Housing Specification Blog

Home truths about housing longevity

November 28, 2012 Alexandra Blakeman Planning & Legislation

Today HS welcomes H+H’s Managing Director, Mark Oliver to the blog. He talks about the importance of providing a frame requirement for building longevity.

Mark Oliver

In an environment of increasingly stringent regulations for new builds, it seems odd that no one appears to be asking for a minimum lifespan for a building. This crucial question has apparently taken a back seat to other design considerations.

It is noticeably absent from the recent London Housing Design Guide too. Acting as a blueprint for housing built in the city, the guide gives consideration to room sizing and waste disposal but neglects to frame a requirement for building longevity.

Though there does seem to be a general acceptance of the 60 year figure, moves are being made to introduce a 50 year reference period for Life Cycle Assessment studies. Considering the 60 year figure, which is the basis of BRE Environmental Profiles,  seems to have originated as more of a financial model (being used as the time over which financial assets are written down) I would argue that implementing a 50 year reference period to LCA studies is a bit of a step backwards.

Recently a colleague of mine tried to re-mortgage his house (a lightweight timber structure) to build an extension. He was unable to on the grounds that his lender was not confident that its life expectancy would exceed 20 years. In comparison, I had just successfully negotiated a re-mortgage to extend my own house – a masonry structure built in 1840.

Clearly the anticipated life span of a building is influencing decision making but with no real established way to measure this factor.

Then I started thinking about our own housing situation in the UK: 39% of houses are over 65 years old. What’s more if we continue to build houses at the current depressed rate then any house built today will need to last for over one thousand years

Making longevity an objective would have a huge impact on the way buildings are designed and built. For builders, the way houses are built would be significantly impacted because designers would have to lend consideration to the embodied as well as the operational carbon footprint of new buildings.  Given how long our houses are going to need to last, this is surely a more sustainable approach.

Consider a recent NHBC Foundation study which compared operational and embodied CO2 in different types of new build houses. It used 60 and 120 year life cycles upon which to base the calculations. However, nowhere is there any data that supports the assumption that all of the building types will actually last for 120 years. The performance of the buildings is being assessed without accurately evaluating their personal longevity.

The fact is we urgently need new housing to accommodate our growing population. All construction uses resources, so the fewer houses we have to build the better. It is definitively not a sustainable approach to build houses to a fifty year life expectancy.

If we establish a focus on building energy efficient structures with efficiency built right into the fabric, then now would be a good time to consider some kind of longevity calculator that would work in a similar way to SAP calculators. This way we could define an acceptable and logical minimum lifespan for the structural elements of the building fabric.

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