Single leaf, internal wall insulation

[harveytimjohn]

Hi, I know this is a topic discussed loads across the forum. However I'm still a little unsure what to do, please help anyone!

I've just bought a house last summer that has a conservatory, and two of the wall are only single leaf brick. And as such when it's cold; we get chronic condensation all over the walls! The walls are now really mouldy and dripping wet most of the time, which makes the space unusable.

EWI is not possible so I was thinking of internal insulation. So my question really is what's best?

Could I simply fix some kingspan or celotex type insulation with the integral plaster board directly to the wall? Would this stop the wall getting cold and thus stop the condensation.

Or, should I use batons leaving an air gap? My only worry with the batons is this may lead to a mould farm growing inside the cavity itself?

Many thanks in advance!

Tim

 

[Infoelec]

Hi Tim, I've experienced the same problem before.

1.Remove all plaster back to brick

2. Apply Vapour Barrier to the wall.

3. Screw some treated battens to the wall

4. Insert Kingspan / Celotex or if budget is tight polystyrene

5. Board over with moisture resistant plasterboard (if you want to use normal plasterboard then staple the vapour barrier over the insulation and board

6. Skim and be sure to leave a small ventilation gap (e.g.) skirting

 

[Grenage]

Don't you need to leave a 25mm gap from the wall?

 

[Infoelec]

No you don't need a gap if you add vents. Use a vent at the top and bottom of the plasterboard to encourage airflow.

For added protection weep vents can be fitted outside.

Venting the ridge can also help if accessible.

 

[Grenage]

Hi Infoelec,

If it's filled from wall to board, there's nowhere for the air to circulate, is there?

 

[pinenot]

Air will always get in, it's it's nature. Also you could try waterproofing/repairing the external brick surface, to limit water ingress, as you state the room is inhabitable therefore there should be little or no internal moisture to cause condensation!...pinenot

 

[Infoelec]

Air will get it into the space behind the insulation through positive airflow. This is accelerated by vents. I advise you use vents and my way will help increase space, you are putting a vapour barrier before which enables moisture to stay back and exhaust out not in.

 

[Grenage]

Cheers for the clarification; it's always good to know why, and not just how.

 

[harveytimjohn]

Thanks Infoelec,

That's a real help. I,ll probably need to leave a gap at the top anyway, because the wall will protrude into the conservatory and I can't plasterboard up to the plastic roof. So will need to put some edging around the top edge and leave it at that.

As far as airflow into the room itself, I leave the windows on the latch at the moment anyway. Condensation definitely worse with the windows fully closed too!

Do you think i could get away with leaving the original plaster on?

I think the problem is made worse at the moment because the paint on the walls is of a silk type and just doesn't breath, so could sand that back quick enough. But the real problem is just the sheer coldness of the walls.

Now I've just got to decided wether to run a radiator out into the big cold conservatory! Any thoughts??

Cheers Tim.

 

[Infoelec]

Best idea would be to remove the plaster or you may get mould growth / detritius falling behind the insulation.

Matt paint is best for breathability.

Radiators do help providing the heat will stay in the conservatory.
Condensation can be removed by using a mechnical extractor fan if you wish to have one.

Anything else let know.

 

[pinenot]

If were talking vinyl emulsion, then none of them are breathable (a modern day myth, vinyl is plastic and forms a monolithic membrane once cured) so your right to think it's not helping, it's sealing the wall from both directions, as it were. But if you seal the wall externally, stopping any moisture ingress, what your left with is the simpler problem of condensation, to eliminate,reduce.
Condensation is the ability of moisture in the rooms atmosphere to condense on a cold/dew forming surface! Moisture is always in the air, Old (pre 1940ish) houses were built to breath through most of their large surfaces and they had drafts (ventilation), modern homes are built both of waterproof materials and fairly draft free, so no breath ability and limited ventilation.
The upshot is if you take care of all of the above, not just one, you will be able to cure the condensation. There are plasterboards available which have insulation bonded to them which also has it's own internal vapour control, that would probably be your best bet, this is one - www.british-gypsum.com/products/gyproc-thermaline-super - other will also probably be available, and don't forget the ventilation, either a blowing fan or an extractor...pinenot