EWI vs no insulation

mirrormatrix · 11-09-2024 8:39pm #1

Renovating a 1960s house and sticking new windows in. Originally thought to use EWI at the same time and move the windows out a bit, but I'm unsure about it now. House is bare brick bottom half with some sort of render on top half. Bricks appear to be cavity block.

Not planning on getting ewi on side as side passage would be made too narrow (60cm) by added insulation.

Talked to an insulation company and they recommended ewi on top, pump the bricks on the bottom and maybe internal insulation on the side of the house. Apparently a lot of houses in the area have had ewi just on the top half of the house.

Looking at the forum, seems like alot of people saying pumping cavity block is not worthwhile? I've seen some houses in the area with ewi top and bottom with brick slips over it, but that would be in the minority.

I guess ny question really is: if I'm not planning on insulating the side of the house, am I wasting my time looking at ewi at all? No interest in going near seai so fact I won't get a grant isn't an issue either way.

ThAnks

crashpilot · 12-09-2024 9:49am

Aye fairly pointless pumping a cavity block. There will still be cold and possibly damp ingress from outside to internal.

And I don't see the point of half EWI ? It's either all or nothing with that. The point is to seal the envelope of the house.

Maybe in your case get the bare brick rendered, and stick some insulated plasterboard on the internal walls.

Mellor · 12-09-2024 11:26am

https://www.boards.ie/discussion/2058368633/ewi-vs-no-insulation

Is the bottom block work or brick. You describe it as both in that post?

The suggestion from the installer is terrible. There will be cold bridges everywhere. Inulation needs to be as continuous as possible

mirrormatrix · 12-09-2024 7:42pm

https://www.boards.ie/discussion/comment/122608335#Comment_122608335

Sorry if I was unclear. Both the top and bottom are the same as far as I can gather, but the top has some sort of render on it, while the bottom looks like bare brick. I can see from the vents upstairs that it is cavity block, which I guess will have thermal bridging if pumped, everywhere that isn't part of the cavity in the blocks?

mirrormatrix · 12-09-2024 7:44pm

https://www.boards.ie/discussion/comment/122608004#Comment_122608004

Yeah, this might be a better way to go. Losing a bit of internal space, but at least it means that we still have a side passage entrance to the house > 60cm.

mirrormatrix · 12-09-2024 7:52pm

20240825_145943.jpg

This is taken from the vent downwards into the wall space. I'm assuming this has to be cavity block?

monseiur · 12-09-2024 7:55pm

As others have said when it comes to EWI it's all or nothing, there are no half measures. Forget the EWI and go for internal insulation instead and upgrade your attic insulation to at least 300mm - roughly 12 inches in old money. Also install good quality windows and doors preferably triple glazed if the budget allows. Pay particular attention to reveals and avoid cold bridging. Consider a storm porch at front with a patio door or similar.

mirrormatrix · 12-09-2024 8:19pm

https://www.boards.ie/discussion/comment/122609997#Comment_122609997

Planning on upgrading the windows alright. Biggest other concern with iWI is mould, which I heard canbe a problem with cavity block?

Curious about your thoughts on the storm porch. Have one at the moment but the wife wants it gone as she considers it dead space. Would today's composite doors not provide a good enough seal as to be pretty air tight?

12-09-2024 8:25pm

If you going insulated plasterboard use airtightness tape on the joins and install active ventilation or you are really asking for trouble down the line. To many horror stories of black mould behind the drying if you allow moisture to build up in the house and then allow it to migrate through the plasterboard. Use double foil layer urethane backed plasterboard and glue it to the walls with foam.

mirrormatrix · 12-09-2024 8:45pm

Jesus I'm starting to wonder if there's any point insulating the walls at all with all these horror stories about. Might just do the windows and attic and forget about touching the walls.

It's not like it's cheap, and you can always pay your way out of bad insulation with more heating.

12-09-2024 9:07pm

https://www.boards.ie/discussion/comment/122610202#Comment_122610202

Do it right and it's highly effective. We have fairly stable warm temperatures all year round. Clean dry air and haven't had the heating on since April.

