‘EnerPHit’ costings

‘EnerPHit’ costings

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.

Hove ‘Passivhaus’ is working

The boiler went off by accident in January (so the building was unheated) but being so well insulated nobody noticed for 3 days!  That’s what you get from a Passivhaus – surely how all new building should function in the 21st century?

Hove ‘Passivhaus’ nearly there

Hove ‘Passivhaus’ nearly there

The internal fit out is nearing completion, moving on to the driveway next month.  The external solar roller blinds still allow a fair amount of visible light through as can be seen in the third image (where the top window is protected but the lower window is not).

























Project 117 Airtightness result 0.35

Fantastic news today, the rebuild of a Victorian cottage in Brighton has achieved an airtightness of 0.35 ACH so way below EnerPhit and acheiveing full Passivhaus performance.  The homeowner has toiled on the project for 5 years and the result of a lot of hard work and dedication has paid off.


Hove ‘Passivhaus’ TOUR

So the ‘Passivhaus’ new build tour at 31 Old Shoreham Road, Hove BN3 6NR is tomorrow evening, Tuesday 20th June at 7pm.  Please arrive on time as I expect we will have to lock the gate when the tour begins.  The site is just off the junction of Shirley Drive and Old Shoreham Road and there is parking nearby but not on site.  Hard hats are mandatory so please bring one if you have one as there are only one or two spares on site.  I imagine the tour will take around an hour and a half and we may retire to a local pub afterwards.  The tour is fully booked.

Hove ‘Passivhaus’ TOUR

There will be a site tour of the ‘Passivhaus’ new build at 31 Old Shoreham Road, Hove BN3 6NR at 7pm on Tuesday 20th June.  The timber frame will be partially complete so it’s an exciting time to see the build.  Hard hats are mandatory so please bring one if you have one as there are only one or two spares on site.  I imagine we will retire to a local pub afterwards.  Please let me know if you plan to attend, even as late as on the day / evening.

Hove ‘Passivhaus’ timber frame

Hove ‘Passivhaus’ timber frame

The timber frame has arrived from Latvia with panels fully assembled including insulation, plasterboard and even conduit ready to receive wiring!  The photos below show just one day on site.  It will be interesting to see how the plastic sheeting handles the British weather.

days work



PassivOFFICE – Slab

PassivOFFICE – Slab

The Isoquick insulated raft is manufactured to the exact size required and clips together in a matter of minutes with an integral upstand eliminating cold bridges at this awkward floor / wall junction.  The DPM is laid into the bowl and the reinforcement can be fitted and the slab simply poured tamping level with the top of the upstand.  This photo shows the Isoquick in pink, the black DPM and  the timber forms a slot in the slab for the sill of the sliding doors to provide a level threshold.


PassivOFFICE case Study

PassivOFFICE case Study

This blog describes the construction of a small garden office for a client in Lewes designed to the Passivhaus standard.  The building is a simple box and the footprint measures only 4m by 3.5m externally.  One wall is formed of lift and slide doors orientated south-east, balancing the southerly solar gains with a pleasant aspect to the garden.  There is a window to the south west to provide summertime secure nigh-time ventilation (in conjunction with the doors being lockable on trickle).  A solar sail erected in the summer will control overheating.  A pair of very quiet Lunos single room heat recovery extractors will provide high indoor air quality and reduce energy consumption.  The floor is a 300mm Isoquick raft with integral upstands / kerb eliminating thermal bridges and providing a bowl into which the reinforced concrete slab is poured and tamped level with the top of the kerb.  The slab will be polished as the final floor finish and provides thermal mass to regulate the internal temperature. Walls are timber I beams with pumped Warmcell clad in 100mm of woodfibre and timber rainscreen.  The roof is PIR with a wild meadow green roof.  Heating will be very minimal and is provided by an electric radiator.   Although the Passivhaus logic has been applied, with U values around 0.10, PHPP modelling suggests a heat demand around 45 KWh/m2/year significantly above the 15 KWh/m2/year limit but the discrepancy is due to the high surface area to floor area inherent for a very small building and the minimal internal heat gains for this office (not having all the associated kit a house might contain).

PassivOFFICE section WEB


Passivhaus airtight letter box?

Has anyone found a through the wall letter box solution which is at least airtight if not also somewhat thermally broken for use in airtight / Passivhaus construction or is the only way to mount the letter box externally?

PassivPOD preview

AECB members met at the offices of Koru Architects in Hove last night for a preview of the PassivPOD designed by Koru Architects and JMD.  PassivPOD is the response to the Sunday Times competition to design a Passivhaus lake side holiday home and shortlisted entries will be officially launched in the Sunday Times this weekend, Sunday 22nd June.  Readers can then vote on line for their preferred scheme and the winning entry will be built.

Certified Passivhaus Tradesmen

The first ‘Certified Passivhaus Tradesmen’ have graduated in Germany this week and the course materials are to be translated into English later this year.  The Passive House Institute is looking for potential course providers.  This is an exciting step in the right direction to narrow the performance gap and produce high quality buildings which are essential to effectively reducing our carbon emissions.

For information on how Jim Miller Design can assist with your Passivhaus project please get in touch.