New studio, trying to figure out ventilation/makeup air

SquareOneBeads · #1 2011-09-15, 2:02pm

We just moved into a new house and my new glass shop will be a 10x10 room in the basement.

In this room there is a window and i was hoping to put my ventilation exhaust and maybe my makeup air entrance thru the window. The window is about 18" x 9". If I run a duct, from the window to about the middle of the room for the makeup air, would that be far enough behind me for proper ventilation?

Does anyone have any ideas for how I can seal the hole so that it doesn't leak when it rains? The window is very close to the ground since it is a basement window.

Does anyone have any sources for exhaust fans? I would like at least a 600-700 cfm fan. Do I need a fan to draw in the makeup air, or will it just flow in as air is being expelled? In my last studio I had two huge windows behind me that I would open which worked perfectly but this isn't an option in this house so I'm having a hard time trying to decide what to do.

BAGGEDCHEVYS · #2 2011-09-16, 7:48am

Congrats on the new space Heather. First off you never want to pull make up air from the same place as your exhaust air. If the window is your only option you might have to do som outside ducting to seperate the two by a distance. I would use a push pull system with two inline fans from a hydroponics shop. You can use variable speed router controllers on the fans that can be picked up at harbor freight or the hydro shop (they get them from harbor frieght) the controllers will allow you to dial in the volume of your out take and intake air. the C.A.P valuline fans from discount-hydro.com are 745 cfm for the 8 inch and 780 for the 10 inch. I would go with the 8 as it will be cheaper all around and there isn't much differance in cfm. I assume your room is 10x10x8 making it 800 cubic feet so the 745 would exhaust your wholeroom in a little over a minute. As far as ducting I would use thesolid duct and as little flex duct as possible. The going through the window. Depending on the window you can remove it or half of it from its casing and replace with a piece of plywood that has been coated in water proofing roofing spray. They make 8 inch vent end caps that have wire mesh and a swinging door to keep draft and critters out and they turn down to keep the rain out. Yay for the new space and new studio. Hope this was oh some help.

artsyuno · #3 2011-09-16, 7:55pm

Your fresh air entrance and bad air exit need to be 10 linear feet apart. Running ducting inside your studio won't create that distance if the spots of origin are the same.

Dale M. · #4 2011-09-19, 9:01am

Typically if one designs system properly they only need one fan, (not a push-pull) system.

Nature abhors a vacuum, when you extract air from room via fan you create a partial vacuum (low pressure area). Nature being as it is will push your make up air into vacuum or low pressure area. All you have to do is provide a makeup air "path" (open door - window - dedicate port).

Dale

BAGGEDCHEVYS · #5 2011-09-19, 10:07am

Heather may have reasons for wanting to go through the window. Maybe the basment only has one window and the open window open door design isn't applicable. If there is only one window and one door in the basment and the door leads into the house you would have to have open windows or doors in the house or the house would become a negative pressure. Now in the winter I'm sure she would like to try and keep her house warm instead of sucking all the warm air from the house and out into the neighborhood... Your return air ducting is not immune to static pressure and would still suffer from static pressure with or without a fan. So without the fan you would need to run a munch much larger return air duct, given the 18x9 window opening you might be able to get a 7 and a 8 inch for a wilthout fan situation. I think that's too small seeing that the fan is an 8 inch or 740 cfm and the reduction to 7 plus static pressure would drop that cfm number by a bunch. Unless you know how many twists turns and how many feet. Of ducting on both intake and exhaust and ducting size you can't do any math on the static pressure it will create. That's the joy of a push pull system with variable speed controllers it allows you to dial in your set up because sometimes designs on paper and by the bok and with the right math just don't work. There is a reason the some of the best down draft side draft paint booths, open front welding cubes and open front paint booths use a push pull........ its because it works

Dale M. · #6 2011-09-19, 12:51pm

Not arguing the window access or need of duct to separate air intake from exhaust to get the required 10 feet between the two....

The concept of intake air duct and exhaust duct both needing fans is just not true.... If you consider that you have 10 feet of intake duct and 20 feet of exhaust duct, and diameter of duct is 8 inches, you calculate fan capacity for 30 feet of 8 inch duct (plus hood opening) .... The actual studio "void" is a constant (with air leaks) but does not calculate in fan capacity or TOTAL DUCT length. And if you know the actual number of turns and degree of tuns total static loss can be calculated for system...

http://www.artglassanswers.com/forum...php?f=22&t=583

Dale

BAGGEDCHEVYS · #7 2011-09-22, 11:31am

Couldn't disagree more.

