Windows and external wall insulation

manape

have been reading a few threads here and was hoping someone can clarify. Our house is badly insulated. Single hollow block construction. Needs new windows and we want to do EWI as well. The cost to do both now is very high. If we do the windows first and have them pushed out to be flush with the outside of the wall can it be left like this for say 1 year before we do the EWI or does it have to be done together. I’m hoping if the windows are installed correctly and sealed that this won’t be a problem.

monseiur

As you are replacing windows chances are that the sills/cills may have to be replaced with metal or PVC to suit - best wait another year and do the lot together.

MicktheMan

OP, it is always best to wait until you have the resources to do both in one job.

But if this isn't a runner for some reason then the new windows installed normally now can always be moved out flush when the ewi is being done in the future

This obviously adds some extra cost but may be a solution

Gusser09

Do the windows now and the WWI installers will be able to do the insulation in the future. Do not do EWI first though as windows are impossible to fit after without damaging the EWI.

hesker

Are you sure your house is hollow block.

If so you should get advice before proceeding with EWI. For one you might have a difficult time with air tightness. Secondly the EWI requires mechanical fixings that need to be solidly embedded to a certain depth. Installers should be doing pull out tests before proceeding but I’d expect most don’t bother.

To answer your original question you can fit thermal supports on your walls and fit your windows on these. They reduce thermal bridging and can be done before EWI. Can be a bit of work especially if you have a particular bumpy render. They seal best against flat block work.

Calahonda52

https://www.boards.ie/discussion/comment/123259230#Comment_123259230

Can u post a link to these thermal supports , interesting idea

rodderss

Can i ask how much the ewi will cost, i need to do something soon aswell .

hesker

https://www.boards.ie/discussion/comment/123259848#Comment_123259848

Way more than it should. Your best bet is to decide if you are going for SEAI grant or not then contact installers

hesker

https://www.boards.ie/discussion/comment/123259807#Comment_123259807

Triotherm is one make with a supplier in south west. Good guy to deal with.

There is at least one other make but I can’t recall the name. They’ve both been discussed on here before. Edit: the other one I’m thinking of is Compacfoam

The fitting is fairly straightforward but you may have to knock off render in order to get a flat surface or maybe apply a smooth render first. It’s either that or you end up applying a lot more sealant than in the instructions.

Plus you will need to cut off your concrete ledges.

Afterwards I sealed further with Pro Clima extoseal encors butyl tape to ensure it was water tight. I found other types of tape just didn’t do the job right. EWI installers will say the EWI fitting will achieve water tightness but I didn’t want the risk.

manape

good to know. Yes I’m sure it’s hollow block. Looks like it should not be a problem getting EWI on hollow block from what I read. A few houses near me with similar construction have had it done.

manape

yes we’re getting insane quotes now. Gone with both seai registered and not. Getting quotes for ~20k for a semi D not that large from both.

Calahonda52

https://www.boards.ie/discussion/comment/123259990#Comment_123259990

Thank you for this

For the benefit of others I have added a few links: the download is very informative

https://www.prodomo.ie/thermal-brackets/triotherm-for-windows-in-insulation-level/

Triotherm+ in EWI.pdf

https://www.partel.ie/product/compacfoam/

rodderss

Would pumping the walls be an alternative or not.

Calahonda52

https://www.boards.ie/discussion/comment/123263046#Comment_123263046

No as its hollow block

rodderss

https://www.boards.ie/discussion/comment/123263162#Comment_123263162

I can do it as its a cavity with aero board , is it very effective though.

monseiur

https://www.boards.ie/discussion/comment/123260541#Comment_123260541

Surprised to learn that it's possible to fix ewi to a hollow block wall, assuming ewi is up to 100mm thick. Any idea what type of fixing is used considering that the 'wall' of the hollow block + plaster is almost half the thickness of the ewi.

Lumen

https://www.boards.ie/discussion/comment/123259117#Comment_123259117

What happens when the windows need replacing?

Nigzcurran

Any fitter who's good at their job can get a new window in any opening without destroying the place.

Gusser09

https://www.boards.ie/discussion/comment/123273075#Comment_123273075

Cross the bridge when you come to it. Fitting windows with exisiting EI is a messy job and causes damage.

whizbang

I cannot believe folk still think EWI is usefull on a hollow block construction. Might as well hang it on the garden walls.

Hollow block is almost always uncapped, meaning all heat loss through the inner leaf of the block simply drifts up and out to fresh air. It wont change a thing by keeping the outer leaf nice and warm and dry, the heat still rises up through the cavity.

Even capped walls will still loose most of the heat through the capping, where there's little room to insulate.

Can pumping be done from the top of an uncapped cavity ?

Lumen

https://www.boards.ie/discussion/comment/123286036#Comment_123286036

There are installers using urea foam to fill hollow block walls but I think they're taking the piss.

It's possible that these products do something useful, but because they don't fit easily into the category of insulation because of obvious cold bridging they can't be certified.

ray o

What exactly is hollow block? Cavity blocks?

whizbang

Because often confused with cavity wall construction, this is hollow block = cavity block

micks_address

whos saying external insulation is not effective on hollow block? our estate is hollow block and lots of the houses have been done - i was wondering what happens with existing pvc soffits and external insulation.. is it best put up new before getting the insulation done? ours is done 20 years and wouldnt be amazing..

Calahonda52

https://www.boards.ie/discussion/comment/123356380#Comment_123356380

best prtaice is to bring th ewi up through the soffit to meet the attic insulation