Insulating bedroom above garage

[Lindsay Webber]

Hello. We have a freezing bedroom above an integral garage. We had the floorboards lifted and wool type insulation laid a few years ago but it is still cold. Would you recommend attaching Kingspan boards to the (plastered) garage ceiling under the bedroom? If so, how should these be attached?

 

[JohnD]

if you have already insulated the floor (properly, so there are no draughts blowing under the skirtings) you should next look at the ceiling and the walls.

put your hand against them. Cold?

what is the roof construction?

 

[^woody^]

Basically your insulation is crap

Draughts in the floor void are a major source of heat loss - gaps around built-in joists and the celling/floor perimeter

Kingspan type insulation should be below the floor boards to be effective, not on the garage ceiling. As thick as you can, or 100mm and the remainder quilt

 

[Lindsay Webber]

Thanks Woody. The issue we have is that we cannot lift the current carpet as it was only recently fitted so my question would be would it be worth fitting the boards to the garage ceiling or not at all?

 

[^woody^]

Not unless you are certain that the floor void is completely sealed, otherwise it will be a waste of time and money.

 

[kingandy2nd]

I’m in the process of building a new bedroom over a garage, and building control have asked me to fit 75mm kingspan / PIR to the ceiling before plasterboarding.

I guess the challenge for you will be hitting the joists with the screws through the PIR and the existing plasterboard.

I don’t think it would be a waste of money for you, but equally as woody suggests if there are loads of gaps around the floor joists (where they meet the walls) it may not be fully effective.

If you want to do a full job, you may wish to consider removing the plasterboard from the garage ceiling, addressing any gaps in the floor joists with expanding foam, then fit your PIR and then new plasterboard on top.

It will add to the cost of the job, and you may find there weren’t any problems with joist gaps after all…but the finished job will look better with a normal plasterboard ceiling in the garage rather than PIR on show.

 

[^woody^]

building control have asked me to fit 75mm kingspan / PIR to the ceiling before plasterboarding

Why have they asked for it to be fitted to the ceiling and not to the floor underside?

Or have they just asked for insulation to be fitted 'somewhere' to tick their box? Bearing in mind that inspectors are not designers and their objectives are not to create a warm room for the homeowner.

 

[JohnD]

Not unless you are certain that the floor void is completely sealed, otherwise it will be a waste of time and money.

If the floor void has been properly filled with mineral wool, it doesn't need anything more. If it hasn't been, it should be.

Without lifting the carpet and having a look, you won't know. The carpet itself will block draughts, except for any gaps such as under skirting or round pipes.

If the floor void has been properly done, you should next address the ceiling. Finally the walls.

If the previous builders took up the floor and laid mineral wool, it would have been pretty easy to do a good job. I did a similar room above my garage. I did also use pink foam round the edges, pipes etc.

I think it is a mistake to leap to the idea of cladding the ceiling below.

 

[kingandy2nd]

Why have they asked for it to be fitted to the ceiling and not to the floor underside?

Or have they just asked for insulation to be fitted 'somewhere' to tick their box? Bearing in mind that inspectors are not designers and their objectives are not to create a warm room for the homeowner.

Good questions.

BC person number one came round and asked for 100mm acoustic wool to be fitted in floor.

BC person number two came round (to look at something else) and I questions how to fit acoustic insulation because we have posi joists - my question was do I put wool in between joist only or in between joists and inside the posi joists. BC person advised inbetween joists only and then 75mm PIR below posi joists.

BC person 2 cost me an extra £350 in PIR, but I imagine it will help with keeping the bedroom warm.

The only options were to install from below as eagar boards already glued and screwed to posi joists.

 

[kingandy2nd]

For full disclosure, as I had plenty of wool, we put it inside the webs of the posi joists too. Cutting and fitting of rolls was delegated to my other half as I don’t like the itchy stuff

 

[JohnD]

I don’t like the itchy stuff

Neither do I, but I have no problem with the brown variety treated with Ecose.

 

[kingandy2nd]

Neither do I, but I have no problem with the brown variety treated with Ecose.

That’s the stuff we used…I didn’t realise it was any different so I steered clear and my other half did it. She’s a trooper