Last Friday and Saturday we opened up the house for International PassivHaus open days. (Seems funny writing that - who woulda thought that’s something we would be end up being involved in.) Anyway, we are proud members of the passivhaus community so it was a pleasure to share the love.

I would write all about our wonderful tours, but luckily one of our visitors has kindly saved me the trouble -

http://londonecohouse.com/blog/uks-passivhaus-retrofit/

Couldn’t have put it better myself!

Chris Huhne pops in!

The Minister for Energy and Climate Change - Chris Huhne - visited the house this morning. With the Green Deal launching next year, the tour was part of the Minister’s ongoing fact-finding into low energy housing.

He seemed to be impressed by the technical work we have done, as well as the finished product. However, quite understandably, his main concern was in respect of the scalability of a project of this complexity.

The UK needs to significantly reduce the energy consumption of its existing stock if we are to meet our carbon targets and reduce dependence on imported heating fuel. In our view, “deep retrofit” of much of the housing stock - like what we have done here - must happen in order to meet these objectives. Anything less will mean either missing our targets and/or just re-visiting the same properties in the future, which is expensive and doubly-disruptive.

Even after this morning’s visit, we are still worried about the degree of standardisation proposed in the Green Deal and are still trying to work out how it will deliver the level of investment required to make these deep retrofits happen.

Photo, left to right: Edward Borgstein, Akta Raja, Chris Huhne, Tom Pakenham

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.

1. Gas consumption - 5.8 HCF, or 180 kWh (@31 kWh per HCF) - note, this is just for cooking
2. Electricity consumption - 1,837 kWh or 14.35 kWh per day (over 128 days)
3. Solar PV output - 330kWh (since 9th January 2011)
4. 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.

Pressure testing

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:

1. the temperature of the fluid coming into the tank is 50 degrees celsius
2. The temperature of the water at the bottom of the tank has already been heated up to 24 degrees celsius
3. 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.