The first winter in our new house was extremely cold. In fact, it was so bad, that Christine got chilblains on her toes!
One of the first things we did to tackle the cold, was to install insulation under our suspended timber floor in the living room. Thankfully we have a little dummy cellar that allowed us easy access to install the insulation boards from below, so that we didn’t need to take up the floor boards.
You can find general information about insulating under floorboards here.
We ordered the insulation boards online and after they were delivered, it was my job to crawl into the cellar and spend some time with the spiders, sow bugs and rubble that call this place home. It was rather uncomfortable, but I heroically stood up to the challenge.
We divided the work between us. To start with I measured the distance between the joists under the floorboards. As most of them weren’t parallel, I measured at both ends and in the middle to ensure a perfect fit of the insulation. Christine then cut pieces off the rigid insulation board according to my measurements (actually a bit wider so that they would definitely fit with no space on either side).
I then placed the underfloor insulation board between the joists.
As the joists were sometimes at an angle, the bottom opening between them was smaller than the gap at the top, just under the floorboard. This made it hard and fiddly to get the board into the correct position. Furthermore the gaps between the last joists and the walls were uneven, so that a few changes to the boards were needed to get the insulation to fit as snugly as possible. It is important, that no air can circulate around the insulation board; otherwise it would dramatically reduce the insulating effect.
Whenever an insulation board wouldn’t exactly fit between the joists, we filled the gap with a thick foam draught excluder to make sure no air would circulate up to the floorboards.
You have to make sure that any air bricks in the wall are not covered as they are there to ensure a good circulation of air around the joists to prevent rot.
While I was down there, I also insulated the pipes that ran through the dummy cellar. Because we have reduced the heat loss through the wooden floorboards, the dummy cellar will be considerably colder, which will make it easier for pipes to freeze and possibly burst in the winter.
The work insulating our living room floor took us the best part of a weekend, but we noticed a direct change in the room temperature of 1°C for the better. The work should also save us money in the long run as the cost of insulating the floor was about £100 but should save us about £60 a year in heating costs.
To improve the insulation and reduce draughts further, we also insulated the gap between the floorboards and the skirting boards, but we will tell you more about that another time.