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<div class="moz-cite-prefix"><font face="Helvetica, Arial,
sans-serif">I dont understand what you are suggesting then
Corwyn if not 1-4. <br>
So you say: 1. dont lower the window SHGC, 2. dont use operable
shades and 3. dont change comfort expectation.<br>
Sounds like that is exactly what Corson has, and he reports, to
no surprise to me, that there is overheating. <br>
<br>
I am arguing against the dogma of "high SHGC windows are
generally a good solution for low energy homes". I beleive they
are generally a bad solution.<br>
Also I am arguing that current models dont properly predict
overheating (even the much lauded PHPP) and that fixating on a
specific space heating target rather than a total primary energy
target can lead one to poor designs than otherwise. <br>
<br>
Your 1. You are making a major assumption that a house with a
SHGC of 0.23 (pretty low, probably too low to get decent
daylight) is a bad house. What tools do you use to support that
and what metric do you use to measure this?<br>
<br>
Your 2. I was proposing 3-5 time reduction in primary energy use
of homes. Who said anything about status quo? Where did I ever
suggest that this was good enough or the right direction?<br>
<br>
Your 3. All energy targets are dependent on occupant choice.
People can choose to run their homes at 74 or 65F for example.
The target is a modeled number using fixed specified inputs to
avoid this. They can however install, gasp, curtains, and
reduce solar gain or they might even plant trees outside. No
target is immune from this. While we as designers have more
control over space heating and cooling than, say hot water or
computers, I do not think there is much evidence to support the
contention that rigorous space heating targets are much easier
to hit than rigorous primary energy targets. In fact, if you
look at the measured space heating usage of the famous
Krongsberg study, which was a PassivHaus development of a row of
townhouses, the actual space heating energy use varied by a
factor of over 5 from lowest space heating usage to highest
space heating usage even with a consistent target of the same
building design built by the same people, eg almost all of this
variation was due to occupancy. This is MORE variation than one
would see for houses built to the same total energy use. <br>
It is not my experience that a heating target gets more
attention from a builder than a total energy target. Having a
target is what seems to matter.<br>
And of course the environment cares only about total energy use
and energy type, not wether that energy is used for heating,
lighting cooking or TV.<br>
<br>
<br>
</font>
<div class="moz-signature">Dr John Straube, P.Eng. <br>
<a class="moz-txt-link-abbreviated" href="http://www.BuildingScience.com">www.BuildingScience.com</a></div>
On 12-08-16 2:28 PM, Corwyn wrote:<br>
</div>
<blockquote cite="mid:502D3BE1.2060401@midcoast.com" type="cite">On
8/16/2012 12:17 PM, <a class="moz-txt-link-abbreviated" href="mailto:jfstraube1@bell.blackberry.net">jfstraube1@bell.blackberry.net</a> wrote:
<br>
<blockquote type="cite">This whole thread started by mean pointing
out that an obsession with hitting an arbitrary heating number
can result in overheating and high SHGC are part of the problem.
<br>
Without asking people to make many changes in their comfort and
their lifestyle superinsulated homes can make very large
reductions (eg 3 to 5 times less energy that code built) in
their energy use.
<br>
Yes one may be able to get to 5.5 times less energy by asking
people to accept higher temperatures, operate shades or pay 10K
for automatic shades.
<br>
My argument is that there are small benefits to some of these
approaches and high social or economic costs.
<br>
Low SHGC windows, tighter comfort, giving up the arbitrary 15
kwh/m2 heating limit while still accepting the 120 kWh primary
energy number hardly seems like that flawed of a way forward.
<br>
</blockquote>
<br>
I did not say:
<br>
1) People should accept higher temperatures
<br>
2) Operate Shades
<br>
3) Pay 10k for automatic shades
<br>
4) Make ANY changes in their comfort level
<br>
<br>
I am not sure what you are arguing against.
<br>
<br>
My points:
<br>
<br>
1) Low SHGC windows in the house under discussion would *increase*
total energy usage, at the *same* comfort level. I never
recommend compromising comfort levels; I often recommend improving
them.
<br>
<br>
If he replaced his high SGHC windows with ones with s SHGC of 0.23
or lower, the windows would no longer be energy positive, and he
would be better off with a wall instead (which would do nothing to
cause overheating). In general, from a heating/cooling
standpoint, having windows which aren't energy positive is
counter-productive, especially if we expect that people can't be
bothered to open them. (There are, of course, other valid reasons
for having windows.)
<br>
<br>
2) The status quo is not sustainable. Attaining something
sustainable might require a live style realignment. Not attaining
something sustainable will definitely require a new life style.
<br>
<br>
3)(new) I agree that the arbitrary heating limit might not be
ideal. For a builder like Chris Corson, it really isn't, when he
is renovating, and hitting the limit is impossible, he gets as
close as he can. When he is building new, he sees how far *past*
it he can go. For other builders, having that goal actually gets
them to go out of their way to improve heating efficiency; without
the goal they would not have any incentive. For yet others, it
might be a spot where they say 'eh, good enough', when without it,
they would have gone further. My guess would be that most
builders around here fall into category 2, YMMV.
<br>
<br>
A total energy limit does not accomplish quite the same thing, in
that it is so dependent on changeable occupant choices.
<br>
<br>
<br>
Thank You Kindly,
<br>
<br>
Corwyn
<br>
Topher Belknap
<br>
<br>
</blockquote>
<br>
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