External Insulation effectiveness?

Branch

Hi,

I am thinking about getting external insulation on my house. I know its effective and its the best insulation you can get when you don't have a cavity wall like I do.

My house is built in 2001 with 9" cavity blocks and fibreglass backed plaster boards attached onto studs (perhaps 2-3 inches thick. If I get external insulation will I notice a marked improvement on the insulation in my house? Will it like 10% better or closer to the advertised 40-50%? I just wondering what peoples experience is just I don't want to fork out money that could take 15-20 years to break even when at that stage there could be something better.

Thanks in advance.

YoungAndBroke

If your house is built with 9" inch cavity blocks, I don't believe external insulation would be a option for your house. We are using for our new build (still in progress so can't give you any feedback) but we are using 9" solid blocks on the flat. In our house the internal heat will be retained by the solid blocks. If you have cavity blocks, the heat will just flow up between the holes in the blocks. Plus with the insulation already on the inside only complicates things even further

If I understand your build correctly, I don't think anyone reputable should be trying to sell you external insulation. It just won't work effectively with cavity blocks

Ush1

YoungAndBroke wrote: »

If your house is built with 9" inch cavity blocks, I don't believe external insulation would be a option for your house. We are using for our new build (still in progress so can't give you any feedback) but we are using 9" solid blocks on the flat. In our house the internal heat will be retained by the solid blocks. If you have cavity blocks, the heat will just flow up between the holes in the blocks. Plus with the insulation already on the inside only complicates things even further

If I understand your build correctly, I don't think anyone reputable should be trying to sell you external insulation. It just won't work effectively with cavity blocks

I haven't heard of this before with cavity blocks. Heat will always travel up, don't see it being an issue as long as the roof has been insulated/air-tightened.

Unless it's a moisture thing?

BryanF

Ush1 wrote: »

I haven't heard of this before with cavity blocks. Heat will always travel up, don't see it being an issue as long as the roof has been insulated/air-tightened.

Unless it's a moisture thing?

It's BS

External is the only way to go

9in cavity blocks dry lined with mineral wool on a '01 house...

The heat rising through the blocks is something addressed by an overlap of wall & roof insulation which is down to the detailing

YoungAndBroke

Sorry lads but what is BS here? Branch is looking for some feedback on whether it will be worth the investment. If you want most of the heat to flow up to that wall/roof junction, then external insulation might work but I don't think this is where the heat needs to be. It's an expensive method and they want to know if it's worth.

In our build, we took over an unfinishing house (it was up to wall plate level) with a standard 100mm cavity. Pumping that wasn't going to get the level of insulation we needed so we look at external insulation. We were consistently told that we would need to pump cavity to contain heat within the inner leaf. Granted, it's slightly different with cavity blocks but you still have air circulating up between the blocks. Insulation/detailing at the wall/roof junction won't force heat down into the ground floor rooms

Branch, I would thread lightly here. Best bet would be to ring one of the main EWI providers directly (Ceresit, Weber, Sto being the main ones). They will give you advice as to whether it is suitable over and above the installers. We have dealt with the main rep for Ceresit in Ireland and he seems like a decent guy and he'll tell it to you straight. I can PM you his details if you wish

Ush1

YoungAndBroke wrote: »

Sorry lads but what is BS here? Branch is looking for some feedback on whether it will be worth the investment. If you want most of the heat to flow up to that wall/roof junction, then external insulation might work but I don't think this is where the heat needs to be. It's an expensive method and they want to know if it's worth.

Heat will always travel upwards regardless. It's just a case of heating the block/cavity also with EWI, which I believe is recommended.

YoungAndBroke wrote: »

In our build, we took over an unfinishing house (it was up to wall plate level) with a standard 100mm cavity. Pumping that wasn't going to get the level of insulation we needed so we look at external insulation. We were consistently told that we would need to pump cavity to contain heat within the inner leaf. Granted, it's slightly different with cavity blocks but you still have air circulating up between the blocks. Insulation/detailing at the wall/roof junction won't force heat down into the ground floor rooms

Unless heat is escaping elsewhere, where do you think it will go?

