Building Regulations

SPRAY APPLIED POLYURETHANE FOAM INSULATION

The New Maximum 'U' Values allowable from April 2002 for dwellings are detailed below using the Elemental method of Compliance to Approved Document L1 together with the changes made in 2007/08.

Maximum U-values (W/m 2 )

Element

Room in Pitched Roof (New Build)
Room in Pitched Roof (Loft Conversion)
Insulation at floor level only
Flat Roofs
Walls
Floors
Windows/Doors/Rooflights

2002

0.20
0.30
0.16
0.25
0.35
0.25
2.20/2.00*

2008

0.20
0.20
0.16
0.16
0.35
0.22
1.80

*depending on timber or metal frame

ROOF, WALL AND FLOOR INSULATION

Table 1 applies to where Spray Applied Polyurethane Foam is used for insulation only and includes substrates such as; Roofing felt, Sarking Timber Boards, Breathable Membranes, Timber, Concrete, Steel, etc.

Table 1                                                          Roof and Walls

   Floor

'U' Value to be achieved (W/m 2 K)
0.30
0.27
0.25
0.20
0.16

0.14
 

0.12
Approximate Foam depth
65mm
75mm
80mm
105mm
130mm
150mm
175mm

HYBRID WARM PITCHED ROOFS

Table 2 applies to where Spray Applied Polyurethane Foam is applied directly to tiles or slates, i.e. with no roofing felt. The average batten spacing is taken as 150mm centres with 25 x 25mm battens

Table 2                                        

 Hybrid Warm Pitched Roof

'U' Value to be achieved (W/m 2 K)   

0.30
0.20
0.16
Underlined with plasterboard
25mm
25mm
25mm
 
+50mm
+75mm
+120mm
 With loft void and 100mm glass
25mm
Mineral fibre at ceiling level   
+ 60mm

HYBRID WARM FLAT ROOFS

Table 3 assumes 225 x 48mm joists set at 600mm centres under 25 x 38mm counter battens set at 600mm   centres, 19mm ply board and semi-permeable pvc weatherproofing membrane.

Table 3                                                          

Hybrid Warm Flat Roof

'U' Value to be achieved (W/m 2 K)           

0.25 0.160
With counter batten 38mm 38mm
  +40mm +95mm
Without counter battens 85mm 155mm   

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