Main variables examined
| Variable | 1996 – baseline | 2050 – 40% house |
| People and dwellings | ||
| Population (millions) | 59 | 66.8 |
| Household size (people per household) | 2.43 | 2.1 |
| UK household numbers (millions) | 24.231 | 31.8 |
| UK rate of new construction (pa) | 162,000 | 220,000 |
| UK demolition rate (pa) | 8,357 | 80,000 |
| m2 per person | 34 | 38 |
| m2 per dwelling | 84 | 84 (refurbished) |
| . | 74 (new) | |
| Building fabric | ||
| Space heating demand (kWh per household) |
14,600 | 8,300 existing |
| . | 2,000 new | |
| Ventilation rate for new buildings (air changes per hour) |
3.5 | 0.5 |
| Energy uses | ||
| Internal temperature (oC): Zone 1 | 18.3 | 21 |
| Internal temperature (oC): Zone 2 | 17.3 | 18 |
| Cooling temperatures | No air conditioning | No air conditioning |
| Electricity consumption in lights and appliances, including cooking (kWh per household) |
3,000 | 1,680 |
| Energy for hot water (kWh per household) |
5000 | 4950 |
| Supplying energy demand | ||
| Gas boilers: ownership | 69% | 8% |
| efficiency | 68% | 95% |
| Electric heating: ownership | 9% | 10% |
| efficiency | 100% | 100% |
| Community heating with CHP and biomass: ownership |
0% | 22% |
| Micro-CHP: ownership | 0% | 21% (Stirling) |
| efficiency (heat:elec) | 85:10 | 80:18 (Stirling) |
| . | 20% (fuel cell) | 55:35 (fuel cell) |
| Heat pumps: ownership | 0% | 9% |
| Heat pumps: efficiency | 300% | 300% |
| Photovoltaics (electricity production) | 0% ownership | 15% efficiency 20m2 30% ownership |
| Solar Thermal | 0% ownership | 5m2 60% ownership |
| Emissions factors: Electricity (kgC/kWh) | 0.136 | 0.095 |
| Emissions factors: Gas (kgC/kWh) | 0.052 | 0.052 |
on August 29th, 2006 at 10:22 am
I note that you have total ventilation rates for new homes in the above table. The value of 0.5 for 2050 is reasonable (although it could be lower in homes with controled ventilation, other countries go down to 0.4). The value of 3.5 for the baseline does seem to be extremeley high. All of the available studies for the UK housing stock indicate this value is unlikely to be correct. Unfortunately most studies just measure air leakage rates (UK average 0.65 ach) and not the total ventilation rate. However this is usualy seem as a reasonable starting point.
I believe that you used SAP/ Bredem for the heating season energy demand. You may not be aware that there are siginficant errors in SAP in its usage of air leakage results (the wrong value is being used, permeability being substituted for air changes); As ventilation is likely to be the most significant heat loss on a new/renovated home this may be significant for your project. My estimates have shown an approximate 5% total variance on the SAP C02 production over the total UK new build (2006).