Building the Future

Thermal Modelling of Buildings

Chris KendrickOISD: technologyOxford Brookes University

January 2008

Thermal modelling

• Why?

• Toolkit

• Future developments

Why?

• Whole building performance: thermal comfort, energy and CO2

• Passive/Bioclimatic design strategies: solar, natural ventilation

• Optimisation of design (what if…?)

• Building details: thermal bridging, condensation

• Regulation: Building Regulations Part L

Solar radiation

Heating

Cooling

Mechanical ventilation

Artificial light

Through envelope

Equipment and human emissions

Toolkit

• Dynamic thermal simulation

Dynamic thermal simulation

• Model whole building performance

• Real recorded weather data

• Internal temperatures, ventilation rates, heating and cooling energy consumption, solar gains

1 5 J u n 1 4 : 0 0

N suneye

Suncast image: View time = 15 Jun 14:00

Site Latitude = 52.17

Longitude diff. = 5.97

Model Bearing = 110.00

Sun: azi = 237.38 alt = 50.24

Eye: azi = 180.00 alt = 30.00

Dynamic thermal simulation

36.28622.66629.4730121.82Total

3.0821.8895.408028.536Dec

2.9821.8395.209019.598Nov

3.0821.9763.106.259Oct

2.9821.839000Sep

3.0821.932000Aug

3.0821.932000Jul

2.9821.839000Jun

3.0821.9760.15800.16May

2.9821.8391.52802.457Apr

3.0821.8893.491010.868Mar

2.7841.744.894024.131Feb

3.0821.9765.686029.812Jan

Equip.Lights

Auxiliary (fans,

pumps, controls)

Cooling (chillers etc.)

Heating (boilers

etc.)Month

Energy totals in MWh

Building systems energy summary

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

60

50

40

30

20

10

0

-10

-20

Tem

pera

ture

(°C

)

Date: Fri 01/Jan to Fri 31/Dec

Dry-bulb temperature: (warsaw flats2.aps) Dry resultant temperature: f3 block3 (warsaw flats2.aps)

Dynamic thermal simulationNatural Ventilation

Bulk air movement model (zone to zone)

Two dimensional CFD modelling of zone

Thermal comfort

Dynamic thermal simulation

0

5

10

15

20

25

30

35

>20 >21 >22 >23 >24 >25 >26 >27 >28 >29 >30 >31 >32 >33 >34 >35

Deg C

% o

ccup

ied

hour

s

Ambient

Warehouse left 250Lux 10W/m2 DF6.381

Warehouse right 250Lux 10W/m2 DF8.017

Warehouse left 250Lux 5.6W/m2 DF6.381

Warehouse right 250Lux 5.6W/m2 DF8.017

• 3D representation of building and apertures

• Application of sky illuminance for desired latitude

• Calculation of daylight factors over desired plane for each hour

• Daylight rendering

Daylighting analysis

0-300 300-600 600-900 900-12001200-1500 1500-1800 1800-2100 2100-2400

Toolkit

• Conduction analysis

Conduction analysis

• Model building details

• Steady state or dynamic boundary conditions

• Surface temperatures (condensation risk)

• Linear thermal bridging

Conduction analysis

Conduction analysis

Conduction analysis

Future Developments: Dynamic thermal simulation

• Integrated building performance modelling

• Import CAD geometry directly to thermal model

• Building physics module for CAD?- Ecotect- Revit Architecture (plug-in module)

• Improved graphics and animations

Future Developments: Conduction Modelling

• Direct use of CAD geometry- three dimensional representation of curves, slopes

• Import dynamic boundary conditions from building simulation programs

• Improved graphic user interfaces

• Faster computation times

Summary

• Thermal Modelling is being used increasingly to design better buildings

• Essential for passive/bioclimatic design to reduce mechanical inputs for heating and cooling

• Potential to optimise building performance in future climate change scenarios

• Simulation is set to become embedded into the design process as designers strive to achieve zero carbon buildings

Conclusion

• But we still need building physicists!