Victorian ‘EnerPHit’ EWI – Was it worth it?

So the retrofit has now had a couple of winters and provisional figures suggest a saving in gas usage for space heating of around £100 a year, but let’s assume typical user might well use double the heat and so perhaps save £200 a year.  The total works cost £26k so the payback is over 100 years (the sort of figure you get for double glazing) but the story is much more complicated.  The rear elevation was failing with damp walls and crumbing windows so something had to be done.  If I had simply re-rendered rather than insulating and replaced the windows with double glazed units then the cost might have been say £16k, suggesting an uplift for the energy improvements of the retrofit of perhaps £10k (still a 50 year payback).  But there’s the less quantifiable benefits, such as comfort and air quality.  Even though the retrofit was only to the rear elevation, the whole house retains its heat longer and is dramatically less draughty.  The bathroom also has a single room heat recovery extractor and is basically a micro near – Passivhaus and the temperature is around 18 degrees when you wake up on winter’s morning.  EWI and fenestration might last say 20 – 25 years, so only half the payback period if based simply on monetary terms.  What about the increase in the value of the property?  Very difficult to assess, but perhaps £10k.  So in all it’s definitely been worth it, but more from a comfort, rather than financial, perspective. There are a lot of poor quality EWI jobs around and the industry desperately needs to address a multitude of issues (a subject for another time), but if installations fail after a few years or even 5 – 10 years then the sums really don’t add up and it can hardly be called ‘sustainable’ or indeed sensible.  It does make a clear case for high quality kit, well designed and installed if we’re even to come close to being able to call such works ‘sustainable’. As an aside, the issues with the EWI mentioned in earlier blogs are still not resolved but I’ll address these another time.