Would like to insulate a smallish utility room that used to be an old outhouse building before it was joined onto the house.
Previously it was battened out and plasterboarded.
Whats the best way to do it?

Batten it out and fit 25mm celotex in between the battens and board over the top.? Does it need airflow behind it?
If So
Shall I batten the walls then use prebondedcelotex/plasterboard over the top, leaving 25mm airgap behind?

Do I need a vapour barrier behind it too?

Batten it out and insulate using plasterboard backed insulation: The likes of Celotex and Kingspan do them. Tape and seal the joints.

http://www.kingspaninsulation.co.uk/getattachment/39da3ae9-8f6c-4b8e-9220-7ae813d51603/Kooltherm-K18-Insulated-Plasterboard.aspx

Yes, ideally a vapour control layer should be incorporated.

Have you made sure that it’s properly ‘attached’, and won’t bring damp through – eg no dampcourse?

I would not bother battening. Pva bond the wall. Then dot and dab the insulation backed plasterboard straight on..with plaster board adhesive.
If damp is a problem you could go with a damp proof slurry / tanking on brick first. For belt and braces approach!

I’ve already used a paintable rubber damp proof membrane on the walls and first 6″ of the floor

was planning on just using the celotex/pb combo. but went and had a look down at selco and they have 2 types, one using celoxtex with the tin foil layers on and one with what looked liked pink polysterene. Is the pink one water/damp proof?

Never seen the pink one! I would use celotex backed. But if you are sticking it with adhesive . Don’t use the foil backed one. I use one made by celotex and the back is like brown paper as found on plasterboard, so the adhesive bonds to it. Jewson sell it.

Its this one.

[/url]

can this be stuck on and would it need a vapour barrier

I’d be more inclined to insulate the exterior. You’ll be able to manage moisture and condensation better, and having the bricks on the inside with gone you a bit of thermal mass. It does bring issues with sealing with the roof and party wall s though.

Thats not really possible here, plus surely I’d just waste a load of energy heating the brickwalls rather than “bouncing” the heat back into the room

Sorry to hijack, but could you use the kingspan board to insulate a ceiling? We have a utility on the side of the house and get mould on the ceiling where condensation forms as it’s so cold. Would boarding out resolve this?

jim25 – Member
I’ve already used a paintable rubber damp proof membrane on the walls and first 6″ of the floor

Which one did you use by the way? I’m just doing my utility and in a similar position to yourself.

damp paint

This one,

surely I’d just waste a load of energy heating the brickwalls rather than “bouncing” the heat back into the room

not a waste, with external insulation, you get to use the brick wall as additional thermal mass – slower to heat up, but should smooth things out to make it nice and easy to keep warm. Would make it cooler in summer too.

I’ve considered external insulation, but couldn’t do it on the front wall, since we’re in a pretty red brick edwardian terrace.

jim25 – Member
I’ve already used a paintable rubber damp proof membrane on the walls and first 6″ of the floor

i’ve used this for my floor but wish i hadn’t really – apparently (following a lot of DIY net searching) this stuff is meant to be trapped between two solid layers as it stays as a sticky rubber (liquid) state ie: it’s not solid. for floors its meant to have a screed over, but i didnt have the level difference required to meet the existing adjacent tiled floor so had to make do. it lost its stickiness with the amount of dust/grit/cement trodden into it so i tiled straight on it and it seems ok for now – well not movement yet! but the exposed bits behind the skirtings are still ‘sticky’ a month later. not wet but not exactly solid either – definitely soft and could be scraped off 🙁 i’d be tempted to use battens and fix the board to them, better than risking the dot and dab failing to stick to the damp proof stuff and the whole lot falling down! good luck!

Ok. This stuff maybe slightly different them as it’s all dry now over the weekend. Certainly dry enough to touch and lean against.
But im going to batten the walls first anyhow, just to give it some airflow behind as before it had none it was dampish behind when I took off the old boarding.
I mainly used that damp proofing to try and stop and damp coming through the wall from the outside.