Blog by Dr Craig Jones
There comes a time in the life of every building where extensive refurbishment is required. For many a building this seems to bring with it thoughts of starting again – essentially to demolish and ‘rebuild’. The normal practice in modern times seems to be the preference to demolish and replace. Whereas conservationists naturally prefer to retain existing structures so to repair them and bring them back to their former glory. This latter approach retains the existing character and heritage of a building, but proponents of the ‘remove and replace’ philosophy ague about their reduced energy performance. They argue that bringing an asset back to its former glory is no longer good enough, and that they can’t be brought up to modern energy efficiency standards without being entirely replaced. But what does the environmental analysis actually tell us, does it support refurbishment, or does it support replacement? This article takes a look at this intriguing question.
Historically the arguments around repair or replace have neglected this all too easily forgotten embodied carbon. However, it clearly must be considered. Whilst it is true that many older buildings cannot be refurbished to the same energy standards as modern construction the additional impact of new materials must be considered. Through retaining the existing structure the refurbishment requires less materials and therefore less embodied carbon. But is this enough of a carbon swing to sway in favour of refurbishment?
Whole life carbon – embodied and operational carbon
To answer this question correctly the embodied and operational carbon needs to be considered side by side, which is called the whole life carbon footprint. Let’s start by looking at embodied carbon. Embodied carbon is all too easily forgotten and is apparently concealed from our view. In fact, most people are unaware of the high environmental impact of making the products they consume.
The average new build house in the UK releases around 45 tonnes CO2e (carbon dioxide equivalent) in its construction. This is enough carbon to:
- Power a UK light bulb continuously for over 450 years; or to
- Power a TV for 2 hours a day for almost 1,440 years; or to
- Drive around the earth almost 10 times; or to
- Drive all the way to the moon.
[For more information on these see What is a tonne CO2e]
This is just the embodied carbon to construct a single UK house, which are also amongst the smallest houses in Europe and around a third of the size of North American homes. The amounts are naturally more significant for non-domestic buildings and for larger domestic estates.
Operational carbon footprints of buildings
To rebuild the house 45,000 kg of carbon dioxide is required. It therefore takes 34 years before the savings in operational carbon have matched the extra embodied carbon that has been spent to rebuild the house. This is particularly significant, because if you include the time to build the new house it will be around 2050 before the carbon starts to payback. The UK has legally binding targets to reduce its carbon emissions by 80% by 2050, from a 1990 baseline. Rebuilding the UK housing stock therefore doesn’t help us to meet these targets. Instead we must look to refurbishment to help with this challenging target.
Refurbishment of buildings
There are of course many products that do not impact on the operational carbon of a building. The refurbishment of such materials and products typically brings with it a carbon benefit. By retaining existing materials there is an avoided need for new materials and products.
Reducing embodied carbon
Beyond this there are savings to be made through material choices. One of the rules of thumb is timber first. Timber is a natural material that has a wide range of uses and has a relatively low environmental impact to produce. Therefore if timber materials and products are a realistic selection it’s usually a lower carbon option. Timber from sustainably managed sources also sequesters (stores) carbon, which is a carbon footprint benefit. Timber is composed of approximately 50% carbon by mass. Carbon is therefore part and parcel of the material. What’s more this carbon has been extracted from the atmosphere through photosynthesis. The carbon is stored in the timber and away from the atmosphere, until the end of the life of the product. In fact, the carbon storage element of timber means that it is storing more carbon than was released to produce the timber product itself. This often results in a large carbon footprint benefit and partly explains why the timber first principle works well.
Another good saving is the use of water based paints instead of solvent based. A water based paint is around a third lower carbon footprint to make than a solvent based one (Inventory of carbon and energy database). Paint has a high embodied carbon and often multiple layers are used. Therefore using less layers of paint, where possible, is another good way of reducing its impact. Finally, on the topic of paint, an obvious quick win, but one that is regularly overlooked, is that painting less often has a large benefit. Repainting a room, or an object too often makes a considerable difference to its whole life carbon footprint when we are talking about 50-100 year timescales.
Allowing deconstruction – facilitating a circular economy
There are naturally some instances where embodied carbon doesn’t need to be considered. For example, the embodied carbon of additional insulation almost always pays back through operational carbon savings. There are some insulations that have lower embodied carbon to produce. But if this comes at the expense of a considerably worse thermal performance then they are unlikely to be an attractive whole life carbon choice.
Is refurbishment best?
Essentially when it comes down to the choice of refurbish or replacement, to retain or rebuild embodied carbon often becomes a useful ally. The arguments of reduced thermal performance of refurbished buildings should be met with questions of the additional embodied carbon expense of the new build. Whilst there are cases where rebuilding is the best option, there are considerably more where refurbishment is a better choice. Furthermore, without the choice of refurbishment the UK would lose too much charm and too much character from its older and charming building stock. No doubt with the UK’s looming 2016 “zero carbon” homes new analysis will be required.
Finally, it should be appreciated that embodied carbon is only one of many environmental sustainability and circular economy criteria, from which full life cycle assessment (LCA) would add an interesting insight.
A version of this article originally appeared in the 2015 edition of the Building Conservation Directory.
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