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How do I insulate a room with a concrete floor and concrete roof?

mmarkose | Posted in Energy Efficiency and Durability on

This room is used year round. The room has a garage underneath the floor. The ceiling is also the roof which only has a rubber sheeted on the outside. We live in Pittsburgh which is very cold for a good 4-6 months of the year with snow, and reasonable amount of rain in the season.

The height of the room is only 7.5 ft. So interior clearance for insulation is at a premium. Can we insulate from the outside on the roof and subfloor?

The walls are made of concrete block with firring strip, rigid foam, and drywall. I suspect it was a garage once.

Thanks for your help.

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  1. GBA Editor
    Martin Holladay | | #1

    Does the concrete floor bear on concrete walls below? If so, there is no way you can insulate under the floor, because of the thermal bridges beneath the slab.

    The only way to insulate this type of room is on the interior. If you use a mere 2 inches of rigid foam, plus 1/2-inch-thick finish materials, your ceiling height will be reduced to 7'1".

  2. mmarkose | | #2

    Thanks Martin.

    The floor is on concrete block bricks. I understand the thermal bridge now - that explains a few things. There is a bathroom in this room too - do I follow the same routine?

    Is there any sense in putting some kind of radiant heating (electric will be the only option)?

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