Mellor · 13-09-2024 12:10pm

https://www.boards.ie/discussion/comment/122609956#Comment_122609956

I got what you were saying, that's the confusing part. If the bottom is brick, then it's not a cavity block.
Which is prehaps why the install was suggesting different treatments - but I'd probably start looking for another installer, as the suggestion shows a lack of understanding - using two systems like that means a huge cold bridge. And also, if the top is a cavity block, its not wide enough for the bottom to have a cavity

monseiur · 13-09-2024 6:10pm

https://www.boards.ie/discussion/comment/122610095#Comment_122610095

In relation to the storm porch - if you are in an exposed area and the front door is being used a lot during the day a considerable amount of heat is lost. The idea with the porch is that when, say, you're leaving the house you close the front door before opening the porch door (and the reverse when entering) - hence keeping the heat in.

monseiur · 13-09-2024 6:18pm

There seems to be a lot of confusion in relation to the correct terminology when it comes to cavity wall, blocks etc. In my neck of the woods what others call 'cavity block' we call hollow block and cavity wall means a double row of blocks (normally 4 inches) with a gap between with both walls connected/tied together by wall ties

mirrormatrix · 13-09-2024 6:34pm

Thanks for all the input - i'm learning a lot. I think I need to get a couple of other installers out. I only contacted this one as he has done 5 or 6 houses in the area the same way (gave addresses).

To summarise what I have learnt so far (i.e. my options)

EWI is fine if I cover the whole house and reduce the size of the side passage. Cavity blocks should be pumped. Ideally insulation should be taken up behind soffits to attic insulation.

IWI needs a vapour barrier to prevent mould, which I guess will mean I can't hang anything on any external walls without breaking the seal? Also, I should pump the walls if internally insulating?

Cheers

14-09-2024 8:06am

https://www.boards.ie/discussion/comment/122613227#Comment_122613227

If you use insulated plasterboard with foil behind the plasterboard and also on the back of he insulation you are going to be fairy sorted for moisture migration - but what you didn't take on board is that you need to include active ventilation.

However let me say that you should include active ventilation even if using EWI as internal humidity is going to be considerably higher and it will find somewhere to condense out onto if you don't control it. We had to put a kitchen humidstat driven fan into my son's kitchen and his house is EWI. Such fans are a heat leak so a sticking plaster to solve a bigger issue, better a whole house solution.

Never ever consider serious insulation upgrades without factoring in the cost and disruption of active ventilation

standardg60 · 14-09-2024 12:25pm

https://www.boards.ie/discussion/comment/122611920#Comment_122611920

I imagine the OP has this type of construction. The bottom half is a cavity wall and the top half cavity block. Rightly or wrongly the bottom gets pumped and the top gets EWI, seen lots done like this, so the installer is following standard practice.

Mellor · 14-09-2024 1:04pm

https://www.boards.ie/discussion/comment/122615025#Comment_122615025

I'm familiar with the finish he's referring to. I was referring the different widths of the wall types. A cavity wall is ~300mm. A cavity block wall it's 215mm. More common for cavity wall up top to match the width. But it could be cavity block and lined internally. Or you could have a face brink lower - on which case you can't pump.

Many installer may be pumping the lower and EWI on the top. But they have no clue what they are doing if they are.

mirrormatrix · 14-09-2024 1:20pm

https://www.boards.ie/discussion/comment/122614267#Comment_122614267

When you talk about 'active ventilation' are you talking about positive pressure systems? Have been told that these don't operate very efficiently in old builds and you are better off going with e.g. trickle vents on aluclad windows for ventilation. In the past, my approach has been to stick a dehumidifier on in the house constantly and block up the vents.

