Make Up Air?

Shelle · #1 2013-03-12, 12:06pm

Hello all!

My husband just put in a new ventilation system (http://www.andreaguarino.com/VENTILATION.html) for me but we haven't worried about make-up-air yet.

My question is how to get adequate make-up-air into the studio? There is a door to the outside and 2 small windows. I'd rather not leave the door open, but usually leave at least one of those windows open when I torch, but have heard that isn't enough. I have read so many different things I am just confused!!

My workbench is against a wall - sheet metal on the table and on the wall behind it so putting a vent in the tabletop isn't really an option and my vent goes straight out the wall to the outdoors in front of my torch.

Suggestions?? Advice??
I do need something that can be closed when not in use - New Hampshire winters are COLD!!!!

Dale M. · #2 2013-03-12, 12:21pm

As long a opening for makeup air is equal to or larger than your exhaust (duct) you are probably ok... Just remember any duct work that is part of make up air is part of your ventilation "system"... IN other words, length of fresh air duct plus length of exhaust duct equals total length of ventilation system...

So... Open window is probably fine.....

If you want to keep studio warm in winter and cool in summer you can route a large percentage of your make up air from outside (through ducting) to space between torch and wall and this keeps you from robbing studio space of heated/cooled air...

Also be aware any ventilation ducting the uses corrugated or flexible duct reduces the efficiency of a system be causing "static" pressure (turbulence) in duct....

Dale

Shelle · #3 2013-03-13, 3:58am

Thanks Dale!!

Beadanna · #4 2013-03-13, 4:17am

Oh this is great - it means I can probably close the window I always have open thinking it was necessary. I have three vent registers in the table between torch and ventilation. I never put the heater on as I hate the thought of the open window along with the heat being sucked out immediately. I will also put the heater on maybe....

TJ · #5 2013-07-21, 10:50pm

Quote:

Originally Posted by Dale M.

As long a opening for makeup air is equal to or larger than your exhaust (duct) you are probably ok... Just remember any duct work that is part of make up air is part of your ventilation "system"... IN other words, length of fresh air duct plus length of exhaust duct equals total length of ventilation system...

If you want to keep studio warm in winter and cool in summer you can route a large percentage of your make up air from outside (through ducting) to space between torch and wall and this keeps you from robbing studio space of heated/cooled air...

Also be aware any ventilation ducting the uses corrugated or flexible duct reduces the efficiency of a system be causing "static" pressure (turbulence) in duct....

Dale

Dale, I'd like to check on two things with you, please, related to make-up air:

This is a basement room, separated well off of the furnace area. Cold winter climate, so make-up air will come in behind the torch. 936 cfm fan.

One, I am using solid 12" ducting for the exhaust vent, but bought flexible corrugated ducting for the return air vent. I figured the static pressure mattered most for the fume removal side... but now I am wondering if that does not make sense after all...

Two, my make-up air ducting is going out the same small high window that my exhaust vent goes, so I bought an extra 10 feet of ducting to send out further to make sure that I reach fresh air. However, about half of the make-up air ducting is 12" wide (same as the exhaust ducting) and half will be 6". (The exhaust side of the system will only be about 5 feet in length total.) I realize this will slow down/squeeze the air... but does that matter much? Especially considering the extra length?

Thank you!! Without your advice on LE, I would never be attempting a studio at all!

Tami
(almost have the whole thing together, yay!)

Dale M. · #6 2013-07-23, 5:20am

In all the calculations, the total length of duct has to be figured in the calculations....

If you have 10 feet of exhaust, and 22 feet of fresh make up air, you have to do all calculations as 32 feet of duct work....

When you squeeze duct size down (reduce square inches of duct) you are increasing static pressure... Not shape here so much but shape does matter because every time air changes direction (even inside duct) it causes turbulence and turbulence is cause if increased static pressure...

This is why its prudent to use as large a duct as practical, minimum number of bends and avoid flex duct when ever possible...

