solar supplies approximately 83% of the hot water from May to September. It can be

seen from the graph above that the immersion heater is used as the predominant

source of hot water from October to April, particularly in the ‘shoulder’ months of

4 bedroom detached house, Somerset: Hot water (DHW) - total 1563kWh

0.000

50.000

100.000

150.000

200.000

250.000


kWh

Pellet kWhSolar kWhImmersion kWh

Pellet kWh 0.000 0.000 0.000 0.000 4.381 13.834 38.019 48.305 51.122 14.127 14.270 3.886

Solar kWh 113.000 165.000 104.000 53.000 35.000 7.000 1.000 4.000 9.000 63.000 54.000 135.000

Immersion kWh 11.913 4.028 23.732 19.070 83.130 57.140 96.590 46.540 63.560 96.540 67.735 62.160


36

October, March and April when the wood pellet stove is not regularly used and there

is less solar radiation available.

Figure 33 Annual DHW by source

SHW supplies 48% of the hot water requirements for the whole year, slightly less than

the 50-60% often claimed. Part of the reason for this could be the westerly

orientation of the panels.

Figure 34 Monthly SHW output and electricity use of SHW pump

The SHW system contributes 743kWh to hot water over the year monitored, for a

pump usage of 14.9kWh, or 49.9kWh of heat for every kWh of pump electricity.

4 bedroom detached house, Somerset: Annual hot water (DHW) sources kWh - total 1563kWh

Immersion kWh, 632.138, 40%

Solar kWh, 743.000, 48%

Pellet kWh, 187.944, 12%

4 bedroom detached house, Somerset: Solar output Jun 2011 - May 2012

0.00

100.00

200.00

300.00

400.00

500.00

600.00

700.00


kWh

(Sol

ar)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

kWh

(Pum

p)

Solar kWh 581.04 584.03 437.71 334.69 208.02 93.73 65.77 98.37 156.63 341.38 401.78 611.71

Output kWh 113.00 165.00 104.00 53.00 35.00 7.00 1.00 4.00 9.00 63 54.00 135.00

Solar pump kWh 2.63 2.52 2.09 0.92 0.70 0.14 0.07 0.13 0.86 1.46 1.22 1.98


37

4.6.3 Space heating production performance

The 8.4kW Amalfi ‘Ecoteck’ wood pellet heater supplies space heating directly to the

living room by radiative and convective heat transfer from the unit. It also has a back

boiler fitted, supplying heated water to the DHW cylinder coil and to the central

heating system. The heater is filled directly via a hopper filled using 10 or 15kg sacks

of wood pellets. The wood pellets are stored in the front garage outbuilding and have

to be carried into the house manually. The householders were asked to keep a record

of every sack used. The wood pellets were assumed to have a calorific value of

4.769kWh per kg and the heater to be 79.8% efficient as quoted in the manual. As

with the DHW, the central heating circuit was fitted with pulsed energy metering

(flow rate and temperature of flow and return, with digital integrator).

Figure 35 Wood pellet stove annual output by component

The low proportion of heat transmitted through the central heating circuit could be a

result of the low boiler flow temperature set on the heater. After the main

monitoring period it was found to be set to 55˚C, whereas a temperature of 80˚C is

possible. Resetting this temperature could raise the heat output from the central

heating system by 70%. The low flow temperature in combination with the small

(possibly undersized) radiators could have contributed to the perception by the

occupant that the house was hard to heat.

4 bedroom detached house, Somerset: wood pellet stove output kWh (total 3471kWh)

CH kWh, 921.870, 27%

DHW kWh, 187.944, 5%

Direct kWh, 2361.836, 68%

38

Figure 36 Heating by month with average temperatures

The heating system is not required when the inside-outside temperature is less than

6°C due to casual and solar gains within the house. This was determined from the

monitored inside and outside temperatures when the heating system was switched

off in the Spring.

