Information on the assumptions and choices made with our Zero Carbon Home
Climate change is one of the greatest challenges facing humanity today. In order to comply with the greenhouse gas emission reduction targets specified in the Kyoto agreement, the UK government has developed several strategies to reduce emissions related to energy use (DTI, 2007., Scottish Executive 2007). Improved energy efficiency coupled with micro-generation technologies represent a key strategy supporting efforts to meet emission reduction targets in the UK. The UK government’s Climate Change Bill puts into statute the the UK’s target to reduce greenhouse gas emissions by 80% by 2050, below a 1990 baseline (Climate Change Act, 2008). This includes reducing emissions from both the housing and transport sectors.
It is currently estimated that 27% of the UK’s carbon emissions are emitted from the domestic sector (Williams, 2010). According to the Zero Carbon Hub all new homes should be net zero carbon from 2016 (Zero Carbon Hub, 2012). At present, this is a voluntary scheme, but it is increasingly likely to become legislation (Omani and O’Reilly, 2009). Figure 1 illustrates a proposed new definition for zero carbon homes. Zero carbon is composed of energy efficiency measures and improved thermal efficiency through building fabric, air tightness and design to reduce demands. Carbon compliance is achieved via on site generation of low and zero carbon electricity and heating. Allowable solutions include Mechanical ventilation and heat recovery systems, A rated appliances, and retrofitting of existing buildings in local area (Building a Greener Future, 2007).
Code for Sustainable Homes provides the framework for future sustainable building standards in the UK. This code exceeds other international housing standards, such as “Passivhaus” by specifying that domestic energy requirements are met using renewable energy technologies (Omani and O’Reilly, 2009).
For the purpose of our project we have chosen to begin with a zero carbon home. Energy use, particularly space heating, has been reduced through building fabric and design. Appliance efficiency of A+ and above and the use of compact fluorescent lighting reduce electrical demands. By reducing demands, the supply required from renewable technologies can also be reduced. In the case of our net zero carbon home, we aim to calculate the amount of energy generated from photovoltaics which would be required to meet the electrical demands of the dwelling (including appliances, lighting, heat pump and mechanical ventilation with heat recovery system).
We modeled our heating demands using a program called ESP-r which provided a ready built passive house model in Dundee, built to 2016 Building Regulation Standards. The roof area of the building is 90m² in total, and the building floor area is 163.71m², and the internal temperature of the air was maintained at 20oC.
Specification to meet Code 6: Source http://www.ssezerocarbonhomes.com/SSE_ZCH_Case_Study11-1-11.pdf
To achieve “Passivhaus” standard, annual primary energy use must not exceed 120 kWh per m² per annum. Our zero carbon building has an electrical demand of 4555 kWh per annum. This equates to an energy demand of 27.8 kWh/m² per annum. The primary energy required to meet this demand is 72.3 kWh/m² per annum, achieving “Passivhaus” standard.
There are numerous examples of zero carbon homes built to Level 6 of the Code for Sustainable Homes and incorporating design features with renewable energy sources in mind, such as large roof areas orientated to south. Some of these examples can be found at the links below:
Greenwatt Way, SSE (http://www.ssezerocarbonhomes.com/Energy%20Savings%20Trust%20Case%20Study%20-%20Greenwatt%20Way.pdf")
Kingspan Lighthouse http://www.kingspanlighthouse.com/pdf/lighthouse_flyer.pdf
http://www.bre.co.uk/filelibrary/Innovation_Park/Kingspan_Lighthouse_Brochure.pdf
CarbonLight Homes http://www.activehouse.info/cases/carbonlight-homes
Building a greener future: Policy Statement. 2007. Departments for Communities and Local Government. Crown Copyright. London.
Available at http://www.communities.gov.uk/documents/planningandbuilding/pdf/building-greener.pdf
Climate Change Act. 2012. HMSO. UK
Definition of Zero Carbon Homes and Non Domestic Buildings, Consultation, December 2008, HM Government).
DTI (2007) Meeting the Energy Challenge – A White Paper on Energy. TSO. Norwich.
Omani, M., O’Reilly, A. 2009. Feasibility of zero carbon homes in England by 2016. A house builder’s perspective. Building and Environment. 44. pp. 1917-1924.
Scottish Executive (2007) Energy Efficiency and Micro-generation Strategy. Achieving a low carbon future. A Strategy for Scotland. Draft for Consultation. Scottish Executive. Available at http://www.scotland.gov.uk/Resource/Doc/169519/0047225.pdf
Williams, J. 2010. The deployment of decentralized energy systems as part of the housing growth programme in the UK. Energy Policy. 38. pp. 7604-7613.
Zero Carbon Hub. 2012. http://www.zerocarbonhub.org/