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Old 12-13-2011, 11:58 AM   #16
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Moisture in Unheated Room


Or, they could have been the types to leave every light on in the house, run the hvac at cooler temps during the Summer, and higher temps during the Winter, and tended to leave doors open a lot along with Windows to let outside air in.

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Old 12-13-2011, 02:05 PM   #17
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Moisture in Unheated Room


Find a way to spread a plastic sheet on the ground under the room and I bet your problem is (at least mostly) solved.
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Old 12-13-2011, 04:24 PM   #18
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Moisture in Unheated Room


Try putting a sheet of plastic down on a section of the floor. Tape it down all the way around to seal it. Lift it up the next day and see how much moisture is under it or on top of it. Should at least give an indication of where the excess moisture is coming from
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Old 12-18-2011, 12:37 PM   #19
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Moisture in Unheated Room


I finished insulating the ceiling with R-30, and added weather stripping to the door, and both made a huge difference. However, even with the glass doors open, I'm still getting enough moisture off the windows to make a small pool on each sill. Am I at the point where I need to run a dehumidifier constantly? It got to the single digits here last night and is still only in the teens. The temperature is in the high 40s/low 50s in the sunroom and 60 inside most of the time. RH is 51% inside, 53% outside.
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Old 12-18-2011, 12:58 PM   #20
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Moisture in Unheated Room


"Am I at the point where I need to run a dehumidifier constantly?"

What you are witnessing is ambient air at 51% RH at the gauge, but in effect you have 100% RH at the window itself, and hence the condensation. Now what you could do is put a fan on in there to make the 100% RH at the glass come down. Then the condensation will go.

So, yes to answer your question, you can run a dehumidifier in there constantly and what you'll get is a lowering of the RH in the room to levels dependent upon the machine you use. But you'll only be dehumidfying the surroundings, like the soil beneath. You'll get rid of the condensation alright but you'll be emptying the tank fairly frequently and the machine will struggle keeping the RH down at dry conditions...

Try a cheap oscillating fan, about a 14-inch or bigger, first to see if that'll clear the windows. Cheaper than a dehumidifier
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Old 12-19-2011, 08:35 AM   #21
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Moisture in Unheated Room


I tried the fan and it helped a bit, but there's still condensation. I brought the dehumidifier from the basement up, but the compressor isn't running very much. I think it's too cold and the coils are freezing.

So far the only solution I've found to really dry it up is supplemental heat. I hate doing this when I'm already heating the rest of the house and not even using this room.
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Old 12-19-2011, 09:16 AM   #22
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Moisture in Unheated Room


Well then, you've given it your best shot...and sure there's more you could do and farther you can go - but everything in due course.

Let's look at it from a moisture point-of-view here a minute: what you have is moisture in the form of water vapour entering that structure (it comes from somewhere after all) and it is sitting in the air in that form. Now when it meets a surface cooler than the Dew Point, it condenses and turns into water... Now there are a number of ways you can minimize the appearance of condensation and one of them is to heat the air. In doing that, you don't change the amount of moisture in the air - you just change the appearance of it in the form of water.

You already tried to increase the ventilation of the moisture but again that'll only displace the appearance of the moisture. Same thing with the dehumidifier; there you actuallly removed the moisture in the air - but yours didn't seem to work (not sure why. Freezing coils, eh? something's wrong there...).

So your only remaining course is to heat the room. As I said, that'll make the appearance of the moisture dissappear, but it'll still be there. So, the long-term solution is to deal with the water that is coming in.

You haven't addressed that by adding the insulation, sorry. You've just made it easier for whatever heat that is generated in that room to stay in the room and not escape to the outside, but you still have the moisture issue left.

Now the moisture could be coming in from below - or just from the outside. Outside, right now up here, it's 63% RH so there you go: that's where some of your moisture is coming in from.

Electric heat - apart from supplying convection currents (similar to the fan) - has a drying effect on RH, so you can expect the RH in the room to drop.
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Old 12-20-2011, 04:21 PM   #23
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Moisture in Unheated Room


For some reason only the fan was running on the dehumidifier, the compressor was barely coming on. After a couple days, now it's working great. I'm getting about 18 pints a day out of the air. The sunroom's humidity is now equal with the house, and there's no more condensation anywhere. We had a lot of rain yesterday, and now it's in the 20s, and the windows and walls are still dry. I don't have a forced-air system (baseboard hot water heaters), so the humidity stays up during the winter.

Thank you very much for all your help.
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Old 12-21-2011, 06:53 AM   #24
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Moisture in Unheated Room


Ah-ha, well OK then...

18 pints of water eh? That's huge. Just shows you how much - in terms of volume you can measure - is in the air we breathe every day. As time goes on, that volume will go down a bit, so you won't have to be having to empty the reservoir as frequently.

You might want to consider having the electric heater to come on at about 45-50 deg F or so just to help out a bit; it will create a convection current up from the floor and against the window glass, provided it has a free channel to do so but if you have a lot of glass, it won't keep all glass clear.

Glad it's sorted! Good luck.
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Old 01-04-2012, 01:32 PM   #25
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Moisture in Unheated Room


Hi!,
Carlisle's advice is spot on. Two things you may or may not have looked at are, did you check the ground under the floor if it's moist? and can you put a vapour barrier to isolate moisture coming up from the ground?.
Also, is it possible to double glaze the window/s? This should help to keep the inside surface temperature of the glass above the dew point.

If you need to see how condensation works and occurs in seconds, put water in a kettle and allow it to come to the boil. Get a small metal saucepan and fill with cold water. Hold saucepan a few inches from spout of kettle. Instant condensation on the saucepan surface. Now replace the cold water in the saucepan with hot water, and no more condensation.

Air holds water in suspension as a gas. Provided the temperature is above the dew point, this moisture is invisible. Lower the temperature, and the dewpoint is reached, so the water in the air condenses, hence we have dew on the ground every cold morning, even if it hasn't rained.

Cheers! from Joe in Oz.

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