Monday, May 2, 2011

Trying to finish our underfloor insulation

Although we live in the cool climate of Orange, at just over 900m altitude - with snow on the ground for a couple of days most years - we have a house of floorboards because we have a couple of asthmatics. Carpets and asthmatics are just not compatible - but having floorboards at Orange makes for a cold floor in the middle of winter. The solution - to put in under floor insulation.

Last year we installed insulation under the floor boards in the lounge room - at the moment we are desperately trying to finish the underfloor insulation under the bedrooms and the rest of the house before winter arrives.

We are using underfloor insulation that is a polystyrene board with an outer layer of reflective foil on both sides.  The boards work in two ways;
  1. The boards are a polystyrene layer with reflective foil on both sides - so the boards themselves reflect the heat back up into the house and the polystyrene layer reduces heat lost.
  2. By screwing the boards in under the joists between the bearers under the house, then sealing the gaps and joins you have an still insulating layer of air between the floorboards and the insulation boards.
This is Dad at the short end of the house putting the insulation boards under the floor - we tech screw them directly under the joists between the bearers.  I get the job of cutting the boards up on the back deck. 

The kids act as messengers bringing out the measurements for me and taking in the cut boards back into Dad - they think it's great crawling (well walking most the time) in and out under the house.

So is it all worth it?  Not sure how to measure the temperature change or efficiency of having put the insulation boards under the floor... but the rooms that have been done feel less draughty when you walk on the floor boards in bare feet.  The real test is the difference over winter.

For comparison - when we insulated under the floor at our Forbes house and installed a reversible (winter / summer) ceiling fan it brought the winter room temperature up by about 5oC - which meant we did not have to run the heater as hot.

To complete the underfloor insulation is one of our Energymark group household goals on our action plan - to help reduce our carbon emissions through more efficient heating of the house.


  1. We're wanting to do something similar one day. We have carpet in only two rooms and those two rooms are seriously around 5 degrees warmer than the rest of the house in the middle of winter nights. I'm looking forward to hearing whether you think it made a difference. x t.

  2. Hey Tricia. Well before the really cold week arrived (-3oC and snow) we thought that the insulation was working really well... the draughts through the floor boards seemed noticeably less... but this week is has just been cold - too cold. I am sure they are making a difference but it is very hard to measure the change. Marita