'U' Values

'U' Values are calculated using the following formulas:

1÷ sum of resistances for all the individual elements of a structure
Where Resistance = Thickness ÷ Lambda Value

Cavity Wall

• External Finish (render etc & what thickness) • External Brick / Block (type & thickness) • Width of Cavity • Internal Brick / Block (type & thickness) • Internal Finish (dense plaster, lightweight plaster, dot & dab plasterboard etc & thickness • Required 'U' Value

Ground Floor

• Exposed Perimeter (lm) • Floor Area (m²) • General Form of Construction (suspended floor, solid slab etc. / thickness & material) • Required 'U' Value

Pitched Roof

• Internal finish (e.g. plasterboard & thickness) • Vapour Control Layer (type?) • Roof Rafters - centres and size of rafters • Is Insulation between rafters, over rafters or a combination of both? • External finish (typically felt, cross batten & tile) • Required 'U' Value