Internal insulation of garage with stud wall

[GillesF]

Hi all

Our house in Belgium was built in 1899 with an extension built somewhere in the 50's or 60's. This extension is used for our garage (35m²) and kitchen (20m²). The flat roof of this extension was insulated recently at the outside. Next year, we want to renovate the facade of this extension with wood and take this opportunity to also install external insulation so the entire extension is insulated except the floor. We have one problem: one wall is located against our neighbour's plot so it is not possible to insulate this from the exterior. Moreover, this is a "Frankenstein" wall: the lowest part is old bricks and the top part was added later using concrete blocks but not as thick, so there's a recess about 2 meters high.

Since we have no choice than to insulate from the inside, we first wanted to install hemp blocks but this was over 5000£ investment which is simply too much. We are now thinking of creating a stud wall that is a few centimeters away from the old wall (no direct contact), rests on a layer of Ytong blocks and is fixed to the facade and back walls with a damp proof layer between the walls and wood. Then we put a layer of wood fibre boards over the stud wall and the Ytong blocks. Is this recommended? From what I have also read, it is important to provide ventilation between the stud wall and the old wall to prevent condensation?

Below is an image of the situation, the green line is where we want to place wood fibre insulation. The two garage doors have been replaced by 1.


Thanks all!

 

[GillesF]

No one has done this before?

 

[GillesF]

Update: I have chosen another option, namely to insulate the wall in the middle of this extension which separates the kitchen ("keuken" on the plan) from the garage. I have to insulate the ceiling of the kitchen anyway, so if I insulate the midde wall too, then the entire kitchen is 1 completely insulated room. Advantages are that this is a wall made of modern materials so much less damp issues + no beams or other nodes that might make insulation difficult or increase risk. Disadvantages: garage wall is not completely insulated but since there is no heating I don't think it matters much. I will then leave the garage wall uninsulated (see my first comment) and keep it as a beautiful accent wall by not covering up the repointed old wall.

New question: only part of the kitchen ceiling has a vapour barrier and because of this I was thinking of using sheeps wool as an insulation material. The kitchen will be mechanically ventilated and the loft on top of the kitchen's ceiling will also be ventilated, either mechanically or naturally. Has anyone used sheeps wool insulation without vapour barrier?

Thanks!

 

[Glenn586]

Hello Giles,

I've recently internally insulated a second sitting room that had three exterior walls. It was the coldest room of the house. I used 40mm Steico directly onto the existing lime plaster so there is no air gap. This is critical where breathabilty of the wall is required. The result is fantastic. Now the woodburner goes on and within half an hour the room very warm. I think you are right to sack the exterior garage walls, any gain would be negated with a quick blast of cold air under the garage doors. I would also consider kingspan type insulation on the inner walls where breathabilty is not an issue. The same thickness will give you almost twice the thermal efficiency.

I have used sheeps wool insulation in an attic space above our bedroom in a 16th century cottage. It does its job and does have advantages (still very thermally efficient when damp).

Hope this helps.

Glenn

 

[GillesF]

Hi Glenn

Thanks for the reply, great to hear that insulation works well in your room. Our wall makes a recess above 2m height because a thinner construction was used, in that case, we should add extra insulation so it's flush with the insulation below 2m?

Did you install a vapour barrier when you insulated the attic space? Any issues?

 

[Glenn586]

Hi Giles,

I didn't use a vapour barrier. Sheeps wool by nature is one of the best natural materials to control moisture so I let it do it's job.

Glenn