Please can someone check my plan is sensible re hardwalling the house and sealing it with drywall adhesive?

[PotatoSoup]

Hiya, thank you so much for reading this.

I'm trying to get our house a little warmer.

First question is do you know if Hardwall is airtight, please? Wondering about doing an 11mm thick coat all around the house up into the loft. Bit pointless though if it's not airtight?

If it is airtight, I'm then thinking I'd then use drywall adhesive as a polyfiller type substance to seal in any cracks in the hardwall and to seal between the wooden rafters of the loft and the walls and between the first floor joists and the walls. I've seen on this site that people recommend drywall adhesive as a filler.

I'm then going to plasterboard (screw in) and skim all the ceilings with a normal 3mm of multifinish over the top?

I'm then planning on building service walls (25mm battons with plasterboard screwed on) on all the exterior walls so the hardwall coat remains intact and I don't have to do chases in the future for cables etc - I've got a young family and technology is always changing so I'm envisioning lots of changes happening over the course of the next 18 years!!

I'd really appreciate any help or guidance. Thank you!!

 

[cdbe]

Your plan is not sensible. If you think your house is drafty then identify the areas in question and seal any gaps. Unless you're a plasterer then replastering your house will cost you thousands and save you nothing - the heat is largely lost through conduction. Your service walls seem a bit pointless as you will have to bash holes in it to add any new wires (and more and more tech is now wireless). The only thing worth sticking on internal walls is celotex, assuming you have solid walls or cavity walls that can't be filled, and even then it's probably not worth paying to have this done professionally but plenty on here have successfully DIYed it.

 

[PotatoSoup]

We have cavity walls. I don't know if they've been filled or not - I need to find a specialist company to investigate that. The house isn't particularly drafty but we've got the ceilings down anyway so I decided to sort out the airtightness while it's easy to do. I'm good at plastering. Good point re the wireless technology, thank you - I'll give that some thought. It's not a big job to put a new plug socket in, patch repair plasterboard and skim the wall but chasing out is bloody awful. But as you say - I may never need to put another socket in as technology proves I thought most heat was lost through air tightness (lack of...)?

 

[PotatoSoup]

Improves*

 

[flameport]

I decided to sort out the airtightness while it's easy to do.

If you make your house airtight (or near enough), you will also need to install a MVHR system.

If not, you can expect massive problems with condensation, mould and rot.

 

[Mike13]

I saw an article on measuring a "breathing wall", it had a negative U value for the walls, but it required MVHR to make it work.

 

[PotatoSoup]

Thank you, I'm currently in the process of researching MVHR fans

Yeah - I've got everything crossed that the walls are able to release back any moisture using the building materials above. I'll do either CWI or EWI, I think, down the line so the walls can carry on hopefully expelling moisture internally with the help of the fans.

That's amazing that someone got negative U values!! As I'm only fixing up a house rather than it being purpose built into the design I don't expect anything amazing but something's hopefully better than nothing.

Re the fans, I'm leaning towards the individual room ones rather than the one that sits in the loft and does the whole house because that way I don't have to deal with ducts - any recommendations for good fans gratefully received!

I think I've found the answer to the hardwall question - apparently "directly applied plaster to block work over 5mm thick is considered airtight". Hooray!

I'm going to follow the advice of the peeps on here that recommend drywall adhesive as a filler.

Thank you for you input, Folks!! You've given me some fab advice and some stuff to be mindful and - so far - no massive red flags, so I'll crack on Cheers!!

 

[Mike13]

How do room ones do any heat recovery?

 

[PotatoSoup]

No idea!! I shall Google...

 

[PotatoSoup]

"Air is passed over a heat exchange cell which recovers and retains the heat that would otherwise be lost from the extracted air." Do you think it's gimmicky nonsense? I'd just assumed they were a legitimate MVHR system because I'd not come across anyone saying to avoid them ...

 

[PotatoSoup]

• "Whole house MVHR (or MEV) is necessary for very air tight buildings, but can be used for the lesser air tight ones as well.
• Decentral continuous Mechanical Extract Ventilation (dMEV) is recommended for the mid to not so air tight dwellings."

 

[PotatoSoup]

I've just looked at several fans described as "Single Room MVHR Units" and they all use a "heat exchange cell".

 

[Mike13]

You have to then look at the amount of heat they can store, it has to be enough to cover a significant amount of the daily temperature variations, or it will not change the actual bill for heating.

 

[flameport]

You have to then look at the amount of heat they can store,

They don't store any heat.
It's two fans, one extracts warm air and the other one brings in cool air. Heat is transferred between the two so you get fresh air but retain most of the heat.