4.6.4 Rainwater harvesting performance

Figure 37 Monthly rainwater pump usage

Total annual usage from June 2011 to May 2012 was 34.79kWh, an average of

2.9kWh per month. Usage follows occupancy patterns, with the peak being in

4 bedroom detached house, Somerset: Central heating usage 2011/12

0.00

200.00

400.00

600.00

800.00

1000.00

1200.00

1400.00

Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 Mar-12 Apr-12 May-12

Month

kWh

0.00

5.00

10.00

15.00

20.00

25.00

Tem

pera

ture

(deg

C)

kWh supplied Average external temp Average LR temp

4 bedroom detached house, Somerset: Rainwater (RW) pump usage

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

4.000

4.500


kWh

RW pump 2.485 3.088 2.900 1.530 3.240 1.906 4.166 3.340 3.080 3.130 2.645 3.283


39

December whilst family were visiting for Christmas and New Year. For the quoted

600W pump, a usage of 58 hours per year is indicated, or 69.6m3 at a duty of 1200

litres per hour at 3bar pressure. This is approximately half of the total expected water

usage for a house/occupancy of this type.

4.7 Indoor environmental conditions

Four rooms were monitored for air temperature and relative humidity (RH): living

room, kitchen, master bedroom and ground floor study. Carbon dioxide (CO2) levels

were monitored in the living room using a carbon dioxide sensor with pulse output.

Readings were recorded every five minutes using RadioTech sensors.

Figure 38 Temperature/relative humidity sensor and datalogger

40

4.7.1 Temperature and RH

Figure 39 All logged internal temperatures, hourly averages

Figure 40 All logged internal RH, hourly averages

4 Bedroom detached house, Somerset: Living room temperature range

10.0

12.0

14.0

16.0

18.0

20.0

22.0

24.0

26.0

28.0

Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 Mar-12

Tem

pera

ture

(deg

C)

41

Figure 41 Living room temperature range (Max – Average – Min)

From the Figures above it can be seen that the winter average is cooler than usual for

a house of this type. During occupancy in the winter, the temperature hardly rose

above 20˚C.

Figure 42 Living room temperature/RH profile, January 2012

From Figure 44 it can be seen that in winter months the living room is only just up to

comfort temperature.

Figure 43 Living room temperature/RH profile, July 2011

During the summer months, temperatures remained comfortable, hardly above

outside temperature maxima on hot days. It is also interesting to note that the

maximum temperature peaks in the living room are delayed by the effects of thermal

42

inertia (heavyweight floor), although this could also be partly attributable to late solar

ingress through the westerly glazing.

Figure 44 Living room relative humidity range (Max – Average – Min)

From Figure 46, RH is predominantly in the comfortable range of 50-65% with only

occasional excursions above 70% (the lower threshold at which, with prolonged

exposure, mould growth might be a risk). Humidity conditions in the living room are

good, particularly since this room is open plan to include the kitchen. The mechanical

ventilation system is keeping conditions well within healthy margins.

Figure 45 Living room temperature vs. RH plot

Figure 47 summarises the monitored data, showing that both temperature and RH

are broadly in the comfort zone although temperatures are slightly lower than usual.

4 Bedroom detached house, Somerset: Living room relative humidity range

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0


Rel

ativ

e hu

mid

ity %

4 Bedroom detached house, Somerset: Living room hourly averaged air temperature vs RH, April 2011 - March 2012

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

RH %

Tem

pera

ture

deg

C

43

Figure 46 Living room % hours over temperature

With the combination of solar control, thermal mass and large openable glazed area,

there is no overheating problem in this house. Only 0.1% of the 8760 hours in the

year were over the recognized comfort threshold of 26˚C.

Kitchen conditions are not reported here, being very similar to the living room, the

two rooms being one open space.

Figure 47 Ground floor study temperature range (Max – Average – Min)

The ground floor study was reported as cool and difficult to heat, and this is borne

out by the monitored data shown in Figure 49. It remained cooler than external peaks

throughout the summer of 2011. Reasons for this could include lack of solar gains (it

is east-facing), the large area of exposed roof, and the undersized central heating

4 bedroom detached house: Living room overheating - % hours over temperature (deg C) June 2011 - May 2012

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

%

% hours 17.1 1.9 0.1 0.0

>22 >24 >26 >28

4 bedroom detached house, Somerset: Ground floor study room temperature range

0.0

5.0

10.0

15.0

20.0

25.0


Tem

pera

ture

(deg

C)

44

radiator (see earlier comments).

