Too much is actually not possible, but too little is: how thick should your roof insulation be? How much is it? | MyGuide

Too much is actually not possible, but too little is: how thick should your roof insulation be? How much is it? | MyGuide
Too much is actually not possible, but too little is: how thick should your roof insulation be? How much is it? | MyGuide
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Why should you choose roof insulation?

Insulation is without a doubt the most important measure to make your home more energy efficient: in a well-insulated house you use a lot less electricity and/or gas to heat. As much as 30 percent of the heat in the house is lost through an uninsulated roof.

A well-insulated roof also ensures an even temperature in the house, which increases your comfort. Finally, insulation is also useful in the summer, because it prevents the house from getting too hot.

Reading tip: Are you obliged to isolate? And what is ‘sufficiently insulated’?

How can you insulate a flat roof?

You can insulate a flat roof in different ways. The best method to choose depends on your budget, your available space and the structure of your flat roof. In short, you can insulate your roof from the inside and outside. These are some methods that are commonly used:

1. Warm roof
By far the most commonly used system is the warm roof. The insulation layer is placed on top of the supporting structure of the flat roof and immediately under the roof covering. This way you avoid mold or rot problems in the insulation layer. You also prevent cold bridges. For this method you need insulation boards that have a high density and are insensitive to shrinking and expanding, such as PIR boards, XPS boards and rigid wool boards.

2. Inverted roof
With an inverted roof, the insulation lies on the roof seal. A protective or ballast layer such as gravel or concrete tiles is placed on top of the insulation layer to keep the insulation in place. This method is somewhat more expensive than the warm roof, but is especially interesting for renovation projects when the roof is still in good condition. Or for roofs with a limited load-bearing capacity. In terms of insulation, you can only use XPS for the inverted roof. These plates are moisture resistant.

3. Cold roof
With a cold roof you insulate from the inside and the insulation is between the roof trusses or beams, directly under the roof covering. The chance of cold bridges and condensation is higher with this system than with the warm roof. This method is especially interesting if there is only limited space to insulate.

Read more below the image.

How can you insulate a sloping roof?

There are also several ways in which you can apply roof insulation for a sloping roof. Which method is most suitable for your roof depends on the type of roof you have, your available budget and the desired insulation value. You can choose from these options:

1. Via the attic floor
If you don’t use the attic, the easiest way is to insulate your attic floor. You can roll out insulation material directly on this, so that the heat in the rooms below is not lost through the roof.

2. Against the shelter
If your roof already has a roof, you can place insulation on it. Various materials are suitable for this. For example, you can easily install mineral wool blankets yourself.

3. With prefabricated roof elements
These combine insulation and roofing in one panel. They can be installed quickly and easily and offer good insulation values. A handy option for both new construction and roof renovations.

4. With a sarking roof
If it is not possible to insulate your roof from the inside, a sarking roof is an option. The insulation is not in between but on top of the supporting structure of your roof.

5. With sprayed insulation
You can have PUR or PIR sprayed between the beams of the roof or directly onto the tiles. The insulating foam fills all cracks and openings, giving you a seamless insulation layer.

How thick should you insulate?

You can’t actually insulate too much, but you can, of course, insulate too little. If you insulate too thinly or not (well), you increase the risk of mold and condensation in your home. How much insulation you need depends on your plans. If you build, you build according to the BEN requirements. Are you going to renovate and do you want energy performance comparable to that of a new build? Then you can look at the U-value of floor insulation, wall insulation and roof insulation.

If we assume the standards for a BEN home, the maximum U-value of your insulation material may not exceed 0.24 W/m²K. This means for the insulation of your roof/attic floor:
– 18 to 25 cm mineral wool.
– 8 to 14 cm PUR/PIR.
– 16 to 23 cm wood fiber board.

Many factors determine the final cost of roof insulation: the price tag mainly depends on the type of material and the method of insulation.

Finally: are there incentives for roof insulation?

Absolutely, there are various premiums available for installing roof insulation. For example, it is eligible for the My Renovation Premium, the EPC label premium and some municipalities also give premiums for roof insulation. To be eligible for the premiums, you must call on a contractor to install the roof insulation.

Install your own roof insulation? You should avoid these seven mistakes

WATCH: This video explains how much you pay for roof insulation

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This article was written by our partner Livios.be, an expert site that focuses on construction and renovation.

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