Hi all.

I am looking to use 50mm or 25mm insulation foam board with foil backing to insulate some rooms upstairs. These rooms are made from solid brick and at least two of the walls in each room are external.

My plan is to batton the wall and apply pastic sheet. I will then install the foam board and finish off with plasterboard. I am worried that this might create problems at some later date because the walls will not be able to breathe.

Does anyone have any comments on this? I believe there is no damp in the walls at the moment. There is a render on the outside face of the walls and the walls are solid brick.

Many thanks

Trev

General rule for this type of work is.......

Waterproof membrane to outer wall (seams require laps and sealing), insulation block, batons, breathable membrane (minimum laps required but not sealed), plaster board.

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Jaeger.
Senior Member doesn't mean I'm OLD!

darrenc wrote:

I dont think its a stupid question but does show a lack of understanding of how paint works and reasons for certain applications, now dont jump down my throat Jaegar i'm not being funny its just a classic case in point of a well educated professionally trained painter against a general tradesman.

Thanks for the response, much appreciated. I did actually look back over the forum posts afterwards and found similar advice there so sorry for posting. I should have done a bit more searching first.

Trev

Where you have solid walls the movement of water vapour is always from hot to cold, so keeping in mind that the water vapour in a home is created in the home, it will nearly always move through the walls towards the outside (presuming the rooms are warmer that the air outside)

Your plan is flawed by todays standards, as the battons will take up space and they will be a weak link in your insulation.

A better bet is to buy two inch thick insulation board with the plasterboard already attached and stick it to the outer brick wall, taking care to close but them.

If you insulate the ceilings at the same time making sure to tightly fix sheets of polystyrene or similar between the joists (as much as you can get in) then fix another layer of two inch thick polystyrene under the joists.... then, you will have created an insulated box that will keep itself warm.

A room insulated in this way used as a bedroom will hold an all year round temperature of about 20 degrees C, probably not requiring any additional heat.

Stick them with?

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Jaeger.
Senior Member doesn't mean I'm OLD!

darrenc wrote:

I dont think its a stupid question but does show a lack of understanding of how paint works and reasons for certain applications, now dont jump down my throat Jaegar i'm not being funny its just a classic case in point of a well educated professionally trained painter against a general tradesman.

Thanks for all the replies. I suppose its the same old story, I am looking at the costs. I saw some cheap Kingspan 50mm thick insulation board with foil on both sides. The stuff with the plaster board already on it seems a bit expensive?

I know the batons represent a weak spot. Do you think they would take much away from the insulation properties. I suppose its to do with surface area percentage and possible the fact that those areas where the plasterboard touches the batons would be more prone to condensation?

Trev

Wood in itself is a very good insulator, so Perry525 has that wrong.

Modern standards are timber framed buildings for that very reason.

Kingspan is also a much higher spec insulation than the stuff that's stuck on the back of plasterboard.

Just remember to tape the joints with gaffa tape.

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No they're not.


Still waiting for a reply on attachment. The next question would have been barriers.
One water proof membrane and one breathable.

Follow the guidance given and you'll be fine, depth of insulation is whatever you can get for the right budget.

_________________
Jaeger.
Senior Member doesn't mean I'm OLD!

darrenc wrote:

I dont think its a stupid question but does show a lack of understanding of how paint works and reasons for certain applications, now dont jump down my throat Jaegar i'm not being funny its just a classic case in point of a well educated professionally trained painter against a general tradesman.

Wow, excellent, thanks. So I am looking around at all these different insulation boards. What are your thoughts between polystyrene and kingspan standard board with foil backing. Is there much difference in thermal properties. I think someone said the polystyrene represents a possible fire hazard if not used with certain plasterboard?

But I was really wondering if there is much thermal difference?

Thanks again for all your advice, its really really helpful.

kingspan standard board with foil backing will give you about 10 times better insulation properties than polystyrene.

Personally I prefer "Celotex" but the price matches the quality, so if you can get a good price on "Kingspan" go for it.

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Oh, that is a big difference. I found www.secondsandco.co.uk that seems to have some stock at an okay price. I am thinking of going for 50mm thick insulation board.

Does anyone have recommendations on a breathable membrane?

Trev

The system I use is Browning as a levelling and parging coat, then cover the wall side of the board with a 6mm continuous layer of Gyproc dri wall adhesive, I've used this system for five years, before that I used Thistle finish, that worked OK too.

Then they are hanging by the grace of surface tension.

You cannot use adhesive with foil.

Even BG have a Q. & A. on it, on their web site ....
Q: Can Gyproc Duplex Board be installed using the DriLyner Wall lining system?

A: No. British Gypsum only recommend that Gyproc Duplex Board is fixed using a suitable mechanical method of fixing.

So that'll be batons then, you also don't mention any membrane.

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Jaeger.
Senior Member doesn't mean I'm OLD!

darrenc wrote:

I dont think its a stupid question but does show a lack of understanding of how paint works and reasons for certain applications, now dont jump down my throat Jaegar i'm not being funny its just a classic case in point of a well educated professionally trained painter against a general tradesman.

Hi all.

I was just reading the diy tutorial on this site about installing insulation board. If I am right it was saying I apply the insulation board and then put 1inch battens on top of the insulation board and screw the battens to the wall through the insulation board.

Is this the best method to use? I must admit I was thinking that I would batten the wall first with 2 inch thick battens, 60cm apart and put the insulation board in between the battens.

Trev

Battens first, then cut the insulation between the uprights, and tape each edge with Jaffa tape to form a complete seal.

The vapour barrier can then go over the lot prior to boarding or be fixed to the wall first.

Note!!

Standard centers for plasterboard is 400mm.

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