Single leaf/skin utility room - insulation upgrade

[dishman]

Hello all

I have a small utility room extension done in the late 70's early 80's (before I was here) which is single skin in red brick. It is pretty solid with a flat felt roof and in good condition. Internally it has been wood panelled (tongue and groove vertical planks). It is connected to the central heating circuit and is used more as a breakfast room than a utility room.

I suspected however that it had not been given any internal insulation. Without wanting to rip away the wood panelling at this stage I decided to pull out one of the wall socket covers to see if it would give any clues.

As I suspected, it seems there is a lack of insulation (unless there is an intended void around the sockets for fire safety). All I could see was a void, some timber batons (I assume for the panelling) and what looked like some form of membrane (it was black in colour and prevented me from seeing any brickwork). There are no issues of damp in there currently.

Without creating too much work for myself, would/could it just be a case of removing the panelling, putting some ridged insulation between the vertical batons. Then putting on some insulated plaster board, and than re-plastering?

Should any rigid insulation (celotex etc.) going between the vertical batons be up against the exterior skin? Or should there be a small gap?

Many thanks in advance...

 

[noseall]

There are numerous ways to tackle it in terms of thickness and method. Seems like you already have a damp membrane on the outside wall.
50mm x 50mm battens fixed to wall.
Rigid board between battens.
Rigid board across battens.
VCL.
Foil backed plasterboard and skim.
Only trouble is you will move the cold spot (and subsequent condensation problem) to the ceiling unless this is adequately insulated and ventilated.

 

[motorbiking]

You could just remove the battens and frame fix the insulated plaster board on to the brick - or use dob n dabs. Sometimes every Inch of the room is a premium. You should do the roof also and the floor.

 

[dishman]

In your method noseall, would the first lot of rigid board place between the batons be pressed against the walls? Or should a slight gap be left with some form of retaining strip to maintain a consistent gap between the insulation and wall/membrane?

Yes, the roof would have to be done too as although it is a decent flat felt roof, has no insulation either (as far as I am aware). The room itself is very dry and water tight and it has a dpc. So overall, it makes sense to add more insulation I think.

In terms of ventilation, would a single room mvhr make sense? Or maybe a just a discrete extractor with a humidistat?

Oddly, without peeking behind the sockets, I initially thought that there must be some insulation as the room never gets too cold and there is no damp/mould etc. But, maybe winter has not properly hit yet.

Edit: You mention adding a VCL after the rigid insulation. Does something like Celotex not have a VLC built into it as part of the rigid board?

 

[noseall]

In your method noseall, would the first lot of rigid board place between the batons be pressed against the walls?

Yes.
There is no benefit in having an air gap that can not be ventilated. Zero air gap means no where for moist air to migrate.

Yes, the roof would have to be done too as although it is a decent flat felt roof, has no insulation either (as far as I am aware). The room itself is very dry and water tight and it has a dpc. So overall, it makes sense to add more insulation I think.

Ideally you would opt for a (vent free) warm deck method. It is possible to fully fill the void with rigid board insulation but this requires a robust fitting system whereby all gaps are filled and joints foil taped etc.

In terms of ventilation, would a single room mvhr make sense? Or maybe a just a discrete extractor with a humidistat?

Oddly, without peeking behind the sockets, I initially thought that there must be some insulation as the room never gets too cold and there is no damp/mould etc. But, maybe winter has not properly hit yet.
?

I'd use the room, once fully renovated, before opting for any kind of (noisy) mechanical ventilation. Cold Winters usually reveal any weaknesses in poorly insulated rooms.

Edit: You mention adding a VCL after the rigid insulation. Does something like Celotex not have a VLC built into it as part of the rigid board?

The foil sandwich does act as a VCL as long as you robustly install the insulation in terms of taping joints, foam filling gaps etc. We always tape and fill both layers of insulation and use foil backed plasterboards also.

 

[dishman]

Thanks noseall

Sounds easy enough. As long as I am careful to fill all those gaps.

One last point. In your method, would you use a VCL even if the rigid board was foil backed? Or were you describing a method that used a rigid board without a VCL.