Ventilated facade design in hot and humid climateVentilated facade design in hot Ventilated facade design in hot and humid climateand humid climate
Matthias Haase
Dr. Alex Amato
Department of ArchitectureFaculty of ArchitectureThe Hong Kong UniversityPokfulam Road, HK, China
September 2006
Ventilated facade design in hot and humid climateVentilated facade design in hot Ventilated facade design in hot and humid climateand humid climate
• BackgroundPrinciplesCase studies
• Simulation AnalysisResults
• Conclusions
BackgroundBackground• Need for sustainable development• Key role of Building industry
Image credits: Behling, S. Sol power - The evolution of Solar Architecture, 1996, Prestel
Energy consumption (world-wide)
Industry
Transport
Building
BackgroundBackground• Energy responsible approach
Edited by Mat Haase, Image credit: http://www.emsd.gov.hk
Energy consumption (Hong Kong)
Industry
Transport
Building
BackgroundBackground• Energy in buildings in HK
Edited by Mat Haase, Image credit: http://www.emsd.gov.hk
Energy consumption (Hong Kong)
Commercial
34%
Industry 12%
Transport 36%
Residential 18%
Energy consumption (Hong Kong)
Lighting 11%
Air-con 16%
Transport, Sanitary
and others 7% Industry
Transport
Residential
BackgroundBackground• Energy in buildings in HK
Edited by Mat Haase, Image credits: http://www.emsd.gov.hk andhttp://arch.hku.hk/research/BEER/besc.htm
Energy consumption in office Buildings in HK
Transport, Sanitary, others 21%Air-con
47% Lighting 32%
27% of energy in HK is consumed by Air-con and Lighting in commercial buildings
Façade technology
Ventilation
Sun protection/shadowing
Photo-voltaics
Heating/cooling
Passive solar
Daylight
Acoustic protection
Insulation
BackgroundBackground• Possible integrated functions
BackgroundBackground• New concepts for sustainable buildings• Double-skin facades for office buildings
left: Multimedia Center, Hamburg, Germany by Foster and Partners right: Uni, Erlangen, Germany by UBA ErlangenImage credit: http://www.fosterandpartners.com
BackgroundBackgroundWhy double-skin façades?
55.6%
Peak cooling load of office building in HK
Lam, J. C. and Li, D. H. W. (1999) An analysis of daylighting and solar heat for cooling-dominated office buildings. Solar Energy, 65, 251-262.
BackgroundBackground
Why double-skin façades?
• Reduction of peak wind pressure
• Improvement of energy efficiency of façade by
passive solar heat gain in winter reducing thermal losses in winterreducing overall solar heat gain(in summer)support of natural ventilation (with the stack effect)
BackgroundBackground
Why double-skin façades?
• Improving comfort
Thermal: - predicted mean vote (PMV)- percentage people dissatisfied (PPD)- draft temperature
Visual: - daylight factor- glare- view
Acoustic: - intrusive noise
Image credits: Thermal comfort, INNOVA AirTec instruments and MatHaase
BackgroundBackgroundClassification of double-skin façades (DSF)
Box window facade
Corridor facade
Shaft-box window facade
Multi-storeyfacade
Cavity ventilation
natural mechanical
Airflow concept
Externalair curtain
Supply air Exhaustair
Internal air curtain
Main Type
Static airbuffer
hybrid
Haase, M., Amato, A., (2005), Double-skin facades for Hong Kong, proceedings of the Fifth International Postgraduate Research Conference in the Built and Human Environment, The University of Salford, UK.
Principles of DSFPrinciples of DSFPrinciples of airflow in cavity
Externalair curtain
Supply airExhaust air Internal air curtain
Static airbuffer
ext.ext.int. int.
open not open
int. int.int.ext.
Haase, M., Amato, A., (2005), Double-skin facades for Hong Kong, proceedings of the Fifth International Postgraduate Research Conference in the Built and Human Environment, The University of Salford, UK.
BackgroundBackgroundHeat transfer
• Radiation• Q12 = σ A1 Φ12 (T1
4 - T24)
• Conduction• Q = λ A ( T1 - T2 ) / t
• Convection• Q = hc A ΔT
• Traditional performance criteria• U-value, SHGC, meaningless
Reflexion
Conduction and ConvectionConduction and Convection
Second glass layerprimary facade
Qin
Qout
Absorption
TransmissionTransmission
NN11NN22
33
22
11
BackgroundBackgroundBuilding design concept
Haase, M. and Amato, A., (2005), Development of a double-skin facade system that combines airflow windows with solar chimneys, proceedings of Sustainable Building Conference (SB05), Poster session, Tokyo, Japan.
