Air source efficiency and comfort for picturesque Cotswold self-build
Not uncommon among Viessmann customers, the homeowner of this newbuild in the Cotswolds, is a self-confessed building-efficiency nerd. As he puts it, “I’m mad on insulation. I simply don’t want to spend good money on fuel!” Hence, when the opportunity came to create the perfect home for his family in their former garden near Cirencester, getting the energy systems exactly right was always going to be an important focus.
Comfort was as vital as fuel economy, though. As the homeowner explains, “Our previous house was the coldest building we’d ever lived in until we installed underfloor heating. We really do get what a difference proper heating systems make to day-to-day life. So, I did a lot of research! I also knew I’d be creating a well-insulated house so heat-demand would be low, and more importantly, I set out with the concept of having no deliveries of heating fuel or septic tank pump out.”
The perfect solution turned out to be a highly efficient Viessmann Vitocal 100-A air source heat pump (ASHP) for heating and hot water, combined with underfloor heating in the tiled communal areas, radiators in the bedrooms and heated towel rails in the bathrooms. Harnessing the heat latent in outdoor air, the double fan Vitocal unit keeps the entire property warm while providing plenty of hot water for the family in a cost-effective and environmentally responsible way.
Modern comfort and countryside charm
Completed in 2021, the family’s home was a labour of love constructed entirely by the homeowner and just one other builder. Additional support was only called up when absolutely necessary, for the roofing as an example. The property consists of two handsome timber-clad ‘barns’ connected by a short linkway, creating the feeling of an agricultural courtyard. The main house incorporates four double bedrooms, three bathrooms and a cosy snug, while its smaller counterpart contains a vaulted kitchen-diner and sitting room.
Constructed of cement-bonded wood-fibre Isotex blocks and clad in larch, with an anthracite grey aluminium standing-seam roofing system, the buildings are both aesthetically pleasing and exceptionally well insulated. “We’re one point off an EPC A rating, and, from an air tightness point of view, we’re in the top 3% of buildings in the UK!” says the homeowner. “This means the heat pump can operate at much lower temperatures than most other properties. We run the water that goes into the under-floor heating and the towel rails at just 32oc, and we’ve turned off our weather compensation because the levels of insulation mean we just don’t need it.”
In practice, the radiators are rarely used, as the underfloor heating and towel rails, which run on the same circuit, together provide enough warmth for the entire space. In the living areas, the heating is set at 19.5 oc, meaning the circuit comes on at 18.5oc and goes off at 20.5oc. In 2021, albeit when the cost of electricity was much lower than at the time of publishing (March 2023), this costs around £160 per month in the winter (as at February 2022) and £65 per month in the summer. A mechanical ventilation system, meanwhile, provides fresh air for the bedrooms and sitting room.
“It all works really well”, enthuses the homeowner. “The system has been amazing in the production of hot water. There’s never a shortage and it all happens without any intervention from me.”
The ASHP’s outdoor unit is located at the back of the smaller of the two buildings, in a structure built by the homeowner using left-over cladding, so it’s in keeping with the rest of the property. “Many, many hours of thought went into what it should look like,” says the homeowner. “Once I’d decided on my design, I waited until the heat pump’s first service before building it, to check it through with the engineer. He told me that a lot of people put panelling over the front of the pump, and this forces the air down the back of the machine, making it work harder as it’s taking colder air in. By allowing cold air out the front and new, warmer air in the back, my surround allows our ASHP to work more efficiently.”
Funding and support
As the heat pump was installed in 2021, the homeowner was able to claim Renewable Heat Incentive (RHI) funding before the scheme closed in March 2022. Although, at £780 per year for seven years – the level was relatively low due to the building’s high level of insulation – it is helping to offset the purchase and running costs of the heating system.
The RHI grant was secured through Viessmann’s MCS umbrella scheme, Viessmann Access, which aims to support installers to navigate the funding system and secure MCS accreditation for heat pump installations. An installer worked with Viessmann through the scheme to correctly size and commission the ASHP and claim the RHI on behalf of the family.
“Overall, we’re very pleased with our heat pump,” the homeowner summarises. “It’s going to keep us warm for many years to come!”