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Insulating steel I-beam under floor

Postby JT101 » Mon Jan 10, 2011 3:33 pm

Hi Folks

Just starting to realise how complicated this whole energy flow analysis is.

Unfortunately, our outside wall of the upstairs bedroom is sat on top of a steel I-beam, which in turn rests on the patio doors of the kitchen.

The outside of the I-Beam is filled with bricks, so definitely a cold spot.

You can see the white area labelled 'A' in the following image, which is the area of concern:

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Obviously this is a cold spot with a potential for internal condensation to form. I don't see any benefit to cover in a water proof membrane as water would just collect on this on the inside of the steel.

If we fill the cavity with rockwool, we're concerned it will absorb this moisture from the I-beam surface, and get damp. But at the same time we want to heat up the area.

Currently we've decided the best course of action is to consider this cavity as outside the building envelope, and thus we would insulate above and to the left of the cavity with rockwool between the joists, and just under the top lip of the I-beam, attached to the underside of the floorboard.

Any suggestions on the best course of action are welcomed

Thanks in advance
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Simply Build It

Postby stoneyboy » Mon Jan 10, 2011 11:39 pm

Leave the area A open so condensation has somewhere to disperse.
Form an insulated boxing over the exposed lower flange where it projects into the kitchen.
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