Energy conservation
Increasing efficiency
Utilization of renewable energy resources
Building energy consumption
BackgroundBackground
Energy conservation
0
5
10
15
20
25
30
35
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
degr
ees C
0
1000
2000
3000
4000
5000
6000
7000
8000
degr
ee h
ours
min/max temperature heating degree hours
solar excess degree hours cooling degree hours
Climate analysisClimate analysisClimate analysis
Climate analysisClimate analysisClimate analysis
Dry bulb temperature [°C]
Climate analysisClimate analysisClimate analysis
Dry bulb temperature [°C]
Abs
. Hum
idity
[AH]
Climate analysisClimate analysisClimate analysis
Dry bulb temperature [°C]
Abs
. Hum
idity
[AH]
Rel. humidity
[rel. hum]
Climate analysisClimate analysisClimate analysis
Dry bulb temperature [°C]
Abs
. Hum
idity
[AH]
Entha
lpy [h]
Climate analysisClimate analysisClimate analysis
Dry bulb temperature [°C]
Abs
. Hum
idity
[AH]
DBT(°C) 5 10 15 20 25 30 35 40 45 50
AH
5
10
15
20
25
30
Comfort
Psychrometric ChartLocation: Hong Kong, ChinaFrequency: 1st January to 31st DecemberWeekday Times: 00:00-24:00 HrsWeekend Times: 00:00-24:00 HrsBarometric Pressure: 101.36 kPa© A.J.Marsh '00
Climate analysisClimate analysisClimate analysis
DBT(°C) 5 10 15 20 25 30 35 40 45 50
AH
5
10
15
20
25
30
Comfort
Psychrometric ChartLocation: Hong Kong, ChinaFrequency: 1st January to 31st DecemberWeekday Times: 00:00-24:00 HrsWeekend Times: 00:00-24:00 HrsBarometric Pressure: 101.36 kPa© A.J.Marsh '00
SELECTED DESIGN TECHNIQUES:1. exposed mass + night-purge ventilation 2. natural ventilation 3. direct evaporative cooling 4. indirect evaporative cooling
Selected energy Selected energy conservation conservation design design strategiesstrategies
Climate analysisClimate analysisClimate analysis
Case studiesCase studiesCase studies of existing DSF in Hong Kong:
1. Dragon Air office building, Lantau
2. Kadoorie Biological Science Building, HKU
3. Science Park (Phase 1), Pak Shek Kok
4. Governmental offices, Shatin
5. No. 1 Peking Road, Kowloon
6. New emsd hq, Kai Tak
Case studiesCase studies
• Double-skin façade(external air curtain)
• Double-skin cavity acts as external shading device
• Sealed façade with cavity externally naturally vented
Image credit: Meinhardt Facade Technology
(as in Dragon Air office and in Science Park)
Case studiesCase studies• Example of DSF with EAC: Dragon
Air office building by Wong Tung & Ptns.
