Good idea about humidity gauges. I'll see about ordering those.
Humidity issues in basement. Will a heater help?
- Thread starter jalapus logan
- Start date
I'm not in the HVAC industry, so you take take my opinion FWIW, but I think it's pretty much impossible to seal a basement, especially in the winter. The chimney effect from the house will pull outside air in from every conceivable opening. The wind will just add to this effect, as will running any sort of exhaust fan. You are constantly pulling in dry winter air from the outside and heating it up - even in a room with no additional heat source - effectively lowering the relative humidity in the process.
My experience as a woodworker for almost 40 years is that heating a basement in the winter lowers the relative humidity substantially, which pulls moisture out of everything in the room... table cloth included. Dew point is not even an issue in the winter except on single-pane glass windows exposed to the outside, which may get frost on them if the RH rises high enough. The dew point in my basement is below 20º in both heated and unheated rooms, so no worry about any moisture condensing onto anything at all.:wink:
Even without heat, my shop is 48ºF, which is almost 40º higher than the outside air temp. The outside air temp at my place in upstate NY right now is 10ºF and the relative humidity is 46%. Like I said above, the shop is 48º. I just measured the RH down there with my trusty old Taylor sling psychrometer and it is only 31%. That's pretty dry, even without a heat source except for ground heat.
In another closed basement room where the table sits I have two oil-filled heaters going and the air temp is 61º, with RH down around 20%.
Upstairs where I have my pellet stove cranking, the room temp is 75º and the RH is a skin-cracking 14%! Time to fill the humidifier.
So my advise is to go ahead and heat the basement. Although the relative humidity is likely already pretty low, it will be a lot lower once the air is heated, and a lot more comfortable to play in if nothing else. I just looked at the current Lexington, KY weather data and it's just as cold and dry outside right now as it is in the north. Your conditions should be close to what I'm finding here. Whatever you do, though, don't put that heater under the table! I measured the temp at the top of mine with my IR thermometer and it gets over 200ºF. That can't be good for your table to put that kind of heat inches away from the bed. Anywhere you put the heater in the room will have the same effect on the RH of the air because of convection currents.
BTW you need a pretty expensive dehumidifier to take moisture out of air that is below 50% RH, and a damn good one to work at all when ambient temps are below 65º. The condensation coils just freeze up and the damn thing will cycle all day long without removing any water at all. Eventually it will just fry itself trying. Trust me, I've been using the things for almost 40 years in my basement workshop. Dehumidifiers are definitely a summer appliance.
Logan, many Thermometers have a Humidity gauge on them.
I have my dehumidifier set to kick in when the gauge starts to read a higher reading.
I have my dehumidifier set to kick in when the gauge starts to read a higher reading.
I'm not sure if I understand the science correctly, but I was just thinking that you can probably get a meter that will display all three parameters; temperature, humidity and dew point.
A dehumidifier with a "humidity setpoint"? That's a great idea. Last time I used one - which admittedly was a long long time ago - it was an on or off affair.
Fatz
When I refer to a sealed room I am referring to the type of room with equipment our products are used to heating/cooling i.e. data center built rooms. These types of rooms should be sealed (viscous barrier) as much as possible. You don't want outside air coming in...now granted you still will have people coming in and out...but you want to minimize as much as possible. I definitely agree good luck trying to get a completely sealed basement as it most likely isn't possible unless you build it like a data center lol....
High quality digital hygrometers can be had on Amazon for about 10 bucks. I have two of these units + two dehumidifiers and my unfinished basement stays perfect year round. Keep in mind dehumidification should be matched to the square footage of your space and is generally expressed in pints removed per day. 120+ pints per day is pretty stout removal; mine are rated at 70 p/d each.
Pre Flag, that is pretty much what I meant.
When I walk into the shop, if the Humidity gauge is reading high, I turn the knob on the de humidifier until it kicks in.
It will run long enuff to bring it down to an acceptable level.
Usually only have to play with it once or twice during the summer.
When I walk into the shop, if the Humidity gauge is reading high, I turn the knob on the de humidifier until it kicks in.