Calahonda52

OP, this is the detail you need to achieve
From
The first link is for details, second for Irish pricing
https://www.amazon.co.uk/Construction-Technology-Designing-Sustainable-Homes/dp/0717148343/ref=sr_1_fkmr1_1?ie=UTF8&qid=1463079029&sr=8-1-fkmr1&keywords=construction+technology-+trevor+hockey

https://schoolbooks365.ie/index.php?_route_=construction_technology_hickey

Copyright acknowledged.
The issue is that the insulation on the wall must meet with the insulation in the roof, woolly hat like, so check to see if the price includes that, most quotes are just up to the soffit board which is crap

Re the EWI, yes it will improve the heat retention and also the airtightness but what will happen at the window reveals: I suspect it will be very thin

BryanF

YoungAndBroke wrote: »

Sorry lads but what is BS here? Branch is looking for some feedback on whether it will be worth the investment. If you want most of the heat to flow up to that wall/roof junction, then external insulation might work but I don't think this is where the heat needs to be. It's an expensive method and they want to know if it's worth.

In our build, we took over an unfinishing house (it was up to wall plate level) with a standard 100mm cavity. Pumping that wasn't going to get the level of insulation we needed so we look at external insulation. We were consistently told that we would need to pump cavity to contain heat within the inner leaf. Granted, it's slightly different with cavity blocks but you still have air circulating up between the blocks. Insulation/detailing at the wall/roof junction won't force heat down into the ground floor rooms

Branch, I would thread lightly here. Best bet would be to ring one of the main EWI providers directly (Ceresit, Weber, Sto being the main ones). They will give you advice as to whether it is suitable over and above the installers. We have dealt with the main rep for Ceresit in Ireland and he seems like a decent guy and he'll tell it to you straight. I can PM you his details if you wish

So to be clear, you took over a derelict tiger house and drylined it and didn't pump the cavity?

MicktheMan

Branch wrote: »

Hi,

I am thinking about getting external insulation on my house. I know its effective and its the best insulation you can get when you don't have a cavity wall like I do.

My house is built in 2001 with 9" cavity blocks and fibreglass backed plaster boards attached onto studs (perhaps 2-3 inches thick. If I get external insulation will I notice a marked improvement on the insulation in my house? Will it like 10% better or closer to the advertised 40-50%? I just wondering what peoples experience is just I don't want to fork out money that could take 15-20 years to break even when at that stage there could be something better.

Thanks in advance.

EWI is the best type of insulation IF your main heatloss mechanism is conduction through your walls, no question. From what you describe, I doubt heat conduction through your wall is the predominant mechanism. If I were you I would:

Step 1: Have house tested for air tightness.
Step 2: Depending on results of Step 1, address air tightness issues first, then maybe consider EWI (if needed).

Branch

MicktheMan wrote: »

EWI is the best type of insulation IF your main heatloss mechanism is conduction through your walls, no question. From what you describe, I doubt heat conduction through your wall is the predominant mechanism. If I were you I would:

Step 1: Have house tested for air tightness.
Step 2: Depending on results of Step 1, address air tightness issues first, then maybe consider EWI (if needed).

Thanks Mick, good idea. http://b-static.net/vbulletin/images/icons/icon14.png

YoungAndBroke wrote: »

Sorry lads but what is BS here? Branch is looking for some feedback on whether it will be worth the investment. If you want most of the heat to flow up to that wall/roof junction, then external insulation might work but I don't think this is where the heat needs to be. It's an expensive method and they want to know if it's worth.

In our build, we took over an unfinishing house (it was up to wall plate level) with a standard 100mm cavity. Pumping that wasn't going to get the level of insulation we needed so we look at external insulation. We were consistently told that we would need to pump cavity to contain heat within the inner leaf. Granted, it's slightly different with cavity blocks but you still have air circulating up between the blocks. Insulation/detailing at the wall/roof junction won't force heat down into the ground floor rooms

Branch, I would thread lightly here. Best bet would be to ring one of the main EWI providers directly (Ceresit, Weber, Sto being the main ones). They will give you advice as to whether it is suitable over and above the installers. We have dealt with the main rep for Ceresit in Ireland and he seems like a decent guy and he'll tell it to you straight. I can PM you his details if you wish

Hi Young and Broke, yes could you PM please. Thanks.

YoungAndBroke

BryanF wrote: »

So to be clear, you took over a derelict tiger house and drylined it and didn't pump the cavity?

