Insulated drylining versus not

cuculainn

Hi,

I know this has been done to death but I wanted to get peoples opinion on reasons for/for not drylining external wall with insulated slabs


we are currently at our plastering stage.
We have internal block walls. We have a row of AAC blocks to break the cold bridge between the raft and the wall. We have minimised cold bridging around windows and will be carrying out airtightness.

Our plasterer is recommending to dryline with isulated slabs (external walls only) We initially thought it was a good idea but are now thinking that it is not.

We have 150mm pumped cavity which should give a Uvalue of 0.2.
Is there a benifit in drylining?
Considering it will cost about €5000, what heat savings will be made?
If it saved us €100 euro a year ( I doubt it would) that would be a minimum 50 yr payback, which does not make sense.

Also we are going with a low temp heat pump so maybe the thermal mass of the block would be more benifical?

On the other hand we only have one shot at this an maybe we should aim to bring the wall U-value down to as low as possible.

Any help/opinions apprecitated

tred

cuculainn wrote: »

Hi,

I know this has been done to death but I wanted to get peoples opinion on reasons for/for not drylining external wall with insulated slabs


we are currently at our plastering stage.
We have internal block walls. We have a row of AAC blocks to break the cold bridge between the raft and the wall. We have minimised cold bridging around windows and will be carrying out airtightness.

Our plasterer is recommending to dryline with isulated slabs (external walls only) We initially thought it was a good idea but are now thinking that it is not.

We have 150mm pumped cavity which should give a Uvalue of 0.2.
Is there a benifit in drylining?
Considering it will cost about €5000, what heat savings will be made?
If it saved us €100 euro a year ( I doubt it would) that would be a minimum 50 yr payback, which does not make sense.

Also we are going with a low temp heat pump so maybe the thermal mass of the block would be more benifical?

On the other hand we only have one shot at this an maybe we should aim to bring the wall U-value down to as low as possible.

Any help/opinions apprecitated

What thickness insulation on the boards are you going for. What u Value will you attain with it, or without. Your prioritys are correct on the air tightness. I dry lined, if I was going it again, id focus ont he cavity, and not be bothered by possible issues in years to come with mould behind the boards, again, or custom window boards!

cuculainn

tred wrote: »

What thickness insulation on the boards are you going for. What u Value will you attain with it, or without. Your prioritys are correct on the air tightness. I dry lined, if I was going it again, id focus ont he cavity, and not be bothered by possible issues in years to come with mould behind the boards, again, or custom window boards!

Hey tred, thanks for the reply.

we were planning on 38mm (12.5 slab + 25mm insulation)
Our engineer says it will bring the Uvalue down to about 0.17 (from 0.2 without)

Will would also do airtightness plastering behind the drylining.


What do you mean by focus on the cavity? Make it wider?

tred

cuculainn wrote: »

Hey tred, thanks for the reply.

we were planning on 38mm (12.5 slab + 25mm insulation)
Our engineer says it will bring the Uvalue down to about 0.17 (from 0.2 without)

Will would also do airtightness plastering behind the drylining.


What do you mean by focus on the cavity? Make it wider?

I would have made mine wider and not bothered with the drylining. i.e. like what you have. But thats my thoughts. Everyone here has opinions. At the end of the day, you need to ask yourself can you justify the extra money for that gain?. Is the plasterer doing the slabbing for you?.

sinnerboy

Remove doubts now by hiring a BER assessor now. You have to have a BER cert before occupation anyway - so get some added value out of the process by answering your query - in € terms.

BryanF

<removed failed link> but if its too late, or external is cost prohibitive, then drylining is one option.

beware of putting a thick layer of higher thermally resistant material on the warm side of construction. maybe 50mm service cavity with mineral wool over HD insulation.

but if its going to cost 5g anyway go the external ins route!

Poor Uncle Tom

BryanF wrote: »

<removed failed link> but if its too late, or external is cost prohibitive, then drylining is one option.

beware of putting a thick layer of higher thermally resistant material on the warm side of construction. maybe 50mm service cavity with mineral wool over HD insulation.

but if its going to cost 5g anyway go the external ins route!

Please read the forum charter before posting again and don't link to or name a company on thread.