Warm Roof Insulation vs. Cold Roof Insulation – What’s the Difference?

With so much interest in energy efficiency and decreasing our carbon footprints in order to combat climate change, effective insulation is one method that is popular in saving money on heating bills.  Roofs are one of the biggest sources of heat loss within homes and commercial premises, and this heat loss can be significantly reduced through proper insulation.  Whether it’s a flat roof or a pitched roof, all roofs should have high quality insulation to improve the efficiency of the building. 

As we all know, hot air rises which is why it’s vital to make sure that your roof is properly protected against unnecessary heat loss.  If the warm air in your home is being lost through the roof, you’ll notice4 cold spots and draughts and may even experience problems with damp.  This leads to needing to turn up the heating or use it more frequently, resulting in higher utility bills and less money in your pocket.

Flat roof insulation is usually applied as a layer between the property’s ceiling and the roofing membrane and there are two main types:

• Warm roof insulation – this is the preferred option for most roofing experts and homeowners alike as it is so effective when it comes to avoiding condensation issues.  The most common materials used for warm roof Insulation are cellulose, fibreglass and mineral wool.  Warm roof installation is simple to install on a flat roof– as opposed to insulating between rafters, the insulation is just installed on top of the existing surface.  If the roof surface is in good condition, it just needs to be cleared of any debris before securing the insulation boards to it with adhesive so that some type of flat roof covering can be laid on top of it.  This insulation method ensures that the whole roof structure is insulated, providing higher thermal performance and making it more energy efficient than cold roof insulation.
• Cold roof insulation – this is not as “cold” as its moniker may suggest.  Cold roof insulation involves a technique in which insulation is laid between the rafters, which is a relatively low impact way of insulating a roof.  Although the majority of the ceiling below is well insulated, the roof structure itself remains uninsulated, which means that in cold weather, the cold may be conducted through the rafters into the room below.  On a thermal imaging camera, you would easily be able to see the location of the rafters by looking at the ceiling as the wooden rafters conduct heat much better than insulation does.  This is known as thermal bridging.  While a cold roof represents an easy option when first installing a flat roof, it’s a much more complex and time-consuming job if you’re planning to insulate an existing flat roof which involves ripping off the existing roof surface to lay the insulation.  This means that the roof surface has to be replaced, adding to an already complex job.  Cold roof insulation is best installed at the time of construction on when a flat roof is being replaced.