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GBlist: R-20 windows and other (possible) wastes...



Sorry list.... can't resist....

Regarding "leading edge" window developments, green and otherwise.....

In the spirit of "whole building mindsets", and even though I am often one of
the first to proclaim the benefits of energy efficient windows, I also
believe that we do not NEED an R-20 window.... not that the technology that
it might incorporate would be VERY interesting (and I will stay in the
discussion because of that).  We don't NEED one if we treat the house as a
WHOLE and PLAN our window placement, performance requirements and longevity
expectations...

Our friends at LBNL and MIT and NREL and Los Alamos and other places have
shown that windows can be net energy gainers.... both seasonally and
annually.... heating and cooling.... especially when we view ALL aspects of
window performance (U-factor, Solar Gain, Air leakage, etc.)  We can easily
show that a window with a fairly low U-factor, say 0.2 to 0.3 and a
reasonable Solar Heat Gain Coefficient, maybe 0.4, can be nearly energy
neutral in most of the US.  WAIT! ... and in Canada, maybe a bit higher solar
gain is needed and maybe a bit lower U-factor.  Still, R-3.3 to 5.0 is a long
way from R-20.  and even if the surface temperatures would be a bit warmer
and the condensation would be less, will the costs ever justify the MARGINAL
increase in energy savings?  and will the embodied energy of the technology
ever BALANCE against these savings?

OKOKOK, I'm not intending to squelch the discussion.... because it is needed
as a part to raise the most BASIC levels of understanding about windows and
the conservation opportunities with EXISTING technologies.... let alone
electrochromics or vaccum or other "high tech" solutions.... (the passive
solar hippie in me sighs loudly....)

I just wish we would better use what we have today.... I wonder how much
energy that would save?   OH, we have the answer to THAT question...  In a
1996 paper by Dariush Arasteh and Joe Eto at LBNL, they projected that if we
could replace all existing residentiall windows with CURRENTLY AVAILABLE
TECHNOLOGY,  we could save about 4 quads..... annually..... that's 4
QUADRILION Btus..... about 1/20 of the total annual US consumption.....

Of course, this issues is kinda like saying, do we need a 32 valve, fuel
injected 350 horsepower car when Jorg's 440,000 km Honda is still going
strong? (by the way, I drive a Honda too.....) 

Peace to all,
Chris Mathis
MCSquared


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