Insulating above bathroom and CWI advice please.

[PickleLineReject]

Hi guys,

I am planning on insulating the loft space in my FREEZING cold, ground floor, single story extension which happens to be my bathroom, when i replace the asbestos sheets that make up its roof!

At the moment there is no insulation or felt. The lighting consists of 9 x 12v 50w halogen down-lighters and the plaster board ceiling is not foil backed.

If i replace the plaster board with foil backed boards, use breatheable felt under the battens and fit hoods over the light fittings then will i be able to fill the roof space with loft insulation???

Also, do you think it would be a good idea to have Cavity Wall Insulation fitted and if so can it be blown down through the cavity whilst the roof is off to avoid drilling the walls?

Thanks in advance,

PLR.

 

[JohnD]

as it is a bathroom, and some buffoon has made holes in the ceiling, vast amounts of warm steamy air will get into the roof space. So you will have a major problem with loft condensation.

Some things you will have to do:

fit a bathroom exctractor fan, preferably to come on automatically every time the light is switched on

preferably dump those stupid ceiling-hole lamps and seal the holes, otherwise fit caps over them

seal all remaining holes for pipes and cables

insulate any pipes in the loft with Regulation-grade foam lagging (which is as thick as your arm)

ensure the loft space is very well ventilated

 

[mointainwalker]

re; fire hoods

I believe ( not certain) that most of these are ventilated to allow the escape of heat and their real purpose is prevent anything ( insulation) lying directly on the light and causing overheating.

You are causing lots of difficulties for yourself if you keep the spot-lights.

If fibre-wool gets wet ( from condensation) it loses its insulation properties and means all the work and expensive is a waste of time.

 

[ajrobb]

I am slightly confused, is there a pitched roof on the extension (is there crawl space)?

I've just taken down a plasterboard ceiling with spotlights under a slate lean-to roof, the mineral wool insulation was sodden and useless.

I'd go with a vapour barrier and foil backed moisture resistant plasterboard is definitely one way. A cheaper alternative might be ordinary plasterboard with two coats of drywall sealer. I'd be interested if this has been tried and failed.

Cavity wall insulation is notifiable to Local Authority Building Control. I think that loft insulation is only exempt from notification if it's not done at the same time as wall insulation. LABC will want CWI to drop the U-value to no more than 0.55 W/m²/K and roof insulation to no more than 0.16 W/m²/K. Look at Approved Document L1B Table 3.

Untitled

• ajrobb
• 9 Mar 2011
• 4

 

[JohnD]

Foil backed plasterboard will not help much if there are great holes in the ceiling.

You could use Kingspan or simlar boards at great expense which will not get sodden, but the roof timbers still will, until they rot and the roof falls down.