Rafter with Insulation Between and Under
Rafter Dimensions
Rafter Depth		mm	Rafter Width		mm	Rafter Centres
	mm		Insulation %	87.25	%	Rafter %
12.75	%
Building Elements
Element	Material	t(mm)	λ(W/mK)	λ(W/mK)	R(m²K/W)	Notes
External Surface resistance	Rse	NA	-	-	0.04	Fixed
Roof Covering	concrete / slate / clay metal sheeting other		1.0	1.0	0.01	Material
Batten Cavity	No cavity Cavity Ventilated Cavity Unventilated Low Emissivity		-	-	0.09	Cavity
Rafter Cavity	No cavity Cavity Ventilated Cavity Unventilated Low Emissivity		-	-	0.09	Cavity
Between Insulation	Celotex GA4000 Kingspan K7 Mineral wool Other PIR		0.022	0.026	5.77	Insulation
Rafter	As shown above	200	0.13	0.13	1.54	Timber
Bridge Modification	Mod for rafter thermal bridge	-	-	Modified R	5.23	Calculated
Under Insulation	Celotex XR4000 Kingspan K18 Mineral wool Other PIR		0.022	0.022	1.82	Insulation
Internal board	Plasterboard OSB Plywood		0.23	0.23	0.052	Board
Finish	Neat skim Paint None		0.6	0.6	0.005	Finish
Surface resistance	Rsi	NA	-	-	0.1	Fixed
Additional R value		m²K/W	-	-	0	Extra
Results
Thermal Bridge	Resistance through Rafter			3.65	m²K/W
Through Rafter	Total Resistance			7.44	m²K/W
Cold bridge U value	0.274	W/m²K	U value	0.134	W/m²K