Let's use a soft sided hydroponics grow tent as an example.

In a passive air system (vent fan pushing exhaust air out and a open intake vent hole for exchange air). When the intake hole is the same size as the exhaust fan let's use 7 inches the fan will suck the air in the tent on hand since it is the path of last resistance and then will start pulling air infrom the vent hole. The system never catches up or equals out leaving the system in a negative pressure. This is evident by the sides of the tent sucking in. The only way to create a neutral condition is to use a larger vent opening than the exhaust duct size.

Now with a push pull system you can use the same 7 inch duct on the exhaust with a fan on the intake rated below the exhaust fan and use the same 7 inch intake duct size and create a neutral condition. Add on fan speed controllers and you can dial in the system.

BAGGEDCHEVYS · #8 2011-09-22, 11:41am

Couldn't disagree more.

Let's use a soft sided hydroponics grow tent as an example.

In a passive air system (vent fan pushing exhaust air out and a open intake vent hole for exchange air). When the intake hole is the same size as the exhaust fan let's use 7 inches the fan will suck the air in the tent on hand since it is the path of last resistance and then will start pulling air infrom the vent hole. The system never catches up or equals out leaving the system in a negative pressure. This is evident by the sides of the tent sucking in. The only way to create a neutral condition is to use a larger vent opening than the exhaust duct size.

Now with a push pull system you can use the same 7 inch duct on the exhaust with a fan on the intake rated below the exhaust fan and use the same 7 inch intake duct size and create a neutral condition. Add on fan speed controllers and you can dial in the system.

LarryC · #9 2011-09-22, 12:18pm

Quote:

Originally Posted by BAGGEDCHEVYS

Now with a push pull system you can use the same 7 inch duct on the exhaust with a fan on the intake rated below the exhaust fan and use the same 7 inch intake duct size and create a neutral condition. Add on fan speed controllers and you can dial in the system.

An added benefit for some of us is that each individual fan can be smaller.

cheng076 · #10 2011-09-22, 2:42pm

The size of the openings has no bearing on the 'negative' pressure. The relationship of the sizes (in - out) does. If the fan exhausts xxx cfm and the makeup opening is sufficient in size to permit the free flow of xxx cfm then the pressure is neutral.

BAGGEDCHEVYS · #11 2011-09-22, 2:51pm

Then explain why a soft sided hydro tent will suck in if using a 7 inch exhaust fan and a 7 inch open hole if it doesn't create a negative pressure?

Dale M. · #12 2011-09-22, 6:28pm

Let me see if I understand your point, putting aside thousands of hours and millions of dollars spent in research on industrial fume hoods ( GOOGLE SEARCH: “class A fume hood” theory and practice)…. With a few millibars of pressure differential you can cause any plastic film wall to “suck in” or “blow out. The same pressure changes we experiences in our daily lives going into and out of buildings in a world where weather is influenced by these same few millibar changes in atmospheric pressure. When it goes high it gives us pleasant weather, when the pressure drops by a few millibars it brings us inclement weather. So by you observation/opinion, doubling the cost of fans in studio and controllers and purchasing much dollars in instrumentation to get perfect balance, to replace all the research done by learned people in government, private sector and educational institutions based on a plastic film wall in a hydroponics green house….

And why does one assume that a slight negative pressure in studio is bad, it insures that the extraction process is working and it is drawing air from ever conceivable source, be it cracks around doors(better open) or windows (better open) and cracks in walls. And the air flow is going exactly where its supposed to, past studio worker, into torch combustion zone and then out exhaust ducting...

Dale

LarryC · #13 2011-09-23, 9:00am

Put em away boys! Nobody here cares who has the longest one. Some of us are actually trying to learn from these threads.

Dale M. · #14 2011-09-23, 10:06am

Quote:

Originally Posted by LarryC

Put em away boys! Nobody here cares who has the longest one. Some of us are actually trying to learn from these threads.

IF you want to LEARN do INDEPENDENT research and draw your own conclusions........ Its all out there (the internet you know) you just need to look....

As much as I hate to stir up old wounds....

http://mikeaurelius.wordpress.com/ventilation-primer/

Also much written here if you search....

http://www.isgb.org/forum/forumdispl...-Safety-Issues

Dale