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GBlist: Re: SB: in-situ window testing
Nehemiah: Thanks for your posting as attached on the above topic. As
somewhat else mentioned on the SB list, what is the sense of make +R-43
strawbale walls/roofs and then poking holes with R-2 windows
that may even be very air leaky (if reused)? That is why for colder
climates we are researching high performance windows.
Our effort is to do the theory, simulations and fabrication in a short turn-
around real-world application, with Industry partners such as Willmar Windows
and others, without getting stuck in some academic
lab for months or years. In-field applications (in the real-world human
context), not labs, are the key to success or failure (in this application).
High performance windows can be justified for small windows in critical
areas such as bathrooms, kitchens, etc. where heat loss, comfort and
condensation elimination (together with HRV) are the chief criteria.
When working on +R-17 (Center of Glass, or COG) prototypes, initial costs
are expensive, but no different than any innovative technology, cost
come down later. First we have to answer many more urgent questions such as
it can be built, will it stand up to environmental stresses of the
environment, can you see through them, will the suspended mylar of the
inner glazings develop waviness, is there any condensation, does the
shading coeficient have a perceived effect on view or daylight, what
is the marketing response, is there a real need or context, what is the
actual on-site performance, what are the strengths nd limitations of the
technology, etc. All thses must be answered first and cannot be aborted by
the single criteria of $/SF, no matter how important it is.
I thank you for your post and have already made effort to contact LBL.
However, I am still looking for simple, effective, truthful and down-to-earth
monitoring that can be replicated by others that will do the trick, rather than
imported testing rigs from the LBL that are not applicable at this time.
Any practical enlightenment is always appreciated. Have a wonderful day.
Jorg Ostrowski, M. Arch. A.S. (MIT), B. Arch. (Toronto), Ecotect
- in full-time professional practice since 1976 (Straw Bale since 1978),
environmental/architectural design, ecological planning, consulting
on sustainable buildings/communities. Lectures, seminars, workshops.
3 demonstration projects in Canada, +80,000 visitors
- living a conserver lifestyle & working in a sustainable home and office
ACE, ARE, ACT, ASH-Incs., Phone: (403) 239-1882, Fax: (403) 547-2671
Web Site [under construction]: http://www.ucalgary.ca/~jdo/ecotecture.htm
On Tue, 1 Jul 1997, NEHEMIAH STONE wrote:
> On Mon, 30 Jun 1997 12:42:03 -0600 (MDT), Jorg Ostrowski
> <email@example.com> wrote the following on the Subject: SB: high
> performance on-site window test:
> Further to the note of below and further to the on-going thread on high
> performance windows, we have several different window technologies which
> we would like to test in our most recent demonstration project,
> 1) 3 different types of gases
> 2) 2 different types of thermal breaks
> 3) 2 different types of glass
> 4) several different types of low E coatings/films
> 5) several different R-values: from a low of R-5 to R-17 (prototype)
> (all are off-the-shelf, even the R-12 windows, except the R-17)
> 6) 4 different window shades
> 7) 2 SunPipes
> We are hoping to install an R-20 window (using xenon) into the project
> later this summer.
> What is the most: simple, cost-effective, reliable, and appropriate
> on-site test that can be done to check the actual performance and center
> of glass insulation value? Anyone interested in practical advice or
> useful participation?
> Jorg, and others,
> Lawrence Berkeley Lab has been doing in situ testing of fenestration
> products for over a decade in a facility called the MOWITT (mobile
> window testing something or other). The facility has been situated in
> Reno, NV most of the time but I believe it has been sited elsewhere part
> of the time. The people you should probably speak with are (1) Joe
> Klem, (2) Dariush Arasteh, and (3) Steve Selkowitz. I only have
> Dariush's phone number on hand; (510)486-6844. Steve is the head of the
> Windows and Daylighting Division at LBL, Dariush heads up the Windows
> section and Joe operates the mobile test facility. They would have
> better information than probably anyone around on in situ testing.
> On another note, you should probably make it clear when you are talking
> about R-20 and R-15 windows that you are speaking about the center of
> glass values (which will almost always be better than the product's
> overall average value). An R-17 window (as opposed to an R-17 glazing
> unit in the window) would have a U-factor of 0.06. [Note: U-factor is
> the inverse of R-value. Where R-value denotes a products ability to
> resist the flow of heat through it, U-factor is a measure of how many
> Btus flow through each square foot of the product in each hour, for
> every one degree diference between the inside and outside temperatures;
> Btu/(sq.ft. * hr * F).] Just to put that into perspective, a window in
> the National Fenestration Rating Council's Directory of Certified
> Products with a U-factor of 0.14 (much worse than the 0.06) has a vinyl
> frame, three layers of glass with two 3/8" spaces between them, krypton
> gas, a steel spacer, and a super low emissivity (e = 0.04) coating on
> TWO surfaces of the glass. Any guess what such a window might cost?
> Roughly $15.00 per square foot premium OVER the normal cost of window;
> or, an incremental cost of $360 dollars over a standard dual glazed
> product. ... One window! Now if we were to find a way to get the
> U-factor down to 0.06, it is reasonable to expect that the incremental
> cost of each (less cost effective) feature that we would have to add on
> over and above the features already in the equation, would be much
> greater. It is not inconceivable that getting down to 0.06 (and R-value
> of 17) would make the average sized windows cost over a thousand dollars
> On the other hand, if the number we are discussing is the
> center-of-glass R-value (or U-factor), then an R-17 (U-0.06) is
> "reasonably" achievable at a much lower expense.
> Whether the extra expense would be worth it is dependent upon a number
> of other, non-window, considerations. Greater expense is justified if
> you have a verrrrry cold and long winter. ... if your house is
> basically uninsulated and it would cost too much to insulate the walls
> (not too relevent for subscribers to a straw bale construction list, i
> would guess). ... if you use electricity to heat your home (dumb!) ...
> or if you have an otherwise in efficient heating system. the more
> costly your heating options are the more cost effective is a technology
> that would lower your heating requirements. But at almost any design, I
> have a hard time believing that (outside of the arctic circle), R-20
> windows, or even R-17 windows are anywhere near commercially viable
> (cost effective) prices. Please, if I'm wrong let me know the brand and
> type of windows that you know of which have R-15, R-17 and R-20 values.
> Nehemiah Stone
> California Energy Commission
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