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Odd Hatches on Shed Roof


Jim Katen
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I just can't figure out this one.

1970's passive solar house designed by Alfredo De Vido.

It has shed roofs with a huge array of skylights. The upper portions of the skylights end beneath the overhang of the opposite shed. Then, above each skylight panel, is a hinged plywood lid. These plywood hatches aren't waterproof in any way. If I pour a cup of water on them, the water runs around the edges of the plywood and falls straight down into the house.

Now, these hatches are covered by the overhanging roof. But the open side of the overhang faces south -- the direction that the wind blows from during 99% of our rain storms. They're sure to get wind-blown rain on them and that rain is sure to leak into the house. During winter, there's bound to be snow & ice in there.

Why are these hatches there? They're about 22' above the floor, way too high for anyone to ever reach without running an extension ladder up to each one individually. I've seen similar designs where there's a narrow walkway or loft that runs under these so that someone can open them for ventilation, but no such walkway exists here. What am I missing? Is there some passive solar scheme that was, perhaps, not finished? Maybe something involving a vertical wall or panels just along the top edges of the skylights?

- Jim Katen, Oregon

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That brought back memories.

There were all sorts of goofy ideas about building envelope design back then. I worked on a couple architect designed gigs which, in retrospect, ended up as something neither smart nor efficient.

Alterations were made to correct some real or perceived fundamental flaw in the "energy efficient" design, maybe there were some ill conceived idea about tweaking some aspect of envelope performance.

People thought that way then. A lot of them were moving to Oregon.........

That's my guess anyway.

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Jim. I think you left some claws marks on the glass in the second pic. Please go back with some glass cleaner. The sellers are very upset. [:)]

My guess is that there is so much indoor heat accumulating in that peak, that the moisture around the plywood is evaporating? That and soaking into the framework. Did you make any recommendations?

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Jim. I think you left some claws marks on the glass in the second pic. Please go back with some glass cleaner. The sellers are very upset. [:)]

My guess is that there is so much indoor heat accumulating in that peak, that the moisture around the plywood is evaporating? That and soaking into the framework. Did you make any recommendations?

I wrote two separate comments about this area:

Unsealed Panels above Skylights

The roof above the skylight array is not waterproof. The plywood panels at that location have no shingles or other roof covering over them and there’s no flashing around them. When I pour 4 oz of water onto those panels, 4 oz of water falls through them onto the floor below; it isn’t even slightly waterproof. This area is covered by a shed roof extension so, as long as rain only falls straight down, this section of the roof stays dry. However, if the wind blows from the south when it’s raining, water will leak into the house.

36. Consult with a roofer to design and install a method of preventing wind-blown rain from entering the house via the roof area above the skylight array.

FYI – Hinged Roof Openings

The hinged plywood panels just uphill of the skylight array look as if they were meant to be openable, possibly for ventilation. If this was the case, I see no means of reaching these panels to open them manually, and I see no mechanism to open them remotely. It’s possible that this building feature was abandoned at some point in the house’s history, perhaps even during the construction process.

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Is there water damage in the house that looks like it may have been done by those hatches? If your hypothesis is correct, I'd expect to see lots of it.

Marc

Yes, that's the curious thing. There was not the least sign of water damage -- at least not any that I could see from the floor, 22' below.

On the other hand, the interior beams around the hatches were finished with glossy polyurethane that might well resist showing signs of leaks for years, especially if the leaks only occur a few times per year.

The floor below was tile.

All of the walls were freshly painted.

It's just possible that these things could have been leaking during only the fierce storms for the past 30 years and not show damage.

- Jim Katen

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.............................than the 1-1/2 acres of skylights that were on this building.

OK, that (sort of) confirms my first knee jerk response. I bet this thing is a solar oven certain times of the year. The hatches are there to let out the hot air.

Again, just guessing. They're still stupid.

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I got curious....

http://www.allwallsystem.com/design/RValueTable.html

The R value of half inch plywood is .63

The R value of single paned glass is .91

Ok, well, these were insulated glass skylights and they had some kind of super-duper reflective coating on the uppper pane because, with the sun shining, I couldn't see a damn thing through them, they looked just like mirrors.

So I suspect that the plywood hatches are, indeed, thermal holes and the reflective coating probably does reduce thermal gain in summer.

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Like Kurt said, if there are that many skylights it probably is a thermal oven in there, which would likely make those panels some kind of poorly designed ventilation.

Coincidentally, I just say an episode of Modern Marvels were they were discussing the heating method at The Mall of America in MN. There actually isn't any type of mechanical heating system used there at all. All heat is generated from solar gain through their skylights and heat generated from rabid consumers. They actually have to run their a/c system year round.

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Coincidentally, I just say an episode of Modern Marvels were they were discussing the heating method at The Mall of America in MN. There actually isn't any type of mechanical heating system used there at all. All heat is generated from solar gain through their skylights and heat generated from rabid consumers.

Body heat - the best kind, ask any Canadian igloo dweller. [:)]
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