Drawing up a brief for a ‘sustainable’, low-carbon home

So, you have decided to build a sustainable low-carbon home, but don’t know where to start? ‘Eco-house’ proponent, Ranald Boydell, considers the brief you might provide your architect and builder…

IT is easy to imagine that, while many people might want to live in a house that is ‘eco-friendly’ – and seek to pursue high environmental standards if seeking to build their own home – they might also not know where to begin.

In any discussion with an architect or builder, one might wish to kick-off by considering ten chapter headings, the first three being: ‘fabric first’, ‘passive solar design’ and ’embodied carbon’.

A ‘fabric first’ brief looks at the external ‘envelope’ of the building, with particular regard to energy efficiency, involving high levels of insulation and air-tightness.

Meanwhile, ‘passive solar design’ is about maximising the sun’s energy, through the building’s orientation and the placement of windows.

And ’embodied carbon’ considers the carbon emissions during the production (of materials) process and also during the building’s construction. Says the UK Green Building Council, embodied carbon is “the total greenhouse gas emissions (often simplified to ‘carbon’) generated to produce a built asset. This includes emissions caused by extraction, manufacture/processing, transportation and assembly of every product and element in an asset.”

While these three issues are mainly about carbon – with the aim being to minimise carbon emissions over the whole life of the building – the next three are about broader sustainability and environmental issues, and are mostly about the specification of materials used rather than the design.

Firstly, ‘circular economy’: covering a range of issues, such as resource use, recycled materials, reducing waste, and mitigating pollution or the use of toxic substances.

Next, ‘ventilation and air quality’: which is fundamentally about health and well-being, ensuring there is adequate ventilation throughout the house – naturally or mechanically-driven – to avoid the build-up of mould and other toxic compounds.

And then, ‘natural building materials’: simply, seeking to avoid the use of oil-derived, highly-processed or toxic materials.

The next trio of issues are about how the building might interact with ‘systems’ beyond its footprint:

(1) ‘Regenerative design’: how might the proposed building enhance bio-diversity?

(2) ‘Local sourcing’: supporting local employment and reducing transport demands.

(3) ‘Smart systems’: optimising the use of the power grids and other public infrastructure.

And so we reach No.10, ‘appropriate renewable technology’: namely, the use of on-site renewable energy sources such as solar panels, heat pumps, wind turbines, ‘micro hydro’ and biomass boilers.

I’ve placed ‘appropriate renewable technology’ last in the list for a reason, even though it’s probably the first thing many people would think of when asked, What makes a house ‘sustainable’?

The decision to install on-site renewables should be primarily about whether you require to be self-sufficient (perhaps living ‘off-grid’ if your build site is remote and it is considered too expensive to connect to power grids) or whether you have concerns about the reliability of the power supply.

Investing in renewable technology might be a financial decision (especially if supported by government or other grants), as opposed to a sustainability one. Their installation might increase the value of the property, because their manufacture and transportation will involve carbon emissions.

The truth is that much of the power grid is now from renewable energy sources. Specific ‘green’ tariffs from a power supply system that is being increasingly ‘de-carbonised’ are now widely available in the marketplace.

Renewables are a really important part of sustainable housing, but they are probably the last link in the chain, rather than the main driver.

Ranald Boydell has been described as a ‘sustainable homes pioneer’ and the Scottish Borders-based Australian is currently working on several projects to increase energy efficiency outcomes in construction, including a grant-funded project to build a prototype low-carbon home with full post-occupancy monitoring of performance, known as ‘ecohus’. Visit http://www.ecohus.co.uk

Image courtesy of Ranald Boydell

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