Mildew smell in recently renovated porch

lalalaJune 11, 2012

We recently had the three-season porch on our 1936 house converted to a full-year porch. It is a small space (11'x7') that we now use as a playroom. Everything was taken down to studs, windows and door replaced, walls and ceiling insulated, new drywall put in, baseboard heater installed. The only thing that was not replaced was the floor, which is original. The floor is pine and has gaps of a couple of millimeters between the boards. Underneath the porch is a crawl space--just dirt. There was new rigid insulation installed beneath the floor.

Prior to renovating the porch it smelled somewhat mildewy. (We once left the porch closed up during a hot and humid spell, and it got really smelly; it never went away completely.) I had figured that the smell was mostly in the walls, but there is a lingering smell coming from the floor that I notice now that the weather is getting more humid.

Is there anything we can do about this other than keeping the windows open? Would washing the floor with a bleach solution accomplish anything?

Thanks.

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liriodendron

Your new renovation has probably tightened up the room so much that it's preventing the pre-existing small amount of air flow from the crawl space into the room from escaping into the atmosphere. I take it no effort was made to install a vapor barrier in the crawl space?

You might try ventilating the crawl space so that negative pressure pulls air down from the room into the crawl space and out and not the opposite way as it is now. Insulating previously uninsulated spaces in older houses often has unintended negative consequences - you may be trading increased energy efficiency for a disturbance in the existing intra-wall air flows. (That's usually the point of insulation and sealing it up, after all.) But those intrinsic air patterns may have been what was keeping the house dry and sound over many years.

I'm not saying you should never insulate or tighten up an older house but you have to be prepared that doing so may upset an equilibrium, with harmful, or at least problematic, consequences.

L.

    Bookmark   June 13, 2012 at 6:16PM
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worthy

Only one sure solution: the crawl has to be encapsulated.

See link.

Here is a link that might be useful: Building Science Corp. on Conditioned Crawlspace

    Bookmark   June 14, 2012 at 12:55AM
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