Having intake air separated from exhaust by the 10ft (minimum) distance should keep you safe, its the "standard" for most air exchange processes..

Dale

TJ · #7 2013-07-23, 10:53pm

Thanks, Dale. Hopefully since most of my run is 12" wide duct, and the exhaust is only about 5 feet long with one bend, along with a 936 cfm fan, it is all still strong enough.

I may have it up and ready to test by the wknd.

TJ · #8 2013-09-01, 11:51pm

So I got my venting all in, just have not permanently secured the makeup vent in the window yet.

When I did the incense test, it went out the exhaust duct quite nicely. (I still plan on adding a back baffle though.)

But the make-up air vent was pretty much dead.

We closed the door to the room; whoa, lots of air sucking in from around and under the door!

Tried sealing the bottom of the door with a blanket. THEN, the make-up air vent started blowing well.

What's going on? I fear you will tell me that the static pressure is too high due to the corrugated ducting, and the bends to get it behind the torch make it even worse. And, as a result, it is much easier for the universe to draw air from the rest of the basement than to use the makeup duct. And then... please don't say this.... you'll advise that I have to rip it out and spring for the expensive non-flex duct for the makeup vent. (Noooooooo..ahhhhh)

But it IS 10 feet of slightly curving 12" ducting on the outside, despite it being narrowed down to 6" on the inside of the room. I thought that would suffice.

Ultimately, I need to know... can the Make-up air come from the rest of the house first, then default to the makeup vent when the room pressure drops?
My hubby fears all the warm air in the house will be removed by the fan and we will be left with a gigantic heating bill... is this correct?

Or should I always close and block off the door so that it only draws return air from the makeup duct and not the rest of the house? But then I think, no fresh air from behind me at all, that can't be good either, right?

(By the way, the duct is positioned such so that the -20C winter air won't kill me if it coming behind the torch.)

Thanks!
(I did search MAKEUP AIR before posting this, could not find anything about this makeup air not moving, so your help is appreciated!)

Dale M. · #9 2013-09-02, 5:20am

Make up air inlet duct is to small and to many bends.... Same rules apply for make up air as exhaust, large diameter tube (should be same size as exhaust), minimal bends ... Though its NOT pressurized by fan, its still a "static pressure" issue (resistance to air flow)...

Wonderful thing about nature is, it abhors a vacuum and will try to fill it from outside pressure and it will take path of least resistance (door/window)...

Dale

TJ · #10 2013-09-02, 11:16am

I guess I understand that... but the question remains: how do I correct it - in the simplest, and most affordable way possible? I guess blocking off the door is not a good option?

cheng076 · #11 2013-09-02, 11:28am

You say the ducting for the makeup air is 12" diameter beyond the black 'thing' in the window opening? Is it possible to extend the 12" ducting alongside the supply duct, drop it down below the level of the bench and let it flow out from under the bench on all sides? Only one 90 deg bend. No need to direct the makeup air in any particular way as the fan will draw it into the capture hood regardless.

A few years back I did some model tests of various vent system configurations and such a system as above worked fairly well.

PJ

TJ · #12 2013-09-02, 12:26pm

Thanks for your replies.

The "black thing" in the window is just an illusion; I took the photo at night and it is dark outside, that's all. The window is plexiglass we cut holes to fit.

Yes, it is 12" diameter outside, but I made it narrow to 6" so I could still have a little bit of natural light in the room. Even if I give that up now, the rest of the system is secured in the window and it can't come out. I only have a dremel tool to cut the plexiglass, and I worry that I cannot do that now with the plexi vertical in the window. (As crafty as I am, this is my first "tool girl" job!)

I just tried straightening out the makeup duct as you suggested. It still won't blow air with the door to the room open. However, when I close it, it DOES then work. Some air is whooshing under the door and around it still, too. Would that balance of air coming from 2 places suffice?

