Warm feet, thanks to insulation of a solid concrete floor in my house
I live in an Edwardian end-terraced house in Balsall Heath, Birmingham, which has recently had 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 from its own financial reserves, and part funded by the Social Housing Decarbonisation Fund., I am paying for and installing some of the smaller measures myself.
I had a bit of a shock when I took up the old laminate floor in the back living room. I had assumed it was a suspended timber floor like the front room. Imagine my surprise when it turned out to be a solid concrete floor (covered with tiles that were in fairly good condition considering their age)! I should have known by the absence of air bricks at the back of the house under the floor level, but I had mistakenly assumed that they had just been erroneously blocked, as often happens. I should have remembered that solid floor from when I laid the laminate floor 20 years ago on my hands and knees armed only with a manual saw!
So we had to change the insulation strategy for the rear living room. The solution was Superfoil, which goes between the concrete sub-floor and the floor covering, and is wrapped under the internal wall insulation to create a thermal break. This is important because in houses of this type, the walls don’t always meet the floor evenly, creating a thermal bridge which shows up as a red streak when you do thermal imaging. Superfoil consists of multiple layers of foil, and it acts mainly by minimising heat loss due to radiation (whereas under-floor insulation of a suspended timber floor like in my front room, acts mainly by minimising heat loss due to convection of warm air downwards through the floorboards into the 30cm crawlspace under the floorboards).
The first step was during the installation of internal wall insulation to the external walls of the rear living room. This consisted of the co-op’s contractors folding a 30cm layer of Superfoil under the new plaster that went on top of the wall insulation, under the new skirting board, and on the solid concrete floor, ready for floor covering.
We then bought an electric underfloor heating mat and got in an electrician (JB Services) to connect it up and leave it rolled up, ready for the next phase. Which was to tape more Superfoil on top of the whole concrete floor tiles, overlapping the 30cm of Superfoil already there. Then we unravelled the electric heating mat, leaving it turned off at the wall (it also has a smartphone app with thermostatic control/timer). Then we put plywood on top, as recommended by the seller of the next layer – bamboo flooring tiles from the Bamboo Flooring Company in Leicester. We did this in a herringbone pattern.
Update 27 October 2025 – it’s now cold outside but the floor feels warm underfoot, even without the under-floor heating on. The bamboo floor covering is retaining heat much better due to the Superfoil insulation.