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GBlist: If my climate were drier, I wouldn't be a crier



> >Very interesting post, on a first scan it appears that moisture is not a
> problem even in cold climates.This confirms my exp. with cold climate wood
> burning where a large amount of outdoor air is required for combustion and
> chimney suction. I brought in theair quite close to the stove directly from
> the outside and yet i saw the humidity in the house drop as soon as cold
> and thus relatively dry conditions prevail.My airtight house did not vent
> any humidity- instead we distribute the humidity all over, vent the clothes
> dryer inside if not hanging them to dry, etc Occasionally i would see a
> momentary iceflower on the glass of my site built double unsealed glass-
> after you open the bathroom door you notce an amazingly fast spread of
> condensation first down and very quickly into the furthest corner.
> it is amazing how moisture creeps into anything and it diffuses all over..
> I had an occasional water drip problem when ice against the roof would melt
> during mild weather-a tiny crack against the chimney caused condensation
> and ice build-up. it is in such ceiling and attic places that miosture can
> do damage to strawbales as ice can cause large amounts of meltwater to drip
> into one spot on a bale.On the other hand, any house with single glass
> would grab any moisture and lock it up as ice on the windows and cause it
> to be out of the airmass .untill weather warms up and the ice melts and
> then???
> 
> Now to the reason for my post:
> You mention that you first deal with the moisture problem by "DP"
> it blocks the path of the moisture.What is this magic wand? can i have
> some? And what do you think of mixing latex paint with sand and clay as a
> finish adobe coat on interior strawbale? would exterior latex be necessary?
> iplan to run some tests through next year by leaving some bales out to test
> these compounds. I see it s  a way to recycle leftover paint and have a
> little business.Thanx for your opininion and do you think one can
> hammermill any paper and or fiber and or styrofoam (white) into a loose
> blow in recycled insulation? I had enercon recycled paper blown into my
> double stud 8" northwall and it worked well altho there was some bulging on
> the interior as i used 1/8" recycled sawdust panelling and it was not stiff
> enough so i recommend nailing strapping up on the inside
> and i used continuous airtight 4 mil poly, the sticky goop and all.
> It was an investment that paid off ever since.The plastic may not be
> necessary to keep out moisture but careful airtight detailing keeps in the
> warm air and produces  a higher relative humidity in our conditioned space.

Dear Prayan,

Thanks for your e, and your work with AT. 

I'm very big on weatherization because it is the most appropriate of
building technologies. We routinely upgrade the performance of old
buildings to (way) better than new standards. So if you would like some
of the magic, attend Affordable Comfort Conference next May in Madison.

On the subject of straw building, and sidestepping the story of the
Three Little Pigs, those of us in building performance circles have big
worries about these structures. 

Worry #1-decompartmentalized thermal envelope. This thing has caused
trouble in many other framing systems (steel studs, space joists,
envelope walls) and it is always tough to remedy.

Worry #2-low R-value. These walls are coming in at only R-12 due to the
large interstitial spaces between the straw. Now I'm the first one to
discount the importance of wall R-value in way a building works, but
R-12 just doesn't cut it in cold, humid climates.

Worry #3-face sealed stucco systems. This is an exterior wall finish
assemby that has no drainage plain. It's know to be a constant threat to
buildings and is thought to be unsuitable for building in climates with
more than 30" of annual rain. These coatings always leak and if there is
a lot of water, the inside of the wall gets trashed. The key to
performance is the moisture storage potential of the straw and the
ability of the wall to dry to the inside. And that brings up...

Worry #4-interior vapor diffusion barriers. When water gets into the
wall through the stucco, it is much harder for the vapor to get out. If
the inside is sealed, the wall is doomed. (again, in wet climates.) Does
the latex paint act as an efficient diffusion barrier. Dunno. It would
depend on the brand and the gloss too. Less is more!? I would be very
interested in the benefits of clay additive.

I'm not too excited about homemade insulation and that may be just my
blind side. But we know that mixing in other products opens up the pack
and reduces the critical resistance to convection. Bottom line, we are
insulating for a century of thermal performance and we want the optimum
product to get the most conservation leverage. There is the fire,
rodent, and insect protective function of the boric acid that is very
important to long term performance as well. There's no environmental
benefit in a burning building. 

I can't stress strongly enough that moisture accumulates in walls from
convection not diffusion. Plastic does nothing for a wall because it
cannot be made into a pressure barrier. For the same reason, you really
can't give it credit for controlling heated air. What ever solid
sheathing (inside or out) is present does that job. And it really kills
the drying potential of the assembly once it is wetted. Best to leave it
for soil contact.

One the matter of locking up water in a house. Gallons (sometimes
dozens) of water in vapor go through the weather shell of every house
daily. The smudge of frost on windows is literally the tip of the
iceberg.

I hope you have some good news about my worries. We envy you builders in
dry areas. Really, if you can build with mud blocks, just about anything
should work well. Here in Vermont, we know that water is natures great
destroyer, turning everything we build inevitably into soil.

Regards, Fred
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