<div dir="ltr"><div>Laren, <br>this method sounds great. I'm going to give it a try. The <i>Ice and Water Shield</i> product I'm finding is wide. Can I use flashing tape used for windows instead? I have that, and it is already much closer in width to what I need.<br><br></div>Or do you use a product more closely sized to what we're talking about here? <br><br>Thanks. <br></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, May 7, 2014 at 3:29 PM, LarenCorie <span dir="ltr"><<a href="mailto:larencorie@axilar.net" target="_blank">larencorie@axilar.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">From: "Michael O'Brien" <<a href="mailto:obrien@hevanet.com" target="_blank">obrien@hevanet.com</a>><br>
<br>
</span><span class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
I would like to encourage you to set the glass panels in<br>
gaskets or flexible blocks that would hold securely, yet<br>
allow the glass to expand and contract with temperature<br>
changes.<br>
</blockquote>
<br></span>
Hi Michael;<br>
<br>
Your priorities are right on. However, in this case, there<br>
is a simpler way to mount the glass that is easier, more<br>
durable, and also a lot more water tight. That is to lay<br>
the glass on top of the rafters (ideally beams, so they<br>
have adequate width for lap and movement) with a<br>
stop, only at the bottom. If there is foam insulation<br>
available, about the thickness of the glass compressed<br>
(or slightly thinner), cur it to bring the rest of the area<br>
up to level with the plane of the face of the glass. Leave<br>
a very small gap between the foam and glass edges.<br>
Only minimal is needed, for movement, since the foam<br>
will flex. Once the whole plane (roof around the glazing,<br>
in this case) is level, cut strips of Ice & Water Shield, or equivalent, to cover all non-skylight areas. It should<br>
overlap the glass as much as possible, without being<br>
visible from below/inside (or just a nice straight edge,<br>
barely visible). Get a smooth piece of wood (or<br>
comparable) and use it to burnish the I&W shield<br>
where it bonds to the glass, to make sure that all<br>
the air bubbles, and crease lines are rubbed out.<br>
Battens can then be installed over the edges of<br>
the glass (keep screws and nails away from the<br>
glass edges). Wood battens tend to cup, so I<br>
recommend batten material that will not, such<br>
as fiber cement boards.<br>
<br>
Detailing for the lower end of the glass is significantly<br>
trickier than described above. It is highly advantageous<br>
to avoid creating a gutter that would accumulate leaves,<br>
and other roof dirt/debris. Ideally, you want the glass<br>
to slightly overhang the wall, or most outward structure<br>
(even a fairly conventional eave) so that water running<br>
off it, will fall outside the structure. I have often used<br>
an aluminum angle with a short leg, about the same length as the thickness of the glass. No cap or batten<br>
covers the glass along this edge. Just fill any gaps with a quality silicone sealant. Water and debris<br>
should freely slide off the edge of the glass roof.<br>
I did quite a few of these, back in the early 1980s,<br>
with design details to control overheating, and even<br>
used it to heat the domestic hot water. If it has<br>
potential for Summer overheating, why not use that<br>
heat? Under such a roof can be a pretty good place<br>
for a batch water heater. <br><span class="">
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
With big panels it's a significant issue, because if the<br>
glass expands in a frame that can't flex and causes<br>
pressure on along its edges, it might fracture.<br>
</blockquote>
<br></span>
That is why it makes no sense to create rabbets to set<br>
the glass down into a place where it could get pinched.<span class=""><br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
If you look at a cross-section of a commercial glazing<br>
system you can see elastic gaskets between the glass<br>
and frame.<br>
</blockquote>
<br></span>
Standard glazing tape does a very poor job at sealing<br>
site-built glass roofs. The problem is that, because it only<br>
seals the tiny distance between the glass face and a stop<br>
or batten, it lacks the ability to bridge gaps that increase<br>
by more than about 1/16", whereas the taping system<br>
I described, can remain weatherproof, even if the<br>
glass, were to moves an inch or more.<span class="im HOEnZb"><br>
<br>
-Laren Corie-<br>
Natural Solar Building Design and<br>
Solar Heating/Natural Cooling/Energy<br>
Efficiency Consultation Since 1975<br>
<a href="http://www.ThermalAttic.com" target="_blank">www.ThermalAttic.com</a> (many new<br>
photos and pages, coming soon)<br>
<br>
Read my Solar house design articles in:<br>
-Energy Self-Sufficiency Newsletter-<br>
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<br>
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<br>
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