1. Zero Carbon: Implications and Issues
Malcolm Bell
Buildings, Energy and Sustainability Group, School of the Built Environment, Leeds Metropolitan University, Leeds, UK.
Paper presented to: Towards Zero Carbon Homes
5 July 2007, Milton Keynes, UK.

2. Towards Zero Carbon

3. Towards Zero Carbon

4. Compliance packages: Zero Carbon
80m2 Semidetached or end terraced 2 storey house

5. Base Case - TER

6. Zero Carbon (TER of -135% to -150%)

7. Zero Carbon (TER of -135% to -150%)

8. Passive House Standards
Timber frame scheme Göteborg, Sweden (120 m2)
Airtightness 1 m/h
Source: Wall (2006), Photo: Hans Eek
MVHR – 80% with duct heaters
5m2 Solar water + resistance top-up

9. Passive House Standards
Timber frame scheme Göteborg, Sweden, 120 m2
5,868 kWh
6,420 kWh
Source: Wall (2006), Photo: Hans Eek
TER (kgCO2/m2)
Design ≈ 10.6
Actual ≈ 15.3
Under Swedish conditions!
Total energy = 8,160 kWh/a
Source: Wall (2006), Energy and Buildings. 38, pp

10. Implications and issues
Lights and appliances represent between 60% and 70% of carbon emissions.
Over 5,000 kWh/a may need to be generated by zero carbon sources. (more for larger houses)
What chance at the level of the dwelling?

11. Solar thermal?

12. Solar thermal?

13. Micro wind?

14. Micro wind?

15. Micro wind? Manufacturer’s general claims: 1.5 kW (max at 12.5 m/s)
Annual energy generated - 2, ,000 kWhs – depending on position and location.
Carbon displacement – 1.3 tonnes (30% utilisation)
Location:
Average wind speed (DTI database) = m
Energy – 1,473 kWhs
But what about shelter from trees and other buildings?

16. Micro wind?
5.1 m/s
4 m/s
3 m/s

17. Photovoltaic panels

18. Cost and scale

19. Cost and scale Wind PV Solar thermal small scale – 17 p/kWh
large scale – 4 p/kWh PV
Small scale – 55 p/kWh
large scale – 23 p/kWh
Solar thermal
small scale – 9 p/kWh
large scale – 7 p/kWh
preliminary calculations – Barrett 2007

20. Biomass?
Biomass in a 2006 dwelling!

21. Biomass?
Biomass in a 2016 dwelling

22. So what, so far ? Site based generation is problematic.
Solar thermal - useful demand reduction
Wind is likely to be cheaper and more effective at large scale
Biomass may have limited value in CHP but no panacea and an important strategic resource
Need to link new building to strategic renewable provision.

23. So what for the industry?
Source: Wall (2006), Photo: Hans Eek
Focus attention on as low an energy/carbon demand as possible
Deal with generation in a strategic way

24. Does new housing do what it says on the tin?
But!
Does new housing do what it says on the tin?

25. Notional – v – Real heat loss
Plot No.
Predicted Fabric Heat Loss (W/K)
Predicted Ventilation Heat Loss (W/K)
Predicted Total Heat Loss (W/K)
Measured Heat Loss (W/K)
Measured Heat Loss - Adjusted for Solar Gain (W/K) 13
50.6
13.2
63.8
105.4
111.7
402
54.9
20.3
75.2
136.3
153.4
+75%
+104%
The question is: Why?

26. Thermal bridges

27. Thermal bridging & construction
Designed performance is almost always degraded

28. Timber fraction and insulation

29. Airtightness is improving?

30. Sequencing and process

31. Hidden leakage

32. A culture of detailed planning?

33. A culture of detailed planning?
Build – Destroy – Install – Repair

34. Understanding complex heat loss paths
Party wall heat bypass

35. Potential CO2 savings 18,000 tCO2/a
Fabric heat loss is between 40% and 50% greater than currently estimated. Eliminating the bypass would produce large actual CO2 savings
From New Housing built in One Year (~190,000 units)
18,000 tCO2/a
From Existing Stock (built between 1965 and 2006)
694,000 tCO2/a
Assumes Party Wall U Value = 0.5
Assumes 10% semi, 20% terrace in stock and new build
Calculations for semis and terraces only – no estimate for apartments

36. We have been rumbled!
As very low and zero carbon becomes mandatory small things will matter
This time customers will notice!
This time building control will notice!
We cannot hide behind flawed assumptions

37. The industry must change!
It has been said before
But the more it changes the more it remains the same
Old problems persist!
It is time to retool, to retool cultures and processes as well as technology.

38. What will change look like?
A fully managed process – inception, design, construction and support in use.
Performance will have to be guaranteed.
A quality control process based on measurement not assumption
Re-engineering of processes as well as technology will bring economies!
Constant feedback will bring constant improvement.

39. So what does zero carbon mean?

40. The world will not be the same!
Thomas Kuhn
The Structure of Scientific Revolutions
We are entering a new paradigm

41. So what does zero carbon mean?
As in science, so in construction:
It is time for the industry to Retool!