Insulating utility room

Rek88

A little advice would be welcomed.

I have a utility room which I’m fairly certain is an old pantry (1930s house and north facing). It juts off the house so has three external walls and its own pitched roof with no access which almost certainly has zero insulation, the rest of the house had none. We get some serious mold in here as it’s so cold and humid even with the window open 24/7 and a tumble dryer going in the winter. My wife has given me free rein to do whatever to improve the situation for around £300, so my proposal is…

Take down the ceiling and insulate with rock wool, we have several rolls left over from insulating our roof. I also have some PIR board but not sure enough for the job. Install a ceiling fan through the ceiling and out through soffit, this will be a humidistat one to increase the ventilation. Plasterboard out the ceiling. Pvc clad the ceiling so is wipe clean and means I don’t require a plasterer. It won’t look the prettiest but it’s a utility room.

Now the slightly more awkward part. Looking into the room from the door, the right hand wall is cavity wall and has been filled. The left and back walls are not. We believe there was another structure on the back of the house here at some point, and now an ugly conservatory wraps around it. Can I insulate these walls somehow or is it not worth it. I don’t have the room to lose more than a couple of cms due to location of door and the fact that’s it’s a very small room. Would insulating wallpaper make any difference at all? Or dot and dab the thinnest insulating plasterboard?

Finally I will add a small (400x600) towel radiator on the house wall as I can tap into the pipes as they go along the wall to feed a radiator in the conservatory. 

I’m a competent diyer with a workshop full of tools and a plumber mate to do the radiator so this doesn’t phase me.

Anything I may have missed or could be done better. Looking to do it over the Christmas break and I want to do the best job I can.

Cheers

FreeBear

Rek88 said: Now the slightly more awkward part. Looking into the room from the door, the right hand wall is cavity wall and has been filled. The left and back walls are not. We believe there was another structure on the back of the house here at some point, and now an ugly conservatory wraps around it. Can I insulate these walls somehow or is it not worth it. I don’t have the room to lose more than a couple of cms due to location of door and the fact that’s it’s a very small room. Would insulating wallpaper make any difference at all? Or dot and dab the thinnest insulating plasterboard?

If you are lucky, you might be able to get 22mm thick insulated plasterboard - I see a couple of suppliers listing the stuff, but at that size, it looks like EPS. 27.5mm and up, you can get with PUR/PIR (Celotex type) which is a better insulator than EPS or XPS. Dot'n'dab would hold the stuff on the wall, but you'd still want to use mechanical fixings just in case the dabs of adhesive fail.

Personally, I favour the warm batten method and a minimum of 50mm of Celotex (two layers of 25mm) and plasterboard over the top - You could use more of the plastic cladding if you really must....

With a wrap-round conservatory, you have the option of insulating the utility room walls on the conservatory side. But insulating internally has the advantage that you can carry the insulation up the walls above the ceiling and stop cold spots forming at the ceiling junction. Get as much as you can on all three walls and it will be much easier to heat & keep warm.

Rek88

Thanks @FreeBear. Insulating from the conservatory side would be problematic as the utility room walls are about 30cm higher than the conservatory, so there would be an uninsulated area at the top of the wall. I guess this would be a very big cold spot and not something I want.

As a pantry/larder it is very effective, it’s flipping cold in there at the moment. It doesn’t have to be a warm room as we don’t live in there, just more comfortable and mold free. So maybe some thin PIR board with more cladding is a good option. Thanks.

FreeBear

Rek88 said: So maybe some thin PIR board with more cladding is a good option.

It is possible to get some really thin, high performance insulation bonded to a 3mm thick magnesium board. Total thickness is 13mm and with a thermal conductivity of 0.015W/mK. Just make sure you are sitting down when looking at the price - https://www.proctorgroup.com/products/spacetherm

Just don't get suckered in to using a multifoil insulation like the YBS Superquilt - Whilst the stuff may be good at reflecting radiant heat, it does little to stop conductive heat. The latter is more important when insulating a room - YBS also recommend using Superquilt in conjunction with Celotex type boards (I wonder why....).

Rek88

I think it would be cheaper to demolish the two uninsulated walls and rebuilt in more efficient materials  

Thanks for the advice.