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?
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.
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!
A 2 bed eco home, based on the Hockerton Housing Project design, has come up for sale.
This is a private sale, but if you want to find out more (price available on application), please contact us and we’ll pass on your details to the seller.
Half acre incl meadow, lake and woodland
View from above
The semi-detached bungalow is on a plot of land adjoining the Project. It was built by some of the original project members so shares the key design details and, importantly, has delivered on its promised performance. The house is south-facing, with a conservatory to the south overlooking a half acre of grounds and a car-port, storage and entrance area to the north.
Earth sheltering helps insulate the home and minimises the impact on the natural environment.
Triple glazed /low E/gas filled units.
Mechanical ventilation heat recovery.
Electric car charging port.
Energy costs of about £500 a year, less than half the national average.
Water is supplied through a shared rain water catchment and storage system.
There is no mains sewage system in the village. The house shares a septic tank and floating reed bed sewage treatment system.
Boot room with storage.
Utility /shower room including hot water cylinder, sink, washing machine and storage together with basin, wc, shower and towel radiator.
Inner hall [3.1m x 3m] currently used as office and library.
Kitchen/ dining area 6.2m x 3m, with tall glazed French doors with windows over leading into the conservatory.
Sitting room 6.2m x 3m. Window on north wall and tall glazed French doors with windows over leading into conservatory. The rear section of this room [2.2m x 3m] could be adapted to form a third bedroom.
Master bedroom suite includes a dressing area [3m x 1.45m], shower room [1.6 x 3m] and bedroom [3.2m x 3m] with tall glazed French doors with windows over leading into conservatory.
Bedroom 2 [3.2m x 3m] with mezzanine floor over. Tall glazed French doors with windows over [3.25m x 1.8m] leading into the conservatory.
The fully double glazed timber conservatory [12.6m x 3m] has 4 velux roof lights and a wood burning stove.
Double french doors lead into the south facing garden approx 24m x 45m with a shared large pond. There is a hedge to the west boundary and woodland leading down to the stream to the south boundary.
Total internal floor area approx 127m2.
There is a phone and super fast Broadband connection. No TV points.
The property is leasehold with a 999 year lease subject to a token peppercorn ground rent.
Maintenance of the septic tank sewage system and rain water catchment system is shared with the adjoining dwelling.
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.