Underfloor Insulation

Sophie4120

Hi all,

In the interests of saving energy in the long term, we have opted for underfloor insulation throughout our ground floor (suspended timber floor). Insulation is mineral wool on netting suspended between the joists. 

However... post-install, and we're still getting draughts coming up through the sides of the carpets/where the skirting meets the floorboards. The installer suggested it was coming from behind the skirting, and therefore probably from the wall cavity rather than under the floor. Admittedly the draught is stronger where there are bigger gaps between the skirting and the floorboards, but I don't know enough about housebuilding to know if this is correct? 

The reason I'm a bit hesitant to take this at face value is that we're also getting a significant draught coming from another corner of the room that does not touch any external walls... 

Ultimately, I'm trying to guage if it is reasonable for us to expect no draughts from around the edges of the room after we've had underfloor insulation installed? Just feeling a bit disheartened that we still have cold draughts coming through, after spending a lot of money on something we thought would fix it!

jennifernil

I do not think insulation suspended on nets would be 100% draught proof, Kingspan would probably have done a better job, but very difficult to fit to an existing floor.

What you need to do is seal off any gaps between floors and skirtings, if these are large you may need to use something solid.    There was a thread about what to use,  on here, a while back

Sophie4120

Just wanted to update this one - they came back out to check, and insisted that they had installed it correctly.

Some months later we had some electrical cables routed under the floor. Upon lifting a couple of floorboards, we found that the installation was an utter shambles - they hadn't bothered fitting any insulation along four full joist runs, and, where they had fitted it, had stopped nearly a foot from the edge of the room. No wonder we still had draughts! 

It took some battling, but they eventually came back to re-install. This time they took all the floorboards up, it really was shocking how shoddy a job they had done - I guess they had banked on the fact that nobody would go back under the floor to check their work...