Insulation Advice

[franky116]

Hello After moving house a while ago with a garage below the living room and kitchen, we found these rooms to be chilly kind and blamed the windows. When I ripped out the old kitchen units in garage I discovered that there is no insulation in the roof space as they have plaster boarded the roof and even skimmed it. I intend to insulate but was looking for some advise as to the best way to do it as have a couple of options as not overly keen on ripping down the whole roof Thanks to any help given

[harry]

Make yourself a permanent trapdoor into the roofspace.

[meow2222]

Make a hole in the PB between each pair of joists halfway along, inject cellulose, fill. Or lift a couple of floorboards to fill.

NT

[Roger Mills]

What roofspace? It will be all of 7" high, between the joists!

[Roger Mills]

If it was built before the days of insulation, chances are that there isn't a vapour barrier between garage and living space, either.

I would be inclined to tear down the garage ceiling and do it properly - stuff rockwool between the joists, fix a vapour barrier in place and then re-board it. No need to re-skim it - just tape up the joints.

[meow2222]

That's more work for the same result - and cellulose actually performs better in some situations.

The VB must go on the warm side, never put one on the cooler side.

NT

[harry]

Sorry, misunderstood. If there is enough height in the garage blow, apply insulation backed plasterboard to the existing ceiling. You will need an additional layer of plasterboard as it's a garage. (That's if it is to remain a garage.)

The existing ceiling will be a double layer plasterboard or a single layer of thicker than usual stuff. Or maybe even millboard. (asbestos).

[franky116]

- If it was built before the days of insulation, chances are that there isn't a vapour barrier between garage and living space, either. I would be inclined to tear down the garage ceiling and do it properly

- stuff rockwool between the joists, fix a vapour barrier in place and then re-board it. No need to re-skim it - just tape up the joints.-

That's more work for the same result - and cellulose actually performs better in some situations.

The VB must go on the warm side, never put one on the cooler side.

NT

Thanks for the reply's guys Did forget to say its a false ceiling with roughly a 1ft space between the original joists and the boarding. The garage measures roughly 25ft long by 15ft wide.

I was planning on cutting 2 x 2ft strips at 3ft in from the sides thus allowing me access to centre section (roughly 5ft) and insulate, then the same at the sides, then netting in the 2 ft space if required, and re-boarding it back up. (8 x 4 sheets cut in half) I was planning on leaving roughly 1-2 inches at ends for ventilation with a couple of small holes drilled at ends for air as already have a couple of holes for electrical cables as the main meter down there. Was going to use 6" inch fibreglass insulation role, thus leaving a 4-6 inch breathing space between floor and plasterboard.

Does that sound ok or do I still need the vapour barrier ?

[Roger Mills]

Only if built to recent-ish Building Regs. And then it will probably be insulated!

[franky116]

[ Hello After moving house a while ago with a garage below the living room and kitchen, we found these rooms to be chilly kind and blamed the windows. When I ripped out the old kitchen units in garage I discovered that there is no insulation in the roof space as they have plaster boarded the roof and even skimmed it. I intend to insulate but was looking for some advise as to the best way to do it as have a couple of options as not overly keen on ripping down the whole roof Thanks to any help given[/i][/color] -

[meow2222]

VB is necessary. Netting isn't. String can be stapled up where needed.

Insulation between joists is limited by joist conduction. PIR sheet instead of PB would stop that.

NT

[Phil L]

Get the insulation in there any way you can without causing too much damage to the existing ceiling, the way mentioned above will be fine, but you'll have to push and poke the fibre about quite a bit to get it past obstacles etc.

Forget the vapour barrier, you can't get one in without taking the ceiling down and no one bothers with them anymore, they were a fad for a few years in the 80's and 90's but it's rare to see them mentioned on modern new build plans, and even then they are universally ignored by builders and BCO's alike

[Martin Bonner]

See the FAQ for a pretty clear explanation of the problem they are trying t o solve:

If you don't have a vapour barrier, you need to find another way to deal wi th that problem. One solution may be to use rockwool insulation and just l ive with the damage the condensation causes to the plasterboard ceiling. E ventually it will be so weakened you'll have to take it down and redo the i nsulation - but that is probably years away, and what you are doing now sou nds cheap.

[Phil L]

I know how the science 'works', it's just that reality doesn't agree

I'd say decades away rather than a few years, and the ceiling is in a garage. Also, the vapour barrier, if it was needed at all, would be better laid under the carpets of the rooms above, as your link states that it needs to be on the warm side of the insulation

[franky116]

Does that sound ok or do I still need the vapour barrier ?[/i][/color]

Forget the vapour barrier, you can't get one in without taking the ceiling down and no one bothers with them anymore, they were a fad for a few years in the 80's and 90's but it's rare to see them mentioned on modern new build plans, and even then they are universally ignored by builders and BCO's alike[/i][/color]

Did notice when our old house was being built they did not use and just installed netting to hold the insulation until the floor went down, and this was in every room as noticed when doing repairs to plumbing via access hatches. Alas my wife made me sell and move so now have to sort somebody else's missed bits :)

I'd say decades away rather than a few years, and the ceiling is in a garage. Also, the vapour barrier, if it was needed at all, would be better laid

under the carpets of the rooms above, as your link states that it needs to be on the warm side of the insulation

Ok I think then ill try and get the insulation jammed up between the joists and maybe even use something to hold it in place (some fishing netting as live in a coastal town) if required, or if it sits smugly I wont use. There will still be a gap between bottom of joists and plasterboard as have a 1ft gap to start with so if I use 6 inch fibreglass or rockwool it will still leave a breathing space between them. I will leave a small space between outside walls and insulation thus will allow air to enter from the ends and fully circulate the space. This will work out fairly cheap (maybe 100) rather than remove whole roof fit vapour barrier insulate and re board would work out to be expensive.

Ok guys thank you very much for all the advise and different opinions and hopefully our house be that little bit warmer

[Tim Watts]

On Monday 01 April 2013 16:41 Phil L wrote in uk.d-i-y:

In this particular case, as I understand it, there isn't actually a roof over the garage ceiling, but a habitable room? If so, there'll probably not be that much water vapour from the room getting through the floor[1] and you actually want the timbers to breath onto the cold side, through the garage plasterboard ceiling.

Glass wool breaths to some extend anyway (it permits diffusion) - it's not as bad as sealing something up with celotex if damp is likely to be an issue.

I don't see a problem either.

[1] depending on floor covering - and relative to water vapour migrating through a single skin PB ceiling which is the more usual scenario.