Sound Insulation for the Dormer Window

Dormer insulationDakkapel isolatie
The average modern dormer window has excellent thermal insulating properties, but often disappoints in terms of sound insulation. This is due to relatively low mass of the building materials that are being used. The lightweight building material provides little acoustic insulation. By using heavy construction plates or adding mass to your dormer window, sound insulation will be noticeably improved.

Sound insulation for a roof chapel yet to be built

In this situation you can still select which building material to use, because a carpenter or a contractor will build your dormer window. In addition to the usual sandwich panels (PIR foam panels), you can opt for an extra inner shell of Merfoplex. This is a sound-insulating board that consists of two layers of plywood with an Isomat KE core in between. This panel can be processed in the same way as wood, but weighs a lot more and provides a sound absorption of approximately 34 dB(A). The Merfoplex sheets are used for the side panels and the roof of the dormer. This forms an “acoustic shell” inside the dormer window, which blocks sound. Merfoplex is also used against the existing roof decking. If PIR or sandwich panels are not used during the construction of the dormer, you can use Akoesti wool (polyester wool) cavity filling for thermal insulation. This product has excellent thermal insulating and sound-absorbing properties. Moreover, in contrast to the usual glass or rock wool for dormer windows, contact with polyester wool does not cause allergic reactions, skin irritations or respiratory problems. Furthermore, the material is non-toxic and there is no question of dust formation. We advise you to have a double-walled, heavy wall construction made and to fill it with Akoesti wool polyester wool.

Sound insulation for an existing dormer window
The modern prefab dormer window is usually not sufficiently acoustically insulated, but this noise problem is easy to solve. The most economical way to improve the sound insulation is to provide the walls and ceiling with Isomat KE14J (type 14 kg/m²). To do this, start by cutting the Isomat KE sheets to the shape of the triangular walls and the ceiling of the dormer. Make a mold of the corners, if necessary, so that everything fits tightly. Tip: you will of course finish this layer of Isomat with plate material, such as plasterboard or wood of at least 6 mm thick. Therefore make these finishing plates to the same size as the Isomat  parts. You then mount the Isomat parts on the finishing plates with Stauf Extreme Tack. Be careful not to create mirrored parts!

On our tips page you will find the step-by-step plan for dormer insulation

Below you will find the described products to insulate a dormer window

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  1. Isomat KE Fiber
    Isomat KE Fiber
    Sound-insulating mat
    • Heavy plastic ground plane
    • Sound insulating
    • Resistant to water, oil and many solvents and cleaning agents

    Starting at £27.00

    £45.48
    (incl. tax)
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Sound insulation and acoustics in your home
More information about device insulation, door insulation, floor insulation and reducing reverberation in your home can be found on the page Sound insulation and acoustics in your home