ᐅ Insulating the knee wall from the outside: which materials to use and how to attach them?
Created on: 29 Jan 2019 08:09
A
Arcplane
Hello everyone!
We have purchased an old house built in 1960, solid construction, but completely uninsulated. Upstairs, all the rooms have sloped ceilings and knee walls. Behind each knee wall is an attic space that can be accessed through a hatch from the room.
We now want to insulate the knee walls from the outside, meaning not on the room side, but on the attic side. So, it is not exposed to the weather, but it is in a cold attic space.
What is suitable for insulation in this case? Fire safety is very important to us, so materials like polystyrene foam are out of the question. At the same time, it should not be too expensive because we plan to demolish the house completely and rebuild in a few years—if we have the budget for it. But until then, we don’t want to be cold.
There are no rafters in the attic space, so it would be difficult to fix roll insulation. Or should we install battens specifically for this purpose?
The pictures show the attic spaces from inside (and the previous owner's meager attempts at insulation, which we will remove) and the hatch from the outside.
The hatch itself is also a problem: How can it be insulated?
Oh, and we really don’t intend to use the attic spaces regularly; the solution does not need to be walkable at all times. It just needs to be possible to open the hatches occasionally for inspection purposes.
Any advice would be greatly appreciated—it’s already cold up there…
Thank you very much and best regards,
Andreas
We have purchased an old house built in 1960, solid construction, but completely uninsulated. Upstairs, all the rooms have sloped ceilings and knee walls. Behind each knee wall is an attic space that can be accessed through a hatch from the room.
We now want to insulate the knee walls from the outside, meaning not on the room side, but on the attic side. So, it is not exposed to the weather, but it is in a cold attic space.
What is suitable for insulation in this case? Fire safety is very important to us, so materials like polystyrene foam are out of the question. At the same time, it should not be too expensive because we plan to demolish the house completely and rebuild in a few years—if we have the budget for it. But until then, we don’t want to be cold.
There are no rafters in the attic space, so it would be difficult to fix roll insulation. Or should we install battens specifically for this purpose?
The pictures show the attic spaces from inside (and the previous owner's meager attempts at insulation, which we will remove) and the hatch from the outside.
The hatch itself is also a problem: How can it be insulated?
Oh, and we really don’t intend to use the attic spaces regularly; the solution does not need to be walkable at all times. It just needs to be possible to open the hatches occasionally for inspection purposes.
Any advice would be greatly appreciated—it’s already cold up there…
Thank you very much and best regards,
Andreas
Insulation will only raise the temperature of the knee wall. What will probably bother you more is the draft, and a little mineral wool alone won’t be enough to control it.
Seal the joints of the Heraklith boards and the access panel with tape; without major effort, that’s about as much as you can do there.
Seal the joints of the Heraklith boards and the access panel with tape; without major effort, that’s about as much as you can do there.
Arcplane schrieb:
As you wrote: the knee walls are to be insulated from the attic side. Good to know that I at least understood you correctly.
Arcplane schrieb:
It’s also good that this makes sense in this way. There are opposing opinions about this; I only meant that if insulation is done at all, this location makes the most sense: insulating the attic side of the knee wall or the living space side of the dwarf wall would be less optimal placements in my view.
Arcplane schrieb:
Great, now at least I know the terms. Thanks a lot! As I said, normally this could be dismissed as “my pedantry” — usually, only one of the two terms is used, and then the knee wall may also be called dwarf wall (or vice versa, as you did here).
In this particular case both knee wall and dwarf wall “apply,” so the distinction between the terms is more important; otherwise, people quickly talk about the supposedly same thing but actually mean the other — which can lead to choosing the wrong installation side…
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