Architect Simon Sturgis explains the circumstances around whether it's best to retrofit or rebuild.
Interview with Simon Sturgis
For the last 8 or 9 years, Simon Sturgis has been looking at the issue of carbon in construction. This followed a period of doing a lot of retrofit work where it seemed that huge amounts of only partly used materials were wastefully being thrown away. They decided their challenge was to be whether this could be quantified, which developed into the idea of carbon valuing: a valuation using carbon as a currency of sustainability.
“To make anything takes up energy, and depending on where it’s made, it determines the sort of energy”
People were already familiar with measuring energy usage in buildings, but Simon explains they were keen to come up with something equally familiar that related to materials, and the problems around the negative aspects of how they're made.
Where the material is made will determine the kind of energy that is used to make it. For example in Norway it would probably have been made using hydroelectric energy, however in the UK it would more likely have been using gas and oil.
“So it’s really understanding that and trying to redirect our ability to make things away from, if you like, damaging carbon intensive technologies.”
Ensure any new building has the ability to be recycled and re-used
Simon discusses what you should consider if you're thinking about demolishing a run-down old building to replace it with something new. He says that if it's falling apart then it's probably better to take it down and dispose of and recycle it as best you can, but build something in its place that fulfills the durability factor that the previous building didn't have.
In your new building, consider whether it is capable of easy recycling or adaptability and re-use. If you're constructing it from brick then you might be confident it will last a couple of hundred years, but if you're using timber you might say that it's not going to last as long but at least it can be adapted, re-used or moved to do other sorts of things with it.
A change of mind-set is needed
People need to change their way of thinking to a ‘circular economy'. Simon explains that in the City of London office buildings have an average life expectancy of around 17 or 18 years, which clearly is going to have a huge carbon investment. He believes that there should be planning at the outset for a building's eventual disposal, and with the expectation that when you've finished with the building it can be taken apart and the elements distributed to be re-used in other buildings, not necessarily in the same place.
If you intend to re-use things you need to consider right at the beginning how they will be put together, in order to make it possible to dismantle and re-use them, i.e. using a lime mortar that can easily be removed from bricks, instead of cement mortar.
Simon uses the example of a two-storey office/shed type building where, because of its steel bolt and aluminium construction, they were able to help a client to take it apart, move it to a more suitable location, and re-build it, while tidying it up as they went along. They were able to re-use around 70% of the materials and along with significant carbon benefits, it cost 25%-30% less than a new building of the same size.
The cost of recycled products can be prohibitive
This may seem counterintuitive at a glance, but it's cheaper to buy new bricks than old ones. Largely this comes down to the cost of cleaning up the bricks from a dismantled building is high.
However Simon suggests that if the process of cleaning the bricks was paid for through social value, for example being done by people who might otherwise be in prison, then not only could the recycled brick be bought for the same price as a new one, but you're also contributing to social issues and turning the demolition process into a positive one.
You can't necessarily demolish any building
If thinking about demolition, consider the following:
- Whether it has listed building consent or is in a conservation area.
- Possible health and safety issues if the building you're demolishing is next to a sensitive site or railway line, etc.
- Whether there are issues to be resolved due to party walls.
A high standard of retrofit may have the lowest carbon impact
Sturgis Carbon Profiling produced an article looking at carbon emissions over a period of time in 3 different scenarios.
The first scenario was the carbon cost of maintaining an existing Victorian terraced house – principally in heating and energy use.
The second scenario looked at taking that same Victorian terraced house and upgrading it to a high standard. While that does take a lot of material going into the building, it does make a huge difference to the performance and requirement for heating.
The third scenario looked at building an entirely new Passivhaus, with its high levels of insulation and airtightness.
Their analysis considered both the carbon emissions from the materials used, together with carbon emissions from day-to-day use. What they found was that, based over a 60 year period, it was better to retrofit the existing terraced house to a high standard than it was to build the new terraced house. The reason for this is because there is so much energy used in producing bricks and other materials for the new build.
“So it’s not necessarily the case to say you should demolish Victorian buildings if you want to get a highly efficient carbon outcome. You need to make them work better… And in a sense we're doing society a good service by re-using things rather than flattening them.”
Find out more
Visit the website of Sturgis Carbon Profiling
The Hub update
The Hub is an extra learning and networking resource, tying together everything we've learnt from our podcasts, together with extra information and interviews. We have video case studies and currently have a number of short videos showing the different stages of the Long Barrow Passivhaus project that we've been following. We'll also soon be confirming details of our second case study.
Each month we're also adding a new module which lays out different parts of the self-build process in simple steps.
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