Give me a drink!
We have just had our driest spring since records began, or something like that, and the living roof is really feeling the pain. Well, to be precise, one half of it (the bit in the shade) looks wonderful - the essence of an English meadow - and the other half looks like it’s been nuked.
Despite having more than 100mm of soil and little water storage “tanks” underneath, there just has not been enough rain and too much direct (evaporative) sunshine on the non-shaded part of the roof. I took the hose up once, but have since decided that was a stupid thing to do and that I just have to let be what will be.
We’ll keep an eye on it and see what happens. It may be that the best thing for a half-sunny/half-shady roof is to plant each area differently. Sedum is much more drought-tolerant, so that may be the answer.
So, we’re starting to get some data from the house. Admittedly, we don’t have the most advanced monitoring systems - i.e. me with a pencil (apart from the MVHR temperature data, which is quite snazzy, of which more to follow in another post) - but think we’re capturing the key data.
The electricity and gas readings are shown from 23 January 2011 - by which time the MVHR, solar thermal and solar pv had all been commissioned properly - up to today’s date. Both of the solar readings are totals generated since date of comissioning.
- Gas consumption - 5.8 HCF, or 180 kWh (@31 kWh per HCF) - note, this is just for cooking
- Electricity consumption - 1,837 kWh or 14.35 kWh per day (over 128 days)
- Solar PV output - 330kWh (since 9th January 2011)
- Solar thermal output - 1,198 kWh (since 16th November 2010) - total hours of operation (i.e. pump running) is 845 hours. Therefore, the 7m2 of solar thermal is putting out an average of 1.41 kW
The electricity consumption looks high, making me wonder about the extent of our parasitic load and actual power consumption of the MVHR. Theoretically, the MVHR should only use a maximum of 140w for its two fans and there will have been some consumption when the heat pump was heating the hot water, but we need to install a reader to confirm this.
It is instructive to look at the net daily electricity consumption (i.e. incorporating input from solar pv) by month, below:
- February - 20.46 kWh
- March - 14.51 kWh
- April - 10.1 kWh
- May - 8.96 kWh
We will put up some key data from the MVHR datalog soon. Most notable trend so far is impressive stability of internal air temperature.
My how you’ve grown!
Barely 1 month old and the roof meadow is already starting to flourish.
Building the living roof
We spent an afternoon last week putting this living roof on top of the back block, second story flat roof. Like typical desk-based workers, we found the whole thing a lot of fun; though lugging almost 2 tonnes of earth up 2 floors without a proper pulley was also a lot of hard work. Most team members are still sporting some physical ailment or other.
Hopefully, come mid-summer, the roof will look like a wildflower meadow. One week on, the grass has already started to thicken and this new little ecosystem is attracting plenty of interest from the local birdlife. We’ll have to import some worms from the garden to keep our blackbirds happy.
The kit was bought from http://www.sedumsupply.co.uk/, who provided excellent service and were generally very helpful.
We did it!!!
The house has been officially certified as a passivhaus, hooray!
It has not been easy, but today we were presented with our passivhaus certification by the Godfather of the movement, Wolfgang Feist.
Now to get on with the important business of delivering low energy building in the UK.
The pressure test was a pretty nerve-wracking moment for us. Because of restrictions in the project plan, we hadn’t been able to test the house with the airtight layer exposed (which is usually advisable because it lets you find leaks and correct them). This meant we had to have complete faith in the airtightness details that the team had been painstakingly installing over the previous months.
Our final result of 0.49 air changes per hour at 50Pa came within the Passivhaus requirements and made it the most airtight retrofit project in the UK for a few brief weeks, until our sister project at Princedale Road came in at 0.33ach.
We used smoke pencils and a thermal imaging camera to search for the few remaining leaks. The only ones we could find were around the sides of the centre-hung Velux windows, which seemed to be leaking a not inconsiderable amount! With hindsight, Fakro would have been better. Thankfully, the self-designed triple glazed sash windows were completely airtight and we found not so much as a whisper around the frames…
Team Profile 3 - Superstar engineer, designer and project manager
This is Ed. Ed is responsible for much of the detailed design and drawings, with which the guys on site put the house together; not forgetting a whole lot of other work, such as installing all of the ductwork and generally holding everything together. On a project like this the devil is in the detail, so it’s just as well Ed was there with his engineering skills to ensure that every airtightness detail, every thermal bridge, every services connection was implemented just right.