Figure 48 Ground floor study RH (Max – Av – Min)

Relative humidity in the ground floor study is entirely within acceptable limits,

although this could also be partly a result of its low usage.

Figure 49 Ground floor study temperature and RH profile, January 2012

The ground floor study is the hardest room to heat in the whole house, although it is

little used except as a storage room (perhaps as a consequence of this).

4 bedroom detached house: Ground floor study relative humidity range

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0


Rel

ativ

e hu

mid

ity %

45

Figure 50 Ground floor study Temperature vs. RH plot

From Figure 52 two clusters evident: the lower late autumn/winter/spring grouping of

low temperatures (mostly 15-18˚C), and the higher temperature cluster from late

spring to early autumn.

Figure 51 Master bedroom temperature range (Max – Av – Max)

The master bedroom temperature is within the comfort band. However there are

noticeable maxima in the summer. It is also worth noting that supplemental heat

from a Dyson fan heater was employed from mid-December onwards. The high peak

in January is when a thermal imaging study was carried out to assess the condition of

the bedroom South wall after a water leak through the aerial conduit. The bedroom

was electrically heated to obtain a large temperature differential across the wall.

4 Bedroom detached house, Somerset: Ground floor study hourly averaged air temperature vs RH, April 2011 - March 2012

0.0

5.0

10.0

15.0

20.0

25.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

RH %

Tem

pera

ture

deg

C

4 bedroom detached house, Somerset: Master bedroom temperature range

0.0

5.0

10.0

15.0

20.0

25.0

30.0


Tem

pera

ture

(deg

C)

46

Figure 52 Master bedroom relative humidity range (Max – Av – Max)

The relative humidity in the master bedroom is within comfort limits, the anomalous

January minimum figure being due to the extra heating for the thermal imaging

survey.

Figure 53 Master bedroom temperature and RH profile, July 2011

Summer temperatures in the master bedroom are very stable, and hardly exceed

external maxima. The peak delays are evident and in this case must be a result of late

4 bedroom detached house, Somerset: Master bedroom relative humidity range

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0


Rel

ativ

e hu

mid

ity %

47

afternoon solar ingress.

Figure 54 Master bedroom temperature and RH profile, January 2012

A bedroom temperature of around 18˚C is acceptable at this period of the year. There

are spikes during the cold spell 12th – 16th January when the electric fan heater has

been used to provide supplemental heat.

Figure 55 Master bedroom temperature vs. RH plot

The cluster is reasonably compact and within acceptable comfort conditions.

4 Bedroom detached house, Somerset: Master bedroom hourly averaged air temperature vs RH, April 2011 - March 2012

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

RH %

Tem

pera

ture

deg

C

48

Figure 56 Master bedroom % hours over temperature

The master bedroom is not overheating, with only 0.2% of the 8760 hours in the year

over the recognized comfort threshold of 25˚C.

4.7.2 CO2

Figure 57 Carbon dioxide levels in the living room, December 2011

The predominant CO2 level is 400- 800 parts per million (ppm) during normal

occupancy conditions. The spikes in December correspond to gatherings, the highest

level being reached in late December at 2064ppm when there was a large gathering in

the house. It is reported that the windows were opened during this event. The lowest

4 bedroom detached house: Master bedroom overheating - % hours over temperature (deg C)

0.0

10.0

20.0

30.0

40.0

50.0

60.0

%

% hours 51.3 29.2 7.9 0.2

>19 >21 >23 >25

49

level (421ppm) was reached on 11th December when the house was vacant.

Figure 58 Living room CO2 levels, March 2012

From Figure 60, March 2012 shows a typical pattern as regards carbon dioxide

concentrations in the living room. The level rises to approximately 800ppm during

occupancy, dropping to about 400ppm (close to background levels) overnight.