It will run long enuff to bring it down to an acceptable level.
Usually only have to play with it once or twice during the summer.
I may not have understood your original post correctly. I thought you were speaking of using a heater in the winter months, not summer as well. In summer you will definitely need a dehumidifier, but in the winter, heating the room will greatly improve matters by lowering the relative humidity.
The problem you will always be facing is air infiltration from the outside due to the stack or "chimney" effect:
http://www.basementsystems.ca/crawl-space/humidity-flooding/solutions/mold/stack-effect.html
I'm sure you already know that no amount of DryLok or paint is going to stop humid air from entering your basement. The replacement windows will help, but finishing those walls and installing a proper vapor barrier will help a lot more. Still, air is constantly moving up through your home from the basement to the attic, and the taller the home the stronger the pull.
When I bought this place a couple years ago I was thrilled to see that enclosed gutters surrounded the roof, leading to a common drainage system that flows down into a drainage swale 200' away near the back of my property. We moved right after Hurricanes Irene and Lee blasted through our area, and this was the only place out of several dozen homes we looked at that had such a well thought out and dry basement. That was a good time to look for these things, since we had so much ground water in my area that every other home we looked at had sump pumps running full bore.
Despite having the driest basement I've ever seen, when it came time to finish it I went to the extra expense and trouble of using 2" foam insulation with vapor barrier tape over every seam. Then regular 2x4 construction for walls, and over that, 1/2" rock, primer, and 2 coats of good quality latex paint on top of it all. Even with all of that, I still have to run a dehumidifier during the muggy summer months. Nothing like I had to at the old wet basement, though (3 coats of HD Dry-Lok there didn't really help at all, lol).
You just cannot prevent air infiltration in your home in any reasonably affordable way, even on windless days. Nature abhors a vacuum. Any time the interior of your home is warmer than the outside air, the stack effect will create negative air pressure inside because the warmer air rising to the attic and out the vents needs to be replaced. Air exiting at the roof means air will find its way into the basement. However, you can slow it's exchange rate to a degree by finishing the basement using a proper vapor barrier.
Lowes sells a greenboard insulation that has shiplap edges that you tape over. 2" board will cost you about $8/liner foot and provides both an effective vapor barrier and R-10 insulation. You glue it right to the walls with construction adhesive and build your walls in front of it. No problem with black mold like fiberglass has in most basement installations. In the pool room where space was already too tight I used the 1" panels (only R-5 insulation, but the same vapor barrier effect) and used a Hilti gun to attach furring strips on top of them directly to the walls, then put 1/2" rock over that. Yes, I know this is well beyond what you were originally asking, but you will be a very happy camper should you choose to go this route in the future. :wink:
I knew what you meant and I wasn't trying to correct you, just making a point about residential settings.
You'd get a kick out of the AMD chip manufacturing facility they built near me in Malta, NY. The place is enormous, and now they're building another one to make all the chips for future iPhones and iPads. The main building is expansive and very low to the ground. It was explained somewhere that it was built flat like this to help control the air flow better.
Wow, you have given me much food for thought. I have not given much thought about finishing out the basement, but you are making me think that I can actually do that. After a horrible garage project during which a contractor ripped my wife and I off, I found myself learning about construction pretty quick. Though I was out several thousand dollars (what an expensive lesson!), I became pretty familiar with proper framing techniques and local building codes.
This basement is not terribly leaky, which is good. Only during very very wet periods of rain (essentially thunderstorms that dump 6+ inches of water) will I get a couple of trickles of water in a corner or two. Not sure what the implications of said trickles would be, hence my reluctance to finish it off so far.
In any event, thanks again for your thoughts!
Cheers,
JL
Raising the dry bulb temp will lower the relative humidity, but the amount of moisture remains constant.
To dehumidify you have to cool the air to the point that water condenses, then reheat it to keep the space comfortable.
I have the same issue in my basement, get a portable dehumidifier.
To dehumidify you have to cool the air to the point that water condenses, then reheat it to keep the space comfortable.
I have the same issue in my basement, get a portable dehumidifier.