As well as the design, Ed spent almost every day on site during the build to keep an eye on the actual installation of his drawings and to troubleshoot the inevitable mistakes and mis-understandings. This hands-on work was a far cry from the dreamy spires of Cambridge - from where Ed graduated with an embarrassingly good engineering degree (he’s surprisingly good company despite this) - but has turned him into that very rare breed, a practical brainbox.
Ed also worked intensively on our sister project - another passivhaus retrofit up the road in Holland Park - where he successfully managed timetable, contractor, public relations duties and client needs. He was able to take learning from our project and apply it to the work going on there, which conveniently for them was always a couple of months behind. How I wish it had been the other way round!
Ed is now busy bringing his newfound skills to bear on multiple retrofit and newbuild passivhaus and low energy projects around the UK.
Solar Thermal in Action
This is a photo of the solar thermal controls, taken at 11.25 today. It shows that:
- the temperature of the fluid coming into the tank is 50 degrees celsius
- The temperature of the water at the bottom of the tank has already been heated up to 24 degrees celsius
- The system is generating 2.86kw of heat
Not bad for a 8 degree day in February! Let’s see how hot it is by the end of the day…
The eagle-eyed amongst you will notice the transparent tube with pink fluid in it. This is the tyfocor fluid that carries the solar heat from the panels to the solar hot water tank.
Proudly presenting “SuperWindow”
There was a lot of pain in this project, none more acute than the saga of the windows. The whole thing was like an episode of Grand Designs - windows promised in June; still not there in August; arrive in September; much harder to install than expected; 2 glazing sets the wrong size; replacements take another 3 months to arrive (through the “coldest period in living memory”) etc. Luckily, there was no Kevin McCloud winding us up throughout.
But all of the above is a distant memory because what the house now has is a complete set of perfectly sealed, beautifully crafted, incredibly energy efficient windows that pass conservation area rules because they look like exemplary sash windows from the outside (see pic).
And to give our builder - Ryder Strategies - credit, these windows were designed and built from scratch, entirely by his team just round the corner in a little railway arch. In order to do this, Philip Proffit (owner of Ryder Strategies) had to:
- design the windows
- refine the design
- build a prototype
- source the most appropriate wood, glazing and opening mechanisms
- order the correct machinery and profiles for the spindle molder
- set up a workshop
- wait for the machines to arrive
- work out how to work them
- train his carpenter (or perhaps it was the other way round)
- make 16 unique windows
- work out how to fix them with all the surrounding insulation and airtightness nightmare
- pray that they weren’t a disaster
The good news is that they are absolutely great, which is a relief because we were taking quite a risk installing them without any certainty or guarantee. Let’s hope that doesn’t come back to haunt us!
Finally, we need to acknowledge the many entities that contributed:
- Pilkington Glass - provided the glazing, complete with their new e-glass
- Axminster Tools - for invaluable assistance with the design
- Roto - provided hinges, locks and latches
- Anthony Clough - created the initial designs
- The Technology Strategy Board - funded much of the design and workshop setup as part of the Retrofit for the Future competition, which our sister passivhaus project up the road was a part of.
Can’t believe it’s been 6 months since our last blog post. Then again, quite a lot happened in that time, not least that our daughter has arrived (most important, of course) and we’ve moved into this amazing house. The former (pics above) happened in September and we became the first family to be living in a passivhaus retrofit in the UK in October.
To be completely accurate, we haven’t had certification yet, but we’re quite confident about that side of things; but touching wood nonetheless. And, more importantly, as far as my wife is concerned, we didn’t have (m)any curtains or pretty pictures until recently, so that hardly constitutes a finished house…
Anyway, to the bit that really matters - the house is brilliant. It’s absolutely everything we had hoped for. It has a perfect, balanced temperature throughout (even during the ridiculous cold snap despite at that point missing two windows), the air is fresh, it is eerily quiet and best of all, it WORKS! Phew!
I’m sure you’re all chomping at the bit to hear about our successful airtightness test, incredible triple-glazed sash windows, fully-functioning cellar heat exchange, sweet little pv system, upcoming living roof installation, gorgeous low energy lighting, fortress-like front door, oooh so many juicy bits…but I’m afraid you’ll have to wait because it’s Saturday night.