‘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.

FREE surplus building materials

FREE surplus building materials

Coming to the end of the works and there’s a few leftover specialist building materials.  Free (or a bottle of something perhaps) to anyone collecting soon.  There’s woodfibre boards, TR27 PIR insulation, Solitex, Intello, bitumen flat roofing membrane and even some Spacetherm.   Also Foamglas and a single room heat recovery extractor from Environvent

dav

dav

Loft + case study – eaves airtightness

Loft + case study – eaves airtightness

Retrofitting airtightness to eaves is always a tricky detail.  The joists were boxed under and around with OSB / ply which was sealed first with Orcon F and then taped with Tecson Vana.  Solido SL was used to continue the airtightness to the wall as the fleece backing and can be plastered.  The black above the joists is 6mm acoustic strip.

Loft + case study – insulation to walls

Loft + case study – insulation to walls

A continuous 40mm semi rigid woodfibre batt thermally isolates the timber studwork from the (external) masonry party wall to the west with further woodfibre batts between and being water vapour open (and with the lime parge) should be a long term robust solution.  The east party wall is more complicated due to the elevated risk of damp due to the neighbour’s chimney stack and the MVHR ducts so vermiculite was poured all the way down the chimney flues and continued up to insulate the wall in the loft.  vermiculite doesn’t have quite as good thermal performance but it’s ability to flow into every area was critical and should stop flanking noise travelling up the chimney flues and negating efforts made with the floors!

BSBM / July

Great turnout for last nights tour which was very well received.  Next meeting is Tuesday 11th July from 7pm at the Battle of Trafalgar, 34 Guildford Road, BN1 3LW.  Please do bring your ideas, drawings and projects along for an informal discussion!  Everyone very welcome.  Details

BSBMeetup / June – sustainable retrofit tour

Final reminder of tomorrow (Tuesday) nights tour at 92 Livingstone Road, Hove, BN3 3WL at 7pm sharp and then off to the Station pub around 8ish (although there is a table booked from 7pm).  No need to bring any safety clothing but there will be a ladder.  Both the site and pub are within 5 minutes of Hove station.  I will not be contactable tomorrow until the evening so please contact Tim Small on 07970 057 284 if urgent.

Loft + case study – ventilation ducting

Loft + case study – ventilation ducting

The ducting for the ventilation system went in today, 75mm diameter semi rigid plastic piping running down the chimney flues extracting from the kitchen and bathrooms and supplying fresh air elsewhere.  21st century meets 19th century.  Hopefully the whole system will be in for the tour on Tuesday

BSBMeetup / June – sustainable retrofit tour

Just to reconfirm this coming Tuesday 13th June’s BSBM will be ‘ON TOUR’ at 92 Livingstone Road, Hove, BN3 3WL at 7pm for a tour of phase 2 of the sustainable renovation to my own house and then we can head to the Station pub around 8ish (although there is a table booked from 7pm).  No need to bring any safety clothing but there will be ladder(s)!  Note we can also take a look at phase 1 of the works completed in 2014.  Both the site and pub are within 5 minutes of Hove station.  Book is not essential but would be appreciated.  THERE WILL NOT BE ANYONE AT THE USUAL VENUE, THE BATTLE OF TRAFALGAR PUB IN BRIGHTON.

Loft + case study – Triple glazed sash

Loft + case study – Triple glazed sash

Today we installed the new bathroom window, and true to the retrofit mantra of doing it once and doing it right, the window is made from Accoya timber so is dimensionally stable and will last perhaps 60 years plus, the glazing is triple with krypton gas to reduce sash thickness, high performance airtight seals all round, concealed balances within the sashes (which are not visible at all) and reduce air leakage and cold bridging.  This is a window developed over 2 years for another project and should be rolled out to the retrofit market!  Manufacured by Westgate Joinery.  Period detailing to match existing windows and you really can’t tell it’s super high performance.  Beautiful installation of expanding foam airtightness to the frame.

dav

Loft + case study – Internorm window

Loft + case study – Internorm window

The frame to the dormer is now up and the Internorm window and doors went in today.  More on the doors later, but  the window is triple glazed with a venetian blind mounted externally and a further fourth pane of glass to enclose the blind and keep it isolated from the weather.  In the winter the blind can be stowed away to maximise solar gain but in the summer when overheating is the issue the blind can be lowered and because it’s on the outside of the triple glazing it will be highly effective (unlike an internal blind).  The blind can also provide privacy and the fourth pane can be opened to allow for cleaning and easy replacement of the blind should it be required.  It’s a very neat and tidy solution to an awkward problem and does away with complicated and expensive external shading solutions.  Detailed with Intello for airtightness and Purenit to sills for cold bridging.

