I finally finished the second floor of my house which has been under construction for three years now- Hoorah!!
BUT- a new problem has begun…maybe you can help me solve the mystery.
Until two months ago, we have been living in the finished basement, while work upstairs on the first and second floor has progressed at a snails pace (mostly because I am trying to build it without aquiring debt) After insulating and finishing the second floor of this cape into bedrooms for my kids and installing a two stairways (basement to 1st floor and 1st floor to 2nd) – we now for the first time in three yeras have heat in the basement(via woodstove) and on the second floor (via baseboard electric). We walk through the first floor which is still unfinished and uninsulated , in fact it doesn’t even have windows yet, just one steel entry door.
Therefore the outside of the house still remains, you guessed it, wrapped in Tyvek. the problem I have just noticed is moisture on the inside of the plywood sheathing on the unfinished first floor. In fact, behind anything that had been leaning against the inside wall I found frost and black mold. My question is…is this from indoor moisture or outdoor moisture or both?
The heat from the woodstove can rise up the stairway to the upper floors, the heat from the third floor pretty much stays put, but I’m wondering if all the cooling air is collecting on the first floor, rather than dropping to the basement level. Or because it is so cold out (in the single digits lately here in NE Pennsylvania) I’m wondering if the cold outside air is passing through the plwood sheathing, hitting warm indoor air and reaching dew point at the interior wall…
any collective thoughts might be helpful, I thought about temporarily insulating the first floor, but wondered if the mold problem might worsen without siding on the outside…
Replies
Condensation only happens by cooling moisture ladened warm air, never the reverse.
hope this helps.
With or without the woodstove...I think you are right... the Tyvek is a vapor barrier. All of the moisture from your living, breathing, cooking in the basement is condensing behind the Tyvek.
Do a search on mold, and find out how to kill what you have before insulating.
If this thread turns into another Tyvek debate...enjoy...
"the Tyvek is a vapor barrier."
Where did you get that idea. It is an air barrier, plain and simple. It "might" be a bulk water barrier, that is where the "discussions" come in.
Tyvek has a perm rating of 94. Exterior plywood is 0.7
http://www.energy.state.or.us/code/respub/res15.pdf
"Tyvek has a perm rating of 94. Exterior plywood is 0.7 "
Thank you so much for clearing that up for me Bill.
You got anything on mold? Its probably the only thing we can correct at this point.
If this thread turns into another Tyvek debate...enjoy...However beautiful the strategy, you should occasionally look at the results. Winston Churchill
Well epa.gov has lots of details about cleaning it up. But I have already posted what I think or the options for preventing more of it.
Thanks to all who replied, some good ideas to follow up on. If I find a solution that works I'll post it.
KB
You don't have to have cold air coming in. There is no insulation so the inside surface of the sheathing is very cold. The relatively warm and moist inside air hit the cold sheathing and condenses.
I don't know what kind of "temporary" insulation that you where thinking about using, but most like it will not be air tight and the moist air will work behind it and still condense and then you will also have moist insulation.
Stapled polly up on the walls and paying very close attention to all edged might help a lot. But then you will probably have condensation on the inside of the poly.
I think that the best think that you could do would be to put all possilbe effort into get the wiring in, insulated and sheet rocked, even if you insulate and sheet rock over the window openings.
Then when you get the windows you will have to rework insulation in those areas.
But if you don't think that you could get windows and do it right by next fall I think that is your best bet.
The tyvek is defionitly not the problem.
As soon as I read that your first floor is uninsulated, I kew ...
The problem is condensation. Cold is not getting in, heat is getting out. The plywood is cool and provides a condensing surface.
The question posed in the title, where is the moisture... can be answered - when people live in a house there will nbe moisture added to the air. You transpire up to a couple quarts a day through your lungs. You shower. ( I presume) You cook. You mop the floor, etc
Excellence is its own reward!
KB,
What are you planning on insulating with? If you say fiberglass, use the search function and see what's been said about fg. Assuming you heed the advice about fg, I would guess you will choose either cell or foam insulation. You menitoned trying to save as much money as possible, so I would guess cellulose. If you can get the wiring and plumbing in (it doesn't have to be functional, just the stuff that will be covered by insulation) you could staple up the mesh and blow the cells. This will help both your interior temperature (BTW- aren't you cold with no insulation???) and your condensation problem as very little air will move through the dense pack cells.
Just a thought.
Jon Blakemore
I insulated the second floor with Icynene, blown in foam (ceiling, eaves, walls) which made that floor very tight. I had planned on doing the same on the first floor. They say you can wire after you blow it in...but I observed the installation on the second floor and I don't see it happening ( the stuff expands so quickly that overfilling the stud walls is quite common, you don't want to have to dig through it once it's installed...that would defeat the purpose of the tight seal it offers)
I wish I could say I was organized enough to have a good handle on the electrical layout on the first floor...but there are so many variables...the kitchen is not yet designed...a bump out in the master bedroom not yet built...an addition on one end for a great room not yet built or designed...need I say more? I had hoped I could sit tight until I had more time to think about all these things. This moisture problem kinda took my by surprise. I guess in the world of building some things can't be done too slowly.
The woodstove in the basement (where we spend 90% of our time)keeps us warm although there is a mighty draft coming down the staircase. My kids just walk through a cold floor to get to their warm second floor bedrooms. I wasn't really worrying too much about the wasted heat as I live in the woods and firewood is abundant. My one thought was...I have all this leftover 1" foam board insulation I was going to use on the exterior foundation of the addition sitting outside, I wondered if I hung that on the interior stud walls if it would help or hinder. .When I first discovered this problem I noticed that everywhere something was leaning against an exterior wall on the first floor there was frost and black mold on the plywood behind it. My thought is that to make it effective I would need to seal the space form any air movement from within.
Any thoughts?
If you're not concerned about the heat loss through the walls, don't worry about the condensation. This is a small amount of moisture and it won't hurt anything. You could use up the foam board, but in order to effectively block the diffusion you would need to seal dilligently with urethane foam. I'm like you, I have something left over and I just have to find a new and improved to use it up, but to me, this seems like much more trouble than it's worth.
The cold temps will build character for the kids. Or at least that's the spin I would put on it. <g>
Jon Blakemore
Thanks for your reply - I was hoping that some of you out there with more experience building (than I) would instinctively know wether I had a major or minor problem on my hands...hopefully it is as you say, not enough moisture to worry about over the next few months.
Keep warm and thanks,
kb
Maybe a quick fix for a temporary problem is to set up a couple of dehumidifiers on the first floor. With lower relative humidity, you'll have less condensation. You'll just have to live with a lower relative humidity until the first floor is finished. Also, you might look into killing the mold with a spray of bleach and water before you close in those walls.
Everyone has really jumped on this with some good ideas. I'll echo the condesation theory. Warm moist air meets cold dry air. The temperature and humidity is below the dew point, causing the warm air to discharge its moisture onto the surface of the plywood.
Now, you've got moisture, wood, and mold has food and water. Yum!
You're whole house is going to be one giant mold magnet unless you deal with this. You need to add insulation, siding, vapor barriers and an HVAC system.
Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934