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Adapting to Change: New Thinking on Comfort
Cumberland Lodge, Windsor, UK, 9-11 April 2010
How to design a building envelope to provide
thermal comfort and energy efficiency
considering climate change
Irene Pau
Annalisa Simonella
How is the climate changing?
CIBSE TM48: 2009
2080s medium-high emissions scenario
How is the climate changing?
Climate impact
Climate factors
Design factors
Overheating risk and HVAC energy
consumption
Average and extreme summer
temperatures, high solar irradiance,
coincidence of high wet and dry bulb
temperatures
Building façade, form and HVAC
services
Flood risk
Sea level rise, increased rainfall and
soil moisture
Situation (e.g., coastal and/or in
fluvial flood plain), drainage, existing
flood defences, building envelope
and materials
Water scarcity
Changes in seasonal precipitation
and drought risk
- Water efficiency and availability
- Façade cleaning
- Rainwater roof collection
External thermal discomfort
Increased sunshine hours,
heatwaves, wind speed and direction
Building massing, street orientation,
façades, shading, trees,
greenspace, surface water and water
features, location of heat rejection
plant
Green landscape & biodiversity
Temperature, changes in seasonal
precipitation and drought risk; ‘timing’
of the seasons
- Types of suitable planting
- Green façades / roofs
Requirements for the UK building industry
• Target carbon emissions rate
Part L 2010: reduction of 25%
More stringent air tightness values
Lower U-values
• Comfort requirements
CIBSE Guide A:
PMV = ± 0.5, PPD ≤ 10%
Overheating criterion for naturally
ventilated buildings: > 1% occupied
hours with operative temperature
exceeding 28°C
Future adaptation
ASHRAE 55.2004
Thermal modelling: assumptions
• Office ‘module’
• Perimeter area of an open plan office
• Width x depth x height = 9m x 6m x 3.85m
• 75% glazed
• South orientation
• Infiltration: 0.15 ac/h
• Lighting control
• Variable factors:
U-value
g-value and light transmittance
Ventilation/cooling system (natural, mixed mode,
mechanical)
Arup in-house
Oasys Room
software tool
0.14
0.15
0.16
0.17
0.18
0.19
0.20
0.21
0.22
0.23
0.24
0.25
0.26
0.27
0.28
0.29
0.30
0.31
0.32
0.33
0.34
0.35
0.36
0.37
0.38
0.39
0.40
0.41
0.42
0.43
0.44
0.45
0.46
0.47
0.48
0.49
0.50
0.51
0.52
0.53
0.54
0.55
0.56
0.57
0.58
0.59
0.60
0.61
0.62
0.63
0.64
0.65
0.66
0.67
0.68
light transmittance
Glass options: solar and light performance
85%
80%
75%
70%
65%
60%
55%
50%
45%
40%
35%
30%
25%
20%
total solar energy transmittance (g-value)
g-value
light transmittance [%]
0.10
0.18
0.26
0.33
0.38
0.42
0.60
10
30
50
60
65
70
75
Façade options: thermal performance (U-value)
U-value [W/m²K]
1.2
1.5
1.8
Results: CO2 emissions, U-value effect
Carbon Emissions vs. g-value
(Mechanically ventilated, current weather)
CO2 [kgCO2eq/m²/yr]
35
30
25
20
15
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
g-value
U = 1.2 W/m²K
U = 1.5 W/m²K
U = 1.8 W/m²K
0.50
0.55
0.60
Results: CO2 emissions, mechanically ventilated
CO2 emissions vs. g-value
(mechanically ventilated, U-value = 1.5 W/m²K)
40
CO2 [kgCO2eq/m²/yr]
35
30
25
20
15
10
5
0
0.10
0.20
0.30
0.40
0.50
g-value
Current
2020s
2050s
2080s
0.60
Results: CO2 emissions, naturally ventilated
CO2 emissions vs. g-value
(naturally ventilated, U-value = 1.5 W/m²K)
only heating and lighting
40
CO2 [kgCO2eq/m²/yr]
35
30
25
20
15
comfort?
10
5
0
0.10
0.20
0.30
0.40
0.50
g-value
Current
2020s
2050s
2080s
0.60
Results: CO2 emissions, mixed mode
CO2 emissions vs. g-value
(mixed mode, U-value = 1.5 W/m²K)
40
CO2 [kgCO2eq/m²/yr]
35
30
25
20
15
10
5
0
0.10
0.20
0.30
0.40
0.50
g-value
Current
2020s
2050s
2080s
0.60
Results: CO2 emissions, 2050s
CO2 emissions vs. g-value
(2050, U-value = 1.5 W/m²K)
40
CO2 [kgCO2eq/m²/yr]
35
30
25
20
15
10
5
0
0.10
0.20
0.30
0.40
0.50
g-value
Mechanical ventilation
Natural ventilation
Mixed mode
0.60
Thermal comfort, current and 2050s
Comfort
Comfortvs.
vs.g-value
g-value
(U
(U==1.5
1.5W/m²K)
W/m²K)
28 C]
DRT >> 28
hours DRT
occupied hours
[% occupied
Comfort [%
C]
Comfort
30%
24%
22%
25%
20%
18%
20%
16%
14%
15%
12%
10%
10%
8%
6%
5%
4%
2%
0%
0%
0.10
0.10
0.18
0.18
0.26
0.26
0.33
0.33
0.38
0.38
0.42
0.42
0.60
0.60
Mixed current
Mixed 2050
g-value
g-value
Mech vent current
Mech vent 2050
Nat vent current
Nat vent 2050
Summary
• Trend of and optimum solar performance depends on
cooling system
• Carbon performance variation is high for high g-values
• Influence of U-value is limited
• high internal gains, south orientation
• Mixed mode shows best performance (CO2 and comfort)
• CO2 performance should be read in conjunction with
comfort, especially for naturally ventilated option
Building envelope responses (office buildings)
• Improve solar performance – reduce solar gains
Adaptability of external shading devices
Operable shading systems
Electrochromic glass
Replace transparent units with opaque insulating panels
• Improve thermal performance – reduce heat loss
Building types with lower internal gains
• Enhance daylighting
• Combine natural ventilation with thermal mass
Avoid cooling systems
• Adaptive comfort
Further work
• Extension to residential, healthcare, hotels, schools
• Include 4 main orientations
• Consider structural integrity (floods, increased wind load)
• Consider embodied carbon, life cycle approach
Thank you!
Arup
ArupFacadeEngineering
T +44(0)2077552613
Annalisa.Simonella@arup.com
Irene.Pau@arup.com
http://www.arup.com
http://www.arup.com/facadeengineering