<html>
<head>
<meta content="text/html; charset=windows-1252"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix"><font face="Helvetica, Arial,
sans-serif">Exterior shading of 24" overhanging a 8-9' high wall
</font><font face="Helvetica, Arial, sans-serif">works, maybe, May
June July but </font><font face="Helvetica, Arial, sans-serif">does
not help in April or September. These are the bigger problems,
as these months one can often have outdoor temperatures of 65 to
75 and full 200 Btu/hr/ft2 sun hitting windows. <br>
Exterior shades are absolutely the answer. Unless you have a
working couple in the home who are not in the house during sunny
hours. I guess that is unlikely, eh? This can be solved with
automatic controls on automated shades. If you want to spend
that kind of money.<br>
<br>
Orrr, you could just use lower SHGC windows. But if you want to
hit a magic space heating (rather than total energy use) target
using an imprecise program (like PHPP) then I suppose that
simple and low cost solution wont work :)<br>
<br>
This all reminds me of the old debate in the first round of
low-energy houses. One crowd wanted to use more and more glass
and hence mroe energy collection. The other said just insulate
and reduce energy need. Now we have a similar scenario.
Following the dogma of PH, everyone wants to use a high (0.6 or
more) SHGC to push to a rather meaningless space-heating
target, but in many cases lower (0.5 or less) SHGC will avoid
the risks of discomfort due to overheating and provide higher
R-values (almost always) at the expense of potentially slightly
increased winter space heating energy. But if you are willing
to risk comfort, you can save energy in other ways (e.g.
operating the house in winter at a colder temperature). There
are lots of examples of comfort problems already, leading to the
recommendations of lower SHGC (eg between 0.3 and 0.5 depending
on climate) and these will only increases as the houses get
better insulated.<br>
<br>
</font>
<div class="moz-signature">Dr John Straube, P.Eng.<br>
Building Science Corporation<br>
Westford MA Waterloo ON<br>
<br>
<a class="moz-txt-link-abbreviated" href="http://www.BuildingScience.com">www.BuildingScience.com</a></div>
On 12-08-15 1:14 PM, Alan Abrams wrote:<br>
</div>
<blockquote
cite="mid:CADj3_s67CbO3htOFHwHzT-FAw+A_4uGyJvVFoO1W9QJ8iEL3pw@mail.gmail.com"
type="cite">first, the use of exterior shading. southern
exposures in moderate latitudes only require a 18"-24" overhang to
fully protect a 5'-6' window in early summer, and allow full sun
in the dead of winter. E-W windows are almost impossible to
control with overhangs--but can be inexpensively and effectively
controlled with Interactive Shading Devices (aka shutters).</blockquote>
<br>
</body>
</html>