key performance values

This page will be periodically updated as data becomes available. Figures quoted are from calculated (c), estimated (e), measured (m), or certified (x) values, as stated.

Fabric Efficiency
Original Achieved
 Value Value Unit
Windows 2.4 to 3.2 (e)1 0.9 (x) W/m2 K
Doors 3.6 (e) 0.9 (x) W/m2 K
Existing Walls 1.4 to 1.6 (c) 0.12 to 0.17² (c) W/m2 K
Extension Walls N/A 0.14 (c) W/m2 K
Pitched Roof 0.7 (c) 0.10 (c) W/m2 K
Concrete Flat Roof 4.65 0.14 (c) W/m2 K
Extension Sedum Roof N/A 0.14 (c) W/m2 K
Ply Flat Roof 3.0 (c) N/A W/m2 K
Air Permeability 18.4 (m) 1.78 (m)³ m3.h-1.m-2 @50Pa
Heat Loss Coefficient 840 (c) 163 (c) W/K
Heat Loss Parameter 5.42 (c) 0.73 (c) W/m2 K
CO2 EMISSIONS 11,575 (c) 2,040 (c) Kg/yr

1. Reflects the varied ages of double glazed units, estimated using SAP 2009 data
2. Existing walls with external wall insulation (approx 90% of available wall area) will be 0.12 W/m2 K; some small areas, e.g. existing retaining walls, can only be insulated internally, where the U-value will be 0.17 W/m2 K.
3. Target was <2.0 m3.h-1.m-2 @50Pa. There is still some potential to improve upon the tested value in the table.

Energy consumption of the existing house as measured during 2010/2011 was 4,155 kWh/yr for electricity and 24,500 kWh/yr for gas, which serves space heating and hot water. Estimating the amount of gas used for space heating equates to approximately 145 kWh/m²/yr. By comparison, low energy standards, such as Passivhaus, requires the specific energy used for space heating should be no more than 15 kWh/m²/yr. The Passivhaus retrofit standard (EnerPHit), allows a slightly more relaxed 25 kWh/m²/yr.  This means that we have to reduce the energy currently used for space heating by some 85% – a considerable challenge.