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-   -   Passive cooling in AZ with a second roof? (http://www.advrider.com/forums/showthread.php?t=856071)

dentedvw 01-16-2013 03:11 PM

Passive cooling in AZ with a second roof?
 
The company I work for has decided to start deploying buildings in small shipping containers to jobsites, some of which are in the desert. In Arizona, in particular, we have one that get incredibly hot, which is pretty bad for the UPS inside. It's not supposed to get over 80F, which is going to be tough on the little AC unit they speced. I am recommending we start out with a roof over the building, but I am not an architect, and I want to show them a picture demonstrating what I am talking about. I don't think adding half a dozen more AC units is the answer. :deal Especially since we manufacture and service solar generating equipment. Too many AC units, and we might as well just turn off our equipment and go home because it becomes a net loss.

I know I have seen these things before, but I don't know what to call them. Usually they are just steel, and provide shade to a building/trailer/whatever like a canopy.

Whatsit? Where to get info?
Derp?

Also, if you are in Yuma, and want to grab a wobbly pop sometime, drop a line because I am headed down again soon.

troidus 01-16-2013 04:25 PM

Probably nothing available off the shelf. If it's a standard shipping container, you could probably clamp some trusses to the top and put corrugated sheetmetal on top of that. Paint that white to reflect as much energy as possible. Make sure you have enough overhang to shade to the bottom of the structure from midmorning to midafternoon.

PirateJohn 01-16-2013 04:51 PM

On a vehicle you would call it a tropical roof. I have seen them on Land Rovers and MCI buses that were in service in Saudi Arabia. Basically just a second roof skin with maybe an inch airspace between roof skins, you just need some sort of aluminum or steel rib every foot or two to support the second roof. On the MCI bus I saw it at a show in the USA after it had been returned to the States and compared to other buses on exhibit that day it was noticeably cooler.

DaveStockwell 01-16-2013 04:53 PM

You're looking for an aluminum or steel carport. A little Google says Superior Awning in Yuma can supply them: https://plus.google.com/106205160716...ut?gl=us&hl=en

Also consider some baffling inside the container that directs the cold air from the conditioning unit into intake of the UPS units. This will localize the cooling. It there's other electronics you need to cool using plastic curtains to create a cold side and a warm side within the equipment racking will help.

http://www.absolutesteeltx.com/image...rage-Cover.jpg

dentedvw 01-17-2013 09:47 AM

Good ideas, thanks!

P B G 01-17-2013 10:00 AM

I'd be thinking of a reflective canvas tarp with your company's logos on it, mounted above your building, with an awning to shade the entry.

Like a boat lift

doxiedog 01-17-2013 08:50 PM

I had my 5th wheel,under a carport like that.
It made a lot of differance on a 100+ day.

wallache 01-18-2013 11:05 AM

Tempuratues in the shade in the Yuma area can get into the high 110's during the day and in the high 80's at night. A shade canopy will help quite a bit, but extra insulation is your friend.

Purcell69 01-22-2013 04:04 PM

When I had my house in AZ, I had a contractor friend turn my attic into an Igloo cooler. We added insulation between the rafters, up to the roof decking, held in place with wire mesh. The house was evap cooled, with up-ducts venting into the attic. We also added gable fans in thermostats at either end of the attic, set to come on when the attic reached 105 degrees.

Once it was all done, my colling bill was 1/3 of what it had been and the house was a lot cooler (55 degrees vs. 78).

-Joe

RTCHIEF 01-22-2013 05:58 PM

Heat
 
Position is the first thing, under a tree, in a shadow, prevailing breeze.

Orientation is next, the east sun is hotter than the west sun so try and hold down as much square footage as possible. The weakest sun light comes from the north, this being the best direction for doors or windows.

Heat goes to cold. So you need large ventilation openings in the top of your container/building. Power fans work great here. Storage inside the container has to allow for air movement otherwise it becomes insulation/temperature conductor and heat sink.

The outside of your container needs to have non electric conducting material creating a void of several inches to allow for air movement up the sides of your container. The roof should have a pitch of at least 6/12 starting a foot above the walls on one side the other side start 2 feet above the wall and continue it at a 6/12 pitch so it is above the other roof. The first roof will be smaller so it should be sunward if possible. You can cover this exterior with duct wrap, foil faced with the jacketed side out to reflect heat or use reflective metal.

Then put a tent over the whole thing, large vents in the top. The sides should touch the ground, but you should be able to raise and lower them allowing the cool or shaded side to let air in. Keep the sun sides closed.

This will allow for storage between the tent wall and the container. If it really gets hot you can put a sprinkler lawn hose in this void.

RTCHIEF 01-22-2013 06:05 PM

Heat
 
Position is the first thing, under a tree, in a shadow, prevailing breeze.

Orientation is next, the east sun is hotter than the west sun so try and hold down as much square footage as possible. The weakest sun light comes from the north, this being the best direction for doors or windows.

Heat goes to cold. So you need large ventilation openings in the top of your container/building. Power fans work great here. Storage inside the container has to allow for air movement otherwise it becomes insulation/temperature conductor and heat sink.

The outside of your container needs to have non electric conducting material creating a void of several inches to allow for air movement up the sides of your container. The roof should have a pitch of at least 6/12 starting a foot above the walls on one side the other side start 2 feet above the wall and continue it at a 6/12 pitch so it is above the other roof. The first roof will be smaller so it should be sunward if possible. You can cover this exterior with duct wrap, foil faced with the jacketed side out to reflect heat or use reflective metal.

Then put a tent over the whole thing, large vents in the top. The sides should touch the ground, but you should be able to raise and lower them allowing the cool or shaded side to let air in. Keep the sun sides closed.

This will allow for storage between the tent wall and the container. If it really gets hot you can put a sprinkler lawn hose in this void.


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