Advice on Insulating sloping ceiling upstairs

[mpooley]

Hi
My nephew has asked me How he can insulate between a sloping ceiling which follows the slope of the roof with only 100mm gap between the plasterboard and the really gappy Norfolk Pantile roof.
There is no underfelt and it would be difficult to do this externally.

Is there some material that could be poured down from the loft which would be large enough to not get blown out from under the tiles the first time we get a gale? 

My suggestion is that he removes the plasterboard and fits kingspan but he really does not want to do that as he has got enough work in the house already.

any suggestions please?

Mike

[biff]

sausages,!!
          foil covered strips of fiberglass insulation which can be compressed and fed down through a narrow gap.when it is in situ it opens out to fill the void,BnQ do this type of insulation and it is very effective.
                                                                      biff

[clivejo]

You need to be careful as some roofs need air gaps to 'breathe' and could cause dry rot in the wood work if the air gaps are filled. Not sure where your located but in Ireland due to the wet and humidity, the felt/underlay can sweat and cause condensation.

You can get plaster board with different thickness of insulation attached, but these come in big sheets and hard to man handle into a roofspace. Another thing I seen recently was a tongue and groove product, 18 inch by 4ft, both sides foil backed, normally used to fill between cavity walls.  Its handy got up into the roofspace, easy worked with a stanley knife and using a special tape can make a pretty good airtight seal.  I would then attach the plaster board to the front for a decent finish.

[mpooley]

sausages,!!
          foil covered strips of fiberglass insulation which can be compressed and fed down through a narrow gap.when it is in situ it opens out to fill the void,BnQ do this type of insulation and it is very effective.
                                                                      biff

sounds good
what size are they ?
what worries me is that when he pushes it down the gap it might push the nibs of the tiles off the battens
would pork sausages be better     

mike

[mpooley]

You need to be careful as some roofs need air gaps to 'breathe' and could cause dry rot in the wood work if the air gaps are filled. Not sure where your located but in Ireland due to the wet and humidity, the felt/underlay can sweat and cause condensation.

You can get plaster board with different thickness of insulation attached, but these come in big sheets and hard to man handle into a roofspace. Another thing I seen recently was a tongue and groove product, 18 inch by 4ft, both sides foil backed, normally used to fill between cavity walls.  Its handy got up into the roofspace, easy worked with a stanley knife and using a special tape can make a pretty good airtight seal.  I would then attach the plaster board to the front for a decent finish.

thats how i'd like him to do it but he is determined not too as that means replacing all the plasterboard

we are in Norfolk BTW which is apparently the driest county in the UK
can't say I have noticed though lol

thanks

Mike

[biff]

i think they used to come in a roll of 1200wide but already divided up and foil wrapped into 3 x 400mm strips when you pull of the wrapper.
    " sausages" is the brickies term for them, they are stuffed down the cavity for fire prevention and soundproofing. the brickies sausages are 100mm x 100mm x 600mm and installed running vertical between apartments.they work incredibly well and dont bring the damp in.
   however the foil wrapped fiberglass idea really took off about 8yrs ago,it is such a simple idea and so adaptable.there are small perforations in the foil which allow you to gently squeeze the air out when fitting into an akward situation.when you get them in,just jiggle them about with a piece of soft plastic piping and they will open up to fill the void,
      the real deal would be to remove the plasterboard and install kingspan 50mm between the rafters.  however,,,,
                                                                               biff

[Legion]

Some of the spray-on insulations are designed for spraying into gaps (normally cavity wall, I assume), but might be worth looking at for your application?

[mpooley]

Can you buy any for DIY use?

mike

[dhaslam]

The sausage insulation  seems to be available with a moisture barrier that goes on the inside but I am not sure if that is relevant to the situation where there is plasterboard inside it.   The large airgap in the ridges of the tiles should give  lots of ventilation.    The upstairs  must be  very hot in summer as well as cold in winter.   

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[brackwell]

I have a vaulted ceiling roof with these wavy tiles and have decided to lift the tiles and felt and roll down the £3 a roll fluffy stuff.

