Reuse Buildings, Reduce CO2

For old brick houses, it’s as energy-efficient to renovate — and possibly more so — as it is to tear down and build new. That’s the conclusion of a study by the Empty Homes Agency, a UK nonprofit that works to bring empty homes back into use.

Large homebuilders in the UK claim that new construction is many times more energy efficient than older properties like Victorian houses. That’s true for operating energy, counter the environmentalists, but what about “embodied” energy — the energy it takes to manufacture building materials? Until this study, no one had calculated the relative importance of each. After analyzing three renovated and three new houses, the conclusion was this:

Previous studies and much of the accepted thinking on domestic CO2 emissions have suggested that demolishing existing homes and building new homes to replace them will contribute to an overall reduction in CO2 emissions. This study suggests that this is not so, and that refurbishing existing homes and converting empty property into new homes can yield CO2 reductions by preventing emissions from embodied energy that would arise from new build.

In the extended entry, more quotes from the study “New Tricks With Old Bricks.”

New Tricks with Old Bricks
How reusing old buildings can cut carbon emissions
Empty Homes Agency, March 2008

The premise of the study:

Conflicting claims

“New properties are “greener” than older ones”Sunday Times, October 2006.

“New homes are more environmentally friendly and sustainable than at any time in recent history” – Home Builders’ Federation, 2007.

New homes are over four times more energy-efficient than older homes and therefore ‘greener’ – Smart New Homes, 2007.

“New homes can be up to eight times more efficient than a typical Victorian property” – Peveril homes, 2007.

It is increasingly common for developers to make environmental claims for the buildings they produce. A significant body of wider opinion holds that demolition of existing housing and replacement with new housing (built to high energy efficiency standards) is broadly preferable in many cases to refurbishment. A key foundation of this argument is that the operational (in-use) carbon emissions of highly efficient newly build housing can be far lower than those from existing properties. Often these claims are well founded. It is undoubtedly true for example that new homes are better insulated than homes built in the past; when the majority of the UK’s older houses were built there were no mandatory standards governing energy efficiency or thermal comfort. Some claims however are harder to quantify. Assertions of the superior environmental performance of new housing are sometimes used by developers and regeneration planners to justify supplanting existing homes with new homes. It is also sometimes used to explain building new developments when there is an existing supply of unused buildings that could be used.

Why the homebuilders’ claims may fall short:

A contrary argument also exists and is increasingly used by environmental campaigners and heritage organisations in promoting alternatives to new development. Their argument is that new buildings consume huge quantities of energy in their development, energy that could be saved by reusing existing buildings. In addition, the high standards of energy efficiency assumed for new buildings are entirely dependent on enforcement and achievement of very high construction standards.

There are also critical elements missing from the calculation: the carbon embodied in existing buildings, the energy required to demolish them and dispose of any waste (around 24% of all waste is generated by demolition and construction), and the energy cost of extraction, production, transport and use of new materials – not to mention the wider environmental effects of minerals extraction and demolition and construction disturbance.

What’s new about this study:

But would there be a net environmental dividend to [reusing old buildings], as environmental campaigners claim, or, as some developers claim, a net environmental cost? Whilst there has been much research on the environmental impacts of housing, most has focussed on the use of energy used in the home once it is occupied (operational energy). Very little has been carried out into the environmental impacts of building and redeveloping homes (embodied energy). And until this paper none has considered the relative importance of each.

The methods and assumptions of the study:

The research calculated the carbon dioxide (CO2) emitted in the manufacture and transport of every material and component that was used in the construction of the new houses and the refurbishment of the existing houses. This is termed embodied CO2. The research also projected the CO2 that would be emitted by each house over a fifty-year period into the future. This is called in-use or operational CO2. Adding these figures together for each house provided what we termed a lifetime CO2 cost for each house. Fifty years was not intended to represent the expected lifespan of the house but to represent the likely period before a major refurbishment might be expected. This would provide the next opportunity after initial development in which the environmental performance of the house could be reconsidered and changed.

Appendix 2: Limitations

This study has not taken account of the energy used on site during construction or the possible end-of-life costs such as recycling or disposal of demolition waste. This means that the quantities of materials considered are likely to be an underestimate.

The key conclusions:

The study shows quite remarkably that despite very different approaches taken to producing new homes, the total CO2 emissions for each were very similar.

Previous studies and much of the accepted thinking on domestic CO2 emissions have suggested that demolishing existing homes and building new homes to replace them will contribute to an overall reduction in CO2 emissions. This study suggests that this is not so, and that refurbishing existing homes and converting empty property into new homes can yield CO2 reductions by preventing emissions from embodied energy that would arise from new build.

Whilst embodied CO2 emissions associated with building and developing and refurbishing homes are a relatively small proportion of the total CO2 emissions from housing [Ed: 10% for refurbished housing, 28% for new housing], omitting them from future projections of domestic CO2 emissions is highly misleading, overestimating the CO2 savings new homes can make and underestimating the potential of refurbishing existing homes and returning empty homes to use to help cut emissions.

Additional resources

News coverage of the “New Tricks With Old Bricks” report

4 responses to “Reuse Buildings, Reduce CO2

  1. Kent Evans

    I’ve renovated 5 houses, three which my family moved in to. I took attention to the costs redoing the fifth structure and even though there were more contingency expenses than the first four, it cost $65/sq. ft. to rebuild. This is cheaper than building new for sure. A Cincinnati based web site chose to write a feature on this: It is at building-cincinnati.com and the article is archived on June 11, 2008.

  2. Laurence Aurbach Post author

    Thanks for the cost info, Kent. And here’s a link to the Building Cincinnati feature. There’s a description and photos of the rehabbed home in the Lower Price Hill neighborhood. Good work.

  3. chirag

    i as a spectator would like to share my opinion, i feel that rather than co2 levels we should also see the facts that when a building is demolished then the pollution from the dust and free lime that is put into the atmosphere is far more than co2, also the cost must not be considered the sole factor for demolishing a building, buildings surely have attachments in people.

  4. Laurence Aurbach Post author

    I disagree that dust is more of a problem than CO2 (unless it’s toxic dust); human exposure to particulates from demolition is relatively time-limited and can be controlled with proper operating techniques.

    The point about human attachments is important. Steve Mouzon calls this quality in buildings “lovability” and observes that the most efficient use of energy and materials is in buildings that people love, so that they last a long time and contribute a positive feeling to their surroundings.

    Mouzon writes about Lovability on his Original Green website, and in the collection Green Architecture and Urbanism.

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