PASSIVE HOUSE STANDARD BENEFITS
How would you like to have annual energy bills of less than £300? And a significant discount on your mortgage because your house is so energy efficient? These are some unexpected benefits that our clients, Mr and Mrs Bax, have found from their superb passive house standard family log home.
The couple got in touch with Scandinavian Homes in late 2019 as they’d always liked the idea of building their own family home. Having grown up in a Scandinavian timber house, Mr Bax in particular loved the idea of a home made from timber for his own family. A residential specification log home kit was the ideal solution – something rather more than people often think of as a log cabin.
We know that self build is rarely straightforward, so we thought we’d share their story, including the ups – and downs – they encountered along the way.
Initially, our Kuisma model had really captured their imagination, but they knew that the house they ended up with would have to suit the plot they bought.
The couple had already found a site where they hoped to build, with relatives planning to also build similar homes on the adjacent plots. At first, things seemed to be going well, with positive feedback from the seller. However, after a fraught couple of months, they were unfortunately gazumped on the purchase of the site. So, disappointed but not put off, they went back to square one – and started searching for that ideal plot all over again.
After months of searching and frustration, they finally came across another plot, with an unloved, uncared-for wreck of a timber house on it. It was so run down that even finding the house in the garden was a bit of an adventure!
Planning Permission
We worked with them to help them design the type of house they wanted, which was inspired by the original Kuisma house they had liked, combined with ideas from their scrapbook. That’s the great thing about self build – you can get your very own, completely unique, home, designed to suit your own family’s requirements..
For many self builders, getting planning permission is a fraught process that can take months or even years. Mr and Mrs Bax followed the golden rule of successful planning, and did plenty of preparation before they submitted their application. They also called upon Mr Bax’s brother for advice, as he leads the locally based Kent Planning Consultancy.
The previous owner of the original house gave them a letter saying that they did not object to them replacing it – which was one of the potential hurdles crossed before they even moved in. Their neighbours supported them from the outset, with six letters of support entered in favour of the application, which was also supported by the Parish council. Despite being in a conservation area, the positive decision came through in record time, allowing them to build in a location where the character of the housing was already interestingly varied.
Eco Features
Deciding the best self build route can be quite a challenge in itself – after all, building a house isn’t something most families do in the UK. The couple wanted to be very closely involved in their project, so they decided that a shell build offered the best route for them. Mr Bax in particular wanted to be very hands-on, both in planning the whole project, and in the build itself.
The couple had identified several eco features that they wanted to include in their new passive house standard family log home, but needed to make some decisions around what type of foundations would suit the log system best, and of course heating and ventilation options. They opted for a solar assisted heat pump, solar panels, electric cable underfloor heating, and a mechanical ventilation and heat recovery system, with the option of a battery storage system in the future if needed.
After several discussions with the SHL team, they opted for a highly insulated Atlas raft foundation system from Jackon (now BEWI). They also chose a log burning stove suitable for installation in a highly airtight house.
Mr and Mrs Bax started their design off from a standpoint of wanting to minimise their environmental impact and keep their running costs as low as possible, which led to them deciding to aim for as close to the Passive house standard as possible. The ‘Fabric First’ approach is a fundamental building block in the structural design of energy efficient homes, and a super insulated log system works well here. This balances native thermal mass and low heat transfer, with the external walls made from extra chunky logs and lots of insulation. The design SAP rating came in with an energy efficiency rating of 107 (which is well above an A!).
Living on the Build Site
One of the challenges faced by most self builders, is where do you live while your house is being built? The Bax family decided to build an oak frame garage with storage space above, where they could ‘camp out’ while the house was being rebuilt. Much more sensible than a caravan on site! A lot of the household items had to go into storage, while the project went ahead. There wasn’t room in the garage for the car though.
Next it was demolition time! With any ‘knock down and rebuild’ project, there comes that inevitable moment when the existing house just HAS to go. As fitted with their ethos, they managed to recycle a lot of the materials from the original house.
