Finland? I hear excellent things about your country. I hope to visit Finland some day.
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Originally Posted by SDMCF
... Is the visible boarding the underside of your floorboards? If not, what is there above that boarding?
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The visible flooring is called 'sub floor', and is lumber milled with 'tongue and groove' to reduce air flow.
Quote:
Originally Posted by SDMCF
I have been unsure of the implications as regards ventilation and inducing rot in the woodwork. Everyone I ask has different views on that and there are plenty of horror stories about people getting this wrong and causing major problems for themselves. What are your views & plans on this?
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I am certainly not the final expert on this issue. There have been a couple of under-floor insulation projects on EcoRenovator, and I have read about and have seen photos of horror-story results, so it is with a degree of hesitation that I proceed.
The area I live in is described as having a 'maritime climate', which means that I live fairly near a very large body of water (the Pacific Ocean), and for my latitude, the seasonal temperature variations are relatively small. It also means that humidity is high most of the time except for brief periods during the summer.
So the area I live in is prone to having the kinds of problems of which you speak.
I even bought a "
Mold Alert" meter (amazingly accurate) that keeps track of temperature and humidity and continuously calculates mold growing conditions, and I do have mold growing conditions most of the time.
What I have been able to find out is that when humidity-carrying air is cooled below the 'dew point', the gaseous water vapor condenses and becomes liquid water, which is when the problems start.
First line of defense is to install a vapor barrier under the house on the ground. Right now the vapor barrier does not go up the short walls, but when I am through, it will. This should reduce the continuous rise of water vapor from the ground.
My floor joists are 7.5 inches deep. My project right now is to install foil-faced Expanded Poly Styrene (EPS) directly under the subfloor. Since it is foil faced, I need some kind of air gap, so I'm going for 1/2" air gap.
I've been working with rigid foam in my house a lot, and I have struck upon the method of fitting the EPS and leaving a gap of about 1/4" all around. After the EPS is in, I will come back and fill all gaps with one-part foam, so that the EPS is effectively a single piece, with no air gaps between foam-and-foam and no gaps between foam-and-wood. I have learned that EPS can shrink over time, so I will probably return in a few years to tape the foam-to-foam seems.
Currently the R-value of my floor is about R-1.5 (bad) after the work it should be about
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- Floor = R-1.5
- Air Space = 1
- EPS = 9
Total = 11.5
The state I live in recommends R-30 for floors.
Next year, I will put in more, with the goal in mind to get to R-30.
My scheme is to first, reduce the humidity somewhat with vapor barrier, and then prevent the moisture carrying air
from above the floor from reaching the point in the thermal gradient where it would condense.
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Originally Posted by SDMCF
The other issue is restricting the space even further when it is difficult to move around under there already. Your insulation will (I think) be up above the joists and so will not restrict movement, but I have no joists as such and any insulation would just lower my crawlspace "ceiling". That is maybe not too important as there is rarely any need to get under there.
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Your log construction is easy to visualize, and I have absolutely no clue as to how you could proceed, unless you totally isolated and insulated the entire space below your log floor.
And maybe some high R-value insulation above the floor.
Good luck with your project. Keep is informed as to your progress.
Best,
-AC