Seasonal humidity and lack of outside airflow
Hello,
I read through a Q & A on ventalation options for a small tight home, but am not sure I found the answers I need. I live in a 1950″s split level home in Montana. The lower house is a stand alone apartment. Following a remodel prior to my ownership and energy audit, the apartment was deemed to have inadequate airflow. This came to my attention after noticing heavy condensation on the aprtment interior windows and the report of mildew on bedroom windows from the occupants. Temporay solution is a dehudifier, but need to fix the problem with either a spot ERV (Panasonic) or a fanpassive vent combo? At the same time, we are starting to see this issue in the main home, though it was not deemed to have insufficient outside airflow, it currently lacks proper ventilation in the kitchen and laundy (no outside exhaust fans). Welcome any thoughts before I start spending limited funds.
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Replies
Geoff,
A humidifier is not a good solution to the problem of condensation on windows. I'm guessing that you meant to write "dehumidifier," not "humidifier." [Later note: I see that you have corrected your post.]
We need more information. What is the indoor relative humidity (RH) in the apartment with the condensation problem?
Thanks Martin. Correct- dehumidifier was added yesterday. Sadly I do not have a pre-measure of RH, nor a ready method of measurement this year. Let me check the audit we inherited with the home. May be too coarse, but we could visually see heavy condensation on almost every window (all double pane) and at times on the glass entry door. Had started down the path of the Panasonic ERV until seeing your prior posts on passive ventilation.
Geoff,
Is this lower level partially below grade? If so, this might be a variation on a classic wet basement problem.
Before recommending a remedy, it's important to know (a) the indoor relative humidity; and (b) the source of the moisture. If a damp slab is contributing to the problem, ventilation is not necessarily the best option.
Excellent point. The apartment is partially below grade (aprox 4 feet). The area we live in is very dry, appears well drained, and we have no indication of past moisture intrusion through the slab (poured concrete slab and foundation walls). Perhaps a red herring, but I was initially using the report of inadequate outside air ventilation as a likely cause. Would you suggest turning off the dehumidifier, waiting for 24-36 hours, and taking an RH reading? Having similar, though lesser condensation issues in the main home- all above grade. Heat source for both is NG fired baseboard and recently ugraded to a solar/NG combined system (for domestic HW) with a Prestige trimax 110.
Geoff,
There are many possible source of moisture, and any investigation would begin by trying to figure out where the moisture is coming from. It's hard to do this type of diagnosis without a site visit.
Yes, it would be helpful to know the indoor RH without the dehumidifier running.
Thanks again Martin and sounds like I have more homework and may need to bring in a pro before rushing to judgement or making purchases.
The Panasonic ERV will self-destruct in MT in winter- it's really designed to work in a US climate zone 4 or warmer type of climated.
The outdoor dew points in MT are low enough year-round that the humidity can always be brought into a "reasonable" range by adjusting the ventilation rate, and in winter it need not be a very high ventilation rate. Standard high-efficiency bath exhaust fans operated with a dehumidistat control can fix a lot of humidity problems (and maybe even yours.) While HRV would be nice if you have expensive heating fuels, it's not essential.
Thanks Dana. Earlier posts had me wondering as we are borderline by Panasonic's own brochure. Cross that off the list!
I generally get to go to Montana once a year when we ski at Big Sky. I have noticed that almost every window has some condensation (frost even) around it when it is really cold outside. I figured it was from air leaks around the windows because the rooms themselves are very dry - like nosebleed dry, cracked lips dry.
If you are looking for an HRV that might work - the Lunos eGo. It's basically a through wall HRV that doesn't require any additional ducting and can be converted to exhaust only mode.
http://foursevenfive.com/introducing-the-lunos-ego/