What is a Warm Flat Roof?

- In a warm roof the thermal insulation is immediately below the membrane finish
- The structural deck, any voids and the ceiling are at a temperature close to that of the building’s interior
- Condensation control is achieved by using an air and vapour control layer (AVCL) on the warm side of the insulation. This will also control air and heat leakage from within the building.
- The amount of insulation should be enough to maintain the roof condensation above dew point temperature, therefore avoiding interstitial or surface condensation.
- Warm roof voids are not required to be ventilated
- Condensation can be calculated in accordance with BS 5250; 'Control of Condensation in Buildings'

Warm flat roof build up

In a warm roof construction the Sarnafil membrane and SarnaTherm thermal insulation is installed above the structural decking. In principle this keeps the structural deck (usually trapezoidal steel or timber) at more or less the same temperature as the inside of the building.

An air and vapour control layer is required underneath the insulation in order to prevent moisture vapour being transmitted from the building outwards where it could condensate within the roof construction  (interstitial condensation).

Warm roofs are generally considered as very effective for energy use reduction and building performance. However the thermal insulation type and thickness is critical. Sika can carry out thermal and condensation risk analysis for every project inclusive of SarnaTherm insulation. Furthermore a bespoke designed system eliminates any performance and design issues.