Flat roof insulation

The cold deck

If you have a flat roof that needs attention then the chances are that its outside layer – the timber roof and any bituminous felt cover that meets the elements on a daily basis – is what’s known as a Cold Deck.

The Cold Deck is the most common and also the least thermally efficient type of roof insulation. Any insulation traditionally takes the form of a layer of mineral wool laid between the structural joists, needing a minimum 50mm (2ins) air flow above, as well as air vents – known as Soffit Vents – on the outside of the roof.

The whole idea is to get a good air flow and therefore prevent condensation, caused by warm moist air coming into contact with the cold roof deck and condensing.

Condensation can lead to all sorts of problems including rotten timbers and decking, damp mouldy ceilings and damp insulation.

Good ventilation is essential, particularly over kitchens and bathrooms where the moisture levels are high. This ventilation carries away the warm air as well as the moisture that you are trying to remove.

The warm deck

Providing you with what’s known as a Warm Deck is the S&P Roofing solution to ventilation and condensation problems.

Effectively, your insulation, in the form of a modern polyisocyanurate (PIR) layer, is fixed to your external ‘cold’ roof deck, with a waterproof membrane directly bonded to the insulation.

This provides a far superior thermal efficiency over mineral wool, and will make your new roof pay for itself in no time at all.

Tackling your Cold Deck sooner rather later can also pay dividends .If the existing roof deck is in a satisfactory condition it should be possible to use the existing felt as the vapour control layer, once again saving you money. In most cases this can easily be cleaned, prepared and made ready to receive a suitable polyisocyanurate (PIR) insulation and waterproofed using an EVA membrane such as EVALON®

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