Kit Home Case Study: Hanse Haus

Having lived in their house for the past 15 years, Richard and Rachel Stent watched the dust rise as it was bulldozed to the ground. 'I'll never forget the day we moved into this house,' says Richard. 'It was the day our eldest child was born.' Since then, the family grew, as did the desire for more functional living space.

'We chose Hanse Haus because we liked the idea of dealing directly with the manufacturer and, having visited the factory and sample centre in Germany, were impressed with the quality.'

The Stents didn't have any issues with getting the necessary planning permission – partly due to the fact that the site had already had a previous residential dwelling of similar size on it, but the details of Passivhaus standards (including insulation, air tightness and energy efficiency) were also included with the application.

The Energy Efficient Result

While they had a good idea of what they wanted in terms of design, Richard and Rachel worked together with a Hanse Haus architect to finalise the specifications for the house. The result is a contemporary family home with lots of natural light. The living/dining room, for example, has huge windows and patio doors, which means that not only is the view over the garden and towards the coast maximised, but the natural solar radiation is used efficiently to heat the house. Also, the precision and detailed technical construction ensures that the house is completely airtight, and that no heat can leak out through joints or gaps.

As Stephen Huber from the Scottish Passive House Centre points out, 'The super-insulated shell and windows, together with a highly efficient "Paul" mechanical ventilation heat recovery, take the annual heating consumption down to 13 kilowatts per metre squared. The use of a modern heat pump and a solar thermal system means the primary energy demand for domestic hot water, heating and auxiliary electricity is cut down, ensuring very low running costs. Plus, this house is on the highest level of emission savings.'

Despite this massive cut in energy consumption, the indoor comfort and air quality is still top of the range. 'Although energy efficiency and associated low running costs hadn't been a primary objective when first setting out to build our own house, it became more apparent that these factors did make long-term economic sense. In the end, the fact that we've built the house we wanted, which is also a Passivhaus, is the icing on the cake,' adds Richard Stent.

Next, the house arrived from Germany by lorry. 'The erection crew prepared the site with a vapour membrane on top of the concrete slab, ready for the walls to be secured on top and, within no time, began to construct the house. Watching the construction crew manoeuvre the crane to arrange the walls with precision measurement, matching specifically with the ground works, and position conduits for waste pipes was especially impressive. By lunchtime all exterior walls, each with pre-fitted triple-glazed windows and patio doors, were in place as well as many of the interior walls and we could really start to get a feel for the individual rooms. By the end of just one day, the ground floor as well as the ceiling cassettes were in.'

'We didn't get to the site until late in the afternoon the following day by which time the first floor was in along with all interior walls. Having only seen our new home on paper or as a model image, it was amazing to actually walk around it for the very first time.'

'The two-day construction culminated with the traditional 'Topping Out' or Rickfest ceremony, which I'm told has long been an important component of timber frame building. The head of the crew known as the Zimmermann placed a Christmas tree on the highest point of the house to symbolise the natural elements. Why a Christmas tree, I asked? Apparently, it's in recognition of the evergreen's ability to survive the harsh winter. A ceremony was then performed to placate the gods and protect the house from harm. The Zimmermann finished off by smashing a glass against the side of the house in recognition of it being a strong building that would withstand the weather to be thrown at it. Along with the crew, other Hanse Haus associates and some family and friends we'd invited along, we raised a toast.'

'Those couple of days were quite extraordinary in that, we went from the foundations to a two-storey house and, other than observing the build, which was evidently top quality and extremely efficient, the only work I did was to give the crane driver a lift home one evening!' says Richard.

Within just a few weeks, the first fix plumbing was completed, as was all the electrical work. The plasterboards were fixed and the baths and shower trays were all fitted. Screed was down on the floors and the coloured external render had been put on. Everything else was done in the weeks that followed and eager to move out of the caravan they’d been living in, the Stents spent their first night in the house.

'In the design process, there were some things that we weren't in control of such as the staircase, although we're really pleased with it. Like everything, it's manufactured to a very high quality.The same goes for the windows and external doors, which are really solid and robust as well as being triple-glazed. The house is quite exposed and we used to hear the wind whistling through our old house but it's so quiet now.'

'Although energy efficiency wasn't a primary objective when we first set out to build our own house, the fact that I don't have a gas bill landing on my doormat any more, puts a smile on my face. We had oil-fuelled heating and hot water in our old house, which cost a small fortune. Imagine how big that bill would have been after the cold winter we've had, and the increase in fuel costs. Our new house feels so much warmer in comparison and that's without having any heat on,' finishes Richard Stent.

Tips For Other Self Builders

We asked Richard Stent to give us the benefit of his experience:

• It's essential to be fully involved in the design process of a house and pay attention to the details. When we went to Germany for sampling of fixtures and fittings, we’d made a decision on where we wanted everything to be placed but over time, you get to reflect on things like the position of the lighting, for example. Some things have worked out wonderfully well for us but for other things, like the lighting, we had to make a few minor tweaks, as well as a few compromises.
• If you're working as well as self building, be realistic about what you can actually do. We run our own business, so although we were very involved with the design and the fixtures and fittings for the house, our involvement with the actual build has been minimal.

The exterior of the house has an off-white render and a zinc pent roof. The exterior walls are 30cm thick. The house has large triple-glazed windows to maximise solar gain, as well as external blinds, which are a standard product to Hanse Haus homes, although in this case, they are specific to Passivhaus standards.

Interior

The house provides 250 square metres of living space.

Front access is via a front porch, which is external to the rest of the house, and is preferable on a Passivhaus as it acts as an air lock preventing external air from entering directly into the house.

The interior walls are 12cm thick and the house also boasts the Hanse Haus solid wall system, which combines the advantages of timber SIP and solid wall construction. 'The walls have a stud every 300mm and they are completely glued on both sides with OSB boards. That makes them loadbearing and the fixing of wall units, including heavy kitchen units for example, is possible everywhere,' says Hanse Haus architect, Bianca Keil.

Utilities

Heating
The house has a modern heat pump and a solar thermal system. There is a reduced underfloor heating area on the ground floor as a back up for cold winter days when there’s been a limited amount of sun to heat the house passively. There is no boiler.

Water
Mains water

Ventilation system (with heat recovery)
The house has a mechanical ventilation system with heat recovery. This system is used for the demand-based supply of air to and extraction of air from low and ultra low energy houses. Used air, which is often contaminated with pollutants, such as moisture and odours from kitchens and bathrooms is continuously extracted. This regulated room ventilation leads to a reduction in heating energy requirements.

Insulation
This house achieves outstanding thermal insulation. With detailed technical construction, particular attention is paid to the building envelope - the shell - to make sure it's completely airtight, ensuring that no heat can leak out through joints or gaps.

Certification
The whole construction process of the Passivhaus and the individual structural elements, such as the walls, windows and roof are verified by the Passivhaus Institut in Darmstadt, Germany. This Passivhaus certification provides official confirmation that the building is built to the correct specification.