Figure 59 Hours at indicated CO2 concentrations for monitored time

Carbon dioxide levels were well within guidelines for health (not above 1000ppm for

extended periods, very good being 400-800ppm). Only 0.95% of monitored hours

were over 1000ppm, corresponding to larger gatherings in the house. It should

however be remembered that the usual occupancy is only two people in a house that

may be occupied by four to five if a couple with children live there. The findings

correlate with the reported behaviour in the house as regards ventilation. Windows

4 bedroom detached house, Somerset: Living room carbon dioxide concentration March 2012

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

28/0

2/20

12

29/0

2/20

12

01/0

3/20

12

02/0

3/20

12

03/0

3/20

12

04/0

3/20

12

05/0

3/20

12

06/0

3/20

12

07/0

3/20

12

08/0

3/20

12

09/0

3/20

12

10/0

3/20

12

11/0

3/20

12

12/0

3/20

12

13/0

3/20

12

14/0

3/20

12

15/0

3/20

12

16/0

3/20

12

17/0

3/20

12

18/0

3/20

12

19/0

3/20

12

20/0

3/20

12

21/0

3/20

12

22/0

3/20

12

23/0

3/20

12

24/0

3/20

12

25/0

3/20

12

26/0

3/20

12

27/0

3/20

12

28/0

3/20

12

29/0

3/20

12

30/0

3/20

12

31/0

3/20

12

01/0

4/20

12

02/0

4/20

12

03/0

4/20

12

Car

bon

diox

ide

ppm

4 Bedroom detached house, Somerset: Carbon dioxide ppm in living room March 2011 - May 2012

0.00

1000.00

2000.00

3000.00

4000.00

5000.00

6000.00

ppm range

Hou

rs

total 5392.67 1598.33 223.17 42.08 26.50

400-600ppm 600-800ppm 800-1000ppm 1000-1200ppm >1200ppm

50

are not opened during the winter except during gatherings, and are opened in the

warmer weather as a response to temperature rather than humidity levels.

4.8 Key findings

• The overall energy use is broadly in line with expectations given the nature of the

house and the occupancy levels. However, measured primary heating energy use

is lower than expected from the SAP calculation and perhaps reflects the

problems experienced with the central heating system. The low boiler

temperature could have been a cause of this, and could easily be adjusted to give

50-70% higher heat output from the radiators. The SAP calculation predicts

primary space heating energy use of 5797kWh per year, whereas 3283kWh was

recorded based upon wood pellet usage, or 57% of that predicted.

• Within the top-line electricity use, there are some potential savings to be made.

The central heating pump is on continuously, leading to approximately an extra

245kWh of electricity being used. The MEV fan is also on continuously with little

variation in consumption. The total baseload of 194W is considered high

compared to most dwellings of this size, particularly for a low carbon design such

as this house, and is an unnecessary carbon penalty.

• The rainwater system was found to supply approximately 69.6m3 of non-potable

water for toilet flushing and the washing machine. This equates to about half of

typical usage for two occupants in a UK house, and is worth the negligible carbon

penalty given the UK water shortages both recent and predicted.

• All pumps and fan electricity consumption is more than covered by the PV. The PV

panels are performing as expected, although it was not possible to measure the

amount of electricity exported. The SHW system provides nearly half the hot

water requirements of the household (48% through the year). This is completely

carbon neutral as the pump will always be powered by the PV. Overall, the house

meets the Code for Sustainable Homes Level 5 requirement regarding carbon

neutral water heating, pumps and fan energy, assuming lighting uses less than

2.5kWh per day.

51

• The house is experienced as being cool and hard to heat. The solar façade is west-

facing rather than the optimal south orientation, and thus lacks the expected

beneficial solar gains in the spring and winter. The wood pellet heating system

with manual refuelling is not used as much as it might be if refuelling was

automatic. One consequence is that the immersion heater is used more than

expected, especially during the ‘shoulder’ periods when solar radiation is limited

but the wood pellet boiler is not in use. Heating water using the immersion heater

is the most carbon-intensive form of heating possible on site.

