Got an interesting problem….
Camp up in the White mountains of NH. It’s a simple 2 story, platformed framed, insulated walls with no ceiling in 2nd floor and insluated rafters topped with metal roof. The interior finish is mostly 6″ T &G pine on the first floor and all of the second floor. Here’s the problem I can’t solve….. water condensation.
We leave large pots on the stove filled with water to supply hot water for showers and dishes and little humidity. The steam condenses on the roof which is insulated with R19(I think) and usually covered with a foot or more of snow. As the converted water works it’s way down to the eaves it eventually drips on the floor, beds, etc.
I can’t figure out how to provide proper insulation, while allowing the moisture to escape so it doesn’t condense. The goal would be not to reframe an attic, but that would be the only way I can think of to allow moisture out without losing heat. We can’t cross ventilate now because there is no attic. There is good ventilation from eave to the ridge with baffles and good air flow so the roof stays cold. And the insulation works well, so well in fact, it readily converts the moist air to water until it runs down and drips. We need to solve this problem so we can finish the rest of the second floor with the T & G pine.
It’s unnatural to injest so much moisture but it’s much more comfortable. Without a central unit to regulate the humidity it’s kind of running wild. The best I can think of is to creat some kind of trough near the outside walls to collect the water, but that seems kind of stupid. I’m wonder what happens when you build with SIPS and all the moisture can’t escape. I’ve never built with SIPS, has anyone else?
Any and all thoughts would be wonderful!!
Replies
When the air hits dewpoint, the water vapor will condense out of it.
Seems you have two choices: (1) increase the temp of the building surfaces or (2) reduce the humidity. Choice two would seem easier. Stop introducing so much water vapor into the space.
Any house would have the same problem if you got that much water in the same cubic feet of space. Best I can do. Sorry.
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Joe Nashville,
Your camp needs a ceiling air barrier. This could be rigid foam insulation, polyethylene, or simply drywall. Whatever product you choose as an air barrier, it must be installed properly: no air leaks at seams or penetrations. If you use rigid foam, tape the seams with approved tape. If you have wiring or plumbing penetrations, seal around them with canned foam. If you expect poly to be the air barrier, all seams must be sealed with black acoustical sealant.
Once you have installed a ceiling air barrier, you will stop exfiltration through your ceiling assembly. What is happening now is that the interior moisture is hitchhiking a ride with the exfiltrating air, and the moisture is condensing on your metal roofing.
A cathdral cieloing like yours is the hardest to prevent this kind of problem and you are multiplying the negatives by constantly adding humidity with your hot pots on the tov.
You have to remove the t&g cieling first, then you will probably see a lot of wet mouldy insulation you'll want to remove.
After cleaning up, you have two ways to proeed - eithre re-insulate with a vent provided above the insulation or have it insulated with spray polyurethene foam wgicch is a VB itself
The other option woud be to re-insulate with FG and install a perfect vapour barrier over it before re-doing the cieling finsh. Yhe problem with that solutionb is that you will be driving a few hundred holes in the VB while redoing the cieling
Got another idea for you - insulate with foam panels. rip XPS to fit between the rafters 2" thickand place near bottom of rafter allowing vnting above - then applly another layer of foam totally across the bottom of the rafters to stop thermal bridging and eal up the seams to make it act as a VB. Now screw strapping through the foam to the rafters and nail the new cieling to those staps.
Whatever methodology you use, you HAVE TO keep that moisture from getting beyond the ccieling surface or iot will condense and feed moild, ruing the building and possibly your health
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ditto....
and get the thermal mass temp up...
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I just built an SIP house in that area (ossipee lake). I'm installing a heat recovery ventilator to address the moisture issues. We'll see how it works out next winter. Where is your place located up there?
Tom
Douglasville, GA
Not to muddy the water, so to speak, but if this is a camp, you probably use it weekends, right? And in the cold season when you first get there on a Friday night, it's pretty cold inside, right?
You might try to get the interior temperature up before putting the water on to boil. Depending on how big the place is, and how cold it is, this could take a while.
I had a similiar situation once and it was helped immensely with the installation of a ceiling fan. It didn't stop the condensation if there were pots of water boiling on the stove, but it did circulate the air so that the place came to a uniform temp much more quickly than it did before the fan was installed.
Lots of good suggestions here.
Yes it is a mostly weekend camp. But weekends which start on at least Thursday night during snowmobile season. It's on Stratford Bog, north of Groveton, south of Colebrook. It is usually low thirties on arrival, takes a bout hour with a good fire to get the chill off and another hour to get comfortable. The water usually doesn't get put on until sometime later, we're talking many hours between getting settled and water coming to boil. The condensation isn't entirely consistent either some days are worse than others. I haven't given it much thought, but it could be related to outside humidity as well.
What it's related to ios the diferential between inside temps and outside temps. The greater the difference, the more dew-point condensation you will have.
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Living in the Wht Mtns of NH myself i can see where you would be frustrated with your current problem. During our winters, no matter what type of heat is used, our homes dry out considerably. Attempts at humidification can vary from condensation on the interiors of windows to a situation like yours. Personally i would try a heat recovery ventilation system, American Aldes comes to mind. You can use the system with a humidistat which allows you to set the level you want. An advantage to this is that you will not have to change the interior architecture of your camp.
Buy a hot water heater,they can be fueled with propane if you do not have electric at the camp.The waterheater can be outside in a shed.The propane tank outside the shed,You can pipe in the water to a sink or simply just a bucket.
I used to farm part time, barn had no hot water. I took an inner tube from a tractor tire and fitted a hose bibb and a fill valve to it. Filled with water while the tube layed on a 275 gallon gas tank that was in the sun. You needed a rag over the hose bibb handle in the heat of the day to open it. The water came out hot enough scald a guy if he wasn't careful.In the winter on a sunny day I could get hot water,not scalding like the summer.Try it, might work for you,depending on amount of sunlight.Hose bibbs and valves can be gotten in pvc, easier to seal with the rubber tube.I used brass, because I had it laying around.I think I used formagasket to seal it.
mike