Now even tougher | Features

Tough as old boots: The new U-values …
U-values for building envelope	2002 version of Part L	Possible standards for 2005
Roofs	0.16 to 0.25	0.16 or 0.13
External walls	0.35	0.25
Ground floors	0.25	0.20 to 0.22
The average of all windows, doors and rooflights	2.0 to 2.2	1.80
… and the new airtightness rules
	Permeability (m³/h/m² at 50 Pa)
Type of building	Current requirement	Possible requirement for 2005
Naturally ventilated dwelling	10	10
Dwelling with balanced whole house ventilation	10	5
Naturally ventilated offices and retail	10	10
Offices and retail with balanced mechanical ventilation	10	7
Industrial and warehouses	10	7