52

5 Conclusions and recommendations

5.1 Key findings

• The difficult relationship between the occupants and the developers concerning

delay in handover, quality of construction, refusal to repair defects etc. has

overruled many positive aspects of the development leading to an adverse impact

on the forgiveness factor by the occupants.

• Major misunderstandings like the purpose and type of ventilation system installed

indicate large gaps in the handover process. Timing of the handover was

inconvenient as it occurred on the first afternoon of the shift, while some

construction was still on-going. Information provided is perceived as minimal with

little information about the role of different equipment.

• The handover document, although containing relevant section headings, lacked

user focussed information on trouble shooting and maintenance. Some parts of

the manual are in a foreign language. Occupants feel that they have had to work

out the operation of various systems themselves and correct defects with the help

of local tradesmen.

• The occupants are happy with the design and visual appeal of the development

but the poor quality of supervision highlighted by windows being fitted inside out,

poor layout of fittings in the bathroom, leakage in WC etc. have created a

undesirable experience.

• The impacts of a less than optimum handover were clearly felt throughout the

occupant interviews. Written and demonstrated information on the function and

maintenance of all service systems is essential for all energy efficient homes.

• The importance of construction detailing is highlighted by many issues like the

misplaced drainage pipe and unsuitable paving material. A design process which

anticipates each step of the usage process both in the layout and in the service

systems is vital for successful design.

• The monitoring shows predominantly good air quality and the dust free

environment has played a role in controlling a dust related health condition of one

53

of the occupants. On the other hand, the low winter temperatures have been

perceived to cause health risks.

• The post occupancy survey and monitoring has detected vital information for

increasing internal temperatures, and is a valuable source of knowledge for future

work.

• Low hot water usage, lower than assumed internal temperatures and boiler

setting, conservative estimates of boiler and PV efficiency have led to measured

energy consumption being less than the SAP predicted energy usage. On the other

hand the SAP calculation carried out for these houses neglects to include energy

consumption by the MEV fan which runs constantly throughout the year and

assumes that the central heating pump is switched on only during the heating

season, while in reality it is on throughout the year.

• The bottom line is that although the house meets Code for Sustainable Homes

Level 5 requirements, the occupants are not happy. The key issues behind this are

identified as the mismanagement of handover, lack of pre-defined protocol for

fine-tuning and repair of service systems, missing attention to detail in

construction finishes and design layout. On a more positive note the monitoring

process has helped to reveal that the critical concern of low internal winter

temperatures can be easily rectified.

5.2 Improving pre and post-handover processes

• It would be useful for the guide to contain information on where to buy and fit

spares (e.g. lighting), common problems, trouble shooting and maintenance

instructions in clear, simple language.

• The impacts of the hasty handover conducted at a stressful time – during the

‘moving in’ process- suggests that handover should be in 2 stages, one initial just

after move in, one later when the occupants are less stressed and have more

questions after trying out the system themselves.

54

5.3 What worked well

• The open plan layout with large windows and balconies has been a success in

creating a light internal environment. The occupants are pleased with the high

ceilings on the upper floor and the extent of daylight received in most areas.

• The high thermal mass provided by the concrete tiled floors along with the good

shading by the balcony controlled peak summer temperatures mostly within 25

deg C.

• The photovoltaic array supplies more than 50% of projected electricity usage and

provides more energy than is obligatory for Code Level 5 minimum requirements.

It has not had any maintenance or service issues, although the occupants would

like more information on how to detect any problems.

• The solar hot water system was sized for a family of four and is currently

underused because of the lower than planned occupancy, providing 48% of

overall yearly hot water requirement. Automatic /programmable controls to

switch on the immersion heating will increase the satisfaction of the occupants.

• The rainwater harvesting system had initial fitting problems but proceeded to

work effectively; occupants have learnt to maintain the filter system although this

was not mentioned during the handover process. The system provided about 69.3

m3 over one year (a half of the typical water usage by two occupants in the UK).

