Attic Insulation

le_baz

Hi,
I have a house that was built in the 80's. The attic was also converted in the 80's so it has no insulation apart from the 200mm blanket between the joists. In winter the place is freezing as the heat just goes out through the roof. When the attic was converted the minimum 2" air gap was left between the attic ceiling and the roof. Is it possible to get this insulated without pulling down the attic ceiling? I hear that foam insulation can be used. Is this true?

Any advice welcome.

Ta

Poor Uncle Tom

Attic ceilings can have quilt insulations added above quite easily. Vertical side walls in attic spaces can have insulations added in the void spaces with a bit of work and any sloping sides can be 'drylined' or have a layer or two of insulated plasterboard added. All together it is a lot of work but well worth it.

RKQ

le_baz wrote: »

Hi,
IWhen the attic was converted the minimum 2" air gap was left between the attic ceiling and the roof.

Ensure you maintain 50mm clear air gap between felt and insulation.

Its well worth insulation the horizontal ceiling and vertical walls with fibre glass of rockwool. Its relatively easy to do - but getting into confined spaces can be akward.

Install 75 - 100mm on sloping part of ceiling but ensure you maintain 50mm clear air gap between felt and insulation - otherwise the risk of dry rot is high!

Then dryline the sloping ceiling internally with kingspan bonded to plasterboard - if head height allows.

Also ensure 250mm plus insulation between first floor joists, in void / crawl space.

le_baz

RKQ wrote: »

Ensure you maintain 50mm clear air gap between felt and insulation.

Its well worth insulation the horizontal ceiling and vertical walls with fibre glass of rockwool. Its relatively easy to do - but getting into confined spaces can be akward.

Install 75 - 100mm on sloping part of ceiling but ensure you maintain 50mm clear air gap between felt and insulation - otherwise the risk of dry rot is high!

Then dryline the sloping ceiling internally with kingspan bonded to plasterboard - if head height allows.

Also ensure 250mm plus insulation between first floor joists, in void / crawl space.

Unfortunately this is my problem. The sloping part has only the minimum 50mm gap between the felt and the wall. There is no room to add any insulation. The sloping wall has 2 velux windows and is nicely finished with T&G. Will I have to get someone to redo the sloping wall or can I fill this gap with some type of insulation that will not cause dry rot?

RKQ

Your house was built in the 80's - its extremely important that you maintain 50mm clear air gap between felt and any new insulation. Bitumen felt needs ventilation, as it does not breath!

There is no insulation, with IAB cert, that can fill this gap without aiding the development of dry rot. Do not block this ventilation.

Remove the t&g and dryline the sloping ceiling as outlined above. Any insulation is better than none. Increase vertical and horizontal insulation thickness.

What is the exact depth of your roof rafters?

le_baz

The depth of the roof rafters is actually 12cm! I should have measured it properly before.

Therefore the gap between the felt and the sloping wall is 12cm.
So what can I use to fill the 7cm gap that I now have without removing the T&G ? I have access to this space.

RKQ wrote: »

Your house was built in the 80's - its extremely important that you maintain 50mm clear air gap between felt and any new insulation. Bitumen felt needs ventilation, as it does not breath!

There is no insulation, with IAB cert, that can fill this gap without aiding the development of dry rot. Do not block this ventilation.

Remove the t&g and dryline the sloping ceiling as outlined above. Any insulation is better than none. Increase vertical and horizontal insulation thickness.

What is the exact depth of your roof rafters?

RKQ

It seems you have 70mm to play with.
I'd recomment 60mm high density foil insulation or 60mm hemp, along the slope - maintain 50mm air gap.

I understand why you want to keep the t & g but you should try to install some form of vapour barrier (plastic) to prevent moisture entering the roof space.

Its not an ideal situation but any insulation is better that none!

Increase the ceiling over the attic to 250mm thick fibre glass. Install 100mm fibre glass to vertical wall with a vapour barrier, maybe consider covering the external side of these stud walls with 60mm or 70mm thick kingspan.

Fully insulate between and over the floor joist, in the crawl space to keep the heat in the ground floor.

Good luck:)

Carlow52

Just to add to what RKQ suggests

1: take off the T+G
2 screw 2 * 1 along the inside face of the rafters, touching the slating lathes
[if u can rent a small electric stapler then u can nail these lathes]

this creates the 50mm air gap

3 get 70mm foil faced solid insulation and cut it to TIGHTLY in between the roof rafters.
4 tapes all joins with alu tape.
5 fix another 50mm or more, depending on space and budget, of foiled backed across rafters.
6 Tape as before.

If this is done right the foil acts as ur vapour barrier.


7 Fit 12.5mm plaster board, using long PB fixing screws.

8 Refix T+G by nailing at an angle into PB [ electric stapler will come in here again.

9 Ensure all access holes to crawl space are very airtight

Buy the summer shorts!