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Floor it! The race to insulate is on after new study on raised timber floors

Posted by Sam Tonge on 1 September 2017 at 11:03 am

New research has provided some food for thought when considering heat loss from within the floor of your home. Suspended timber ground floors in the study were found to lose twice as much heat as had been previously estimated. This means that if you live in an older property it’s likely that the capacity for increasing your floor’s thermal efficiency is much greater than you may have originally thought.

The research paper has studied in new detail the role of suspended timber ground floors in perpetuating heat loss within residential properties. Approximately 6.6 million homes were built in the UK before 1919, when suspended timber ground floors were the leading method of construction.

With this design, suspended timber floorboards are attached to floor joists, which are then suspended above the subfloor of the foundation. These joists are raised above the subfloor on small supporting walls called tassel walls (or sleeper walls). Such a design can leave space for ventilation preventing moisture build-up, however it also results in thermal inefficiency from high energy consumption for space heating which then quickly seeps through gaps in the building fabric.

The results of the study found varied heat flow throughout the suspended timber floor properties tested, with increased heat loss near the edge of houses. U-values ranged between 0.54 ±0.09 W/m2K, away from the external wall perimeter, to values nearly four times as high (2.04 ±0.21 W/m2K) along the edges.

These results show much greater thermal inefficiency of suspended timber ground floor properties than expected. This might lead you to question whether such properties can play a bigger role in helping us meet our national carbon emission targets as part of our commitment to the 2015 Paris Climate Agreement.

Here at YouGen we would like to reflect on these results as a renewed incentive to fill in our floors to keep ourselves warm and our carbon emissions down.

Insulation has long been recognised as a fundamental part of retrofitting older homes to improve their energy efficiency. A fabric-first approach effectively fills the gaps between walls, ceilings and rooftops, as well as floors too.

If you’re looking to insulate but you’re not sure what type of floor you have, a good way to tell is by looking to see if you have airbricks outside. If so, this tends to indicate that you have a suspended floor, meaning there’s plenty of room for insulation. This could be in the form of mineral wool or loose fill insulation hung in netting. You would also need to seal any gaps between boards, and between the floor and the wall to ensure airtightness and effective draught-proofing (see our recent blog entry on balancing airtightness with ventilation).

Some old homes can be considered hard to treat, with work requiring the expertise of a skilled carpenter. Care must also be taken with the structural aspects of the house, to avoid excess build-up of moisture. In some cases the floorboards may be too delicate or valuable to lift up, meaning the only option is to seal the gaps in between them. For detailed guidance, it’s worth checking out the document provided by Historic England which is specifically targeted at those looking to insulate suspended timber floors.

Ultimately, there is no one size fits all solution, so it’s important to make sure that your insulation works for you and your home. Although the study shines new light on the potential for suspended timber floor insulation in improving energy efficiency and reducing carbon emissions, such construction methods form only a small proportion of our housing stock. This means that floor insulation must be combined with a wider-scale approach which includes effective insulation across the house along with draught-proofing and adequate ventilation.

More information about Insulation on YouGen.

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Image credit: ACME

About the author:

Sam has contributed to our blog since 2016 and previously worked for the National Energy Foundation.

He became interested in green energy after completing a degree in Geography (BSc) at Royal Holloway, University of London. 

Sam is passionate about renewable energy and is committed to spreading the word about the role it plays in delivering environmental sustainability. 

If you have a question about anything in the above blog, please ask it in the comments section below.

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