No, despite a few builders telling us to insulate on the internal side of the wall, I never wanted to go that way. To be clear, we took over a derelict house and after much deliberation and back and forth between architect, engineer and builder, we knocked it down to the footings and rebuilt up with 9" solid blocks on the flat. We are all very happy with the decision. When knocking it down, we discovered so much crap in the cavity, bird nesting material and builders lunch wrappings, and radon barrier was installed pretty poorly. It allowed us to put quinnlites in at floor and roof levels to reduce thermal bridging. Blocks are up now, roof is going on, windows are ordered and ewi will be started once they are in. I can post pictures if you need proof

I did a lot of research into EWI before going with it. It makes so much sense for a new build and I could rabbit on about it for several posts but I don't think that will help the original poster in anyway. Branch, I do struggle to see how you would get payback by using it with hollow cavity blocks. I think MicktheMan has the right of it, get some independent advice, go from there.

Branch wrote: »

Hi Young and Broke, yes could you PM please. Thanks.

PM sent, let us know how you get on. I'd be interested to hear what the experts say

mp31

YoungAndBroke wrote: »

No, despite a few builders telling us to insulate on the internal side of the wall, I never wanted to go that way. To be clear, we took over a derelict house and after much deliberation and back and forth between architect, engineer and builder, we knocked it down to the footings and rebuilt up with 9" solid blocks on the flat. We are all very happy with the decision. When knocking it down, we discovered so much crap in the cavity, bird nesting material and builders lunch wrappings, and radon barrier was installed pretty poorly. It allowed us to put quinnlites in at floor and roof levels to reduce thermal bridging. Blocks are up now, roof is going on, windows are ordered and ewi will be started once they are in. I can post pictures if you need proof

I did a lot of research into EWI before going with it. It makes so much sense for a new build and I could rabbit on about it for several posts but I don't think that will help the original poster in anyway. Branch, I do struggle to see how you would get payback by using it with hollow cavity blocks. I think MicktheMan has the right of it, get some independent advice, go from there.


PM sent, let us know how you get on. I'd be interested to hear what the experts say

Sounds very interesting...I don't need proof but the idea is appealing and I'd like to know more so could you PM me pictures please (or post if you prefer)

chillit

hi Youngandbroke

what depth of external insulation are you going for?

do you have any current prices of the supply and installation

YoungAndBroke

Hi chillit, we put it all out to tender with 200mm spec'd. The builder bundled it altogether in one price so I don't know the final price. Not sure if he does either but it's on him to shoulder it now.

I did get a few prices before going to tender, most guys were saying around the €100 per sq foot for the ceresit system. But there were some fairly large disparities in the how different guys totalled up the surface area. And there are other cheaper systems than Ceresit which may or may not be of the same level of quality. I have a mail with a few details (contacts/prices). If you want, I could dig it out and share it with you. They are mainly Dublin or midlands based.

I did find that the depth of insulation doesn't have a major impact on the price, the real cost for EWI is labour and the render. I think there was €10 per m2 in the difference between 150mm and 200m so we felt it was worth it. 200mm EPS gives us a u-value of 0.15 which is passive level.

YoungAndBroke

mp31 wrote: »

Sounds very interesting...I don't need proof but the idea is appealing and I'd like to know more so could you PM me pictures please (or post if you prefer)

I pm'd you a link to a document on the environ.ie site as I can't post them here as I am a new user. I think this might be of more use to you than pictures from my site as it covers all the buildup of different junctions when building with block on the flat and external insulation

Troy2013

YoungAndBroke wrote: »

I pm'd you a link to a document on the environ.ie site as I can't post them here as I am a new user. I think this might be of more use to you than pictures from my site as it covers all the buildup of different junctions when building with block on the flat and external insulation

Could I trouble you to PM the link to me too please?

Thanks in advance!

YoungAndBroke

No problem, sent

Alf Veedersane

FWIW, the following is from S.R. 54:2014 Code of Practice for the energy efficient retrofit of existing dwellings

7.3.2.3.8 External insulation and hollow block walls
The use of EWI on hollow block walls can lead to thermal bypassing in gable walls as these are not capped and extend beyond the insulated ceiling. This will reduce the thermal performance of the wall and lead to a poorer U-value. The thermal bypassing should be prevented by the filling or sealing of the voids. One method is to introduce a suitable sealant (e.g. adhesive bead or spray foam) into each block at roof insulation level on the gable wall or as per product certification so as to prevent the bypassing. Walls at eaves are normally closed by a solid block but should be checked
and sealed where necessary.

That's backed up by the NSAI Agrement certificates for the individual external insulation systems.

Alf Veedersane

Ush1 wrote: »

How can the walls extend beyond the roof?

Gable walls extend beyond insulation at ceiling level.