Insulating old house

[ladwey]

Hi -- I'm renovating an old property. It's a former agricultural building, about a hundred years old, and the walls are two skins of brick (well, brick and mixed rubble and other junk) faced with flint in lime mortar. It needs proper insulation, but I'm conscious that there can be moisture issues where an old house needs to 'breathe'. Is the right thing to do to mount something like this (https://www.ecomerchant.co.uk/steic...EMAIL_ID]&mc_cid=461db9764b&mc_eid=4b36733a66) on the walls, since it allows moisture to dissipate? I'd been assuming that I'd have to use insulation board battened out from the existing walls, and to install vents behind them to allow air to circulate. If this saves me all that work -- and adds less to the thickness of the walls -- then I'd prefer to use it. Also, if I'm way off-base, I'd be grateful for any advice. As ever thanks in advance.

 

[George_engineer]

I used wood fibre internal wall insulation and have been very happy with it, performing better than anticipated, probably due to having a slow decrement delay (colloquially understood as 'thermal mass') compared to PIR type insulation.

You can get modern insulations to work with older buildings but there is a slightly higher risk associated with that approach. Other interventions like heat recovery ventilation (or just ventilation) and changing heat emitters to be low flow temperature can also boost efficiency and comfort.

 

[ladwey]

Really glad to hear you've had a good experience. The plan is to have an air source heat pump, so those areas where I can make a lot of changes (the downstairs floors, the walls of the new extension, etc) are very well insulated; there will be underfloor heating throughout the downstairs, and either larger, heavier radiators or low flow ones where possible in the upstairs. I'm trying to work out the best approaches to those areas where I can't be as invasive with the changes I make.

The Ecotherm guy I spoke to on the phone recommended removing the old plaster inside (which I'm doing anyway, since it's in a terrible state), levelling the internal masonry with a breathable lime plaster, fixing the boards, then applying 'Breathaplasta' in 2x 4mm layers, the first with a glass fibre reinforcing mesh embedded in it. Is that roughly the process you ended up carrying out?

 

[George_engineer]

I kept much of the original lime plaster because it was sound enough.

2x4mm layers might be a bit think because the wood fibre boards can have steps between them. We used Limegreen solo as that was the system then, but same with fiberglass mesh. We also used mechanical fixings instead of the adhesive, although again the original lime plaster was mainly very flat so didn't seem to make much difference.

We have a air to water ASHP which runs underfloor heating and large (although not excessively) radiators, upstairs and downstairs.

If I were doing it again, I'd put in a much smaller air to water ASHP to run the ufh and hot water tank and then put a multi-split air to air heat pump for the upstairs bedrooms. This would allow for heating and cooling in summer.

I didn't think of it at the time. ALthough I believe it wouldn't have been allowed under the RHI grant system so it might not be allowed under the current grant. But really it makes a lot of sense, especially if you have solar panels.

When my RHI expires I will definitely look at retrofitting air to air heat pumps for the bedrooms and may even disconnect the wet heating upstairs.