I also still worry that if that duct is not directed right at the draw of the fan I will freeze to death in winter. My hubby says to tell you that the weather is similar to North Dakota. A blast of -22C wind on my legs, even for a second, would be nasty! I am starting to wonder if anyone has a working system in cold weather without extra heating...

Please, more advice?

Dale M. · #13 2013-09-03, 7:09am

Air flow takes the path of least resistance.... Mother nature has decided the door has less resistance to air flow than your duct work..... See other discussions (in Safety and Studio threads) about size and bends in duct work.... And the flex duct you are using for make up air is absolutely the worst thing you can use for ducting... The corrugation that make it bendable are the cause of so much static pressure it makes it difficult for air flow....

Also the intake for make up air needs to be at least 10 linear feet from your exhaust air so you do not recirculate the gasses you are trying to evacuate from your work space, this also adds to air flow problems..... Make up air duct needs to be as big as practical, and really bigger is better... IT would appear you make up air duct is 4 inch flex, and its just to small... 6 or 8 inch rigid duct with formed turns would be a lot better....

Dale

TJ · #14 2013-09-03, 10:35am

Intake is 10 feet away on the outside, I made certain of that, thanks to your writings, Dale.

The flex ducting is actually 6", it just looks so small next to my exhaust side because it is all 12" rigid ducting there.

I have read everything on LE that resulted from a search of "Ventilation" and "make-up air" as well as "ventilation" with "return air". I was ust so hoping to preserve that bit of light left in the window. Sounds like I have no choice but to put a 12" duct on that side, too.

laserglass · #15 2013-09-04, 5:00am

when you narrowed the duct to 6 inches, that is the issue....since you did this, you might as well have run it all with 6 inches....make up duct should always be larger than the vent duct....but an open window directly to the outside in the room should work fine for your duct.....just remember, you are bringing in outside air, so when its cold or hot as hell outside, that's what you are bringing in.... a heat exchanger in your make up air duct would help with this.... the bucket at the end of a tube hood that was shown in the photo, is a poor design for a vent hood....to tall off the work surface, no side or back baffles....yes incense will go up it but put the incense where the torch will be, and light it in place with your ventilation running, not before hand.... do not worry about where the smoke goes, can you smell the incense at all???? if so your ventilation needs work....

Dale M. · #16 2013-09-04, 7:47am

Evidently there is a misunderstanding about duct sizing....

http://www.artglassanswers.com/forum...php?f=12&t=273

http://www.artglassanswers.com/forum...7a4b11630dc7ca

Dale

losthelm · #17 2013-09-04, 10:06am

Would adding a fan or blower assembly to the make up air line fix the issue?
From looking at the setup the outlet has the fan and the inlet is just the duct work.

I may be putting in a similar setup in the next few years and have a dual squirrel cage blower assembly salvaged from a dust collector.

As it is I'm working in a shed and find a ceramic electrical heater under the work bench helps a lot for October-April I have a lamp on the same switch to make sure I don't leave it running after a session.

TJ · #18 2013-09-04, 2:09pm

Losthelm, I'd like to know that too (and yes the outlet has the fan, the other side is just ducting)... but I am still wondering if I can just CLOSE THE DOOR on the room, as the makeup air vent DOES WORK then. No one has explained to me how/why that would be bad (or if it would be). I'd really like to know though. I need to understand.

I know, I may have to resort to a space heater most of the year, but that sometimes blows the breaker if I am not careful.

Dale, I read them all... I do understand your point (needs to be equal drag/distance/area on each side), only was hoping to find a workaround, misguided as that may be!

Mark, I mentioned earlier in the thread that I do plan to add baffles around the back and some of the side (using metal flashing), I just don't want to get that stuff in the way when I am still trying to permanently position the makeup air ducting, so I have left it for last.

