Clive Spencer - Case Study
Could you tell us any interesting facts or remarkable features about your project?
The aim of the project was to produce a healthy, uplifting and highly sustainable new home, but this process had to start with the removal of the old bungalow, which we had established was beyond economic repair. We wanted to recycle as much as possible, so we started by salvaging and selling the wood burner, wrought iron railings, hot water cylinder, all other metal and wiring, polycarbonate roofing from the carport, all roof tiles and even the walk in bath. Unfortunately we could not salvage the period kitchen, as it had been badly damaged by damp and rats. We de-nailed as much timber as possible for sale and the timber that was not suitable for this process was taken away by a local wood recycling company. The UPVC windows and doors were deglazed and recycled too. The standing walls, which were almost all concrete block, were crushed and used as hardcore for the new house and driveway. None was removed from site. No excavated soil or stone was removed either and as a bonus we now have quite an impressive rockery, which is a haven for wildlife. We ended up using two skips, mostly to remove a relatively small amount of plasterboard from the ceilings and for the rubber membrane and compressed straw roof board that had been used on a large flat roof extension.
The new house was constructed with a timber frame. The primary insulating materials used in the walls and roof were Warmcel, which is a Natureplus certified product composed of recycled newspaper, and Pavatex insulation board, made from untreated compressed wood fibre sourced from sawmill offcuts and chippings. Fermacel was used throughout the interior, instead of plasterboard, which not only has better eco credentials, being made from recycled gypsum and recycled cellulose, but also offers better fire protection, an improved acoustic performance, has greater strength and a higher thermal mass, which is an important quality in a lightweight timber frame construction. We kept the house carpet free to efficiently use the thermal mass provided in the floor structure too. Space heating and hot water are provided by an air source heat pump and internal ventilation uses a mechanical heat recovery system with metal ductwork, which avoids the use of plastic and has no issues with off-gassing. To keep the internal environment as healthy as possible, all paints are eco water based and emulsions are derived from clay, both of which are breathable and free from any nasties. The first floor balcony was constructed of galvanised steel and designed as a free standing structure that was bolted to the house, this avoided the use of any cantilevered components that would lead to thermal bridging.
We were keen to not use MDF in the house, so a plywood kitchen appealed to us. We scanned the country for suppliers, but realised we could cut down the road miles and save money, by getting a local carpenter to make it for us. We have a 3500l rainwater harvesting tank, which was primarily incorporated to irrigate our two allotments, although it has also been routed into the house and can be used to flush toilets. A photovoltaic array was installed on the flat roof, although I am still waiting for battery technology to improve and prices to fall before installing one. All appliances and lighting are rated at A+ or better and we do not have a tumble dryer, as the laundry room has drying racks.
After taking advice from a number of people with experience of Passivhaus buildings, I decided not to install underfloor heating, but instead used radiators. They are relatively large, to compensate for the air source heat pumps lower flow temperature, but we have been extremely happy with the responsiveness they provide and as all surfaces in the house are within a degree or two of each other, floors never feel cold.
During the design phase, we were advised that the Passivhaus Planning Package (PHPP) had highlighted a risk of overheating, so we incorporated an external blind on the largest east facing window, as overhead shading is relatively ineffectual on east and west facing elevations, whilst an oversailing roof detail was used to shade the south facing clerestory windows. Another measure that was taken to protect against overheating was the inclusion of effective ventilation, with most windows having the option to open. The problem of overheating highlights the importance of using the PHPP in the design process and we have been very appreciative of the features that have been incorporated to address the issue. The more obvious solution of reducing the glazed area was something we wanted to avoid, because of the far reaching views we are lucky to enjoy.
The self binding gravel for the driveway avoided using higher embodied carbon alternatives and although we were advised that it may have some drawbacks when used in conjunction with vehicular traffic, we have been very pleased with our choice. Another area where we wanted to make carbon savings was by furnishing the house with as many secondhand items as possible. Conveniently we had chosen a midcentury theme and although it probably did take longer than buying new, eventually we were able to find the majority of the items we wanted on the secondhand market.
Our data collection has shown, compared to the UK average dwelling, we are using 88% less energy for heating, 75% less total primary energy, whilst water consumption is more than 50% lower. Our final airtightness test result was 0.3 air changes per hour, twice as good as that demanded for Passivhaus certification. Monitoring over a 12 month period has also shown the house to be carbon neutral (excluding plug loads) and energy use for heating, per square metre of treated floor area, is within the figure required for a Passivhaus.
Floorplans & Elevations
Clive's Experience at the Centre
How many times have you visited The National Self Build and Renovation Centre before?
I have been to the NSBRC at least 10 times.
Did you use any exhibitors at the NSBRC? If so, who?
What did you enjoy most about your visit to the NSBRC?
Would you recommend the NSBRC to a friend, and if so, what aspects of the Centre would you recommend and why?
I have found having an understanding of the building process to be extremely useful and because the NSBRC is such a good place to acquire information, using any or all of the options mentioned above, I would recommend it to anyone without hesitation.