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How should I ventilate a tight weekend getaway cabin that smells very musty.

pizza's picture

Hi. I thought Breaktime went away and now it's back?! Great!

I have a small 12 ft x 12 ft cabin (in south eastern PA) with a gable shingled roof that was built in the early 1980's. It is standard stick framed with batt insulation, celotex sheathing and aluminum sided. It is on a slab that did not get a plastic sheet under it prior to the slab being poured. So the floor is exposed concrete. We've used the cabin for weekend getaways and the occasional week long stay. It only has electricity and no running water. It is only one room inside for sleeping. No heating except for a space heater and that rarely gets used as we do not use it in the winter. There are a total of four very small windows and one door (at gable end of the cabin). The door and two of the small windows flanking it are on the gable side of the house and the other two windows are in each side wall and the back of the cabin has no windows. There is no HVAC at all in the cabin. The interior walls are wood paneled (like was popular back then) and the ceiling is tiled with that fiberboard type squares (for lack of a better term) that was also popular back then.

It is closed up most of the time when not in use and has developed a very musty smell inside so much so that I suspect a mold issue although none is visible.  It is a very tightly built cabin. There is an upstairs/attic that is accessed from the ouside by an exterior stair. The upstairs does not get musty.

How can I ventilate the musty downstairs either passively or actively to get a better exhange of fresh air while no one is there and or all year round? Best practice?

I was considering first testing for mold with one of those kits from the big box store. Then, regardless of the results, sealing the top side of the slab with a siloxane sealer. Then install some sort of system (active or passive) to ventilate it year round whether it was occupied or not. I suspect that although it is not visible the mold is at a level that could be dangerous because I get a burning in my nose after I sleep overnight in the cabin (And I've stopped doing that now for several years). We would like to remedy this situation so it can be safely used as a getaway again.

I'm also considering, after sealing with the sealer, that I install a floating engineered floor consisting  of 15 mill vapor retarder (.1 perm rating) and then two layers of 1/2" exterior ply then engineeried flooring on top of the ply. This was detailed in an article in FHB.

But then after that how should I get that exchange of air? Any thoughts and suggestions? I'm loooking for detailed suggestions on the mechanical or passive system such as type of fan to use, automatic control, heaters, dehumidifers on automatic, cutting holes for vents etc.

How would you exactly go about solving this issue?

Thanks in advance!

First I would be concerned (post #215387, reply #1 of 4)

First I would be concerned about the junction between framing and slab.  If the sill plate is standard lumber then it is likely already rotten in spots.  Even "standard" treated lumber would likely be getting a little gamey.

But as to ventillating, since there's no plumbing inside you might as well install some passive vents.  Three or 4 low along one side and another 3-4 high on the opposite side.  Of course, be sure they're screened, and take thought of keeping snow from blowing in, either by closing the vents in winter or by using some sort of baffle structure outside (though one that won't attract bird and insect nests).

You might also consider installing one or two powered vents, on a timer.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Cabin ventilation (post #215387, reply #2 of 4)

I'm thinking about going with the powered fan on a timer and adding a passive intake vent opposite it on a wall. When I make the hole thru the wall and thru the exterioir aluminum siding how do I neatly finish the cut aluminum edges of the hole? With J channel? This is old aluminum siding that is in great shape. Do they still make J channel for aluminum siding?

Where to buy powered vents? (post #215387, reply #3 of 4)

Any good sources for buying powered vents Smallish ones?

Never worked with anything (post #215387, reply #4 of 4)

Never worked with anything other than bathroom vents personally.

Browse the Broan catalog online, I guess.  Probably pick the smallest one you can find -- 60 CFM should be plenty.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville