ᐅ Window Replacement, Reveal Insulation, and Window Sill Installation
Created on: 9 Jun 2025 23:56
A
atomic2000
Hello, I had a new kitchen window (triple glazing, Ug value) installed in my residential house built in 1986 and would like to insulate the reveals.
At first, I wanted to use Multipor reveal boards for insulation but I’m not sure how to handle the window sill with this. These boards are 2cm (0.8 inches) thick and quite brittle. If the new window sill is made of Dekton, glass, or something heavy, I’m concerned that the reveal board might give way under the weight.
Is the area under the window sill usually insulated, and if so, with what material? Is it possible to use a Wedi board?
What alternative materials or methods are available instead of Multipor? If I stick with the same system, it will be quite expensive for just one window and I would have to discard a lot of leftover material afterward.
Attached is a photo of the window. On the left and right sides of the window sill space is old foam. The new window was installed as follows: interior wind barrier, then Soudal MF 167 foam, then compressible tape. The window was, of course, also screwed in.
According to the building documentation, the wall structure is as follows: 11.5cm (4.5 inches) exterior plaster, 4cm (1.6 inches) air gap, 6cm (2.4 inches) core insulation, 17.5cm (6.9 inches) internal masonry KSL.
At first, I wanted to use Multipor reveal boards for insulation but I’m not sure how to handle the window sill with this. These boards are 2cm (0.8 inches) thick and quite brittle. If the new window sill is made of Dekton, glass, or something heavy, I’m concerned that the reveal board might give way under the weight.
Is the area under the window sill usually insulated, and if so, with what material? Is it possible to use a Wedi board?
What alternative materials or methods are available instead of Multipor? If I stick with the same system, it will be quite expensive for just one window and I would have to discard a lot of leftover material afterward.
Attached is a photo of the window. On the left and right sides of the window sill space is old foam. The new window was installed as follows: interior wind barrier, then Soudal MF 167 foam, then compressible tape. The window was, of course, also screwed in.
According to the building documentation, the wall structure is as follows: 11.5cm (4.5 inches) exterior plaster, 4cm (1.6 inches) air gap, 6cm (2.4 inches) core insulation, 17.5cm (6.9 inches) internal masonry KSL.
A
atomic200011 Jun 2025 23:37I measured again, and with a 20mm (0.8 inch) XPS board, it doesn’t fit. When I insert a hex key for the lower hinge, the distance from the key to the wall is 25mm (1 inch).
Questions:
1. Would a 10mm (0.4 inch) XPS board (Ultrament construction board) provide sufficient insulation for my wall assembly?
2. How many millimeters should I account for the full-surface adhesive plus plaster?
3. Would the 10mm (0.4 inch) XPS board be able to support the weight of a window sill made of Dekton?
4. Is XPS a health concern, for example due to fire retardants?
Questions:
1. Would a 10mm (0.4 inch) XPS board (Ultrament construction board) provide sufficient insulation for my wall assembly?
2. How many millimeters should I account for the full-surface adhesive plus plaster?
3. Would the 10mm (0.4 inch) XPS board be able to support the weight of a window sill made of Dekton?
4. Is XPS a health concern, for example due to fire retardants?
N
nordanney12 Jun 2025 07:47atomic2000 schrieb:
I measured again and 20mm XPS board is not enough. If I insert a hex key for the bottom hinge, the distance from the key to the wall is 25mm.
Questions:
1. Would 10mm XPS (Ultrament construction board) be sufficient insulation for my wall setup?
2. How many millimeters should I account for the full-surface adhesive + plaster?
3. Would the 10mm XPS board support the weight of a window sill made of Dekton?
4. Is XPS a health risk, for example due to fire retardant additives? 🙄 Instead of worrying about trivial details, just do it.1. What do the calculations from an engineering firm say?
2. As much as you want to apply.
3. That board carries nothing. The window sill simply rests on it.
4. If you eat it, I can imagine it might be harmful.
Sarcasm off.
JUST DO IT!!! Adhesives are a few millimeters thick; plaster is almost negligible if you only skim coat and sand. And yes, the window sill doesn’t care what it rests on. And no, XPS won’t harm you at all.
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