Image credit: www.draigonair.com and Meinhardt Facade Technology
Case studiesCase studies• Example of DSF with EAC: • Science Park (Phase 1) by Simon Kwan• Building here: with PV integrated
Case studiesCase studies• Example of DSF with EAC: • Kadoorie Biological Science building by Leigh & Orange• Building here: with HVAC system components in cavity
Case studiesCase studies
• Airflow window(internal air curtain)
• Shatin Govermental Offices
• No. 1 Peking Road
• New emsd hq
Image credit: Meinhardt Facade Technology
one room
Case studiesCase studies
• Airflow window(internal air curtain)
• Heat is concentrated in cavity
• 10% exhaust air: savings in overall cooling energy possible
• Improving thermal comfort
AHU
Exhaust air
Second glass layer
Visible glass
Case studiesCase studies• Example of AFW with IAC: Shatin Governmental Office by ASD• Active window (developed by Meinhardt Façade Technology)
Image credits: HK Construction Ltd http://202.66.146.82/listco/hk/hkconstruction/annual/2001/sum.pdf
Case studiesCase studies• Example of AFW with IAC: No. 1 Peking Road by Rocco Ltd• Active façade system (developed by Permasteelisa Group)
Image credit: Permasteelisa and Mat Haase
Case studiesCase studies• Example of AFW with IAC: New emsd hq by ASD• 2 upper storeys• Refurbishment
Image credit: emsd and Mat Haase
SimulationSimulationSimulationdouble-skin facades
basecase DSF AFW
SimulationSimulationSimulationdouble-skin facades
basecase DSF AFW
Internal glass layer
External glass layer
Internal movable blinds
Spandrel panel
AHU
Internal glass layer
External glass layer
Internal movable blinds
External glass layer
Internal movable blinds
SimulationSimulationSimulation• Thermal building simulation coupled with
airflowsimulation DSFDSF roomroom
SimulationSimulationSimulation• Thermal building simulation coupled with
airflowsimulation
• DSF
SimulationSimulationSimulation• Thermal building simulation coupled with
airflowsimulation
• AFW
facade 1
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
12 18 30 42 54 66 78 90 102 108
height
Cp
04590135180225270315
Cp over height
wind direction
SimulationSimulationSimulation
Façade 1
Façade 2
Façade 3
Façade 4
DSF2DSF2--22 DSF2DSF2--33DSF2DSF2--44
• Results
Monthly results for simulation of DSF at different heights
SimulationSimulationSimulation 0 200 400 600 800 1000
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
cooling load (kWh)
basecase with reflective glass basecase solar control glass
DSF1 DSF2-1
DSF2-2 DSF2-3
DSF2-4
Control strategiesControl strategiesControl strategies
• Controlling solar radiation
• Controlling HVAC
• Controlling exhaust airflow using
a climate sensitive regulator
Movable louvres
Visible glass
AHU>200W/m>200W/m²²
HVAC controlHVAC controlHVAC controlAir velocity AND temperature
Haase, M. and Amato, A., (2005), Double-skin facades and Thermal comfort, proceedings of Healthy Buildings HK Conference, HKCII, HK.
Climate sensitive regulatorClimate sensitive regulatorClimate sensitive regulator
AA
BBCC
DD
• Enthalpy balance
Haase, M. and Amato, A., (2005), Double-skin facades for Hong Kong, proceedings of the Fifth International Postgraduate Research Conference in the Built and Human Environment, The University of Salford, UK.
• Results
Monthly simulation results for DSF and AFW with and without climate control
SimulationSimulationSimulation
0
100
200
300
400
500
600
700
800
900
1000
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
cool
ing
load
(kW
h)
basecase DSF1 DSF2
AFW1 AFW2
with climate control
without climate control
• Results
Annual simulation results for DSF and AFW with and without climate control
SimulationSimulationSimulation
-10%
-5%
0%
5%
10%
15%
20%
basecase DSF1 DSF2 AFW1 AFW2
annu
al c
oolin
g lo
ad sa
ving
[% o
f bas
ecas
e]
• Results
Simulation results for basecase, DSF and AFW
SimulationSimulationSimulation
0%
5%
10%
15%
20%
25%
30%
basecas
e (int
ernal
shading)
basecas
e with
refle
ctive
glass
baseca
se sol
ar con
trol g
lass
DSF1-1DSF1-2DSF2-1DSF2-2
annual3 hottest monthshottest month
ConclusionsConclusionsConclusions
• Possible to design an energy efficient DSF system• Amount of energy through the building envelope resulting
in cooling loads can be reduced by designing a ventilated airflow window that is optimised in respect to heat transfer
• Airflow through the DSF depends on the cp-values of the façade, estimated the cp-values for different building shapes and heights did not influence the performance of the model with DSF
• The EAC uses buoyancy to reject solar heat gain• Possibility to reduce annual cooling loads as well as peak
cooling loads • EAC with a climatic control better in reduction of cooling
loads in the hot summer period• IAC does not reduce cooling load• Best results depend on an enthalpy based control that
extracts air in order reduce the cooling load
ConclusionsConclusionsConclusions
Planned future work
• Validation with measured data• Detailed daylight analysis • Solar assisted extract air device • LCA of different façade systems
Ventilated facade design in hot and humid climateVentilated facade design in hot Ventilated facade design in hot and humid climateand humid climate• Background• Simulation
Analysis Results
• ConclusionsThank you
Thank Thank youyouQs?Qs?
http://thegreenroom.arch.hku.hk