by greenspree » Fri 04 May 2012, 08:47:31
$this->bbcode_second_pass_quote('davep', 'S')CF, you may find that rock-based insulation between the basement and the house could be very good thermal mass, slowly radiating heat into the ground floor. But I'd need to know more about what you intend using. Something based on clay would be ideal for retaining heat. You certainly shouldn't need any kind of heat insulation between the two, given your heat source is below ground.
Mineral wool (or rockwool, common brand name Roxul) is mostly air, as are all batt insulations and will provide very little thermal mass. Thermal mass also has no effect on heating costs if you are paying for your heat source, only if the mass is collecting free heat (i.e. solar heat) and releasing it when needed.
Heating an unused basement is very wasteful and I would recommend insulating between living and non-living spaces.