Hollow block external insulation general questions

micks_address

Hi folks,

We have a semi detached house, built late 70s, hollow block construction. Boards have been applied with 'dot and dab' method. When we moved in 22 years ago the walls were all that embossed wallpaper which was impossible to take off so my dad put fresh plasterboard directly over and we put coving in the rooms (upstairs) to get a smooth surface. We just recently replaced the windows and doors with triple glazing and im wondering about external insulation at some point. We had the attic insulated in 2017 so thats ok. I suppose what I'm trying to weigh up is if external insulation will make a dramatic difference to the house? We have gas central heating and at some point in the next ten years will inevitably end up with a heat pump. To keep the running costs of that down I'd like to have the heat loss as low as possible. Last heat loss calc from BER (a2) when we had solar installed was 2.1. Ber assessor said new windows and doors will definitely reduce that. Upstairs we have relatively new rads in all the rooms and removed all the micro bore pipework last year. Downstairs we have a couple of large rads to replace and then potentially go the heat pump road if and when appropriate.

We have relatively large windows in the font of the house, patio door in the living room and mostly glass in the kitchen, door, three side by side windows.. Whats the general drop in heat loss with external insulation? Would the extra boards over the dot and dabbed boards have added any insulation? They weren't foil or foam backed.

The other question I have is around cost. I'm thinking its ballpark 20k for external insulation for a semi d with the grant knocking 6k off it?

Cheers,

Mick

10-10-20

Just for clarity - do you have cavity blocks and then dot & dab plasterboard mounted directly to this and covered in wood-chip, and then dot & dab over this again to mask out the wood-chip wall-paper? That's how I read it.

Have other neighbours with similar builds gone the external insulation route at all?

micks_address

https://www.boards.ie/discussion/comment/122088579#Comment_122088579

house is hollow block - dot and dab over that covered in wood chip, then plasterboard over that (only upstairs). Downstairs is dot and dab with smooth plasterboards. It didnt have the woodchip. Yes a few folks in the estate have gone the external insulation route.

Tow

With hollow block they are supposed to insulate up over the walls and into the attic, meeting the attic insulation. This creates a fully insulated box, with no issues from heat travelling through the hollow blocks and out the top of the wall into the attic/soffit/eves.

You may find it is difficult to get a company to do this. They will just go to the next potential customer where they slap on insulation up to the soffit.

MicktheMan

OP beware, your best bet is to have your house properly tested for heat loss first. Then you'll know what and where to spend.

Too many people going the deep retrofit route first only to find afterwards that their house is still hard and expensive to heat and they're €60, €70 or €80k poorer.

ixoy

I believe HLI tests are mandatory, no? We certainly had to do one to ensure it a threshold for a heat pump that wouldn't cause insane prices.

micks_address

Yeah I'm not doing anything else for now. Given the amount of glass we have and now that it's triple glazed im wondering about the potential gain from external insulation. Obviously it would be better. I'm thinking we might be able to get away with something like at 5.5kw heat pump.. I like the idea of a constant home temp as opposed to the blast of heat with the gas etc cycle

Busman Paddy Lasty

If you are in no rush you could set your boiler temp to 40 degrees and see how you get on through a full winter. Is your house A2 already? Must have decent insulation in place?

We have similar type house with EWI done but kept gas boiler. Our seemingly good HLI of 1.6 ish was somewhat undermined by having 4" holes drilled in the walls. I'd be cautious enough re air tightness before going heat pump.

MicktheMan

https://www.boards.ie/discussion/comment/122091566#Comment_122091566

HLI is not a test but is rather the result of a calculation based on many assumptions and therefore, imo, should not be relied upon for deciding to spend 10s of 1000s on upgrades.

micks_address

https://www.boards.ie/discussion/comment/122091854#Comment_122091854

Yeah it's a2, a lot of that is down to the solar, few year ago we were d3 and got a new condenser boiler, heat controls, that brought it up, we then had the attic done which brought it to b3 and the solar brought it to a2.

Busman Paddy Lasty

Quirk of the BER system is solar alright. In 2022 my house would have been an A but under most recent DEAP it's a B1. Probably not a bad thing as people associate BER with warmth.

Your place seems very well sorted. Good luck in the long run whatever you end up doing, and post about it :)

For us, rads at 50 degrees is what we'll try this winter. And get a visual heat loss survey if house isn't warm enough.