Loft + case study – party walls

Loft + case study – party walls

The party wall where the chimney has been removed was in a terrible state (as expected!) with holes visible into the neighbour’s chimney flues so a brick skin (shown partially complete) has been added to strengthen the structure and give a basic level of airtightness.  Additionally both party walls are being plastered in lime which will allow any existing and future moisture from the brickwork to migrate into the void between the new stud wall and escape through the roof (details to follow) and to further improve airtightness.  There is also a strip of Perinsul blocks (black on the photo) above the steel to reduce cold bridging and the second photo shows how this integrates with a Purenit sleeve to form a continuous thermal envelope around the steels (in grey) in this tricky configuration.  Note there is also a Spacetherm blanket around the back of the steel which can be seen in an earlier blog.  These hi-tech materials are rarely used in traditional buildings but are tools of the trade for high performance buildings and while they are expensive both in material and labor costs there is a significant reduction in heat loss, improved thermal comfort and additional safeguarding of the building fabric, and I would expect a payback over the lifetime of the building.

BSBM – TOUR sustainable renovation

I’m planning a tour of the latest stage in the renovation to my house, most notably a loft conversion which is in full swing and should be at an interesting stage for the BSBM meeting in JUNE on the 13th.  So instead of meeting at the Trafalgar I’m suggesting meeting on site (92 Livingstone Road, Hove, BN3 3WL) at 7pm and then we can head to a local pub around 8ish.   I’ll reconfirm nearer the time, but please let me know if you’re interested.  Phase 1 of the renovation was completed in 2014 and included external wall insulation and triple glazing.

Loft + case study – wall plate

Loft + case study – wall plate

An Intello membrane has been wrapped around the sole plate (support for the new dormer facade) which will be taped to the plaster below and to the wall / fenestration above which makes this awkward detail airtight for minimal effort and cost.  Keen eyes might notice that the floor joists are not treated to avoid unnecessary chemicals.  The tin roof is proving be be a great investment, allowing protected & dry working conditions and saving £££s every day by reducing temporary works.

Loft + case study – steels

Loft + case study – steels

The steels supporting the new loft floor bear into the party walls and until the neighbours undertake loft conversions this will be a significant heat loss.  The beam ends have been encased in Purneit (a structural insulation left over from another job) with 10mm of Spacetherm blanket behind.  Without going to the expense of 3D thermal bridge calculations it’s impossible to determine the improvement but simple U value calculations suggest both the Spacetherm and Purenit reduce the heat loss by a factor of 3.  The black paint is Blowerproof which provides the airtightness which is especially critical here as the brickwork is thin and weak.  The second image shows where the Purenit has been routered  to seat the steel bearing plate with the Spacetherm behind

dav

dav

dav

Loft  + case study – chimney

Loft + case study – chimney

The chimney is being removed down to the loft floor to gain space, simplify moisture / thermal / airtightness detailing and critically to provide access to the 6 chimney flues to run ventilation ducting throughout the building for the MVHR.  With the tin roof there’s no need to weather proof over the weekend!

dav

Loft + case study

Loft + case study

So phase II of my house renovation starts shortly, mainly a loft conversion but also moving the bathroom and installing MVHR with the aim to further improve the comfort and energy consumption of the house.  Phase III (if it ever happens) will be secondary glazing and internal wall insulation (IWI) to the front.  The plan includes rebuilding the pitched roof, loft floor and part of the chimney so I’ve opted for a ‘tin roof’ which should recover the additional cost of around £2k by allowing work in all weather conditions (so maintaining the programme), working dry at all times thereby improving build quality and removing the need for temporary weather proofing.  Here’s the scaffolding prior to the sheeting being applied.

dav

dav