Insulated Plasterboard on internal walls advice

keano25

as above going to fit on all external walls, what is recommended?

62.5mm or 52.5mm?

No insulation in the cavity of the wall.

Metric Tensor

Pump the cavity instead. It is WAY more effective and also cheaper.

Unless there is some reason not to pump the cavity? (i.e. timber frame or no cavity?)

If you have to go this route then the quality and type of installation are more important than the 10mm difference between the two slabs. After that more insulation is better than less in the vast majority of cases.

Ask the supplier to do a moisture calculation to make sure you aren't going to have mould growing behind the dry lining.

Rabbo

The advice is not to do it.

The insulation will be in the wrong place, the inner leaf of the block wall will remain cold and the moisture-laden air that will inevitably get through the insulated plasterboard will condense on the block wall causing dampness and mould growth behind the plasterboard.

The insulation companies will say that there is a moisture barrier between the insulation and plasterboard (foil) but unless you tape the foil of each adjoining board together and to the adjacent ceilings, walls and floors, it's not going to be effective.

If you have the funds for it, external insulation is the optimum solution and there is a generous SEAI grant available for it.

Otherwise, I would opt for pumping the cavities if there's more than 40mm width available in them. You could possibly supplement this with some limited insulated plasterboard as long as it is correctly specced so that the dew point remains in the cavity and not on the inside block leaf.

keano25

Why are so many people using insulated plasterboard on the internal of external walls if it's as bad as you say?

Bigus

keano25 wrote: »

Why are so many people using insulated plasterboard on the internal of external walls if it's as bad as you say?

I think they are very effective .

I can't see how the moisture laden air will get any where near the cold leaf , and I've just fiited insulated boards in similar scenario, vast improvement.

dfader

Bigus wrote: »

I think they are very effective .

I can't see how the moisture laden air will get any where near the cold leaf , and I've just fiited insulated boards in similar scenario, vast improvement.

Have you ever been involved in a renovation and taken off old ones in a house? See any mold?

Calahonda52

keano25 wrote: »

Why are so many people using insulated plasterboard on the internal of external walls if it's as bad as you say?

Why do people smoke?

Calahonda52

Bigus wrote: »

I think they are very effective .

I can't see how the moisture laden air will get any where near the cold leaf , and I've just fiited insulated boards in similar scenario, vast improvement.

Nobody is arguing about the vast improvement in the warmth, its the hidden mould problem that is at issue over the long term

http://www.josephlittlearchitects.com/articles

keano25

Calahonda52 wrote: »

Nobody is arguing about the vast improvement in the warmth, its the hidden mould problem that is at issue over the long term

http://www.josephlittlearchitects.com/articles

I just read the link, from what I can gather there is no problem with internal insulation once original plaster is removed from the wall?

keano25

Bigus wrote: »

I think they are very effective .

I can't see how the moisture laden air will get any where near the cold leaf , and I've just fiited insulated boards in similar scenario, vast improvement.

What width did you fit bigus?

BryanF

keano25 wrote: »

I just read the link, from what I can gather there is no problem with internal insulation once original plaster is removed from the wall?

Eh I'm not sure that's the best course of action. Plaster layer offers some level of air-tightness. Would you not just pump the cavity ?

mjp

Building new house at the moment and wondering do I need to dryline walls. Will be pumping 150mm cavity and going with Underfloor heating aswell as hoping to get maximising airtightness as possible in building.

Heard insualated boards more important in buildings where you have rads as heat is coming from rads on wall rather than floors.

keano25

BryanF wrote: »

Eh I'm not sure that's the best course of action. Plaster layer offers some level of air-tightness. Would you not just pump the cavity ?

I can't imagine pumping the cavity will give the same level of heat retention tho?

Gumbo

mjp wrote: »

Building new house at the moment and wondering do I need to dryline walls. Will be pumping 150mm cavity and going with Underfloor heating aswell as hoping to get maximising airtightness as possible in building.

Heard insualated boards more important in buildings where you have rads as heat is coming from rads on wall rather than floors.

What has your architect specified?
And more importantly, what has the preliminary BER report calulated that is required?

Metric Tensor

Your cavity is probably 100mm thick.

You are proposing to install 50mm of insulation inside the wall.

So the cavity insulation can be half as good as the drylining insulation and provide the same heat retention!

I think what you might be thinking about is thermal mass. If you insulate the cavity you will have to heat up the inner block in the wall as well as the room whereas with the internal insulation you won't - BUT thermal mass is generally a good thing. The block will hold the heat and pass it back into the room over time and will stabilise at the temperature of the rest of the house so will never be as cold as the outer block - thus giving you a more gradual, steady heat profile.

