A deep green retrofit is always going to be more sustainable than switching from fossil fuels to renewables – and is much more sustainable than building new. This is being reflected in the changing workload of many ecological architectural practices, including Halvorsen Architects, which are increasingly taking on more retrofit projects than new-builds. This has to be the way forward for the construction sector if we are going to reach net zero by 2045.
We were recently asked to advise on a deep green retrofit of a four-bedroom detached house in Haddington, East Lothian. The 1989 house has a timber frame, with a rendered blockwork outer skin. It was draughty and cold, with patchy insulation, a lot of air leaks and cold bridging. It had a 15-year-old solar-powered water heating system with a heat exchanger, supplemented by a gas heater.
The aim was to make the house as airtight and well insulated as possible (given the existing structure) and to eliminate gas altogether.
The renovation included stripping back the fabric to the floor joists and removing the plasterboard and polythene sheeting on the external walls. A vapour barrier was wrapped around the floor joists and filled with 300mm of insulation. Breathable membranes were fitted inside the timber frame and additional insulation added in the form of insulated plasterboard as the final internal layer.
Particular attention was paid to taping all joints between wall and floor membranes, around doors and windows, and around cable and duct penetrations – an area that is often overlooked. Having no water circulating (see below) also reduced the potential source of leaks.
The existing water-heating system is being replaced by a combination of radiant panels and a heat recovery system.
The refurbished rooms have individual Blauberg heat recovery units. These have the added benefit of combating humidity and condensation – which can lead to damp and mould, together with associated health problems.
Other rooms have been fitted with highly efficient ceiling-mounted radiant panels – an electrical heating technology that uses infrared radiation to warm people and objects directly, as the sun does, rather than indirectly by heating the air. They were recommended for rooms not in constant use, as they heat the occupants very quickly, even when it’s very cold outside. The client is very happy with these heaters and finds the individual control for each room, for both types of heating, an added benefit.
Energy is provided by new photovoltaic solar panels on the roof and a battery system, charged on a cheap, night-time tariff, or from the solar panels. The client says that the home energy management system (mySigen app) gives a very comprehensive control of the system and energy monitoring.
The benefits of retrofit are huge. They provide long-term energy savings and lower carbon emissions. A higher proportion of each pound is spent on labour and a lower one on materials, thus creating skilled jobs and saving natural resources. It is vastly cheaper to repair an existing house, than to build a new one – £240,000 for a newbuild, on a greenfield site, versus a variety of costs to repair a vacant one, but for comparison, six houses on the High Street in Perth, at the then top-range £80,000.
One of the biggest absurdities is still the VAT situation (which isn’t a devolved matter). The 20% VAT applied to the repair of homes, compared to zero for new build, is a major financial drag to renovation. This must change.
