insulating ceiling from inside - advice needed

[seneca]

Hi folks,
not sure this is the right forum and please bear with me as I try to explain (it's tricky)

My hallway is always difficult to warm in the winter. It's a wide space and has the staircase in it. the sloped ceiling above the stairs has no rooms above it, just the sloping outside roof. So, any heat in the hallway tends to rise to the ceiling and the large are of sloping ceiling above the stairs. There it has only wallpaper, plasterboard, roof baton and then roof tile. There is no insulation, so the heat goes straight out.

I would like to insulate this sloped ceiling area above the stairs, but without ripping off the plasterboard etc to get to the roof beams. Is this possible? I reckon I have around 8cm to play with, maybe a little more, without it being obvious I have put a false ceiling there (the whole section is framed by a coving type border.)

Don't know much about the materials needed, but I imagined:

- batton against the ceiling (through plasterboard into roof beams - once located!)

- finding some kind of thin insulation sheet (what's the thinnest, most efficient kind) between the batons.

- plasterboard onto batons (maybe the kind with foil on it)

- wallpaper over plasterboard, so it matches the rest of the hall.

Is this plan plausible? is there a better way of doing it? what materials will i need? I'm a reasonable competent diy-er, but would like to make as little mess as possible (too much traffic in hallway and stairs.)

any advice would be greatly appreciated.

 

[noseall]

70mm foil backed celotex or kingspan would do the trick.

 

[^woody^]

You wont achieve much/anything

All the heat is hitting the ceiling and then moving up the stairs. This will be the same if you insulate as your problem is air currents more than heat going out - as the heat goes up, it pulls cooler air along behind it.

In effect its a chimney.

And in some cases, by "over insulating" you could make the area more draughty, and so feel even colder

You may as well just put 80mm of quilt between the rafters and refit the plasterboard with foil-backed type

 

[seneca]

problem with quilt between the rafters is how to get to the rafters. Remove all the roof tiles? (rather not have to do that!) or rip the plasterboards off from inside (not quite sure what I might encounter and don't want to bring anything down (especially on top of me!)

I understand what you mean about the chimney effect, but there's not a lot I can do about that, other than to block of the stairs area behind a stud wall.

"70mm foil backed celotex or kingspan " - how would this be best done. I am sure it would involve batons and plasterboards, but can you give me a few tips about how to, the order of materials and where the gap should be?

thanks for the responses

 

[alittlerespect]

British Gypsum do a 'Gyproc Thermaline Super' board which is made up of PIR insulation with plasterboard finish (there are similar products from other manufacturers - choice of manufacturer may be down to price and availability).
All you need do is stick the board to the existing ceiling with an approved adhesive and the job is 80% complete, you may need to add a couple of screw fixings to hold the board in place while the adhesive sets which can be left in place. The other 10% of the work is to tape and joint and decorate.

A further 10% is to check before you carry out this work that the ceiling void is properly ventilated which may require some external eaves vents being fitted. Job done!

By way of an example: An 80mm board will give a significant improvement in thermal insulation and would meet the requirements of the Building Regulations for the conservation of fuel and power in existing buildings, however, you may wish to consider a 100mm thickness board which would surpass these requirements and provide the same level of insulation as for new build.

Best bet, go to your local builders merchant and see if they can obtain a small sample of the boards for you to try at home - you won't need to physically fit the board - just offer it up or pin it up with some bluetack to see which would be best suited to your particular circumstances.

For further information on these boards check out the British Gypsum website at www.british-gypsum.com

Regards

 

[seneca]

I've removed a small section of the "plasterboard" and found that it's 1cm of plasterboard (i think) and then that old form of wooden strips (don't know what they are called) with lots of mortar/plaster between them.

Anyway, there is a 12cm space between the board and the underneath of the roof tiles. I must say it is a bit worrying that if a roof tile were to slip/fall out, the rain would be falling directly onto the back of my ceiling.

The family are going away for a week, so I can go the whole hog and rip the ceiling off and insulate between the rafters. Or seeing as the ceiling is made of those wooden strips, should they be left alone. For all I know they might be important. I don't want to do something that may cause future damage. What's the best thing to do?
wouldn't the 80mm quilt be difficult to stay up between the rafters? Might some kind of solid block type insulation be easier to get up there?
does there need to be a gap for ventilation? If so, is the gap between the insulation and roof tile, or between insulation and plasterboard, or both? Whats the best soild insulation and plasterboard to go for (I've got a wickes and Jewson near by.)
sorry for so many questions, but I know it is important roofs are ventilated.

 

[seneca]

I’ve made a small hole through the plaster and lathe to have a look at what’s underneath. There is no sarking board or felt (a bit worrying, but other than removing the roof, there's nothing I can do about it.) The rafter is approx 12cm, so I should be able to use 70mm insulation with the 50mm gap above. This should leave the bottom of the insulation flush with the bottom of the rafter. I can now use a board which has plasterboard (12.5mm) on one side and insulation on the other (25mm.) I plan to fix this to rafters with screws. The plasterboard has a vapour barrier and there is foil on both sides of the 70mm insulation between the rafters. The only gap is above the insulation – 50mm. Does this sound ok? Is it ok to have the 2 bits of insulation, between and below the rafter, touching? I don’t need a gap between those do I? I won’t have a problem with all those vapour barriers will I (three in total). I got these exact specs from an online insulation dealer and kingspans own data sheet, so presumably they are ok.

I have been looking online and came across Kingspan tp10 (70mm) for between the rafters and kingspan k18 kooltherm dry-lining board (37.5mm.) I can’t find anywhere near me in Birmingham that sells these so I’ll get them online.

Does this sound ok?