Updated – 13th June 2022
Simply to turn a high maintenance high energy 1955 house into a low maintenace low energy 2013 home:
- Improve insulation to current standards
- Reduce maintenance burden
- Generate considerable PV electricity
- Solar water heating
- Make better use of existing footprint by improving utilisation of upstairs space
- Biomass heating system (changed to ground source heat pump during building)
- Active ventilation with heat recovery
- Unique statement on positive environmental impact within National Park
Condition before Modification
Bungalow built in 1955, with dormer extension added first, then a flat roofed kitchen, then a flat roofed dining room and rooms were then added in both ends of the roof on either side of the dormer room. The original house was of its time, energy efficiency was not helped by the multiple extensions / modifications. When we purchased the house in 1996 many of the windows had been replaced by double glazing, over the next 10 years we made the house cosier in minimal ways – stopped draughts and where accessible added more roof insulation. The house was oil heated as Swainby is not on the gas grid. We looked into carrying out modifications in 1996 and 2004, but both schemes were judged unacceptable being in the North York Moors National Park and within the Swainby conservation area.
In 2008 we decided to take the plunge and reduce energy use radically, so we engaged the architects EcoArc to produce recommendations which would bring the house up to the best energy efficiency standards. In the end it took until 2011 to get planning permission with revisions meaning that we committed to effectively a rebuild. Once the work was started it was just as well as the quality of the original house and the extensions were very poor, upstairs room floors which weren’t reinforced, extension walls that were bonded by the plaster not by the bricks, …
Anyway we finally moved out on 1st October 2012 of our cold house and moved back in on 1st April 2013 to our cosy home.
It didn’t take very long to take the old house apart.
It took longer to put the house back together, reassuring to see beams that were actually suitable to take furniture upstairs safely.
The brief to EcoArc had been very much fabric first, so in priority order – external wall insulation, fully insulated roofs, replace all windows with highly insulated timber (NYMNPA requirement) frame windows, minimising unwanted air leaks, ventilation system with heat recovery, replace oil boiler with multifuel biomass boiler, fit efficient wood stove in living room, insulate ground floors, insulate 1st floor floors, solar hot water, and solar photovoltaic panels.
Roof fully insulated with Kingspan between beams within rooms and 600mm thick Rockwool layer in attic space.
Triple glazed windows whether possible, triple glazed Velux windows were not available.
External wall insulation with Kingspan covered by a silicone render, effectively a blanket around the house.
Original brief had been a multi-fuel biomass boiler, however the sourcing of wood pellets which came from abroad didn’t seem to make sense and integrating a high temperature boiler with lower temperature renewable technologies did not appear to be possible. So a heat pump was considered to make this more environmentally efficient, then as the floors were going to be insulated the decision was made to install underfloor heating downstairs and upstairs.
The underfloor pipes were laid in a template downstairs embedded in a quick drying screed onto which a high thermal conductivity engineered timber floor was placed. Upstairs the underfloor pipes were laid into a preformed mineral labyrinth with the timber floor placed directly on top. Each room has a thermostat connected to a separate underfloor heating circuit.
We considered not having underfloor heating upstairs relying on the houses insulation and heat rising. In practise the upstairs underfloor heating gives flexibility, warm feet, warm shower rooms and allows us to keep the downstairs temperatures lower. We have found we turn the upstairs underfloor heating on a month after the downstairs heating, so November versus October and off a month before the downstairs heating, so April versus May.
We opted for a ground source heat pump (GSHP), attracted by the higher efficiency and lack of external sound. The ground source is two 80m bore holes in the garden.
The bores feed into the Nibe F1445 (8kW) heat pump the maximum electrical input is 2.6kW, giving a minimum coefficient of performance (CoP) of 3 when hot water is being produced. The heat pump looks like a large refrigerator, with potential for complex control, but once it is set up you normally leave it alone. Any alarms such as power cuts result in alerts via email as well as displays on the heat pump.
In order to increase efficiency further and provide ventilation air is extracted from bathrooms and exhausted through a mechanical heat recovery unit which is integrated with the GSHP.
Solar thermal panels on the roof reduce the need for the GSHP to produce high temperature water.
We also installed a rain water harvesting system which we collect the rain form the house roof then use for washing clothes, flushing toilets and watering the garden
Cosy low energy home with no fossil fuel burning.
Things to Notes
We started this process 14 years ago and carried this out the work nearly 10 years ago, and we have learnt a lot since then. However, I wouldn’t do much differently apart from employ a deep retrofit co-ordinator to help oversee the process. I did most of the project management and was learning on the way, a retrofit co-ordinator would have provided the extra knowledge to make sure everything worked together and attention to the critical details was taken throughout the build. At the time I decided the 25% of build cost RIBA standard architects fee for overseeing the build was beyond our budget, in hindsight rather ambitious. So I do wonder if there were small mistake on the build which is means the house could be even more energy efficient.
The house took a bit of getting used to, as we moved in while painting / final fitting was going on in early April it seemed not as cosy as we hoped, but once all that had finished it was really cosy. We learnt that the house is well insulated so needs little heat to keep it warm and so only has a low level of heat input, so it couldn’t cope with doors / windows being left open on cold days. We now know to control heat input into the house and heat loss.
In winter we set the room thermostats and leave them, we keep the sitting room a degree cooler, so we have an excuse to use the wood burner, really for aesthetics, but it also is our only source of heat in case of a power cut. In summer the house stays cool, cooler than outside if we use blinds to stop solar gain or open the Velux windows to get a great chimney effect throughout the house.