External wall insulation to side and rear only?

Thanks @shweeney. So hard to know what to do. We'll be changing the windows as part of refurb. So new windows, coupled with extension being well insulated and on the gable end, we're likely to experience noticeable overall improvements in overall comfort/temp.
If we do EWI we'd probably fill the cavity.
If we fill the cavity we'd probably do UFH.
Effective UFH would put a premium on really good airtight/insulation detail.
If we do UFH then might be tempted to do some sort of mechanical ventilation.
Kind of tempted not to be swayed by the availability of grants, and to save money. Then again, this is the one & only chance at this, so an extra 20k (or whatever it might be for EWI etc) might be worth spending.
 
Cousin in England had a house with suspended wood floor, there was a 3' gap underneath. They slung an 'underfloor' a foot or so under the floorboads, of netting, and filled it with what looked like attic insulation. Says it's made a huge difference. First time I'd heard of it, not sure if it's done here.
 
I have 1-2 foot raised floors. There is a void under the floor. Big step from front to back of the house.
We put ceiling wire in grids and installed rigid kingspan sheets on top of the wire. Installed two layers marine ply, thin layer of ply and then timber flooring in one area and tiled flooring in the remainder. Massive difference with the reduction in heat loss. The air bricks are still there to allow for air flow but the floor is warmer. Better than messy rolled out insulation.
 
Interesting, thanks for the input @Gordanus and @Sconeandjam

Am surprised neither used airtight membrane on the warm side when doing what sound like good jobs. Some good info here: https://great-home.co.uk/floor-insulation/

In our 2 rooms with suspended floors and serious drafts I did a hack-job myself with 6mm ply laid on top of the existing floorboards before we put down deep underlay and carpet. Crude but has worked really well.
 
Did you do it yourself or did you get a company to do it? I'm wondering what a quote for it would be, do you know any companies who'd do it?
 
This was completed about 10 years ago and airtight membrane was not really the thing. If we were doing it now than we would include in the refurb but only in the walls. House was in bits when we bought it so stripped back to bare brick and went from there.
 
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Gordanus said:
Did you do it yourself or did you get a company to do it? I'm wondering what a quote for it would be, do you know any companies who'd do it?
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My husband is a Dryling Contractor and does this work for a living. On our next house he would do part air tightness but not the full airtightness as I like the gas heating and cooker. Prices for fitting depend on the part of the country and the insulation prices are going up shortly so do not leave it too late.

Dont forget if you install the full air tightness membrane around the whole house you cannot have a gas cooker or gas heating. So full electric!
 
You have to work with what you have at the time.
 
Sconeandjam said:
Dont forget if you install the full air tightness membrane around the whole house you cannot have a gas cooker or gas heating. So full electric!
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That's the first I've heard of this. Would you mind elaborating on this or perhaps sharing a relevant link?
 
Sconeandjam said:
Dont forget if you install the full air tightness membrane around the whole house you cannot have a gas cooker or gas heating. So full electric!
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I'd have concerns about anyone working in this area who is not aware that all modern gas boilers are room-sealed.
 
Leo said:
I'd have concerns about anyone working in this area who is not aware that all modern gas boilers are room-sealed.
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Working in a housing estate and they are not allowed to install gas appliances in the property. I think the houses have heat recovery system.
 
Sconeandjam said:
Working in a housing estate and they are not allowed to install gas appliances in the property. I think the houses have heat recovery system.
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Not allowed to and it's not possible are two very different things. It is absolutely possible to have a room sealed gas boiler in a highly air-tight house.
 
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