My question is about insulating the ground floor. I have a crawlspace under the floor which is vented and therefore quite cold (average temp in the winter is 4 °C and in the summer 13 °C plus there are loads of cold winds).
I think I would like to do it without stripping all the flooring – I would like to use the crawlspace to insulate it from below.
I have spoken to some 'well versed colleagues' and there is no consensus – options that have been suggested so far are
- Squeeze blocks of styrofoam between the joists from below
- 'Hug' entire floor with insulation foil from below
- Take glass wool and 'hang it' between the joists with some foil or panels
Now I am not sure which method is best (or none of the above?).
Can you please suggest best course of action?
Best Answer
There's nothing wrong with fiberglass insulation beneath the floors. It will be, most likely, the most cost-efficient solution.
If you have a situation where critters like the insulation, well you have a vented crawl space! Critters get in there.
If you have an issue where the insulation gets moist and sags, the problem is not the insulation, it's a moisture/humidity/temperature issue! If you have, especially during the summer, humidity circulate beneath the home and begin to soak into the insulation, you have a more serious problem and using a different insulation only ignores or covers it up.
Not knowing exactly where you are, putting plastic sheeting on the bottom of the joists is a potentially dangerous idea! You are setting up a temperature difference between subfloor and bottom of joist, and then trapping moisture in that area. A plastic 'vapor barrier' in this area can cause a substantial amount of condensation on the joists leading to wood rot.
Plastic on the soil.