Yes, it's one of the top recommendations (internal wall insulation) on my EPC and have had a survey. 60mm PIR boards would be used. Turns out I wouldn't have to sacrifice much space but would have to pay a bit extra replacing the cornices.
There are some regional grants in the UK that can cover a large portion of the amount. For me, it is £7.5K, with the quote I received at £9K. This would not have covered the kitchen or bathroom.
Going by EPC recommendations and numbers alone, I can reduce my energy requirement by about 40%.
Be super careful internally insulating an old house. This can cause _a lot_ of humidity problems if not done _exactly_ right. Very often, there is no way to do it exactly right!
I would recommend you to consider breathable internal insulation materials, combined with breathable finish layers of course! Some hints.
Roof (or attic floor) insulation is the most important. I imagine those have been done properly already.
Walls. There's industrial products for walls, like Xella Multipor. You may also want to have a look at eco products, especially if working on the place yourself. Hempcrete is a fairly forgiving material that works rather well for this purpose. Rather expensive to have it installed, but easy to do yourself.
Ground floors. Have a look at foam glass [0] insulation. It both stabilises and insulates, is moisture and fire proof, not horribly expensive and saves you from having to put in a layer of concrete. Not super well known yet, but growing in popularity. A wonderful material and super easy and forgiving to work with. A no-brainer really in many cases...
The one key rule that you should always follow is to have your water-impermeable layer on the warm side of the insulation.
So, I'd recommend against breathable internal insulation, because that will make your solid wall (water-impermeable layer) colder, but still exposed to the humid inside air, and this could cause condensation on that cold wall. As an example of this, I have rubbish double glazing, and when the temperature drops outside, if I have just the curtains drawn (which don't really provide any insulation) then I'm fine, but if I lower the thermal blackout blinds, then I get loads of condensation on the inside of the windows, which I remove with a window vac in the morning.
Breathable external insulation is less of a problem, because it warms up the wall, while exposing it to the comparatively dry air from outside, so you shouldn't get any condensation.
> The one key rule that you should always follow is to have your water-impermeable layer on the warm side of the insulation.
This very much holds true in 99% of modern homes.. except if you build your entire wall breathable. That is how we did our walls. From inside to out:
- breathable paint. Lots of conventional options available. We made a really nice casein paint with low fat cottage cheese and lime paint as the main ingredients :-)
Agreed, houses with insulation have a vapour barrier behind the plasterboard for this reason: counterintuitively, the warm internal air carries a lot more moisture than the cold air outside. The partial pressure of water vapour is higher inside the house than outside, so the dew point of the internal air is higher than the outside temperature (dew point depends on water content).
If there's a way for that moisture to diffuse through the wall from inside, through the insulation, to the cold structure (which would be colder than before due to the internal insulation), the conditions are right for condensation to form. Those conditions are: surface temperature ≤ dew point.
Condensation can be prevented by a combination of:
1. Reduce the rate of moisture diffusion from the interior (seal the rooms and use a vapour barrier)
2. Lower the dew point of the air in the "cold" structural areas by ventilating the cold space to outside, so the moisture can exit (this is why houses have air bricks, vents in the roof, etc.)
3. Prevent the building structure from being colder than the internal dew point (i.e. use external insulation)
Had to sign up for this. Take extra care to use appropriate materials for a house this age or you'll create more problems than you solve. Solid stone walls need to breathe!
Make sure you've spoken with a surveyor specialising in heritage property too.
I intend to use rockwool for the floor and roof crawl space.
Luckily I have a relative in the field who can share advice. I am conscientious of the condensation issue. There's a company local to me who use hemp boards which are porous. What you say is definitely something to consider given the extent of work involved, and to possibly undo.
There are some regional grants in the UK that can cover a large portion of the amount. For me, it is £7.5K, with the quote I received at £9K. This would not have covered the kitchen or bathroom.
Going by EPC recommendations and numbers alone, I can reduce my energy requirement by about 40%.