Thermal Imaging - Anderson Mechanical Services provides

Thermal Imaging

By

Colin Pearson

Head of Condition Monitoring – BSRIA

In Association with

Anderson Mechanical Services

Loughgall,

Armagh

BT61 8HZ

www.andersonmechanical.net

Email: [email protected]

My background

Head of Condition Monitoring at Research and Specialist Consultants, BSRIA.

PCN Level III thermographer

Chairman of the UK Thermography Association

Fellow of BINDT

Member of CIBSE

Associate Member Institute of Acoustics

14 years experience in building thermography

5 years experience in acoustic testing

Chairman Thermography Training and Certification Working Group

BSI and ISO CM & NDT committees.

10 years in research & consultancy for farm buildings

BSc Environmental Engineering

5 years with mechanical and electrical contractor

4 years with lighting manufacturer

Today’s Presentation

Current Building Regulations

Testing vs. Assured Design

Thermal Imaging Basics

Buildings

Benefits

Acoustic Testing Basics

Benefits

Training and certification

The future

Current Building Standards (Regulations)

The Building Control Act 2007 Ireland (Building Standards)

Technical Guidance Documents (Approved Documents)

Parts A to M (L: Conservation of Fuel & Energy, E: Sound)

Specifies the minimum acceptable standards

No testing specified

Are these providing the right quality of buildings?

Testing vs. Assured Design

No matter how good the design and the Building Inspector, there is no way to be sure of thermal insulation or noise isolation without testing!

Pre-Completion Testing

Thermal insulation problems don’t show until it gets cold

Acoustic problems don’t show until the neighbours are noisy

The only way to be sure is to test!

Testing provides quality assurance

Thermal Imaging - Basics

Infrared

Material properties

Imaging systems

Benefits

Common faults

Survey method

Understanding results

Infrared radiation

Discovered in 1800 by William Herschel

“There is a heating effect from solar radiation beyond the red zone of the visible spectrum”

Detection improved by thermoelectric thermometer (Nobili – 1830)

The radiated energy is due to molecular vibration (Maxwell theory of EM radiation - 1873)

Intensity of radiation depends on temperature (Boltzman) = T4 (Stefan’s Law) = 5.6686 x 10 –8 Wm-2 K-4

All objects above absolute zero emit IR

Wavelength of peak radiation depends on temperature (Wien’s law)

Quantum Hypothesis (Planck – 1906)

UV

AM radio

TV & radioTV & radio

Microwaves

Infrared

VisibleX-rays

1m 10m 100m 1km100mm10mm1mm10µm 100µm.1nm 1nm 10nm 100nm 1µm

Wavelength

100nm 1µm 10µm 100µm 1mm

InfraredVisible

SW LW

The infrared spectrum

Important material properties

Emittance

Transmittance

Reflectance

Background temperature

Size

Distance

Thermal capacity

Emittance, reflectance & transmittance

r + a +t =1

Imaging systems

1960s-70s systems

Imaging systems

1970s systems

Thermal imaging cameras

Imaging systems

21st Century systems

Low noise images - 80 mK thermal sensitivity

High definition images –640x480 pixels resolution, 307,200 picture elements

Full speed 50 Hz images

High usability with voice and PDA interfaces

Sophisticated analysis software

Benefits of thermal imaging

Quick inspection

Results clearly shown in pictures

Shows precise location of fault

Shows severity of fault

Shows compliance with regulations

Improves quality of products

Building fabric thermography


Defects

Cold bridging

Missing insulation

Air leakage

Slipped insulation

Gaps in insulation

16.0°C

27.0°C

16

18

20

22

24

26

insulation gaps - walls

Thermography locates air leakage

25.5°C

31.0°C

26

27

28

29

30

31

behind plasterboard

Gaps in insulation

-4.0°C

5.0°C

-4

-2

0

2

4

Cold bridges - steelwork

21.2°C

26.5°C

22

23

24

25

26SP01

SP02 SP03

SP04

Cold Bridge location 2

30.0°C

36.0°C

30

32

34

36

Air leakagelocation

30.0°C

36.0°C

30

32

34

36

19.118.4

15.8

3.9

2.8

0.2

0.000

2

4

6

8

10

12

14

16

18

20

0 50 100 150 200 250 300

Distance, mm

Tem

pera

ture

, °C

Block Brick

Insula

tion

Cavity

Air

Air

Pla

ster

Good structure U value 0.35

18.2

17.1

- 6.9

- 5

0.8+ 0.000

2

4

6

8

10

12

14

16

18

20

0 50 100 150 200 250 300

Distance, mm

Tem

pera

ture

, °C

Block Brick

Mis

sin

g Insu

latio

n

Air

Air

Pla

ster

Poor structure U value 0.85

16.3

14.5

- 11.2

6.4

0.8+ 0.000

2

4

6

8

10

12

14

16

18

20

0 50 100 150 200 250 300

Distance, mm

Tem

pera

ture

, °C

Block

Brick

Mis

sin

g Insu

latio

n

Air

Air

Pla

ster

Mortar in poor structure U value 1.41

Mortar

Dewpoint of 20°C air at 80% rh = 16.5°C

Mortar in poor structure U value 1.41

Chimneys / Flues

Case study 1

retail building, 130x75 metres and 6-9 m high

interface detail left a 73mm strip uninsulated

=30 square metres of cladding with a U value of 3.5W/m²K instead of 0.35W/m²K.

