What’s the Difference Between a Warm Roof and a Cold Roof?

When we talk about a warm roof vs a cold roof, what we’re really talking about is the insulation of the flat roof. Basically there are two options to choose from when insulating a flat roof: warm or cold.

Warm Roof Insulation

Installing a warm roof can be extremely straight forward and simple to do. Warm roofs offer a superior thermal performance and therefore come with a higher cost.

With a warm roof, the insulation is installed on top of the existing surface rather than in between the rafters. The great thing about a warm roof is that if your existing roof surface is in good condition, you don’t need to do much to it. Simply brush off any debris that is present, secure insulation boards to the surface and then lay down your flat roof covering over the top.

Because the warm roof method makes sure all of the roof structure is insulated, it’s a more energy efficient option over a cold roof.

Cold Roof Insulation

Despite its name, a cold roof does actually provide some insulation but it is named as such because the insulation is laid between the rafters. A lot of empty space is found between rafters which makes it a pretty low impact roof insulation method. This is because when the weather is cold, despite the majority of the ceiling below being insulated well, the rafters are not and therefore the cold will conduct through them and enter the room below.

The wooden rafters conduct heat much more than insulation which means you end up with something called thermal bridging.

Cold roof insulation is most commonly used when a flat roof is first being created because it’s a relatively easy process. However, cold roof insulation on an existing flat roof system is anything but simple. It requires the existing roof surface to be ripped up so that the insulation can be laid in between, before a new roof surface is then placed over the top. So it makes the job entirely more complex and increases the timescale of the project extensively.

Which one is best for me?

A cold roof is best when you’re initially creating a flat roof and is cheaper than a warm roof, but does provide an inferior thermal performance.

A warm roof is much more straightforward to install and provides a superior thermal performance and is therefore more costly. It should also be noted that a warm roof adds height to a flat roof and so cannot be used on balconies and extensions with doors that lead onto the roof.

For more information on any commercial & industrial roofing services, contact us at NWIR 0800 046 1500.