Have we ever mentioned how thermal mass keeps our homes warm in winter and cool in winter?
No doubt if you have visited us you’ve heard the stats and felt the benefit, but a day like today makes the benefits all the more evident.
The thermal comfort of our homes is met through the application of three key design principles:
Thermal mass to store heat in the summer months to keep the home cool in summer and warm in winter
Passive solar gain to reduce the need for space heating and artificial lighting
Super-insulation and buffer zones to provide a reduced temperature gradient between the inside and outside of homes.
So on a day like today we shut the triple-glazing between the living space and buffer zones, along with curtains and shutters if we are out and about, to keep out warm air and solar gain; and let the thermal mass soak up the heat when we are around the house. We have built passive ventilation into our buffer zones – otherwise known as skylights in the conservatory and porch area – which are vital to keeping the temperatures in those spaces comfortable.
Given the warnings yesterday from the Committee on Climate Change, we think cooling, or overheating, is an issue that needs addressing as part of the government’s home energy strategy. It should not be an add-on as there can be a conflict between approaches that keep heat in during winter and keep it out over summer.
The positioning of insulation in a construction element was completely disregarded by SAP up to and including SAP2005, and continues to be ignored by RdSAP. But it is essential if you want to get the heat storage benefits of thermal mass throughout the year for cooling, heat storage & release. Our walls, floor and roof could have the insulation placed on the inside, which would give exactly the same U-Values and hence RdSAP result, but completely different and appalling thermal performance of the house as a whole in warmer weather. Instead of being absorbed into the thermal mass, the passive solar gain would continue to raise the temperature until vented in some way.
Even though this is beginning to be recorded by SAP, RdSAP does still not differentiate between internal and external solid wall insulation. Neither assessment reflects the benefits in their overall assessment of thermal comfort. If the Government wants to prepare homes for the 21st century, and beyond, these tools will need to both recognise and reward the way external insulation can“lock in” the mass of the walls to deliver summer cooling and winter heating.
Visitors to Hockerton come expecting a tour of our homes, but the first stop – whether the visitors are permaculture pioneers or planning professionals – is our orchard and allotment area.
We are often asked why we haven’t just focused on low energy housing but we were clear from the beginning, 20 years ago, that a sustainable lifestyle has to balance social, environmental and economic factors. This cannot be delivered by architecture alone.
In 1997 the Building Research Establishment published a General Information Report GIR53 which was entitled “Building a Sustainable Future-Homes for an Autonomous Community”. Within this report it was pointed out that at that time the average family produced about 4 tonnes of CO2 through car transport, 4 tonnes of CO2 in heating the family house-yet twice that amount of CO2-8 tonnes was associated with food consumed by such a family each year.
This is because food is often the product of intensive farming which uses fossil fuel based fertilisers and is then transported thousands of miles to our shops where it is stored until it is transported to our homes, usually by car.
So by focussing on heating costs and transport alone without addressing food production we would miss out on impacting half the CO2 emissions we could potentially address.
Hockerton thus incorporated a land management plan in its design, which as well as providing an environment for wildlife to flourish would contain an organic growing area.
Over the years our food production has added to our organic allotment. We now have and orchard with fruit trees, bee hives, chickens and a flock of sheep.
The added bonus of all this is that we are kept in touch with the natural cycles of nature, spend time outside in our green gym and benefit from food produced to high standards and on our own doorstep.
So if you are thinking about your own sustainability projects, don’t forget the opportunities for food production which could outweigh the reductions in CO2 from household energy saving measures that you take.
One of our longest-standing residents reflects on her time at HHP….
This is the 20th year since we joined HHP. We had recently returned from volunteering in Namibia and felt that sustainable development needed to start in the affluent West. We had relocated to Nottingham as I had a medical job there and Simon was looking after our small son Luke and looking for some way of using his engineering skills and doing it sustainably. By chance he came across HHP who were looking for a family to join them and the rest is history!
In those days (1995) I think we were more about sustainable and autonomous housing and climate change was not such an obvious issue but of course that has all changed and Simon now spends a great deal of time thinking about Renewables although our core business of demonstrating and promoting zero energy and sustainable housing continues and has lost none of its relevance today.
We moved into our brand new house in February 1998 after 18 months in a caravan with by then 3 small children. Simon had contributed to the self-build and being on site allowed him to juggle the family and building whilst I went off to a warm comfortable hospital every day! Our neighbours at the time were in a similar position which allowed some complementary childcare and a lot of mutual support!
Over the 20 years the Project has grown in so many ways. We had not realised the amount of interest it would generate with about 30,000 visitors, a significant amount of media interest and a small business that has continued to promote sustainability and provide employment for some of the residents.
Families have come and gone and we are now the last original family. Our children are grown up and Flo who was born when we were in the caravan is doing A levels and considering her future. It is perhaps not surprising that Luke is studying permaculture and small-scale organic horticulture in Leeds and Naomi is down in Falmouth studying Environmental Science. Their childhood in this wonderful site has been spent in the woodland and lake, in a small community of children and adults where they have had the freedom to explore and learn in safety. Parenting them has been easy. It is a pleasure to see other small children growing up and enjoying this space that we have helped to create.
As old families have moved on it is sad to lose that collective memory of the first days and the struggle to get planning permission and the houses built. We will be the last to remember why we did things this way or that and why that particular phrase in the secondary rules was written that way. But new families have brought in fresh energy and ideas and keep the direction of the business gently changing depending on interest, skills and available time.
Simon and I have no plans to leave and this lifestyle and place is perfect for us. The apple trees are in blossom and the new plants in the polytunnel are thriving and ready to go out. As the spring sun floods the conservatory after earlier rain, I am as excited as ever to throw open the doors to the bedrooms and know that the temperature in the house will stay in the low 20s until November.
After 20 years here our lives will change as the children leave and we have a bit more time for ourselves. More time to spend on the land, more time to sort out 20 years of childhood paraphernalia and more time to sit in the kitchen, conservatory, garden or lakeside depending on the weather and the season just enjoying this extraordinary place we helped to create!
We know we’re lucky having access to nature on our doorstep, and the ability to help it thrive, so we’re very keen on The Wildlife Trust’s campaign for a Nature and Wellbeing Act which would give everyone – particularly children – access to nature and improve its status in national and local government decision-making.
The ambition of the Act, and the delivery mechanisms, have been likened to the Climate Change Act, and has its own implications for our response to the climate change – by building our local environment’s resilience.
But we don’t like to just sign a petition if we can also take some personal action.
We’re reviewing our land use, as we’ve recently renewed our agricultural tenancy, and our first job is to start planting hedges to balance our agricultural use of the land with our aim of improving the site’s biodiversity. This balance is core to the land management plan that supported our original planning application and s106, but more than that these wildlife corridors support the natural environment that in turn supports our health and wellbeing.
Woodland Trust has tree-planting packs available for others to develop these natural spaces in their school, community or farm.
Hockerton Housing Project is featured in a new book, The ‘One Planet’ Life: A Blueprint for Low Impact Development. The guidebook has been written ‘for everyone on the path towards a way of life in which we don’t act as if we had more than one planet Earth. The book also represents a manifesto for a change in attitude towards land use’.
You can get a taster in this informative blog about our development by the author David Thorpe, who is also a founder and core group member of the One Planet Council, and former director of publications at CAT.
If you want to see it for yourself, come on our next tour.