UK energy performance incentives WON’T work!
It cost me £1800 to properly insulate a 4m * 2.3m old solid wall
Materials:
Battens, dpc tape, 40mm cellotex, vcl, wood wool board, RK70 lime plaster.
Steps:
1. Remove any existing gypsum plaster on cold brick (£200)
- Test wall for asbsestos and send of kit
- Remove existing plaster to make space for insulation. (Hire extractor fan, don’t be in the house for a week from dust, cleanup, vaccum)
- bag up and dispose of a local recycle yard
2. Insulate and plaster (£1600)
- £500 materials
- £780 labourer 3-4 days
- £320 plasterer 2 days
(No need to paint because RK70 looks great and will kill any damp)
Total £1800 for a 4m wall.
Disclaimer: You may save £400 on a cost effective labourer, or save £1000 if do most of the labour yourself, although thats your time not working and it takes double with less experience in measuring and working with building tools. Also consider the electric connections, water pipes, radiator, window configuration. Note: I got my plasterer at value because he wasn’t a traditional lime plasterer and just had some practice with hydraulic lime with 2 coats. Generally £1800 is good ball park including all labour and materials.
My solution was to mitigate damp, allow air flow, maximise with modern insulation (i.e. PIR board) and benefit from breathability with a mixed combination.
Gotchas:
1. Don’t use breathable insulation where you don’t need it because it cost twice as much and takes double the space. Just ensure you have enough airflow between the wet brick and the insulation. Modern houses have this.
2. Don’t just use plasterboard and normal plaster because, despite the airflow above this old house will have higher humidity and its still predisposed to mould. Sure the PIR can grow mould too, but sandwiched between an airgap on ones side and lime on the other, the moisture will suck instead onto the lime plaster or the brick lime mortar.
3. Use a hydraulic lime, and don’t pay for a traditional lime plasterer. They don’t need to come back 3 times. Using something like breathaplaster or RK70 is sufficient in 2 coats with a mesh. Why use lime? It kills mould.
4. You can actually use lime plaster on modern plasterboards, just use a primer like baumit DG27. The only benefit here is you might save 3mm thickness and risk mould growing under it should moisture accumulate.
Conclusion
I have optimised my insulation cost as much as possible and have since done 2 more walls which is the semi detached part of my house. So I’ve spent roughly £6000.
My EPC rating has gone up from 61 points to 67 points. Still a D, but a little cosier.
If I were to get a heat pump installed, solar panels etc I’d be looking at another £10,000. (which includes the government grants)
So for the average old house you are looking at £6 — 8,000 just to to be insulated to a decent level to get an efficient heat pump solution.
If you buy an old house and renovate it before moving in, you might save yourself a £1 — £2000 on removing the old render, letting the dust settle, and then doing all the insulation in one go, but its not practical while you are living there to do the whole house. Also, its an extra cost to keep the mortgage or rent on it while not living there doing renovations.
Given the new technology, lack of installers, knowledgebase, future problems, I’d guess I wouldn’t see a financial return on the bills in my lifetime. I commend anyone who does it but for the average person who owns an old house — they don’t have the money.
