Heating and hot water for UK buildings make up 40% of our energy consumption and 20% of our greenhouse gas emissions. It will be necessary to largely eliminate these emissions by around 2050 to meet the targets in the Climate Change Act and to maintain the UK contribution to international action under the Paris Agreement.
It’s been widely welcomed for highlighting the stalling of Government policy in recent years. But one point sticks out to us in particular:
New-build. Buildings constructed now should not require retrofit in 15 years’ time. Rather, they should be highly energy efficient and designed to accommodate low-carbon heating from the start, meaning that it is possible to optimise the overall system efficiency and comfort at a building level.
The document expands on the potential for heat pumps and district heating, but where is the option of zero-heating? Why not build homes so they don’t need central heating? Whose heating system helps with summer cooling? And use solar PV and wind to top up efficient immersion heated water stores when renewable power supply surpasses time-critical demand?
It can be done, with existing technology and skills, at roughly the same cost as a new home built to building regulations alone, and here’s our energy use from the last 15 years, and a related temperature study to prove it.
The average energy use by the homes at Hockerton Housing Project has consistently been less than a third of that used by the ‘average’ UK household, and two-thirds of that demanded by the Passive House standard.
So why is this approach not being followed more often?
The Government’s preferred energy performance calculation (RdSAP and SAP) can’t calculate the benefits from interseasonal storage.
There is no great commercial incentive to lobby for this low-tech and affordable approach. It profits residents rather than manufacturers or standard-setters.
There’s an assumption that high thermal mass, in the form of concrete, is inherently bad. It’s not if it removes the need for heating, reduces maintenance, and increases the durability of the home. Parity with timber-framed homes is reached at about 20 years.
That’s it.
And here’s the small print:
5 homes, averaging 2 adults, 1-2 children
Increase use over time reflects increased home-working and children becoming teenagers. Savings in the general population are not mirrored as homes at Hockerton have always had energy efficient lightbulbs, sought the most efficient appliances, and had energy-aware residents.
Temperature tracking was undertaken when home was drying out and with low occupancy in that first winter, so not a perfect study, and overheating is now minimised through shading of conservatory sunspaces during summer. Even before this, the instances of overheating met the requirements of the Passive House standard.
When space heating is required, it can be delivered by small electric heaters with far lower capital and operational costs. Such occasional use is included in the usage graph above.
Readings are taken manually so some of the quarters are thirds, or very small quarters. One particular peak can be put down to our Christmas party in 2012! If anyone wants to fund/test automated reads, do get in touch!
Every 3 – 4 months we read our 50 power and water meters to check how we are doing in terms of consumption, generation and export.
Each household pays for their share of consumption relative to use, with any income from the export of renewable energy shared equally between us.
The resultant figures help us remain aware of our use, not least because we see it relative to (or in competition with?!) our neighbours. It also reminds us how well these houses perform. This can become easy to forget when the house is your home – until heatwaves like this week, when we could feel the difference as the thermal mass soaked up any heat that made it through shaded windows.
* Our average daily energy use was around 23% of a standard house (per house, not incl the garages).
* We exported 38% of what we generated, compared with 48% in the winter
* We earn around 4p for a kWh exported but pay on average 7.5p per kWh we use, so over the last 4 months we’ve missed out on energy worth £145.
* In the last 4 months we’ve generated the equivalent of 95% of our total household use (not including our shares in our community-owned wind turbine of course).
* And we are using 260 litres of water a day per house on average. Potable: non-potable is 1:11. This is a similar ratio to that in the first quarter but an increase overall. Average usage per person is 82 litres, compared with Code for Sustainable Homes Level 5 and 6 target of 80 litres – perhaps due to higher number of washes during peak vegetable gardening season!
This week we popped in to one of the homes that we retrofitted in 2010/11 as part of a Government-funded project, Retrofit for the Future, to find out how it was performing.
The headline finding is that the house is now using 9% of the energy it previously used for space and water heating; down from 12493kWh to 1133kWh. Overall energy use has been reduced by 75%, with the carbon emissions from the remaining use offset by a cost-effective investment in off-site renewables.
