The difference between warm and cold flat roof construction

Maintaining your flat roof in winter
February 3, 2017

If your flat roof needs renovation, you’ll be faced with the choice between warm and cold flat roof construction. Traditionally, the cold roof method of construction and insulation has been common, but as the way we live our lives has changed, the warm flat roof construction method has become the preferred choice. So what’s the difference, and which method of flat roof construction is better for your home?

Cold flat roof construction

A cold flat roof uses an insulation technique where insulating material is packed between the roof joists, and at least a 50mm (2-inch) air gap is left between the insulation and the roof deck. This is a relatively cost-effective way to insulate a flat roof, but during the colder months, heat is lost through the roof via the uninsulated rafters.

The other problem with a cold flat roof construction is the way we live our lives. We spend more time indoors cooking and washing, leading to condensation issues that need to be addressed by good external ventilation. Without soffit or mushroom vents, a flat roof above your kitchen or bathroom can become damp and rotten.

Warm flat roof construction

In a warm flat roof construction, the insulation is simply installed over the existing flat roof, first checking that the vapour control layer is intact. By insulating the entirety of the roof, you eliminate the cold spots where thermal bridging and heat loss can occur. Heat is conserved with no need for extra ventilation, and the only limit to the thickness of the insulation is the roof profile.

Both thermally efficient and cost-effective, the warm flat roof is ideal for the British climate. However, the higher profile of a warm flat roof construction makes it unsuitable for balconies or where a door opens directly onto the flat roof.

Ask the professionals

If your existing flat roof needs repair or replacement, and you’re in the Luton, St Albans and Stevenage area, then BPL Roofing can help. We’re specialists in flat roof construction techniques and will be able to advise you on the best solution for your property, so contact us today or call FREE on 01582 455025.

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