A refused planning application isn’t usually an outcome people are pleased about, but for Paul and Belinda Wilson the news triggered a chain of events that led them to building their ideal Passivhaus home.
“One of the guidelines in the council’s feedback was to design something special, and they agreed an energy-efficient house might be looked on favourably,” Paul says.
“We didn’t know anything about Passivhaus until we started researching ideas in 2014. Then we heard eco architect Alan Budden speak on an online podcast and the concept really resonated with us.”
The Wilsons’ self-build story began nine years before this, however. They bought a detached 1940s house with nearly an acre of garden. The grounds were some 30m wide with a gated side entrance, sloping down away from the back of the house.
The property was familiar to them, too – once owned by friends. “We always thought it would be a great place to live because of the beautiful views across the countryside,” says Paul. “In the back of my mind I thought there could be an opportunity to build in the garden one day, but we had no firm plans.”
Time passed and Paul decided to take early retirement in 2012, prompting the couple to really think about how much time they spent looking after their large garden. “The idea to build was a slow burn,” says Paul. “I began to play around with various concepts and in early 2014 we moved onto a house design with the architect who had previously created our extension.”
With little guidance from planning at this stage, the garden was roughly divided into two – with the new house designated to the side of the plot so the original dwelling could maintain its views.
The Wilsons followed the local vernacular of country farmhouse-style properties built with timber cladding and brickwork.
“In hindsight the design became bigger and bulkier than we wanted so we understood why the planners didn’t like it,” says Paul. “After the refusal they gave us a much clearer steer, which was basically a design subservient to the original house. It looked different and had something special about it.”
The couple began to investigate green builds and, in mutual agreement, parted ways with their first architect in search of a sustainable design specialist. By chance, Belinda came across Alan Budden, from Eco Design Consultants, who was full of ideas.
“Alan is a certified European Passivhaus designer and spoke enthusiastically about this type of build,” says Paul. “We realised this was exactly what we wanted to do. When we met up we got on well. Alan produced a drawing with all the Passivhaus principles but he was also great at understanding how we wanted to use the house.”
Another factor before starting construction was preserving the views of the original house. Since the plot slopes across as well as down, this meant sinking the new home two metres down in one corner and building one half as a single storey.
“This design is much better proportioned and Alan kept us focused, so we have the rooms we need with no wasted space,” adds Paul. “The loft above the garage has been really useful for providing extra storage.”
In August 2015, the Wilsons submitted their second planning application – this was free of charge, as the council waived the fee on reapplications within a year of refusal. This time there were no question marks and in October they had approval for their new home.
By now, the couple had begun researching how to construct their Passivhaus on a budget of £530,000. They’d spoken to a few German kit house companies and even had the chance to see their facilities while visiting their daughter, who had moved there a few years back.
The couple were impressed with the swift build method and the competitive prices on offer. At the time the exchange rate was still favourable, too. However, there were aspects of the service that didn’t appeal.
“In a Passivhaus, the target for the number of kilowatts to heat one square metre of useable floor area per year is 15kWh/(m2a) or below,” Paul explains. “Some of the kit house firms we spoke to said they could achieve 18-20kWh/(m²a) but we aimed for lower.”
Other issues were cost uncertainty, lack of flexibility and the interpretation of Alan’s design based around modular components. “In an early drawing, we felt one company had compromised our design too much and they wanted £5,000 to finalise it before they’d commit to a total price,” Paul explains.
“They also said building to Passivhaus standards would add 15-20% to the cost, but we needed to work to a fixed price. In my view, this route would only be cost effective if you used a kit company’s in-house design services and were prepared to accept their standard details.”
Paul continued looking for a solution, but felt frustrated that he couldn’t find a company who would stand by a lump sum price and take responsibility for building to Passivhaus standards. With more than 35 years of construction experience behind him, he realised he’d have to put together a package of contractors himself.
After more research, Paul began talking to MBC Timber Frame. “What’s key is that MBC builds the insulated foundations and the Passivhaus-standard timber frame, including taking responsibility for the airtightness of their finished shell,” he says. “Other companies don’t offer this and will only work off prepared foundations, so the onus would have been on me to get this right.”
Nick Hull Builders – experienced in Passivhaus projects – provided the site management and general trades, while Paul procured the timber frame, windows, roof and mechanical ventilation and heat recovery system (MVHR).
The groundworks started in May 2016, and turned out more expensive than expected, but they managed to save in the finishes and overhead costs to make up the shortfall.
In June, MBC erected the timber frame in a remarkable four days and spent another week making the shell waterproof and airtight. When they fell a little bit behind, the team worked over a weekend to finish in time for the Monday delivery slot for the windows.
“The pressure was on me to make sure Internorm delivered the windows on time as MBC needed to come back and do their air pressure test,” says Paul. “The assessment gave a rating of 0.21 air changes per hour (the building regs have a backstop equivalent to 10) and then we had to ensure the membrane didn’t get punctured while we carried on.”
Paul managed the trades, with strict deadlines to keep control of the costs. “If you keep the project on schedule then you don’t have to worry too much about overspending because the biggest variables are time related,” he explains.
Paul sourced a solar photovoltaic (PV) roof system stretching to 91 individual units – but installation didn’t go to plan. “We thought it made sense to have a roof made of the solar panels rather than employ a roofer and then a PV installer,” he says.
“Our product is great but there was no engineering detail for the integration around the edges and eaves. We were let down and I had to spend more on the flashings and trims.”
The Wilsons discovered some unexpected benefits of following Passivhaus principles, such as the high quality materials needed.
For example, Paul describes Internorm’s triple-glazed windows and sliding doors as superb. “The glass in the door weighs nearly a quarter of a tonne but it glides open with one finger,” he says. “The handles are so well made there’s a joy in opening a window. Friends come to the front door and can’t believe how substantial it is.”
The couple’s project ran exactly to Paul’s budget and timeline – with the exception of a drawn-out delay from BT. Ironically, this had been the first order they placed, back in April before work began.
Overall, the pair found the experience extremely rewarding and are pleased their home won in the sustainability category at the Bedfordshire Design and Craftsmanship Awards in 2017.
“Living here is an entirely different experience from any other house we’ve lived in,” says Paul. “It sounds peculiar but thanks to the planners, we’ve ended up with a much nicer and far more comfortable home than we ever thought we wanted.”