We visited after one year and found that actual energy use was 47% less than that predicted by SAP. There has been a further significant fall since then. Over the intervening years, the average energy use has been 30% of the use originally predicted for space and water heating, ventilation and lighting; and total average use has been 50% of use in that first year.
We expect heat usage to remain steady at this lower level (for the current occupancy patterns) as the fall can be attributed to one-off factors in that first year:
the building was drying out
the thermal mass had no heat stored as the build completed in early autumn
the winter of 2010/11 was particularly cold
Use of energy for appliances and cooking remains the largest influence on energy use, forming two-thirds of annual use on average. As highlighted in previous posts this is very dependent on working patterns and the number of residents. The final 3% of energy use is by the metering system itself – with metering on 8 rings in the house to enable this analysis.
Last, but certainly not least, was the residents’ feedback. The most notable problem was a rain sensor on the automated Velux windows in the sunspace, but that has been repaired quickly enough, and the occupants continue to enjoy the comfort of their old but cheaper-to-heat home.
Date posted: January 28, 2016 | Author: HHP | 1 Comment »
Earlier this year we heard Helena’s reflections on 20 years at Hockerton Housing Project. Now we hear from our newest neighbours, Deb and Pete, 2 years after moving from the local market town of Southwell…
“My husband and I moved in to Hockerton Housing Project just over two years ago. We are in our early to mid fifties and have a son of 27 years of age, who at the time was living in Japan but since then has come home to HHP which he loves!
We had lived in an ordinary house in Southwell for over 25 years and it was a big move for us albeit only a distance of 2 miles.
Why did we make the move? We knew we loved growing things, in fact we had an allotment in Southwell for a long time; we knew we wanted to have farm animals but didn’t want to be tied down by them or for that matter the growing; and we knew we wanted to live as sustainable a life as possible!
But we were worried about the unknowns of cohousing – the amount of work we would have to do in the community, privacy, and how we would fit in.
Two years on we wonder what on earth we were worried about.
It is great to have sheep, that I look after (by choice) on a day to day basis, but someone else is always around to look after them when I want to go away for the weekend or on holiday. It is the same with the people who look after the chickens, they just tell us when they are going away and someone volunteers to look after them until they are back.
As for the growing – it is a 1/5th of the work of looking after your own allotment and so much more satisfying than seeing food wasted when there is a glut of something. I have a well-used jam and chutney pan and a fully-stocked freezer to see us through the winter for fruit and veg. Our bees produce our own honey which tastes simply wonderful…in fact it’s a strong favourite with the extended family and hence I managed to get through 12 jars last year!
I have learnt from others to deal with the ewes lambing, there is always someone else about to help out when intervention is needed, and sharing the lambing experience is just awesome. We had 16 lambs this year, 8 boys and 8 girls so have a flock of 32 altogether. Amy, my next door neighbour who is ten is going to be a fab little shepherdess…next year I could almost leave the lambing to her!
No longer do I get in my car and go miles to purchase flowers for my little flower business instead I walk out into my garden or up to the cutting garden at the allotment to select seasonal sustainable flowers which smell gorgeous. That was something I never dreamed of doing until I moved here. I nip into our cooperative’s office a couple of times a week to check the inbox and promote and manage tours – it’s a twenty five yard walk from my back gate. I guide tours when we have them for schools and universities with other residents and also do catering for conferences when they are held in our purpose built sustainable venue.
In terms of privacy, my life is more private here than it ever was in the middle of Southwell. As residents there is a great respect for each others’ privacy but this all happens without being made explicit.
This is actually how I hoped life would be, it is idyllic. You do have to pinch yourself every day when you turn round that corner at the end of the road you come into another world. So many local people come and say I never knew that this was here and are blown away by its beauty and how warm our homes with no heating really are!”
If you want to find out more, do come and see for yourself on our next public tour on 19 September – booking essential!
Have we ever mentioned how thermal mass keeps our homes warm in winter and cool in summer?
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.
