I need help with a moisture problem. this may get a little long so bear with me. I did a remodel on my house (started 8/1/08) added about 420sq.ft. In the process I added a new 95+ furnace and nu-wool insulation. Most of the exterior walls were stripped and the insulation was installed then. I also stripped the siding and the areas that I did not tearout were insulated from the outside and housewrapped the entire structure. I had the furnace temped in about the beginning of November. There was about 65% humidity all winter, ice on my new windows. This spring the air conditioner was installed and ran as much as possible in an attempt to reduce moisture levels. This did not work, I brought home a humidity meter from work and measured in the house 63.5% and in the crawl 74.9%. I blocked the vents in the crawl and conditioned the space ( return and supply air vents) but I think this was a bad decision, the crawl does have vapor barier down and glued to the block wall 12″ up. Constructive advice is appreciated. Thanks
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Are you living here? Where do the dryer and bathroom vents go? Cooking ventilation?
Where is this house? How cold does it get in winter? How high is the ground water on this property? Could there be any roof leaks that have saturated your wool insulation?
Yes I live here. 240cfm bathfan.700cfm hood. Watertable is not an issue, sand. Nothern Ohio. No leaks. I was a professional remodler for many years. This is the first time I have encountered this, could it be I made the envolope tight enough that I'm traping the moisture in? look in the gallery "50s ranch remodel"
>240cfm bathfan.700cfm hood.<
where do these vent to? attic, exterior or nowhere?
It's pretty hard to make it too tight, meaning it would take alot of effort. How many people live here? Do they use the exhaust fans when they shower? Is the hood actually used when cooking? I assume the 95% furnace is PVC vented with outside combustion air. Check it out, the moisture is coming from somewhere.
Yeah, I agree. Even with the walls stripped down it would be hard to make a 50s structure "too tight".(But maybe not impossible. Sounds like Dewey was pretty obsessive with this thing, so it's worth considering as a possibility. But other possible causes should be investigated first.)(Dewey, how obsessive WERE you with regard to air sealing the structure? Describe some of the steps you took.)
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Here is what I did: I caulked and foam sealed the walls and windows before they insulated. No vapor barrier as per the instructions from the Nu-Wool dealer. I did not insulate the band joist yet. The bathfan is a dual inline 240 cfm that does both baths with sealing dampers above the inlets. I installed tyvek on the exterior. Yes the fans go to the exterior. Just a little obsessive.....but the gas bill went way down and I mean way down. I just don't understand the moisture thing. I have a rinnai demand hot water tank so both of my heating appliances draw exterior air. by the way thanks for chiming in guys.
Well, first check for the obvious, and make sure that the fan and heating exhausts aren't positioned such that they could be drawn back into the structure (eg, through crawl or attic vents). Make sure the vent ducts didn't get disconnected accidentally at some point. Make sure that the condensate from the furnace is going down a drain and not accumulating on the vapor barrier in the crawl.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Yes I have done this. Crawlspace power vent is what I am considering.
I think it might be good to try a cobbled-up vent fan in the crawl first, and see if that makes much difference. If it seems to help, make it permanent.But, with that done (and everything else double-checked), if you aren't seeing a significant improvement within about 9 months after installing the last large batch of drywall, you should probably start considering a heat recovery ventilator.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Its been since Feb since the drywall and plaster have been finished. I even let the plaster sit for 45 days b-4 painting. That was my next query was a heat rec. ventilator. thanks Dan.... Hows the fishin in MN?
I live in the only county in Minnesota without a natural lake.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
I'm guessing you tightened up the house but did little to cut down vapor transmission through the floor. And if (as is likely) there is ductwork in the crawl, you may be sucking moist air from there through the return ducts.
Normally an unventilated crawl will approach 100% humidity, except when the weather has been particularly arid. Ventilated and with a vapor barrier it will be lower, and it's a little surprising it is as high as you say given the presumed quality of the vapor barrier. So maybe you should look for some other possible causes of the high humidity in the crawl.
I presume you have an appropriate bathroom vent fan (venting outside, not into the crawl or attic) and it is used when anyone showers. And I presume that any lengthy cooking (making jelly or such) is done under a similarly vented exhaust fan. And, of course, there are no obvious leaks in the roof or walls, and no obvious plumbing leaks.
Do be aware that new drywall contains a lot of excess moisture, and therefore a new house will be "damp" for a year, more or less. But if you did most of the drywall work 6-9 months ago things should be showing some improvement by now.
Sorry that there aren't any obvious answers, just more questions and some "maybes". But that's the nature of problems like this.
You're not running propane are you? If so (not natural gas) that's your answer.
"You're not running propane are you? If so (not natural gas) that's your answer."Why do you say that.First, for the furnace, and WH, and dryer, if it is gas they are vented outside so that would not have any affect.And the stove, if it uses either NG or propane, burns a hydrogen/carbon and oxygen and gives off water vapor. Would not think that there is a huge difference between the two for the same BTU's generated..
William the Geezer, the sequel to Billy the Kid - Shoe
Yeah, the only problem would be if he was using a salamander or other ventless heater during construction.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
And actually propane has a higher ratio of carbon to hydrogen and presumably would produce a little less H2O per BTU.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
I don't think it is the crawl space that is the problem. You said you have poly on it and even glued it to the foundation. And I wouldn't condition the crawl. Your RH measurements seem consistent. W/out knowing the temps that go with them, they aren't of much use, really. Sounds like the crawl humidity is about the same as the house ... assuming it is cooler there (cooler temp, higher humidity given the same condition). Should the crawl be lower than the house? ... assuming it is sealed from the ground and has no moisture source, you might think so, but I'm not sure about that.