Once the plot was prepared, the insulated raft system was quick to install. As soon as all the formwork and radon membrane were in place, Mr Bax installed the rebar himself – a time-consuming job, but one that saved labour costs as well. As he said “The most painful part of this build so far was laying, cutting, wire-tying this awful steel. Oh, and we didn’t know there was a wire tie gun that takes a fraction of the time either! Pipes lagged and ready for concrete tomorrow.”
Restricted Space
Once the house kit arrived, an amazing telehandler operator called Josh (who is apparently a jouster in his spare time!) managed to get everything onto site without incident, despite the limited access and a few slightly frustrated motorists who had to wait for the lorry to be moved. When both trailers had finally been unloaded, the congested site meant that some of the logs and other materials ended up piled up on the foundation. This in turn meant that several logs had to be moved more than once. This is definitely something to bear in mind if you have a relatively small plot!
Fortunately, as soon as the main walls started to go up, there was a bit more space to move around the plot. Log walls go up pretty quickly but the logs and beams are definitely heavy. In a less congested site, a small crane would have made things easier. If you have the space this would certainly make building your log home quicker and easier.
Most log homes have ‘cross-jointed’ corners, where the logs intersect. However, the Bax family noted that Scandinavian Homes offered a rather different option – beautiful dovetail corners. They loved the way that these give a much more clean, contemporary look. Once they had treated the timber with Barrettine preservative and Osmo UV-Protection Oil, the logs really glowed.
One aspect of the build which took a bit longer than anticipated was the construction of the roof, and meant that the assembly cost was also over budget. Roofs with dormer windows are quite complex to build, as the rafters need careful cutting on site (and the individual lengths all vary).
The Bax’s custom design has some beautiful windows in the gables.
They aren’t just a pretty picture though – they are triple glazed with low-emissivity glazing, and would meet the energy efficiency requirements for a Passive house. (For the geeks out there, they have a U value of 0.76 W/m2K!). Other features that make this Passive house standard log home ultra energy efficient include a hefty 200 mm of Rockwool wall insulation and 300mm of insulation in the roof, as well as well sealed, airtight breather and vapour membranes.
Paying attention to this detailing really paid off, as the final air test on completion (this is a measure of how draughty or not a house is) came out at an impressive 2.5 cubic metres per square metre (the average value of an air tightness test is just under 5).
Planning your interior finishes tends to get most people excited. We just love these floor tiles which Mr and Mrs Bax chose and had laid. Aren’t they beautiful? These have been laid over the electric underfloor heating cables, laid by Mr Bax.
Family Teamwork
With Mr Bax and his father doing almost all the internal construction and finishing work themselves in evenings and weekends, completing the Passive house standard family log home took several more months. But this meant that everything was done to an incredibly high standard. Of course they called in the professionals for wiring and plumbing, but almost all the rest of the internal work was done themselves, with Mrs Bax doing a lot of the decorating. All in all, the family really feels that this is their house, and yes, they moved in before Christmas!
One advantage of using beautiful, chunky logs to construct your home is that the internal cladding profile can be the same. This makes the interior stunning – just look at the finish here, which was achieved by many hours of painstaking work!
A Warm and Efficient Passive House Standard Home
The beautiful log burner has ended up being their main source of heat – when needed on the very coldest days. When they do light it, it tends to keep the house warm for days even if it is only lit for an hour or two.
The running costs of the house are very low – their energy bills have ended up at around £10 per month for most of the year rising to no more than £35 a month in winter. To date their annual energy bills have been less than £250, which is impressive especially when you consider this is a relatively large detached house with 186 square metres of living space.
The air tightness test (a measure of how draughty or not a house is) came out at an impressive 2.5 cubic metres per square metre (the average value of an air tightness test is just under 5).
The overall energy rating came in at 112, and this has meant that they now get a useful discount on their mortgage through the Ecology Building Society for the rest of their mortgage – more than paying for the eco features they opted for. As predicted, when inside with the windows closed, you’d never know there was a railway running past the house, you really can’t hear it at all.
Building your own home is many families’ dream. It’s also down to meticulous planning and accurate attention to detail as well – the time it takes is well worth it and you’ll end up with a house that you absolutely love.
