cafe heating/cooling load skylight

[onlinetips]

skylight 25x25, with 16 bronze tinted skylights. will be a cafeteria underneath for 10-15 people. 14 ft high walls. constant volume system.

With U=1.0 and SC=0.73 for a singele 1/4" coated skylight, the cooling load comes to ~ 10 tons (4500 cfm) with Trace 700.

What is good estimate of U-value, SC.
Is 4500 Cfm too high? total area is 600 sf. almost 8 cfm/sf? what is good tonnage estimate?

pic attached.

 

[onlinetips]

Project in washington dc. interior space with its own interior walls.

 

[ChrisConley]

Single pane glass? If so, SC = 0.8 is not a bad number, U = 1.1.

25"x25" or some other unit?

10 tons / 600 sqft = 60 sqft / ton.... which is pretty high. Typical cafe numbers would be 200-400 sqft/ton (from rules of thumb).

 

[onlinetips]

25 FT X 25 FT. THE WHOLE CAFE IS 25 FT X 25 FT AND ENTIRE ROOF IS MADE OF SKY LIGHTS. A GRID OF 4X4- EACH ONE IS 6 FT X 6FT WITH ALUMINUM FRAME SO 6X4=24 FT PLUS ALUM MAKES IT 25FT X 25 FT. IT HAS BROWN TINT AND IS 3/16" THICK. AT 200 SF/TON = 3 TON WOULD BE LOW. 7-8 TONS SOUNDS BETTER??

7 TONS X 400 CFM/TON = 2800 CFM. ABOUT 5 CFM/SF.

IS 5CFM/SF TOO HIGH?

 

[IRstuff]

A typical house rule of thumb is about 1 ton/600 sq ft, but even that's overkill, at least, for Orange County in California. We're running 1 ton/700 sq ft with no problems, here.

You're essentially wanting to put about 6-7 times the capacity of what a typical house might need. I could see going 1 ton/200 sq ft, because of the humidity and higher body and equipment load.

Are you thinking you need to freeze everyone so that the turnover is higher?

TTFN

FAQ731-376

 

[ChrisConley]

Any higher solar loads. Most houses don't have glass roofs.

 

[IRstuff]

True enough, but we do have skylights and our roof is essentially drywall, whatever's left of the original blown-in insulation, plywood, and aluminum.

TTFN

FAQ731-376