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

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.

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

manape

Getting it done. Will report back in the winter with benefits, downsides and any other information that might be handy.

Bargain_Hound

Surpirsed to hear how ineffective it appears to be installing EWI on cavity block built houses. In Dublin where I live, most houses were commonly built with brick cavity fronts but cavity block side and rears. I'm seeing a large number of these now getting retro fitted with EWI on sides and back with cavity pump at front - I would love to know the overall effectiveness.

My own house is cavity block and my initial suspicions are priority should be sealing the drafts throughout the block cavity as its uncapped ( as mentioned above ). There are drafts behind all wall and it seems EWI won't solve heat retention issues.

Very poor attention to detail when it came to construction of these mid-2000's build houses.

andy125

I have had ewi and windows push forward on a cavity block house built 1980s, the difference is quite substantial, no mold anywhere in the house anymore, no damp windows, great sound insulation, heating on for 1 hour during winter is enough to keep house warm (2 hours if deep in minus outside) , house never drops below 19c in winter.

I am sure there is heat loss in the cavity at the cappings through convection but its not as extreme as is been made out, air tightness is much more important and ewi does transform the living conditions greatly compared to not having it.

kwat

Sorry to hijack this, but has anyone ever seen external insulation done without external window sills (new windows were installed at the time also)? Was given a choice and builder recommended to go without them for a "cleaner" finish. Wasn't convinced but he said he'd slope the edges to allow water to run off. I'm not convinced this was the right decision - there really isn't much of a slope and water does gather when it rains, although evaporates pretty quickly. I have called the supplier who said they'd come back to install sills if preferred but said as it's a silicone render there shouldn't be any issue.

I'm just not convinced and am worried this will cause a problem over time. Has anyone seen anything similar? I'm yet to spot a sill-less house anywhere and have been looking!

Calahonda52

KWAT, post a picture pls

10-10-20

The render staining after about 3 years will be enough to make you think you're back in 80's Dublin