Guy we got a quote from was recommending a hole in the wall with a hit/miss vent, which I felt was really pointless, as it would negate the benefits the insulation would bring.

mirrormatrix · 14-09-2024 1:20pm

Yes, this is basically what i'm dealing with in terms of the look

14-09-2024 1:22pm

https://www.boards.ie/discussion/comment/122615255#Comment_122615255

I am talking about some form of Mechanical Heat Recovery Ventilation. These are best as whole house systems but there are more localized versions.

I wouldn't touch positive pressure ventilation with a barge pole.

standardg60 · 14-09-2024 1:29pm

https://www.boards.ie/discussion/comment/122615182#Comment_122615182

Yep I get what you're saying, the 'cavity' in these walls is probably just the gap left to bring the lower wall out to match the cavity block width, so maybe an inch at most, but pumped they are.

cobham · 14-09-2024 1:33pm

I saw mention on this thread of triple glazing. My understanding is that it is recommended for noise issues and the difference with heat loss is negligable or is it related to cost of same v. heat retention? Also I believe triple glazing lessens daylight strength through the panes.

mirrormatrix · 14-09-2024 1:33pm

https://www.boards.ie/discussion/comment/122615182#Comment_122615182

Appreciate the feedback. Measuring 30cm on bottom half of house. Top half has a variance - 25cm at rear and 21.5cm on front. Can't make head nor tail out of that as there's no insulation on it.

14-09-2024 1:37pm

https://www.boards.ie/discussion/comment/122615317#Comment_122615317

It maybe possible to get double glazing which matches triple but it's unlikely to be much cheaper as it will need to have special coatings and argon filled gap to match the insulating value.

We went for triple and it gets condensation on the outside on cold nights - never happened with our previous double glazing.

standardg60 · 14-09-2024 1:39pm

https://www.boards.ie/discussion/comment/122615318#Comment_122615318

Ah that makes more sense, even though I grew up in one I never realized the bottom wall was thicker than the top, so the top block must be only across half the internal leaf.

mirrormatrix · 14-09-2024 1:57pm

https://www.boards.ie/discussion/comment/122615338#Comment_122615338

Yeah I think you're right. Finally, this is all starting to make some sort of sense

14-09-2024 2:03pm

https://www.boards.ie/discussion/comment/122615255#Comment_122615255

From what your installer is saying to you in general it sounds as though he has little understanding of any of the issues regarding insulation - I would seek other opinions.

You want someone who understands the energy flow and moisture dynamics enough to understand what aspects of the install are critical to success and yours sounds as though he hasn't a clue.

The ramp up in demand for upgrades coupled with a lack of expertise means there's a lot of cowboys out there.

Mellor · 14-09-2024 2:28pm

https://www.boards.ie/discussion/comment/122615318#Comment_122615318

300mm is a cavity
215mm is cavity block (as you seen in the vent)
250mm could be masonry with a 50mm cavity.

There's a ot going on there. Best solution would be full wrap external insulaton imo.

mirrormatrix · 03-12-2024 10:25pm

OK coming back to this thread now as I've had a chance to have more of a think. External insulation is out downstairs as I have a narrow side passage that I'm not willing to lose. Internal can be done downstairs but upstairs is not possible as I have (rather foolishly) put some new fitted wardrobes in that only have about 30mm from edge of door to the external walls.

Any issue do you think if I just internally insulate the downstairs of the house and just leave the upstairs uninsulated? Am I opening myself up to the threat of mold?

As an alternative, I guess I could externally insulate the front and back of the house and just leave the side passage uninsulated?

DrPsychia · 13-12-2024 11:53am

https://www.boards.ie/discussion/comment/122919187#Comment_122919187

Yes you are opening yourself up to problems, you will have more concentrated thermal bridging.

How wide is the side passage? instead of 100mm EPS, you could install 50 or 75mm on the passage side which is better than nothing.

mirrormatrix · 13-12-2024 4:58pm

Side passage is 800mm, so pretty much no space for insulation unfortunately. The bins are practically scraping the walls on the way up and down it as is.

I'd prefer internal throughout to be honest but I screwed myself with the wardrobe thing.

EWI vs no insulation

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