Ventilation ideas for blow grade basement?


Old 10-19-06, 11:48 AM
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Ventilation ideas for blow grade basement?


All the walls of my basement are below grade and there are no windows. Just a door and stairwell that leads up to daylight. The basement has 8' walls. The only good news is that, unlike most basemetns, this one stays very dry all year round except for July/August where the humidity might spike up to around 60%-65%. The rest of the year it is between 30%-50%. There is no water entering from the walls or floor. Nonetheless, there is a constant musty odor and I'm baffled as to what's causing it. The only explanation I can think of is that the walls are covered with fiberglass insulation wrapped in a poly type of paper similar to Tyvek. Could this be traping water vapor outgassed from the concrete walls?

I would like to remove the insulation and install some type of ventilation to control the odor and to mitigate a slight radon problem. Any suggestions? Thanks.
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Old 10-20-06, 03:45 AM
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Technically, a basement that is totally underground is geothermally correct all year round. That is, the temperature will not vary, since the ground stays the same temperature at its lowest depths. With that in mind, completely sealing the room with insulation and vapor barrier can have its benefits and drawbacks. It is not giving you any insulation value beyond what the ground provides. It is, however, tending to keep any possible air flow from happening behind the insulation, so any moisture is being trapped there. Now, if you do not plan on using the area as a living space, you may be able to install a forced air ventilation system to move the air by penetrating a wall and installing a vent. But from your description, you could basically get by with a really good dehumidifier. Is there a drain in the floor at any point? You could drain the dehumidifier directly into it, and never have to empty the bucket.
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