The rules | Features

U-values for building envelope
	Current U-value	Proposed new U-value after six months	Proposed new U-value after 24 months
roof	0.16-0.25	0.20-0.35	0.16-0.25
external wall	0.35	0.35	0.30
ground floors	0.25	0.3	0.25
average of all doors, windows and rooflights	2.0-2.2	2.2	2.0