5.4 What did not work well


facing while in reality it is west facing. Consequently the anticipated solar gains in

the spring and winter are not received.


rated as very unsatisfactory in the BUS survey. This has been confirmed by

monitoring results which show that the average temperature from October to

March is mostly between 15 and 20°C (Figure 42).The low boiler temperature,

heat loss through the continuous MEV and the undersized radiators contributed

to unsatisfactory winter comfort levels. Consequently the measured heating

55

energy use is less than expected. Boiler temperature setting can easily be adjusted

to provide 50-70% higher heat output from the radiators.

• The need to manually feed the wood boiler made the system labour intensive and

less likely to be used in the shoulder months (autumn and spring). Lack of

designed storage for the wood pellets has been a major issue. Movement and

storage of 1 ton of pellets per house should have been resolved and integrated in

the early stages of site and building level planning.



Developers have not been willing to pay for the repair of defects caused by faulty

installation, thereby increasing the dissatisfaction above that of the initial distress

to the occupants caused by the defects.

• Access paths to individual houses from the car parking space are not smooth

enough for wheelchair and pram access.

5.5 Areas for future work

• The need for continuous mechanical extract ventilation system should be

investigated as the home is not exceedingly air tight with an air permeability rate

close to 2.8 m3h-1m-2 @ 50 Pa and monitored relative humidity levels are well

within the comfort range of 50-65%. The MEV fan partly contributes to a high

baseload of 194 W. Interstitial condensation monitoring would be useful in

detecting if the MEV system needs to be used throughout the year. Requirement

for MEV should be reviewed in the light of house usage and occupancy rates on an

individual case by case basis.

• One of the main concerns expressed by the occupant has been the need to check

if the immersion heater needs to be switched on; if this could be done

automatically it would save them anxiety and perhaps reduce the use of the

immersion heater. At present, the immersion heater is switched on if water from

the hot tap is not hot enough or in anticipation of high hot water demand after a

cloudy day.

56

5.6 Comparing with SAP predictions

• Low hot water usage, lower than assumed internal temperatures and boiler

setting, conservative estimates of boiler and PV efficiency have led to measured

energy consumption being less than the SAP predicted energy usage. On the other

hand the SAP calculation in this case neglects to include energy consumption by

the MEV fan which runs constantly throughout the year and assumes that the

central heating pump is switched on only during the heating season while in

reality it is on throughout the year due to a commissioning fault.

Appendix A: Data tables

Ecos Homes

The Old Apple Store, Stawell, TA7 9AZ UK

Data tables use standard benchmarks. Frequency histograms, benchmark assessment graphics and percentile plots may also be viewed on the private, case-sensitive, web address: http://homepage.mac.com/busmethodology/9000/index.html Publication quality jpg graphics at 300 dots per inch are available on request. Pdf file resolution is 300 dots per inch. Web graphic jpg resolution is 72 dots per inch.

HousingStandard

© BUSMethodology 2011

This document is not intended for distribution in the public domain. Restricted by license.

Data page index

Age (Age) : 35!Air In Summer: Dry/Humid (Airsdry) : 1!Air In Summer: Fresh/Stuffy (Airsfresh) : 2!Air In Summer: Odourless/Smelly (Airsodourl) : 3!Air In Summer: Overall (Airsover) : 4!Air In Summer: Still/Draughty (Airsstil) : 5!Air In Winter Overall (Airwover) : 9!Air In Winter: Dry/Humid (Airwdry) : 6!Air In Winter: Fresh/Stuffy (Airwfresh) : 7!Air In Winter: Odourless/Smelly (Airwodourl) : 8!Air In Winter: Still/Draughty (Airwstil) : 10!Appearance From The Outside (Hseappearance) : 37!Are You Normally At Home ...? (Athome) : 35!Basic Data For Benchmarked Variables : 42!Bus Comfort Index (Buscomfindex) : 31!Bus Satisfaction Index (Bussatindex) : 32!Bus Summary Index (Bussummaryindex) : 33!Comfort: Overall (Comfover) : 16!Control Over Cooling (Cntco) : 11!Control Over Heating (Cntht) : 12!Control Over Lighting (Cntlt) : 13!Control Over Noise (Cntnse) : 14!Control Over Ventilation (Cntvt) : 15!Design (Design) : 17!Dwelling Type (Dwellingtyp

Documents

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