(another) Wall Insulation Question

engrish?

Hi,

I live in a 1950's concrete house, the walls are almost solid (it feels like there is a gap of an inch or so when you drill through in places) and they are freezing all of the time. I am hoping to make the house very warm by next winter.

We have a bad problem with condensation. There is no ventilation in the house and as the walls are so cold, the condensation forms by the top of the wall and rolls down (in the kitchen / dining room the walls often look like they are crying when we are cooking). I spoke to my neighbor who had the same problem until he insulated the walls. I have looked at the options, cavity is impossible as the cavity is so small and uneven (solid the whole way through at parts), external insulation is too expensive leaving the only viable option as insulated plasterboard.

The house is small, so I would like to lose as little as possible. That being said, I want the house to be warm as possible! I had a look at some insulated plasterboard in chadwicks, 30mm backing. I have the following questions if anyone can help:

1) Will this make a big enough difference to the internal temperature? Should I go for a thicker insulation?
2) In the downstairs rooms, there is semi solid flooring running right up to the walls. Should I remove the flooring at the wall so the plasterboard runs straight to the floor?
3) Do I need to put in air vents if I install the plasterboard?
4) Do I need to treat the walls before I stick the plasterboard up? I was planning on bleaching to kill any mould. I have stripped the wall paper.
5) Do I need to install it in the window? ie where the wall runs towards the window.
6) Will I lose much heat from the external wall between the ground floor ceiling and the first floor floor?
7) I think I remember seeing a builder use a silver foil (like you use behind a radiator) between the insulated plasterboard and the wall - is that a no no?

Thanks a mil

BryanF

you need a ventilation strategy: 4inch holes in each room or window vents + mechanical vents in WC's and kitchen (or whole house mech vent system).. by 'almost solid' you mean 'hollow block' or 9inch block sometimes known as 'breeze blocks' or 'cavity blocks' (not to be confused with 'cavity wall')

1. yes to the first and no to the second
2. maybe, is this suspended floor with ventilation underneath?
3. you need to put in vents regardless, if you don't, putting up the insulated plasterboard will merely be masking the problem in the short term
4. depends on plaster type, any gypsum should be removed
5. ideally yes, but this whole conversation is in need of a caveat re - the issues of internal insulation: interstitial condensation, moisture penetration, thermal bridging, window condensation due to cold surface & high humidity caused by lack of ventilation and so on..
6. take a linear measurement and multiply by depth, then imagine that as an area of the wall, that your not bothered to insulate, lets just use the tesco slogan - every little helps...
7. silver foil yes bad idea. do you have rising damp as opposed to surface condensation? as in if you actually have damp walls then this needs to be solved first. and as a last resort these could be tanked. but generally its a vapour control layer you want to the room-side of the insulation..

its a pity the EWI is out of your price range, may I ask have you priced it and factored the gov grant? are you in a semi-d or detached? i appreciate in a detached house with alot of wall area the costs are high, but imo its a much better option than dry-lining

engrish?

by 'almost solid' you mean 'hollow block' or 9inch block sometimes known as 'breeze blocks' or 'cavity blocks' (not to be confused with 'cavity wall')

I'd say you are right there, the wall is about 24cm thick!

maybe, is this suspended floor with ventilation underneath?

Yes but no, there is no ventilation underneath



you need to put in vents regardless, if you don't, putting up the insulated plasterboard will merely be masking the problem in the short term


Ok



depends on plaster type, any gypsum should be removed


Forgive my ignorance, but how can you tell if its gypsum? the plaster on my walls is pink if that helps!



ideally yes, but this whole conversation is needs a caveat re the issues of internal insulation: interstitial condensation, moisture penetration, thermal bridging, window condensation due to cold surface,high humidity caused by lack of ventilation and so on..


Ok - But could I use a thinner piece of insulation so that I dont cover part of the window?



take a linear measurement and multiply by depth then image that as an area of the wall that your not bothered to insulate, lets just use the tesco slogan- every little helps...


Is there a way around this? I have a lot of spare rockwool, would it pay to lay it under the floorboards between the ground floor and first floor?



silver foil yes bad idea. do you have rising damp as opposed to surface condensation? as in if you actually have damp walls then this needs to be solved first and as a last resort these could be tanked. but generally its a vapour barrier you want to the room-side of the insulation.


Definitely Condensation. It occurs on the surface of the wall, at the top of the wall. easily washed off with bleach and water.



its a pity the EWI is out of your price range, may I ask have you priced it and factored the gov grant? are you in a semi-d or detached? i appreciate in a detached house with alot of wall area the costs are high, but imo its a much better option than dry-lining

I'm in a semi d but I just dont have the money to do it. I will be doing this job with the money I can afford, which is about €150 per month. It will be slow but its not a huge house and I will have it done by next winter!

Thanks

BryanF

2.it should be vented! have the external ground levels changed? it maybe worth looking at the ventilation, air-tightness and insulation of the floor at same time
4. yes thats probably gypsum take it back to the block.
5. yes
6. yes but again Vapour control is best to the inside of all works
7. ventilation!

engrish?

Great stuff, thanks.

engrish?

Hi,

I'm just about to get cracking into this. I just wanted to check if I definitely need to remove this layer of plaster... I've taken a photo of where I removed the TV bracket so you can see the plaster and the bare wall. The man in Chadwicks said to make sure as it does not always need to be removed.

Any advice is greatly appreciated.

Thanks

cgc5483

engrish? wrote: »

Hi,

I'm just about to get cracking into this. I just wanted to check if I definitely need to remove this layer of plaster... I've taken a photo of where I removed the TV bracket so you can see the plaster and the bare wall. The man in Chadwicks said to make sure as it does not always need to be removed.

Any advice is greatly appreciated.

Thanks

Looks like what is in my house. Its poured concrete I reckon. Mine was built in the early 1950s as well. The plaster was falling off like that in places,especially where it was drilled.

How are attaching the insulated plasterboard. If using mushrooms should be ok not to remove the plaster but if using bonding directly to that plaster you will probably have problems as it will peel off in many areas

BryanF

cgc5483 wrote: »

If using mushrooms should be ok not to remove the plaster but if using bonding directly to that plaster you will probably have problems as it will peel off in many areas

did you read my post above

if dry lining Remove the plaster (as much as is possible)

this is relevant as this inner (soon to be COLD) wall will be the likely location for any internal moisture to condense - the plaster in the picture will retain moisture and be a breathing ground for mould

External wall insulation is a much better option over dry-lining in single leaf/ mass concrete construction