would require an extra 2kW of heating

nearly 8000 kWh a year extra heating

cost of over €1000 a year

generating nearly 4000kg of additional CO2.

Extract from the thermographic report - before

Note: this is inside of building but outside was warmer so the poorly insulated areas show up as warm


Construction defects


Construction defects

Remedial action

Building Regulations Part L2 (2002)

“The person responsible for achieving compliance should (if suitably qualified) provide a certificate or declaration that the provisions meet the requirements of Part L2(a);

or they should obtain a certificate or declaration to that effect from a suitably qualified person. Such certificates or declarations would state:

a) that appropriate design details and building techniques have been used or

b) that infra-red thermography inspections have shown that the insulation is reasonably continuous over the whole visible envelope”

But are the buildings acceptable?

Normally rely on skill and experience of thermographer

No guidance on what is acceptable

Standards and Guides do not set criteria

Proposals in England and Wales for certification by a competent thermographer

What needs to change?

Certification of competence

Define acceptable limits

Show how to prove compliance

Certification of competence

PCN Level 2 Civil

Possible ‘House Thermographer’ certification

How do you show compliance?

Show thermal anomalies

Differentiate between real thermal anomalies and confounding factors

such as localised differences in air movement, reflection and emissivity

Quantify affected areas and their severity

State whether the anomalies and the building thermal insulation are acceptable

Approach

Select critical temperature factor

Select acceptable defect area limit

Measure surface temperature difference caused by each anomaly

Measure or estimate area of the defects

Critical surface temperature factor

Defined by risk of condensation and mould

Surface temperature factor, fRsi

Proportion of temp. diff. across fabric rather than internal boundary layer

Tsi – Te

Ti - Te

Critical surface temperature factor fCRsi

Surface temperature factor that will lead to condensation or mould growth in lowest design temperature

0.75 often used

fRsi =

Allowable area

Must maintain high standards without alienating construction industry by failing too many buildings

0.1% is suggested as suitable for large commercial and retail buildings

This leads to about one failure in six

Surface temperature and area measurement

Temperature measurement is common feature of a thermographic survey

Area measurement is often a feature of analysis software requiring:

Object distance

Angular field of view

Setting threshold temperature in software

Pixel counting

Computation of area below threshold temperature

Conditions and equipment

Suitable conditions, equipment and repeatable method required

Follow existing standard – eg BS EN 13187:1999, Thermal Performance of

buildings – Qualitative detection of thermal properties in building envelopes – Infrared method (ISO 6781:1983 modified)

Method

Internal survey usually best

Requires image of every anomaly

image square to any features of the wall or roof.

viewing angle perpendicular to surface imaged

interfering sources of infrared radiation such as lights, heat emitters, electric conductors, reflective elements minimised

Requires calculation of building surface area

Analysis

Adjust each image for distance, background temp & emissivity

Place area analysis tool to enclose anomaly

Set threshold temp. for area according to internal & external temp.

Use pixel counting tool and calculation from image parameters to find area below threshold

Repeat for all anomalies

Use summary table to add all areas below threshold

Limitations

This method may not be suitable for:

Heavyweight structures, particularly where the main insulating element is near the outside surface

Buildings where much of the internal surface is obscured, eg by false ceilings.

Energy efficiency survey

Heat loss through structure can be shown by surface temperature

Calculated from temperature difference across boundary layer

Depends on constant boundary layer resistance and known internal temperature

Example

Impact of introducing testing

Projection, because we don’t have it yet

Improved average thermal performance about 200kWh/yr for a house, or 37kg CO2 emissions

Extra cost of construction €0 just applying best practice

Extra cost of testing €15/house based on 1/10 sample

Extra cost of remedial action

Conclusions

There is a practical, repeatable semi-quantitative method of assessing thermal insulation performance

It is being used by thermographers in England and other countries worldwide

It may be used to show compliance with Building Regulations

Infrared cameras are being produced with software to identify defective areas

Contact

Anderson Mechanical Services

77B Main Street

Loughgall,

Armagh

BT61 8HZ

www.andersonmechanical.net

Email: [email protected]

Tel: +44 28 3889 1320 (NI)

Tel: 048 3889 1320 (ROI)