[GSBN] no Timber frame for Alberta house
sarahkh at lightlink.com
sarahkh at lightlink.com
Sat Sep 17 02:26:39 UTC 2011
I want to respond to Alex's assumption that a rugged timber frame is a "must"
for dealing with the Chinook winds.
Timber frames are not all that stiff. The bracing of a frame -- a few short
braces per wall -- is far less extensive than the
bracing of a stud wall by diagonal board sheathing, let alone plywood. And
as timbers dry and shrink, some of the braces will
become less tight than they were at raising day. The old timber framed barn
I used to live in creaked in the wind. I once had
a conversation with Bruce King about timber frame and straw bale, and he agreed
that the plastered bale wall is stiffer than the
frame, and provides the bracing for the building if it is strong enough.
I would conclude then that if a house is going to be slammed by powerful winds,
the more uninterrupted expanses of plaster
on inside and outsides of the walls, the better. As we discussed at our winter
meeting, timbers break up the plaster walls
quite a lot, requiring all kinds of fussing around with air fins, caulks, gaskets,
and the like. These would also be potential air
leakage points, made more significant by the strong winds pushing and pulling
air around the house. I'd go with a hybrid
approach, with roof structure held up by door and window framing and a minimum
of additional members inside the bale walls
(a la Clark Sanders, and others), and posts and beams in the middle of the house
helping to hold up the roof or ceiling.
Timber ledgers fastened to exterior walls could catch the ends of timber joists,
if those are part of the design. This approach
ought to be cheaper as well.
I would also want to see a strong and well-cured plaster on the walls, and supported
on the foundation. This would be the
key to the house's wind resistance, in my mind. Supporting it on the foundation
means the house would be best off with a
continuous foundation at the base of the walls.
I'm not an engineer, so other strategies might suffice, but I believe this approach
would be the strongest and most reliable
over time.
Tying the house to the ground structurally would not only tend to make it stronger,
but also help make it able to weather
periods of no heat without freezing. This was a key design criterion of the
Buffalo House project in South Dakota, organized
by the Intertribal Council on Utility Policy and Laura Bartels. The HUD houses
built by the Tribal Housing Authority on the
Rosebud Lakota reservation were generally built on piers AND badly insulated.
They cost a fortune to heat in the Great Plains
winters, and when people were not there paying for heat, the pipes froze.
So the Buffalo House is a model project to show
that a HUD-style size and shape can be built with straw bales over a crawlspace,
with passive solar consideration in the
window design. Not only is it intended to be heated for much less cost, but
it is supposed to demonstrate "passive
survivability" i.e. not freeze when someone isn't home. Even if a homeowner
intends not to stop paying the heating bills in
the winter, this model suggests that there is a thermal advantage to putting
a house on the ground, and it is designed for a
similar climate to Alberta. (Intertribal COUP has a website for those interested.)
Thanks,
Sarah Highland
>
>
>A majority of the strawbale houses, built to the Passiv Haus standard, that>
I visited in Europe a couple of years ago, were
built on piers. They had >massive insulation in the floors as well as the walls,
usually with strawba>les in the floor. All of
these houses had free air space between the groun>d and the top of the piers.
I asked whether this was a contradiction with
>the goal of maximum energy conservation. The reply was that the moisture r>isk
created by blocking air flow is a serious
consideration, and sufficient> insulation takes care of the energy loss problem.
>
>Although Canada's maritime provinces don't have the extreme weather of Albe>rta,
I believe that many of the SB houses
there are built on piers. Kim Th>ompson (sp?) may be able to tell us.
>
>Derelict
>Derek Roff
>
>On Sep 15, 2011, at 12:54 PM, ejgeorge at riseup.net wrote:
>
>> Hey Mark & Alex,
>>
>> That's what we did for our house. Pier foundations with posts sitting on
>the piers but the floor cantilevers out a bit to
hold the bale walls (we we>nt with a full wrap instead of infill for less thermal
bridging and improve>d airtightness). The
entire floor cavity (including cantilever) is insulate>d with blown cellulose.
We then stacked stone underneath for a faux stone
f>oundation to 1) cut wind from blowing underneath and 2) aesthetics.
>>
>> You can see some of the details in photos on Aaron's website:
>> http://www.tugleywood.com/
>> (under photos, under Dennis-George House)
>>
>> It certainly was the quickest and cheapest option, but has some cons too,>
including all the general cons of uninsulated
crawlspaces such as critters> and convective heat loss under the floor (though
I have to say, the dry-la>id stone around the
perimeter did a surprising job cutting that down).
