Green Building Blog

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What makes a house an eco-house (in Britain)? November 7, 2011

Filed under: Britain,Politics of building,Project outputs and findings — naturalbuild @ 9:11 pm

I have recently started work on creating a publically accessible database of eco-houses. I want to help publicise the diversity and creativity of eco-building. I have previously defined an eco-house as a building which minimises resource use (in construction and life -cycle) while also providing a comfortable environment in which to live. Yet this is quite vague and avoids having to really determine when a house is ecological enough and when it is not.

It seems like a really simple thing to do and there are numerous standards by which eco-houses are measured (such as Code for Sustainable Homes, AECB and BREAM Eco Homes). However, my concern is that as soon as a checklist is created some really innovative buildings are excluded and others do just enough to reach the standard but miss the bigger picture of what an eco-house is. So I want to find a way of defining an eco-house that includes the sheer diversity of eco-buildings we have in Britain (the database is starting with a focus on Britain and will hopefully expand later).

It needs to include a self-built low impact development using straw bale, just as much as a high-tech developer-built home. I need to find a simple set of criteria which I can use to determine what homes should be included in the database. It needs to be simple in order to be open and accountable to users, and to be as inclusive as possible while also setting a high bar as to what an eco-house should really represent. I have devised a list whereby if a house has any one of the criteria below then I consider it to be an eco-house:

  • Reduce energy use in some form (i.e. ground source heat pump)
  • High level of insulation
  • Use of renewable technology (photovoltaic’s, solar water heating, wind turbine)
  • Solar passive design (or shading)
  • Extensively used reclaimed or recycled materials
  • Reduces waste produced (for example eco-sewage systems or recycling of brown water)
  • Double or tripled gazed windows with a U value of 1.5 Wm2k or lower
  • Low carbon or zero carbon house
  • Rainwater harvesting or water collection systems, low water-use appliances, reductions in run-off
  • Deliberately small or compact design to reduce resource use
  • Green or grass roof for increased insulation
  • Grass roof for wildlife
  • Use of ecological materials like adobe, straw, sheeps wool, hemp, sand bag, reclaimed bricks, or wood (if FSC or reclaimed)
  • Passivhus standard
  • Deliberate avoidance of using environmentally damaging materials (such as concrete, lead, bricks etc)
  • Built using locally available materials
  • Heat recovery systems
  • Level 5 or 6 Code for Sustainable Homes
  • AECB Silver or Gold Standard
  • BREAM Eco Homes Standard level ‘Excellent’
  • Energy Performance Certificate (EPC) Rating A
  • Air tightness of less than 5 m3/m2hr (air movement) at 50 Pa

I would be interested to hear people’s opinions on this list and whether it is acceptable to enable buildings to be considered ecological by doing just one of the above. There are obviously important relationships between these criteria. For example, installing photovoltaic’s on a poorly insulated house is not very efficient, just has having highly insulated walls but low quality windows reduces the effectiveness of the insulation. However, to account for the relationships between these criteria significantly complicates defining an eco-house. There are an infinite set of possibilities available as we redesign our homes, but how do we define in an age of such building diversity when a house is an eco-house?

[7th November, Leicestershire]