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Six months in and we鈥檙e finding that life in a Passivhaus is suiting us very well. The air quality and temperature is good 鈥� there鈥檚 a pleasant warmth in the air 鈥� it鈥檚 not hot, it鈥檚 just comfortable. There鈥檚 also a serenity about a Passivhaus, thanks to all the insulation and triple glazing. We鈥檙e actually finding that we are oversleeping some mornings because of the absence of outside noise.

As for the MVHR system 鈥� myths about which abound 鈥� you would actually have to make a supreme effort to hear it at all. We鈥檙e also enjoying the solar space and the feeling of having the outside inside. In different lights and on different days, you see it differently 鈥� we like effect of the light playing across the room. We鈥檙e growing a passion flower up the inside of it which is flourishing, although we found that growing tomatoes and cucumbers inside it didn鈥檛 work for some reason.

Summer

We had a lovely first summer in the house. We had been slightly worried about how it would go as the solar space (our idea) has larger amount of glazing than in a typical Passivhaus. It had all been modelled in PHPP of course (and a certain factor of overheating allowed for) but we were still a bit anxious as to how it would perform in reality.

Fortunately the external blinds and large roof overhang really helped keep the internal temperature cool and we don鈥檛 think we鈥檒l need to bother building an extra pergola/ vine outside for more shading.

During the summer, the MVHR also has a 鈥渟ummer bypass鈥� button which can be used and means that the heat in the outgoing air is not passed through the heat exchanger so that incoming air is a bit cooler. We only did have overheating on a couple of really hot days in the summer. However, we have learnt a really effective way of dealing with it called 鈥淢editerranean purging鈥� (recommended by Passivhaus expert Mark Sidall at one of the Green 好色先生TV Store training days).

Apparently in Germany 鈥淢editerranean purging鈥� is often used to prevent Passivhaus鈥� overheating on really hot days. This means that during the day you close windows, close blinds etc (but keep  MVHR on)  but from dusk onwards you open the windows so that the cooler night air comes in and cools the thermal mass through the night. So you bring the thermal mass temperature down at night and then you keep it down by not letting the warmer air in during the day (apart from what the MVHR brings in).

Once we鈥檇 started to do that we didn鈥檛 have any problems. The MVHR was still bringing in the hot outside air but because it takes a long time for the thermal mass to change it wasn鈥檛 until late afternoon that it was beginning to have an influence. So we鈥檙e learning how to fine tune the house.

To further help keep the house cool in the summer we could have had the air supply pipe leading into the MVHR unit underground which actually lowers the temperature 鈥� but that would have been another 拢10,000 on top of the price of the house. So for the hottest 3-4 days of the year, you can compromise and use the purging technique to stabilise the temperature. That鈥檚 what the Mediterranean do 鈥� they have shutters.

Temperature variation and thermal mass

We鈥檙e also finding that temperature is not completely constant throughout the house and that there can be variations between rooms. This is often to do with the heat gains from the sun. The other day was a lovely morning and we left the shutters open to let the heat in. If you sat directly where the sun was radiating the temperature was around 26 degrees 鈥� and it felt warm as if you were sunbathing almost. But if you moved somewhere else, away from the windows the temperature was between 22 and 20. It will be interesting to see what happens over the winter with this as the sun is beginning to lose some of its strength now.

The other interesting thing that we鈥檙e noticing is to do with thermal mass of the building. You鈥檇 think that when you opened the window the house temperature would go down rapidly 鈥� it does while the window is open obviously but as soon as you close the window the heat鈥檚 back up again 鈥� thanks to the thermal mass inside the house retaining the heat. We鈥檙e interested in how our house 鈥� built using cavity wall construction 鈥� would compare with a timber framed one in terms of temperature changes. We鈥檝e heard that timber frame Passivhaus buildings can have much steeper changes of temperature. If you open the doors here in winter for 20 minutes, it wouldn鈥檛 make a difference. Whereas if you did that in a timber frame Passivhaus you could lose the temperature very quickly. This could be a case for heavyweight construction like cavity wall as a way of offering thermal mass as a buffer against rapid temperature changes.

Where鈥檚 the manual?

We鈥檝e had to give the MVHR control panel some minor tweaks now that the autumn is here. In the early morning the downstairs was cooler than the upstairs (around 18 degrees celcius). This was something to do with the 鈥渘ight lowering鈥� setting on the MVHR 鈥� designed to help ambient temperature go down to 2 degrees to 18 degrees at night 鈥� which we鈥檝e now adjusted for the autumn.

Although a Passivhaus is simple to live in in many ways, it would be really good if a Passivhaus came with a manual, as things do change subtly with the seasons. It would also be really valuable to have a forum for people who live in Passivhauses to share ideas and experiences 鈥� there are still so few of us in the UK that this would be a valuable resource.

Monitoring and bills

LeedsMet University have put various temperature and CO2 sensors around the house. They are also taking measurements of the outside temperature -鈥� because you need to relate what鈥檚 happening inside to what鈥檚 happening outside. They came and took readings a couple of weeks back and they could tell from the readings when we鈥檇 been away for a few days. Because we weren鈥檛 living in it the temperature slowly decayed because we weren鈥檛 putting any of our own body heat into it. Fascinating stuff.

Our first quarter bill for gas has been 拢31 (46 units of gas), some of which was for the standing charge not gas. We also keep a note of the meter readings per month. Our other utility bills have also been very low 鈥� due to installation of low water WCs and taps, and showers and use of LED lights. The solar thermal and solar PVs on the roof are also contributing to this. We haven鈥檛 needed to use the boiler from April to September as we got all our hot water from solar thermal panels 鈥� the boiler has just sat there wondering whether it鈥檚 been connected. The only gas we used was for cooking. The gas for August that we used was 59p. We really got riotous in September 鈥� it went up to 拢1.32.

Further thoughts

We are really pleased that Chris Huhne and Jonathon Porritt have recently given their support to the Passivhaus approach which will help raise awareness and put Passivhaus onto the political agenda.

Since the recent launch of Green 好色先生TV Store鈥檚 technical film on the Denby Dale Passivhaus and 鈥淔uture Passiv鈥� documentary we鈥檝e also found that we鈥檝e become minor celebrities (accent on the minor) in the Dale. It is good that the information is getting out there. We hope that we can help dispel some of the myths about Passivhaus. We wanted a comfortable home and that is what we鈥檝e got 鈥� it鈥檚 a smashing home.

As part of a Passivhaus Trust organised event, the Denby Dale Passivhaus will be open to visitors (by pre-arranged appointment) from Friday 12 to Sunday 14^th November between 11-5pm. To arrange a visit please email chayley@greenbuildingstore.co.uk or ring Chayley on 01484 461705.

For a lively and up-to-date discussion about the practicalities of Passivhaus go to the