Had considered 1)pouring down from the top Silvaperl Perlite but when i worked out the volume required and hence cost and weight. 2) Shoving a stiff board foam board up from the bottom but then realised it would not get past the noggins and again the cost.

Your supposed to leave a 1" gap on top of the insulation for ventilation.  It would not be a clever idea to insulate without felt being present.

Ken

[mpooley]

I have a vaulted ceiling roof with these wavy tiles and have decided to lift the tiles and felt and roll down the £3 a roll fluffy stuff.

Had considered 1)pouring down from the top Silvaperl Perlite but when i worked out the volume required and hence cost and weight. 2) Shoving a stiff board foam board up from the bottom but then realised it would not get past the noggins and again the cost.

Your supposed to leave a 1" gap on top of the insulation for ventilation.  It would not be a clever idea to insulate without felt being present.

Ken

when you say "  It would not be a clever idea to insulate without felt being present."
can you expand on that please as im not sure why that would be?

[clivejo]

when you say "  It would not be a clever idea to insulate without felt being present."
can you expand on that please as im not sure why that would be?

Felt is a membrane to keep out moisture.  Moisture and woolly type insulation products breed fungus, mould and other types of nasties.

[mpooley]

when you say "  It would not be a clever idea to insulate without felt being present."
can you expand on that please as im not sure why that would be?

Felt is a membrane to keep out moisture.  Moisture and woolly type insulation products breed fungus, mould and other types of nasties.

Ah! Yes I can see your point although we were not thinking about glassfibre or rockwool unless packed in some foil or plastic.
my pref is for kingspan though.

that area just under the tiles is incredibly well ventilated as well, as the Norfolk pantiles seem to keep out the rain pretty well but are very gappy.

thanks

Mike

[scouser]

My house is 100 years old with 'coombed' or sloping ceiling in upstairs bedrooms and a floored/insulated attic.
My problem is how to insulate the large area of void behind the ceiling [the sloping part is covered in lath and plaster, about 1 metre high and 4 metres long].  Removing the old lath and plaster would be a major job and detract from the character of the rooms.
There is limited access from the attic. I thought I might just pour some granular insulation into the voids, [slates nailed to boards sitting on 6x2-inch trusses, about 18" apart] but comments above regarding ventilation have made me nervous.
Also the slating nails project through the roof boards up to one inch.
Is there a type of rigid ventilation I could shove down to rest between the nails and the new insulation ? - would that do the job...... ?
Help appreciated !

[Ivan]

Can you take the roof off? Insulating between the rafters is ok, but you need to leave at least 2 inches void on the cold side of the insulation. Alternatively, and much better, is to convert to a warm roof. This is what I did a couple of years ago to my rear sloping roof -  and it made a huge improvement in temperature in that room. The 'felt' (breathable membrane these days) keeps running water out. The humidity problem is from inside rather than out - ie warm, high humidity air cools as it enters the roof void from the room. It cools, and it's water-carrying capacity reduces. If it falls below the dewpoint, it deposits moisture at the point where the temperature falls below the dewpoint - which is somewhere inside the insulation. Therefore you either need plenty of ventilation topside to remove this moisture as it forms, or you stop the warm air getting there in the first place.

Ideally, you need to fit an impermeable layer to the inside ie polythene on the upper surface of your plasterboard ceiling, but I didn't want to re-do the ceiling, so we took the tiles and membrane off and removed the existing insulation. Using silicone sealant, I sealed everywhere against the upper surface of the plasterboard - down each rafter both sides, along all the plasterboard joints and at the tops/bottoms, also ensuring that the voids in the wall cavity were all sealed at the top (polyurethane foam) and the voids are sealed at the top between plasterboard and walls. It's not ideal, but saves a lot of hassle. You could also paint the upper surface of the plasterboard with impermeable paint. I think mine was foil-backed, which is obviously impermeable apart from the joints.

Then I installed PU insulation between the rafters - approx. 150mm. Then added 60mm polyurethane above this, and then a semi-permeable foil membrane over the top of this. Each overlap in the membrane was sealed with silicone between the two layers and gaffer tape over the top. Joints between membrane and walls similarly sealed. Then counterbatton over that and horizontal battons over that to take the tiles.