GBlist: Re: Natural sealants

Marc J. Rosenbaum (
22 Feb 97 07:57:10 EST

Thanks for everyone's thoughts thus far on this one. This is an unusual
circumstance - a rustic second "home" which is an object of incredible beauty
and craftsmanship, and also the leakiest building I have ever blower door

I don't yet know precisely what the owner's criteria were in approving
materials and techniques - perhaps i should get clearer on that before we
continue the discussion. To my way of thinking, the criteria couldn't have
been "most sustainable", because, even as Hal is clear to remind us that we
don't have very good tools to evaluate this, I'm pretty certain that the roof,
which is clear Alaskan yellow cedar on the inside, and red cedar shingles on
two inch exposure on the exterior, isn't a great choice in northern New
England. And a building with a design heat loss of approximately 80
Btu/hour/ft2 is just plain awful!

I am proposing that the failed straw-clay walls be torn out, and that a
double-stud wall, sheathed in fiberboard (which has been used elsewhere in the
house) and filled with dense pack cellulose, replace it. I would like to seal
the fiberboard to the timber frame to be the air seal. That's the most
important location. I also think that sealing some wood-to-wood joints at the
point where the rafters meet the top plates will be helpful. So those are the
types of places I have in mind. They are not critical for keeping water out of
the building, and they are on the interior side of the insulation, so they are
warm and out of the weather.

I wish you could see this house. The wood is all hand planed with Japanese
planes - no finishes at all - and it feels like glass. But the blower door and
the fancy IR camera told the story - what a thermal disaster!

This house confirms two of my prejudices, which you all are invited to take
contrarian views on:

1) The more one is trying to do something very unusual, the more one needs a
qualified design professional. I have done troubleshooting on homes that cost
as much as 2 million dollars where fundamental and serious errors were
committed and were nearly impossible to fix.

2) People can make some very bad buildings in the cause of "natural" or
"sustainable". Until such time as we have rigorous tools, I will continue to
believe that energy efficiency is near the top of the list of sustainable
criteria. And human habitability is perhaps even higher - this building, with
its masonry heater, is barely possible to keep above freezing on a winter day!

Anyway - I am going to agree with Hal that I don't have much of a basis to
determine whether one thing is more sustainable than another in a building, and
I think we might all be mindful of our claims in that area. And at the same
time, I am grateful to Bower and Bunzick (the Johns) for their suggestions. In
the absence of formal criteria, we have only our heads and our hearts (analysis
and intuition?) to guide us in the decisions that those of us actually
designing and building have to face on a daily basis. In other words, I gotta
fix this house!


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