Warm Roof vs. Cold Roof: What’s the Difference and Which Option Should You Choose?

March 10 2020 0comment

Warm Roof vs. Cold Roof: What’s the Difference and Which Option Should You Choose?

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The debate of whether to create a warm or cold roof is often a contentious one. What usually determines whether a roof is cold or warm is how the insulation layers have been applied. So, what kind of difference does this make, and which option should you choose for your roof? Please read on for details.

Working or walking on the roof is as dangerous as any other work at height project. Ensure you have the right fall protection in place, such as post and chain barrier, to enhance your safety and that of your workers.

Cold Roof

Cold roofs aren’t as cold as the name suggests. You’ll have to lay the insulation between the roof’s rafters. And since there’ll be a lot of empty space between the rafters, this technique can be a relatively low impact way to insulate your roof. 

While most of the ceiling below will be well insulated, the rafters (roof structures) are not insulated at all. Therefore, cold temperatures will more likely conduct through the rafters and into the room, especially during the cold weather. Thermal bridging will occur since wooden rafters usually conduct heat much more than insulation. 

Cold roofing can be ventilated or non-ventilated. Should you decide not to ventilate your roof, you need to ensure there’s a breathable membrane placed between the structure (rafters) and the insulation. 

If you choose to ventilate, it’s important that you do so when installing the roofing for the first time. Why? Because insulating an existing flat roof can be time-consuming since you’ll first need to completely rip up the existing surface to gain access to the rafters. You’ll then lay the insulation before placing a new surface over the top. 

Warm Roof

Warm roofs are designed to keep the entire roof structure warm. Unlike cold roofs, the insulation in warm roofs is installed on top of the existing roof surface rather than in between the rafters. Therefore, you won’t have to rip up the surface. The area below the insulation will be as warm as the rooms below.

Providing your existing roof deck is in good condition, all you need to do is to simply clear any debris present, place insulation boards on the surface and lay down your flat roofing covering over the top. This technique offers a more efficient thermal performance, but can be very costly to install. 

A warm roof adds weight and height to your flat roof. Therefore, when designing a warm roof, ensure to put the added insulation weight into consideration to avoid overloading which is a serious danger to your safety. You may consult a roofing professional to help you determine whether or not the final weight will exceed the maximum weight limit. 

Which Option is Best for Your Roof?

Knowing the difference between the two methods may not be enough to make an informed decision on the best option to use for your flat roof. You need to also consider the advantages and disadvantages of each method.

Advantages of a Cold Roof

➢    Easy to install when initially creating a roof
➢    Cheaper than a warm roof
➢    Makes use of otherwise wasted space
➢    Low impact insulation

Disadvantages of a Cold Roof

➢    Can be quite challenging for an existing roof
➢    Inferior thermal performance

Advantages of a Warm Roof
➢    Makes it easier to eliminate thermal bridging
➢    Thermally efficient
➢    Prevents damp and decay by allowing moisture to escape
➢    It’s simple and straightforward to install
➢    Cost-effective

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