>>
>> Also, I don't think it's as sturdy as a full foundation would be - e.g. i>f
someone really slams a door or the washing
machine gets unbalanced on the> spin cycle, you can feel the whole house vibrate
for a second. That could >be partially due
to the height of our piers (only 16" or so on one side of >the house but 3 1/2'
or so on the other as the grade slopes down).
This mig>ht be more significant when considering your cousin's wind extremes.
We're >somewhat exposed on a plateau and
get some good winds, but nothing near the> extent he'll be dealing with!
>>
>> Feel free to contact Aaron & I if you have more questions or want more de>tails.
>>
>>
>> ej
>>
>> ej George, CSBA
>>
>>
>>
>> Quoting "Mark Piepkorn" <duckchow at potkettleblack.com>:
>>
>>> Hi folks,
>>>
>>> A question or two from Alex Wilson, who some of you know. If you don't,
>see
>>> http://www2.buildinggreen.com/about/people/alexwilson
>>>
>>> I attempted to write a brief synopsis here of his contributions to impro>ving
the built environment starting way back
before "green" was a word that> went with "building," and failed utterly. Suffice
it to say that he's more> than earned our most
thorough and considered responses. Please be sure to >CC him at alex at atwilson.com
>>>
>>>> My cousin Allyn is considering building a timber-frame/straw-bale house>
on a piece of land he owns in Alberta,
Canada. It is land adjoining his si>ster's ranch in the foothills of the Rockies
of southwestern Alberta. He wa>nts to build it
really cheaply and was thinking that he might save money by> avoiding a full
perimeter foundation--and going with piers or
something li>ke that. But I don't see how he would support the straw-bale walls
in this >case.
>>>>
>>>> Any thoughts on that? Have you ever heard of someone doing that?
>>>>
>>>> Any resources I might recommend to him on building a low-cost timber-fr>ame/straw-bale
home? Or any really neat
designs you've seen?
>>>>
>>>> The Chinook winds there are wicked, so I think a rugged timber frame is>
an absolute must with straw-bale. Right near
the ranch, they've recorded a> _full week_ where the steady wind _never dropped
below 60 mph_ and a full >hour where the
steady wind never dropped below 100 mph!
>>>>
>>>> My cousin Lucy (Allyn's sister, who owns the ranch), with her then-husb>and,
built a timber-frame with in-fill straw-
bale walls maybe 25 years ago,> and as far as I know it's working great. The
bale walls are a huge benefit> in sound
deadening. With the very strong Chinook winds in the spring, the >constant noise
of the wind can drive people crazy--literally.
The suicide r>ate goes up in that region, apparently, when it's really windy
and people s>peculate that noise is the main
factor.
>>>>
>>>> Thanks for any thoughts and suggestions you can share.
>>>>
>>>> Hope you are well.
>>>>
>>>> Cheers,
>>>>
>>>> -Alex
>>>>
>>>> 39 Leonard Road
>>>> Dummerston, VT 05301
>>>> /On sabbatical from BuildingGreen, Inc. through November, 2011/
>>>> 802-257-0019 (H)
>>>> 802-579-4858 (C)
>>>> www.atwilson.com <http://www.atwilson.com>
>>>> Twitter: http://twitter.com/atwilson
>>>>
>>>> /"Anyone who believes exponential growth can go on forever in a finite
>world is either a madman or an economist."
Kenneth Boulding, circa 1980/
>>>
>>>
>>> Strawbale on piers is doable. It's a reasonable choice for budget-minded>
owner-builders, especially if they have big
wood for the floor sills as a >readily available local commodity. The thing
with that scheme is dealing wi>th the floor
insulation.
>>>
>>> It's easy enough to calc spans using common charts based on estimated we>ight.
Considering his local soil qualities may
be important.
>>>
>>> I think the best owner-builder designs are the simplest ones. Keep it si>mple
and well thought through. Don't wanna be
building some fancy folly for> years to come; get it over with and get on with
life. He might enjoy looki>ng around
www.balewatch.com
>>>
>>> With your permission I'd like to forward the pertinent parts of your not>e
to a small email list populated with a raft of
strawbale hotshots.
>>>
>>> I hope the sabbatical is doing wonders.
>>>
>>>
>>> Mark
>>>
>>>
>>
>>
>>
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>
>Derek Roff
>derek at unm.edu
>
>
>
>
>
>
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