I live in a terraced house in Balsall Heath, Birmingham, which is having major energy efficiency improvements. My house is part of Balsall Heath Housing Cooperative, a small resident-controlled coop with 77 homes. Mine is one of 22 older homes that’s part of the project. The larger measures are being funded by the Coop (part funded by the Social Housing Decarbonisation Fund) and installed by the Coop’s contractors, I am paying for and installing some of the smaller measures myself.
My front room has a suspended timber floor. I did a heat loss calculation on my house, which showed major heat loss through this floor. The Coop appointed one of its regular contractors, L Daniels, to undertake the insulation.
Following a conversation with the contractor, it was agreed that the solution was:
- Risk assess the adequacy of the existing under-floor ventilation, and the condition of the floorboards, joists and foundations, to make sure there was no disrepair, as it’s not safe to insulate if ventilation is inadequate or if there is disrepair to the building fabric
- Pro Clima membrane – an air tightness and vapour control membrane – immediately below the floorboards. Pro Clima is miraculous – it reduces unwanted movement of air, therefore reducing draughts, and allows airborne moisture to pass through it, reducing the risk of condensation damaging the floorboards, joists and foundations. I like to think of it as like the materials that they make professional athletes gear, or spacesuits from – it stops heat from moving where you don’t want it to move, and allows the building fabric to sweat moisture.
- Airtightness tape to seal the gaps where the floorboards meet the external walls under the floor (it’s an end terrace).
- Rigid Recticell insulation batts between the joists to a depth of 100mm.
- This leaves a gap below the insulation of at least 150mm for ventilation.
This complies with good practice guidelines on suspended timber floor insulation published by the government.
I do not have any hot water pipework going under this floor, as most people do where there’s a suspended timber floor. If there is hot water pipework under the floor, then under-floor insulation is also a good opportunity to insulate the under-floor pipework.
It was important to do under-floor insulation before the front room has internal wall insulation, which is due to happen by the end of March 2025.
The impact of the under-floor insulation was immediate, it immediately feels warmer, and you don’t get the ‘warm head cold feet’ feeling that you get with an uninsulated floor. I used an infrared thermometer on the floor before and after and it shows that the insulated floor is warmer than before.
I have calculated the predicted energy and carbon savings from the insulation. It’s important to note that the fuel bills savings are expected to be modest, and that under-floor insulation is primarily a thermal comfort measure, as part of a whole-house package of measures to reduce the greenhouse gas emissions from the house. I will be monitoring the energy and carbon savings over the next 12 months and will publish them on here
I removed the existing laminate floor to enable the under-floor insulation to happen. The laminate was 25 years old and quite worn. Next step is a new floor covering, I have decided to go for bamboo flooring as it has lower environmental impact and I am told by others who have it, that it’s easy to fit. I’ve been watching videos about how to achieve a herringbone effect with bamboo flooring!
One interesting feature of this process has been the relationship between floor insulation and Energy Performance Certificates. The rear living room of the house has a solid floor. I am going to put Superfoil solid floor insulation down in this room. It is not clear what the impact on the Energy Performance Certificate will be. EPCs on homes like this (tens of thousands of them in inner city Birmingham) will typically say ‘suspended timber floor, uninsulated’ which is an easy mistake to make (I myself had forgotten that the back room had a solid concrete floor – when I recently lifted the laminage in the rear room, I saw that it was solid concrete and the memories came back of kneeling down on a concrete floor for two days to put down laminate floor, armed only with a hand saw and my Dad’s Black and Decker Workmate). Because you need to do two different insulation methods in the front and back rooms, I am not sure what impact this will have on the EPC score. We’ll see when the EPC assessor gets here at the end of March to issue the final EPC. Fortunately the other measures will make sure the EPC ends up as a B. But EPC rating is less important than the actual carbon savings – which I will calculate myself – and the comfort of an energy efficient house – which you can’t measure.
