Air Source Heat Pump in Stone House

[Bemak]

54 minutes ago, AliG said:

The ventilation heat loss looks wrong, it should probably be around 1/3 of the fabric heat loss. Even a very airtight house with MVHR would struggle to get to the figure you have.

 

didn't touch the figure (as I didn't understand what way it should go!) 

 

53 minutes ago, AliG said:

I meant to ask this. Rather than the spreadsheet, the actual energy consumption in past winters would give you a good idea of how much you are going to need.

 

ya it's a pity there's nothing there to go on. 

 

I was speaking to a few manufacturers yesterday about what remedial works I can do to the external walls to improve performance. I appreciate its a minefield out there and there are a lot of ways to skin this cat, each with their own critics and supports etc but it sounds ok to me. So it was suggested that I rerender the house externally with a silicone render to help seal up any imperfections in the wall where water might be entering. The silicone render will let moisture evaporate while preventing further water ingress. Sounds good in theory.

 

Internally then they were proposing an aerogel backed stud which would be fixed directly to the existing sand and cement render on the internal walls - and would then be infilled with 40mm fibre wood boards. then you apply a vapour control membrane (reverse diffusion) and complete with normal plasterboard. In theory that wall buildup will also allow moisture to escape the wall but not be drawn back in. 

 

The manufacturer stated that this would improve the u-value of the wall to around 0.5 - which they said is probably as high as you should go for a stone wall as anything beyond that would be super-insulating the wall (their words not mine) which they said would reduce the walls ability to dry out through the new lining etc. 

 

Interesting approach, and one I need to look into more but the application is a lot more straightforward than the full blown approach of removing the existing render etc. 

Edited August 16, 2022 by Bemak

[SteamyTea]

6 minutes ago, Bemak said:

Internally then they were proposing an aerogel backed stud which would be fixed directly to the existing sand and cement render on the internal walls

Where they now.

Two things about aerogel.

It is a dessicant

It is espensive

 

Our @DamonHD fitted it to his timber frame place a fair few years back.  He may well know more about it then most.

[Bemak]

7 minutes ago, SteamyTea said:

Where they now.

Two things about aerogel.

It is a dessicant

It is espensive

 

Our @DamonHD fitted it to his timber frame place a fair few years back.  He may well know more about it then most.

 

They're based in NI. They were saying the cost per sqm including the wood fibre infill worked out at about £25, which I don't think is too bad considering. 

 

Considering the walls are surprising dry, I could just use treated timber battens, maybe with a dpc backing and retain the rest of the spec. If moisture is allowed to escape the build-up, the battens themselves should be low risk?

Edited August 16, 2022 by Bemak

[Bemak]

I need to trawl through more of these threads because I'm sure a lot of what I'm asking has been well discussed

[Roger440]

6 hours ago, Bemak said:

I need to trawl through more of these threads because I'm sure a lot of what I'm asking has been well discussed

 

With regard insulating solid walls, yes, several recent threads.

 

Tread carefullly. Your proposed option further up isnt what i would do.

 

There comes a point where you accept some losses through the walls, concentrate elsewhere, especially air tightness, which will be bad, and see how you can cover those energy losses at the lowest cost.

 

It is, as you say, a minefield. The biggest issue with the various options, is, it will be a long time before you know there is a problem.

 

Ive just stripped and replastered mine with a lime hemp base layer first. (and probably about to do it all again in another house) Partly because its a little flood prone, but also because i know it will be OK. Sure, its a thermal disaster, but its 2 walls (to outside), insulated below and above. Though, now the walls are dry, it feels so much "nicer" than before the work.

Edited August 16, 2022 by Roger440

[Bemak]

1 hour ago, Roger440 said:

Your proposed option further up isnt what i would do.

 

It's not my first choice but I have to work with a budget and be realistic as to what I can do. 

Edited August 16, 2022 by Bemak