Room above garage - odd suspended floor & insulation

14 Jan 2022
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United Kingdom
Hi All,

Looking for some guidance. Our property has a side extension with a bedroom above a garage. We've recently topped up the loft insulation and fixed a leaky window which has helped, but the room still has a cold floor (almost like a heat sink) so doesn't stay as warm for long enough. Running a thermal imaging camera on this confirmed my suspicion as the floor is almost 3 degrees colder than those in the other rooms (all non carpeted currently).

Usually I'd say this would be a simple job, just PIR or mineral wool between the joists, but we have an unusual set-up that might allow for an easier job than lifting all the boards. The bedroom is effectively built on its own separate joists to the ceiling joists of the garage, creating its own isolated sub-floor. I've attached some photos of this and a crude image showing the set-up.

My question is, whether we can just roll 200mm mineral wool on to the floor of the suspended sub-floor? Its quite thick and can take weight, but I don't know if this will have the same effect for heat retention as putting it between the joists. Any ideas?



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