Also - as BryanF has pointed out in a house of an age that it has an uninsulated cavity air tightness is as big a problem as insulation. You probably have draughts left, right and centre. No insulation will help that so you need to fix that too. (Due to blocking thermal looping in the cavity pumped bead does provide a little help in this area - stripping the plaster of the wall would massively hurt it.)

Metric Tensor

P.S. - you'd need to strip all the tiling from the bathrooms, take down all the kitchen units, take out all the window boards and skirting and completely redecorate, including fully plaster and paint the inside of your house in order to dry-line it.

The cavity will be pumped in a day with no affect on the occupants other than making them warmer!

Why not try the cavity first and see how you get on! 2-3k to pump the cavity. 10-15k to dryline properly and end up with a house of hidden problems.

keano25

House is being gutted at the moment so not worried about bathroom, kitchen etc

murphaph

I think you're mad considering dry lining over pumping the cavity if the latter is an option. Far better solution.

keano25

I will messarue the distance in the cavity shortly and report back

BryanF

mjp wrote: »

...airtightness as possible in building...

Heard insualated boards more important in buildings where you have rads as heat is coming from rads on wall rather than floors.

Rubbish, look Around the forum, lots posted about thermal mass and why dry-lining is only a retro-fit consideration when all other options have been exhausted.

More importantly in a new build, what does your BER require? And Where is the air-tightness layer?

keano25

My cavity is only 70mm what's the thoughts of pumping that?

Metric Tensor

Is your outer leaf (a) brickwork or (b) rendered blockwork?

I assume the house (a) timber frame or (b) masonry?

If the answer to both of the above is (b) then in most cases you should pump it. Do you have an engineer, architect or technician involved in the project. If so they'll tell you for sure.

keano25

Ya both B

None of the 3 involved at the moment

Ferm001

After the revelations from the London fire regarding PIR insulation releasing poisonous gases if burned, I would be very reluctant to use any PIR insulated plasterboard.

sydthebeat

Ferm001 wrote: »

After the revelations from the London fire regarding PIR insulation releasing poisonous gases if burned, I would be very reluctant to use any PIR insulated plasterboard.

All organic materials release toxic fumes when ignited, especially oil based insulants. For example, even burning sheep's wool will release levels of cyanide.
The auto ignition point of PIR is 450 degrees centigrade.

So in reality in a domestic situation, if you've temperature of fire at 450 degrees burning in your house, the PIR, in your cavity and /or behind plasterboard, igniting should be down for last of priorities.

BoardsMember

Is there a way to work out what type of walls you have, and so decide if it is possible/worthwhile to pumping them? House is a mid 1920's end of terrace house, part red brick in D6W. Would all similar type age house be the same construction?

keano25

I've asked several local builders and all are saying they've heard of or know of any issues after the fitting internal slabs.

Metric Tensor

Ask them what air-tightness value they got when they tested the last house they fitted with internal slabs.

Also ask them who did the dew point calculation for them.

If they answer those questions well then they are worth considering for your build.


If they tell you that's not relevant because:

a. Some building control/regulations waffle
b. They never did a dew point calculation on their own house and isn't that standing 50 years.
c. "Air-tightness" causes rectal prolapse or ingrown toenails or some other ailment so they don't think it's a good idea.

Then tell them that the internet told you they're full of sh!t.

It seems like you are just going around asking everyone you meet what they think and "designing" your house based on that. If you had very sore ear would you check with the internet and all the lads down the pub before going at it yourself or would you pay for some advice from an expert?

I'm being deliberately over the top here OP and no offense is meant but seriously consider paying an expert for expert advice.

What are you going to spend on this project? 30k? 50k? If you were buying a second hand car worth 50k would you avoid paying a mechanic a few hundred to look it over?

BoardsMember

Interested in these posts about not going for internal insulation if cavity pumped is an option.

I had read loads of stuff about insulation boards internally or dry lining internally (e.g. 92mm composite insulated plasterboard), silicone sealed at floor and ceiling, switches etc, and behind the skirt before skim. I had also read a fair bit about people not seeing much improvement with pumped cavity insulation.

Based on recent informed posts I seem to have got it ass-ways.

Metric Tensor

I think the information you were reading possibly didn't distinguish between benefits achieved from insulation and benefits achieved from additional air-tightness.

The silicone sealing and blocking of air gaps is for air-tightness. There is no reason not to engage in similar activities after or whilst pumping the cavity.

It might explain things!

keano25

So your saying pump the cavity and that's it?

No more no less?

If that's what your saying, great saves me money.

Metric Tensor

Not quite:

I'm saying:

Step 1: Get an expert to check if your house is suitable for cavity pumping.
Step 2: Pump cavity if ok.
Step 3: Address draughts/air-tightness inside.
Step 4: Consider additional insulation inside subject to advice on thermal mass, moisture control and cost benefit analysis.