Flat Roof Insulation – What Are Your Options?

Generally speaking, pitched roofs are easier to insulate. In the best case scenario, you have an attic and plenty of room to work with. Otherwise, you might have a crawl space or venting space you can use to insulate this part of your home.

Flat roof insulation can be more challenging. Since you don’t have the benefit of the above features, you will have to approach it in one of three ways:

  • Install the insulation on the home’s exterior
  • Place it inside the home
  • In the lucky event that you have a crawl space, you can try and make the most out of it
flat roof insulation

Of course, the above options also work for a low-sloped roof. Just be careful to take the necessary safety precautions.

Now, when it comes to the materials you will need to use, you have multiple options.

In this article, we’ll discuss some of the most popular ones – highlighting the main pros and cons of each.

1. Rigid Foam Insulation

This material offers good R-value (better heat retention, lower heat loss) by default. It only increases as you get thicker rigid foam boards. They start at about 5 centimetres thick.

When you use it as flat roof insulation, consider the following:

  • For outside use – Apply the foam boards before setting up the roof covering.
  • For inside use – Apply before adding drywall or paneling.

Look for foam variants that are water resistant for an added benefit. After you’re done installing the boards, you should take one final thing into account.

Rigid foam tends to be very sensible to UV light. Therefore, consider applying an EPDM rubber membrane over the insulation.

Another disadvantage is that you will need to tape the seams between the boards. Otherwise, you will get some improper airflow which essentially invalidates all the work you’ve done.

You can also choose to go with spray foam insulation, which will be the next item on the list.

2. Spray Foam Flat Roof Insulation

The material offers much of the same benefits as rigid foam. On a plus side, this foam deals better with cavities that could weaken your building envelope.

That combined with its energy-efficiency and the fact that it doesn’t attract vermin is also a good reason to go with spray foam.

However, keep in mind that you will most probably need professional help for this.

There are many health risks involved with its installation, and a professional is much better equipped to manage the process.

Make sure you get a verified contractor so you don’t have any unpleasant surprises.

If the insulation process is not carried out properly, it might lead to gaps and holes in the foam that reduce its efficiency.

Don’t want to hire a contractor? There’s one more flat roof insulation option that might be right for you.

flat roof insulation

3. Multi-Foil Insulation

Multi-foil insulation is also an effective energy-saving, heat-loss-preventing material.

Unlike spray foam, however, multi-foil doesn’t require a contractor to install. It is very light and versatile compared to other solutions, so you have a much easier time handling it.

Besides, unlike fibreglass insulation, for example, this material does not generate dust. You won’t need any protective equipment or a breathing aid.

Plus, it offers a built-in radiant and vapour barrier. You no longer need to install one yourself, unlike the other methods.

Also, it takes up little space, so it’s suitable for flat roof insulation.

Which One Should You Choose?

To pick exactly what suits your needs, you might want to try the materials out for yourself.

Spray foam needs a contractor and the rigid kind can get quite expensive. However, you can get a multi-foil sample for FREE.

Claim your insulation sample now, and see what you think! We also offer helpful data sheets so you can learn about how it helps your home, in detail.


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