To reach a 100% cut in CO2 all emissions that are accounted for under SAP methodology (space heating, water heating & lighting) must be zero or negative.
To achieve this:
a highly insulated building fabric is necessary, and some form of micro-generation or other site energy will be required.
Improved insulation
Roof U-Value 0.13 - Wall U-Value 0.15 - Floor U-Value 0.15
Windows & Doors U-Value 0.80
Reduce thermal bridging
Energy Savings Trust Enhanced Details y-value 0.04
Increased air tightness
3 m3/(hr.m2)@50Pa
MVHR 85% efficiency, 1W/(l.s) specific fan power.
Improve heating system
Gas condensing 90% boiler interlock
Considered Renewables
Solar Water Heating & Photovoltaic
Mid Street, Surrey. 1st Code level 5 built in the UK back in 2008