‘EnerPHit’ costings

3 March, 2018 | EnerPHit, Passivhaus, Victorian 'EnerPHit'

So in the end we renovated the entire house from top to bottom, added a loft with en-suite, moved the bathroom and opened up the lower ground floor.  This added a bedroom (now 4), an en-suite and a second reception room which has transformed the house.  Internal floor area has only increased by the loft area from around 90m2 to a still modest 110m2.  Photos will be available once the decorating is completed later in the year and I’ll be blogging on lots of issues as I find time.

Remedial works, i.e. replumbing, rewiring, replastering, redecorating and strengthening etc i.e. effectively making good a building which had been badly built in ~ 1895 and unloved for many decades, cost around £90k.  The loft (including replacing the entire first floor ceiling and chopping the chimney stack in half) and opening up the lower ground floor cost around £65k.  Sustainable measures, i.e. beyond traditional building techniques to Building Regulations standards such as additional insulation, excellent airtightness, cold bridging reduction and the MVHR ventilation system cost perhaps £30k.  The nice to haves, i.e. good quality fittings another £30k, so the total works cost £210k.  As I do this for my day job, I provided the complete architectural services and this would have cost around £40k, and needs to be included, so the real cost is £250k.  (From my experience professional fees for deep retrofit can be as high as 20% if you really want to get the design and build right).  This is a staggering sum of money and raises lots of questions.  I will address the issue of added value once the house is fully decorated and we have estate agent valuations but it is clear that we cannot hope to recoup anywhere near this amount by the increase in the value of the property.  There are some follow-on savings such as (hopefully) negligible maintenance costs for decades to come which offset this amount to some extent.

Is it morally reasonable to spend such a huge sum?  Arguably, someone had to renovate the house at some point and the loft and internal re-configuration have made the house much more useable and the build costs are determined by the UK construction industry.  I find it difficult to justify spending £30k on nice to have’s but quality is a pleasure to use and the bits that wear and brake will be more robust and durable so last longer which is one of the main ways to be sustainable.

We spent £26k a few years back renovating the rear and we still need another £30k to renovate the front (internally insulate and add secondary glazing) so the final bill will be around £300k!  This will mean an average renovation cost of ~ £2,700 per m2 which is the same as high end new build!

What does it say about deep retrofit?  The deep retrofit element (i.e. works beyond simply meeting building regulations and the implicit poor construction performance) might end up being perhaps £60k depending on where you draw the line.  From a purely energy point of view, the deep retrofit might result in energy savings between £500 – £1,000 annually.  Some of fundamental interventions may last the lifetime of the building i.e. 60 – 100 years, others such as the plant and fenestration between 10 – 30 years so the lifetime energy savings could range from perhaps £500 for 30 years to £1000 for 60 years i.e. anywhere between £15k and £60k (but this needs a much deeper analysis to be anything more than a rough indication)

However, the house has been transformed by the deep retrofit element which has delivered comfort – which has improved beyond all recognition, especially the loft which is effectively Passivhaus performance (which I’ll address another time).  The simple energy cost saving calculation misses these more subtle benefits.  What’s the value of improved air quality, better acoustics both externally and within the house, better and longer sleep, less family arguments, improved health!?!  Subjects for future blogs.