Surface thermal resistance. Inside/outside?

[Ian Stirling]

In a PDF I downloaded (Examples of U-value calculations using BS EN ISO 6946:1997)

I find a table "Surface resistance for roofs, walls, and exposed floors m^2K/W".

Heat flow direction Upwards Horizontal Downwards Inside resistance 0.10 0.13 0.17 Outside Resistance 0.04 0.04 0.04 Underfloor space - 0.13 0.17

Is the difference between inside and outside just that wind is assumed to be blowing across the outside?

[Andy Wade]

Yes, although the figures you quoted are somewhat different from the ones I'm familiar with (from BRE Digest 108):

• 0.10 0.12 *0.14*

• 0.04 *0.06* 0.04

• *0.22*

See also building regs. Approved Document L1 for up-to-date tables of U-values and calculation methods.