My stay in a zero carbon house - What are they really like?
Posted by Andrew Eagles on Tue, Nov 22, 2011
Instalment two – Technology – and what it means
Earlier in the year I lived in a zero carbon house for a week. Zero carbon is frequently referred to as the panacea. The great hope that will assist us to get to our Government mandated 
carbon reduction targets. I thought I would write up a summary about how it was to live in one of these homes that are so talked about.
Up to June 2011 there were 31 zero carbon homes with Code for Sustainable Homes post completion certificates in the UK. Scottish and Southern Energy (SSE), and friends, have built 10 of these properties at Slough, 20 minutes west of London. The scheme is called Greenwatt Way development. Perhaps Greenwatt Way is a reference to the scheme being extremely environmentally friendly “Green” and the energy “watts” for the homes partly being generated on site.
I promised to blog about the technologies used at Greenwatt Way. Apologies for the delay. Many of you have written asking for me to complete this. Please see here a short summary.
Electricity production
Photovoltaic – The photovoltaic were an integrated tile system. The costs are likely to be significantly higher than stand alone systems. The PV panels cover almost the entirety of the roof. To the external eye, all that is noticed is that there is a sharper shinier finish.
Currently Greenwatt Way will be enjoying earning a rate of 37.8 pence per kilowatt from these PV systems. This is lower than the refurbishment rate of 43.3 pence per kilowatt. They will receive this income for the next 25 years.
Heat production
Ground source heat pumps – two 17 kW Ground Source Heat Pumps with seven bore holes are used to provide heat to the properties. What heat pumps are good at is heating liquid from -5°C to around 55°C.
They do this by sending fluid into the plastic tubes into the ground. The temperature can range between 10°C and 14°C at 10 metres below the ground.
Biomass boiler – This boiler is a 30kW unit. Biomass boilers are considered to be zero
carbon. The plants being burnt have soaked up as much CO2 in their life time as they will release. Sometimes fuel for biomass boilers can be difficult. It can also be difficult to provide enough space to store the fuel. In this instance SSE did not have a problem, because fuel consumption is low, they receive less than two loads a year.
Heat store – the ground source heat pumps generate heat that is not always immediately used. The large heat store ensures that this heat is not lost. This heat is stored in a large water tank and drawn down when needed.
Other technologies
Energy monitors
Greenwatt way also provided smart meters in the homes. One of the most useful elements to these particular devices was that they had clear and immediate indicators of energy use. When a spike in energy use was indicated, the monitor went red, this meant I really noticed the energy load when the kettle went on.
There is a little confusion about these. Often the term smart meter is used interchangeably with the term energy display device.
Energy display devices illustrate how much energy is being used in the home immediately.
Smart meter is usually an electrical meter that records consumption of electric energy in intervals of an hour or less and communicates that information at least once daily back to the utility for monitoring and billing purposes. Both are useful in illustrating energy use to the householder. Some registered housing providers that are members of our SHIFT best practise group have been providing energy display devices to their residents to help them change behaviour.
Note in order to achieve maximum points under the energy section of the Code for Sustainable Homes the following now needs to be displayed
- current cost so people can actually see how much energy is costing them in pounds and pence
- current CO2 emissions
- visual presentation of data – so for instance a red indicator so people can easily identify when their usage is high or low
- current mains energy consumption in kilowatts and kilowatt hours
- display amount the householder is in credit or debit
- historical consumption data. This means people can compare their current and previous usage in a meaningful way.
Other organisations that deserve credit for playing a part in this development include PRP Architects, AECOM, Glanville Projects, Bramall Construction, Vital Energi, Geothermal International, Solar Century, Waterevolution, Stewart Milne Timber Systems, Belling, Bosch, SmartHome TV, HNBC, University of Reading, BRE and, SHIFT Corporate Partner and V-Phase.
These organisations and in particular Scottish and Southern Energy deserve credit for helping lead the way toward zero carbon. This has enabled other organisations to learn from their experience.
I recently attended the opening of an additional 91 zero carbon homes built at Parkdale, Castleford. I will be reviewing how Wakefield and District Housing Group met this challenge in a future blog soon.
I apologise for taking a long time to get this blog out. There is a great deal happening at Sustainable Homes. We have launched a new service to assist organisations that want to reduce carbon from their existing homes.
Even before we have marketed this we have seen a great deal of interest. If you manage homes and you want to get them to lower carbon do be in touch.
If you build new homes and you want to know more about achieving the Code for Sustainable Homes. You might be interested in our Code for Sustainable Homes training course.
