If you’re embarking on a roof insulation project, whether it be as part of a conversion, extension, new build or just maintenance, you need to first consider whether you will select a cold roof or warm roof style of insulation.  There are advantages and disadvantages to each, read on to find out more.

Warm Roof

A warm roof is where the insulation is attached to the floor decking and rafters, this makes it a quick and easy method, offering the most thermal protection.  This also makes it a more cost effective choice.


One issue to consider is if you have limited ceiling height as the insulation will reduce not only the height of the room, but may impede doors and windows opening too.  Warm roofs tend to be more common with pitched roofs which feature a higher profile where this is less of an issue.  The entire roof is insulated which leads to a better performance, hence the name ‘Warm Roof’.

An example of a Warm Roof set up 

Cold Roof

Cold roof insulation is placed between the floor joists meaning that there is little to no loss in height - although space for ventilation is required.  It is called ‘Cold Roof’, not because it is cold as such, but because it is slightly less efficient than a warm roof, this is because the rafters themselves remain uninsulated.  On a cold day the rafters would conduct some of the cold into rooms below (known as thermal bridging) meaning a lower overall house temperature.  This can be reduced at the floor level with a layer of insulation across the ceiling, this can lower the ceiling by 50mm but will stop thermal bridging.


A cold roof is easier to install at the build phase, trying to insulate between floor decking retrospectively can be both messy and time consuming.

An example of a Cold Roof set up 

Warm Roof Vs Cold Roof

A warm roof is the easiest and most cost effective type of insulation and is an ideal choice for pitched roofs.  On some flat roof extensions and balconies, a warm roof would increase the height and isn’t possible, in this scenario you should choose a cold roof insulation.


For roofing insulation, check out our range which includes insulation board and thermafleece.