[Greenbuilding] re glass panels as porch roof

Benjamin Pratt benjamin.g.pratt at gmail.com
Tue Jan 14 14:18:38 CST 2014


A couple of years ago, we had a tornado in Minneapolis. A few hours later,
after the storm had long since passed,  and ten miles away, a storm door
crashed down in someone's backyard, intact.


On Tue, Jan 14, 2014 at 1:31 PM, RT <archilogic at yahoo.ca> wrote:

> Reuben wrote:
>
>  figured [double-walled polycarbonate] would lighter, easier to fasten,
>> consistent across the full length (5 equal patio doors)
>>
>
> BC John wrote:
>
>  I worry about non laminated glass as tempered can still cut
>>
>
> Clark wrote:
>
>> the first one was torn-off by ice 10 years ago.battens holding the glass
>> down were cedar 5/4 x 3
>>
>
>  The main roof is 7.5/12 (aka 10/16, the golden mean) steel, allowing the
>> ice to slide,that time taking my panels with it.
>>
>
> Reuben mentioned initially that the porch roof would be 35 ft in length.
>
> The IGUs from three, six-ft wide patio doors would yield 12 sheets of
> glass, nominal coverage 12 x 3' = 36 ft.
> (The actual width of the glass would be ~ 34", spaced 1.5" between edges
> of the glass ( {[1/2" bearing + 1/4" expansion clearance for each sheet]
> x2} + 1" batten bearing surface = 2.5" batten
>
> The above bearing/batten details  would be the same regardless of whether
> the panels were glass or plast-ecchhh!.
>
> One of course can use the store-bought extruded aluminum glazing bars,
> clamping bars and batten caps but for residential apps, the cost can be
> prohibitive not to mentioned needlessly high in embodied-energy costs.
>
> Wood is fine for all of the above components so long as it is detailed to
> anticipate and deal with water.
>
> ie It used to be that the local building supply would carry metal studs
> and track made from galvalume stock.
> The track for 2.5" studs could be modified slightly so that it would do
> nicely as snap-on weather-proof caps for 2.5" wide wooden clamping bars
> (aka battens) which could either be pre-painted if desired or left au
> naturel. The modification consists of bending a small lip onto the legs (at
> one of edge-stiffening creases already formed into the channel by the stud
> manufacturer) so that it would catch the edge of a rebate milled into the
> edge of the wooden batten, the rebate designed to function as a caulking
> allowance.
>
> I prefer to custom-bend the batten covers from strips cut from sheet stock
> intended for exterior use and mill bevelled-edge wooden battens, slightly
> narrower than 2.5" at the top face).
>
> No exposed fasteners and no rough surfaces to catch/hold snow or ice.
>
>
>                              *
>
> I think that the concerns about being cut by non-laminated tempered glass
> are unwarranted.
>
> Plain tempered glass is virtually indestructable. Pretty much the only way
> that it can be broken is if the edge receives a sharp impact (which
> includes being pressed up against the shank of a metal fastener due to
> insufficient edge clearance (including expansion allowance) being provided.
>
> I've had door panels that were temporarily leaned up against a porch,
> picked up by winds and thrown a few metres landing face-first on some large
> blast rock (ie sharp edges) without breaking more than a few times. It was
> easy to see where the rock impacted the face of the glass because the
> boulders left a streak of abraded stone dust across the face of the glass
> (which washed off).
>
> I think that it was last year I mentioned on this list where I reported
> that ice & snow accumulations on a almost zero-slope sheet of 3 ft wide
> tempered glass on a walkway canopy, glass supported only along the
> longitudinal edges had deflected 1.5 inches at the midspan of the
> unsupported 3 ft width under the weight of the couple of feets-deep
> re-frozen snow/snow melt ... without breaking. I've had people tell me that
> cows have walked across their sheets of tempered patio door glass without
> breaking it.
>
> In the unlikely event that tempered patio door glass does break, it will
> break by exploding into a gazillion little harmless ~ 1/4" chunks  ... not
> as large dangerous shards as would be the case with untempered glass.
>
> Pretty much the only way to get cut is if one laid down nekkid in a pile
> of the chunks and purposely ground one's flesh into the glass chunks.
>
> I'd venture that laminated glass would be more hazardous because it'd come
> down en masse, all of the broken mass being held together by the
> plast-ecchhh! sheet laminate so while one may not get cut by pieces of
> falling glass, one would get a pretty good bump on the head being hit by a
> 60 pound mass o' glass.
>                                                   *
>
> And an off-topic "heads up" to listmembers who eat chicken nuggets and
> have small dogs:
>
> http://www.youtube.com/watch?v=_ym0rxisOpw
>
>
>
> --
> === * ===
> Rob Tom                                 AOD257
> Kanata, Ontario, Canada
>
> < A r c h i L o g i c  at  Y a h o o  dot  c a  >
> (manually winnow the chaff from my edress if you hit "reply")
>
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-- 


b e n j a m i n p r a t t

professor art+design
the university of wisconsin stout
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