At 77 and 65, Terry and Olwen are the oldest couple to feature in The Street, the Grand Designs series following 10 households each building the home of their dreams next door to one another in a new community in Oxfordshire. Although fit and strong enough to take on a challenge of this magnitude, they were already looking ahead to a time when they might be less mobile.
The result is a modern take on a Spanish dormer bungalow, adapted to their current and future lifestyle and needs. Covered in white quartz and topped with a blue roof, the striking wedge-shaped building has an open-plan, double height living space overlooked by a mezzanine, and an upstairs balcony where Olwen and Terry enjoy sharing sundowners in the evening. Meanwhile, wide access doors, level thresholds and a wet room and second bedroom on the ground floor make this the perfect retirement nest.
It’s also designed to be low maintenance and low cost. “Because I built it myself, it’s very DIY-able,” explains electrical engineer Terry, who also self-built the couple’s last home. “If anything goes wrong, I know how to fix it.”
The building is extremely energy efficient too, having an exceptionally high thermal mass. Built with pre-insulated, lightweight, interlocking Durisol blocks made from recycled pallets coated with cement, it’s topped with reinforced polystyrene insulation beams supporting the steel roof. This, combined with a state-of-the-art, heating and PV power system from Viessmann, means that there is only a 1-1.5°C drop in temperature overnight, even though the heating stops at 4pm. “I’m not an eco-warrior, but I wanted to make this the most economical house to run, so we won’t ever have to worry about big bills,” says Terry.
This thoughtful, future-proof approach has been applied to all aspects of the build and has enabled the couple to include some clever features often missed due to lack of sufficient forethought. One good example is the 300mm concrete screeding that overlays the underfloor heating system on the ground floor and 50mm on the first floor. Due to its ability to retain heat, the thick concrete layer stays at a constant temperature, stabilising the warmth throughout the building. Most underfloor heating systems use a 2in (50.8cm) concrete floor, which cools far more quickly.
“The whole house is like an old-fashioned night storage system – a big tin box full of bricks with an electric heater inside,” Terry enthuses. “In the old days, when electricity was cheaper at night, it would heat up the bricks, then the fan would come on in the day to blow the hot air around. The principle here is the same, but now we heat the house in the day, and it stays warm around the clock.”
Why don’t more properties use thick concrete floors with underfloor heating? “People think about it too late,” suggests Terry. “They tend to design and build, then think about the underfloor heating. When you’re planning low temperature, economical heating systems, you really need to plan ahead, before the house design is finalised.”
Terry and Olwen’s home has been built in accordance with the Passivhaus Planning Package, meaning it has an annual heating and cooling demand of under 15kWh/m2 per year. In fact, it’s just 12kWh/m2. “We haven’t sought certification because it’s just an exercise in paperwork,” says Terry. “But the house is well within Passivhaus standards.”
Research pays off
Terry conducted exhaustive research to maximise the efficiency of every part of the build. Although he knew he wanted an electric heat source incorporating solar energy to avoid burning fossil fuels, and a fuel cell micro CHP system (see box out) he was initially unsure what to choose. He looked into infra-red and direct electric heating but realised that, although cheaper to install, higher running costs make them more expensive in the longer term. Working with Matrix Energy Systems, he began investigating heat pumps.
A ground source heat pump was ruled out due to lack of space, and local geological conditions and lack of room for a drilling rig meant a borehole wasn’t an option either.
Matrix Energy Systems designed a fully integrated heating system, with controls, according to the Brown-Waites’ needs. An exceptionally efficient air source heat pump from Viessmann works together with Viessmann Vitovolt solar photovoltaic (PV) panels and a mechanical ventilation and heat recovery (MVHR) system. The ventilation was needed because the building’s excellent insulation meant minimal heat loss would also limit internal air movement.
The Viessmann Vitovent MVHR system creates an internal flow of fresh, pre-heated or cooled air around the house. It also reuses recovered heat from around the building, reducing demand on the heat pump, allowing it to operate more efficiently when needed and less frequently during winter months.
Terry chose the Viessmann Vitocal 242-S Split heat pump which has a nominal heat output of just 7kW, compared to 30kW for a standard boiler. The Vitocal’s split refrigerant system means the system does not need antifreeze (which reduces output), but it will never freeze in a harsh winter. “The Vitocal also gave us the option to link in a battery later on to store solar electricity if the energy monitoring showed it to be beneficial,” adds Terry.
The full output of the PV is capable of powering the entire heating system, however, at night and on shorter and more cloudy days, where consumption is more than solar generation, then electricity is consumed from the grid. Terry estimates his current (pre-battery) heating and hot water-related electricity costs are just £60 per year.
Programming the system to run itself
Clever programming is the final ingredient that makes the entire building work optimally. The heat pump generates hot water for an hour a day at midday, when there is peak sun. Any excess is stored in a buffer tank. The heating is also timed to operate only during daylight. The building is divided into 11 heating zones, with the bedrooms cooler than the living room` and kitchen.
“We’ve had to adjust our lifestyle,” Terry comments. “We now use electricity to work in tandem with the solar PV generation. Every appliance that can be is pre-programmed to come on in daylight hours.”
Terry has installed a smart home app called Fibaro which is controlled through the virtual assistant Alexa. Sensors throughout the house detect light, temperature and motion, adjusting the environment accordingly, e.g. by closing the blinds in strong sunlight. The couple’s fingerprints are used to control access. “The house runs itself – we don’t need to do anything!” beams Terry. “We can override it manually, though.”
The finishing touches
Light fittings, crafted by Terry himself, in the form of long spirals of clear glass orbs, cascade past the floating oak stairs, forming a dramatic focal point in the bright and airy main living space, while polished dark blue luminescent tiles cover the whole ground floor, subtly sparkling in the expanse of natural light.
To add a touch of cosiness to winter evenings, the couple wanted a real fire. However, because of the remarkable efficiency of the building, they didn’t need any more heat. Fortunately, they found a Dimplex Opti-myst basket fire which looks real yet stays cool. It provides the perfect centre piece to their beautiful living area.
Terry’s top tip
With two successful houses under his belt, Terry is well placed to give sage advice to other self-builders: “Think building fabric first. Forget the flashy kitchens and gold taps – focus on what’s important, such as insulation. You only buy it once, and it will repay itself over and over again.”