A friend of mine had a new duplex built by, at the time, one of the premier 'energy builders'. Everything was 'done right'. His new low-e windows would sweat ... a LOT.
We measured the exhaust cfm in a bathroom w/ a flow hood. maybe 15 cfm from an 80 cfm fan. Rigid duct, I believe. He vented through one of those round eave vents through the side of the house. The painter ... slopped enough paint that it substantially reduced the effective area of the vent.
Bottom line ... you focus on air leakage reduction (housewrap), but you have to compensate w/ proper/good ventilation (exhaust system).
My question, in addition to 'where to' by another poster, is HOW do you exhaust it? Flex duct? Are you really getting the flow the fan is designed to provide? 250 cfm fan won't move 20cfm if you don't let it. Are you running the fans comensurate w/ your lifestyle? Maybe a dehumidistat would be in order.
Personally, I'd give your exhaust system a reality check. Rigid duct? Sealed? Not too long? Positive vent to the exterior? Discharge grille w/ plenty of area/no restrictions? Are you using them? Or are you so 'energy conscious' that you tend to not want to use them much? Remember, controlled ventilation is more energy efficient than uncontrolled (i.e. your old leaky house).
Lifestyle ... lots of cooking? Lots of plants? Aquarium? Lots of showers/baths?
I went into another house once ... brand new energy efficient house. Housewife was Better Homes and Gardens tidy .... and they had mold in their closet walls!! Again, it was the exhaust system not moving enough air. They figured running the fan e.g. 15 minutes after a shower was good enough. A bad install, though and it wasn't moving enough air.
My money is on the exhaust systems ... but that is called from the smattering of info that we readers get ... we can't actually be there :(
As the guy on the radio says, a fan can only blow as much as it can suck. No matter how many cfm you are rated for the fans have to be able to pull that air in from somewhere in order to blow it out. If by some miracle you have it really tight, those blowers are really just working against a vacuum that they are creating so they are moving as much air as you think.
A blower door test would help determine this plus giving you the added benefit of identifying leaks that may be the cause if it doesn't show your house is too tight.
Other questions,
Lots of baking?
50 Gallon Fish Tank?
Indoor water fountains/features?
72 head party shower?
Wife a plant nut?
fan speed on ac may be too high not getting coil cold enough.
my house runs 50-60 % in summer
Right you are. If the leakage ain't there, there isn't exhaust. In the Northwest, at one time they required (by energy code) to install dedicated vent air intakes to compensate for the exhaust air. They were provided in a number of ways. Special vents on windows, individual pop open wall vents or other options (e.g. like interlocking w/ furnace, fan, and damper). No or low flow on the exhaust either means the exhaust stream isn't performing right or the house is WAY tight. Generally, though I wouldn't expect an existing house to be that tight, but like you say ... it could happen.
Might be interesting/informative for the OP to get a blower door test.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
""...individual pop open wall vents..."" Wouldn't happen to know a source for those would ya? I have need of a couple.
Life is Good
Hmmm ... it's been like 15+ years since I first saw them. They were like 4-6" vents with a cover and a special mechanism using a pull chain. You simply pulled the chain and it popped the cover out away from the wall say 1/2". The exterior was more like a standard mini dryer vent or some sort of louver for rain protection. They were used in the early 90s in the Northwest to satisfy the ventilation requirements under the new code. I don't recall the brand/model. I did a quick google, but didn't get a hit (sometimes I can't figure out the best phrase to use). If you still are interested and can't find them, I could make a couple phone calls and maybe cut to the chase.
I will do some more hunting on the net to see what I can find.. maybe Resource Technology has something.
Thanks for the offer, may yet take you up on it.
Life is Good
Hah ... just found a reference to the pop open vents .... interestingly in a recent issue of Fine Homebuilding no less!! Thermaster is one brand .... http://www.efi.org
It also lists similar products from http://www.alesamerican.com and http://www.panasonic.com
The reference is on page 65 issue # 178
I lied ... it's not a 'recent' issue ... a couple years old ... sorry, I thought it was newer 'cause it was laying around in site ... I mean sight ... can't spell and CRS.
Edited 11/6/2009 10:33 pm ET by Clewless1
Edited 11/8/2009 8:46 am ET by Clewless1
Thanks.
Been out of town and just got back into town and onoine. I will check the link out.
Thanks again.
Life is Good
As winter approaches, your problem may be self-correcting. Your heating system just might remove that extra moisture.
But do you have excess moisture? "Humidity" gauges are notoriously inaccurate; mine in Nevada would often read 45% on days that the swamp cooler worked extremely well (proving there was very little humidity at all). About the only truly reliable method of measuring humidity is with a 'sling psychrometer' and some reference tables.
Anyway ... let's assume you have a problem. Get a free-standing dehumidifier. I use one in a basement (in Missouri), and it pulls nearly 7 gallons a day out of the air. According to the display on the unit, this drops the humidity from 78% to 45%. Since the unit only holds about 4 gallons, I have to empty it twice a day.
Does it make a difference? Well, at higher humidity the panelling seams start to pop free of the wall; lower the humidity, and all lays nice and flat.