This second blog entry looks at what is needed to build zero carbon homes as part of an urban extension, and the potential barriers for doing so. In order to design a home that is zero carbon the carbon dioxide emissions from the home have to equate to zero over a defined period, so for example a calendar year. The way this can be achieved is by comparing the carbon needed through a traditional home both in terms of construction and use of the home when built, and offset this by using technology and different building techniques to demonstrate this. Within an urban extension setting this means it can be looked at in a large scale way. For example rather than having individual gas boilers to each house a combined heat and power system (CHP) can be used that only has one connection to a gas grid, and this runs engines within the CHP that provides heat and hot water to all the homes through a district heating system (essentially pipes to all the dwellings). This has a much lower use of gas than having individual boilers to, say, 400 new homes, and the added benefit of a CHP is the generators produce electricity which can be exported back to an electrical grid, which in effect adds to the pot of sustainable energy produced on site and offsets the traditional use of electricity being produced through carbon, as in effect it "gives back". All the homes can have extremely high insulation levels and air tightness, triple glazing, and significant Photo voltaic (PV) panels on the roof. The high insulation and air tightness significantly reduces the heat needed for the home, and the PV panels if singnificant enough can also produce electricity to be exported to the grid along the same lines of the CHP, or alternatively as technology moves forward this electricity can be stored in batteries and used for the house in night hours. It has been proved that this can be delivered and the earlier example of the Bicester Eco Town (*) (**) in the first blog is an example. In terms of barriers, it is currently circa 202 per sqm to build a home to zero carbon over and above a traditional form of construction (Bicester Eco Town 2016) and this does not allow for the additional cost of having a CHP and district heating system (but which is partially offset of not needed all the individual gas boilers and the district gas network as well). Clearly this will put off developers if they cannot see a premium for the homes as it will give them a disadvantage when bidding to buy the land. However, as stated in the previous blog, if the market conditions are correct for a particular location and there is the will of the local planning authority or legislation to allow it to happen, this can ensure the delivery of zero carbon homes. In the UK the purpose of the pilots is to prove to the market it can be delivered on a large scale for a normal profit that property development commands, hence specific legislations to enable it to happen (*) nwbicester.co.uk (**) www.ecobicester.org.uk
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AuthorGerald Walker. BA Hons Economics and Studying for a Masters at UNSW in Property and Development Archives
June 2017
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