Tracey and Roman Iwanczuk explain how they managed to build a Passivhaus on a sloping site in an Area of Outstanding Natural Beauty.
Interview with Tracey and Roman Iwanczuk
Having lived in the US for 20 years and at the point where they were preparing to build a house there, Tracey and Roman made the decision to move back to the UK. Being unable to find a house or building plot that ticked all their boxes, they decided to embark on what initially seemed like a fairly improbable chance of getting planning permission to build a property on their six acre field overlooking the Malvern Hills Area of Outstanding Natural Beauty.
It was a leap of faith
Initial meetings with a planning consultant and a local architect offered little in the way of optimism for ever getting planning permission on the site. But they persevered and found another architect who offered a more encouraging 50/50 chance.
Being a greenfield site they used the Paragraph 55 application process for a house of exceptional design and quality that could enhance the area. As Tracey explains, being a greenfield site isn't always the best use of a piece of land, and their steeply sloping site wasn't practical for agricultural use.
“It was a matter of coming up with a way of saying let’s do something that is a benefit for our environment, our area, and maybe even the people who live around here that makes sense.”
The scheme they came up with was to return three acres of the land to natural woodland by creating an orchard of local species trees.
They also put in a flood prevention strategy for the neighbours below, who's properties had experienced flooding from run-off from the field previously.
The house nestles into the hillside
The house was designed to have a minimal visual impact and be future-proof for any long term needs.
The design came about from a series of 15ft² boxes joined together in a single-storey. The principle rooms are south facing and benefit from the floor to ceiling glazing to maximise the beautiful views, with the other rooms being at the rear.
Despite the glazing, the temperature of the house remains relatively even. The rear wall is built into the hillside so has a lot of surface area that is removed from the equation.
Being built into the hillside to a large extent determined what build system they could use. In order to get the required structural strength they used concrete, and felt less guilty with the knowledge that the orchard they were creating would be off-setting the carbon.
A “long, skinny Passivhaus”
Roman describes the shape of the house as providing its own unique challenges, of which air leakage was probably the biggest. The concrete block walls at the rear get no sunlight, whereas the pre-fabricated concrete plank roof gets a lot of light and a lot of heat. So with different thermal expansion rates between the roof and the walls they used a Passivhaus window tape as a barrier for the airflow and to provide enough flexibility to accommodate any thermal expansion.
A ground source heat supply provides hot water
Excavated soil was used to create a level area in front of the house where they could lay pipes for the ground source heat supply. They chose this over an air source system as it is such a peaceful location that they felt it would be less noisy.
About 80% of the supply is used for hot water, with very little actually being needed for heating. Tracey points out that it does use a lot of energy to run a ground source heat pump and they really notice the difference in their electricity bills in the winter when they're running it to heat the hot water.
When it's sunny they don't need to use the ground source heat pump as they export excess solar power to an immersion tank for the hot water supply.
There is a 30 panel solar array
The array gives almost nine kilowatts of generation capability. There are two first generation Tesla Powerwalls which that feeds, that can store around 14 kilowatts. They don't have the means of exporting power from the batteries, but what they can do is “time shift” the excess energy generated during a sunny day for it to be used to run the house at night.
With advancements in technology, the battery system is one thing that Roman is considering changing. When they were installed the only batteries that were readily available were these kind that sit on the DC side of the system. They are almost directly connected to the solar panels, which means that the system is designed to completely switch off the electricity in the event of a power cut. This is because there could be a danger of feeding the power back onto the grid and electrocuting anyone working on it, but it does mean they can't access any of the energy sitting in those batteries during that period.
The more modern Tesla system works on the AC side. If there were to be a power cut it would isolate the house but still allow the batteries to generate AC voltage.
“If there is a power outage, then your house effectively becomes an island of electricity and you can use whatever power is in the batteries.”
To upgrade to this system will mean a bit of disruption in having to change the location for the batteries, but Roman thinks that it will be worth doing. There is also a second hand market for the Tesla batteries so they can be re-used by someone else.
They have high praise for their team
Tracey and Roman consider themselves to have been very lucky in how smoothly the project generally went. The only real issue they had was with the window supply, which has taken around three years to fully resolve, but they do say to the company's credit they have stuck with it to get a resolution.
Tracey praises their architect who had never done a Passivhaus before:
“He was more than happy to park his architect ego, listen to the Passivhaus consultant and do the right thing to achieve a Passivhaus. He was happy to learn all of this stuff and take it on board.”
They selected a contractor who had also worked with the architect before, and this helped with maintaining good working relationships between them all. Tracey also praises their integrity and says they were very respectful in how they communicated with her.
Think about your window to wall seals!
One area that could have challenged the successful outcome of the project, was the seals between the windows and walls. Despite their Passivhaus Consultant, Nick Grant, flagging up how important it was to get right, it had been forgotten about in amongst all the other decisions that had to be made. It wasn't until a week and a half before people were due to do the render that they realised they hadn't thought about the window to wall seals at all. It was pure luck that they were put in touch with someone who had some spare pieces from their own self build that they could use.
“If that had not been done, it would be a nightmare right now. We’d be dealing with silicone, silicone in windows all the time, just doing all of that stuff that would make life miserable. I can’t say enough to anybody who’s looking at doing a self-build; think about that very, very early on because we only fixed it by accident. It was a very, very lucky accident.”
Roman warns that when you have a window company dealing with the windows, and a builder dealing with the building envelope, things like how those windows will join with the building envelope can become overlooked.
A HEPA filter would be a worthwhile investment
The one oversight that Roman feels they made was the issue of airflow in the house. The MVHR draws in outside air but, being in a rural spot, this can include the smell of burning horse manure! The basic filters are there to get rid of particulate matter, but they don't deal with smells. He recommends the inclusion of a HEPA filter, which he doesn't think is something he can now retrofit because of lack of space. He considers the £500-£1,000 for a HEPA filter would be money well spent, even more so in an urban environment with emissions from exhausts.
ASBP Healthy Buildings Conference and Expo 2020
This is taking place in London on 27th February, and will be addressing the subject of healthy buildings in a climate emergency. Check out the website for the full programme and booking tickets online.
Find out more
Visit the website of Warren Benbow Architects
Follow Nick Grant on Twitter
Please connect with me
Like our Facebook page
Follow us on Twitter