Dale M. · #19 2013-09-05, 8:14am

Quote:

Originally Posted by TJ

Losthelm, I'd like to know that too (and yes the outlet has the fan, the other side is just ducting)... but I am still wondering if I can just CLOSE THE DOOR on the room, as the makeup air vent DOES WORK then. No one has explained to me how/why that would be bad (or if it would be). I'd really like to know though. I need to understand.

I know, I may have to resort to a space heater most of the year, but that sometimes blows the breaker if I am not careful.

Dale, I read them all... I do understand your point (needs to be equal drag/distance/area on each side), only was hoping to find a workaround, misguided as that may be!

Mark, I mentioned earlier in the thread that I do plan to add baffles around the back and some of the side (using metal flashing), I just don't want to get that stuff in the way when I am still trying to permanently position the makeup air ducting, so I have left it for last.

Air flow takes path of least resistance, that is the door if its open, second is duct if door is closed....... Its that simple....

Dale

TJ · #20 2013-09-05, 10:43am

I understand that principle, Dale.

But is it SAFE in terms of my health whilst torching? Or is that insufficient clean air coming from behind/around me? 75-90% of the outside air will be rushing through the ventilation system, recirculating pretty much in a closed loop ( to keep heat in), right back up into the fan, hardly reaching my breathing zone, while 25% or less will be coming from the rest of the house.

It's clear the air movement dynamics are dramatically different between having door open or closed. I can feel it. I understand the dangers of having it open and the draw coming mostly from a closed house. I am not aware if there are any dangers associated with the replacement air being forced almost entirely through a makeup air vent pointed back into the fan, with LITTLE air coming from elsewhere. In your diagrams, it is not a closed room, I assume, but a rather open space. That is my concern: whether it makes a safety difference or not in this regard.

Dale M. · #21 2013-09-05, 3:58pm

As long as a clean air flow is past your face and going out exhaust and torch fumes are going out exhaust, you are about as safe as it gets....

Dale

TJ · #22 2013-09-06, 6:01am

Thanks for your advice and patience, Dale.

I will post a photo again when it is complete/settled.

blueburnsorange · #23 2013-10-07, 6:01am

Sorry to thread-hijack but I figured the title was appropriate enough and generic enough to avoid creating another thread....

Does this look like a valid/safe setup for air intake?

Originally I was going to intake from the small window behind the workbench but flu-reversal concerns have me wondering if just running duct for the intake below the bench is a better choice? The workbench will be 5-sided to maximize airflow.

The back alley is long, I could probably get >15ft linear space apart and both duct runs would be straight with no bends.

Thanks!

Lorraine Chandler · #24 2013-10-07, 8:19am

For me personally I would not have the exhausted air and the make up air on the same wall even if they were 10 feet apart such as one up high and the other down low to the ground.

You are assuming the back alley will have no wind or breezes and the exhausted air and the fresh air will remain separated at 10 or 15 feet apart?

blueburnsorange · #25 2013-10-07, 8:57am

The alley in question has four-story buildings on the front (where my openings would be) as well as the long side walls so there is minimal wind....

Dale had suggested above that a minimum of 10ft between is necessary but like I said, I could probably go longer than 15ft.

Lorraine Chandler · #26 2013-10-07, 11:52am

You don't say where you live or if you rent or own the home but if you rent you may need permission first to install something like this because it could cancel their insurance policy if anyone complained.

Also if it is your home it could cancel your homeowners insurance policy. Check into codes and restrictions before you do all of the work and go the expense as some here have found out the hard way. Lots of threads here on the insurance.

Wishing you best with your new studio and applaud your efforts to stay safe.

Dale M. · #27 2013-10-07, 7:14pm

Several things I am concerned with..... Make up air duct is only 8 inch where exhaust duct is 12 inch.... Make up air duct should be same size as exhaust, when doing fan calculations its easier because you are trying to find static pressures on a total of 36 feet of duct.... Also make up air duct should extend into studio further so it is behind you as you stand/sit at torch.... OR be brought up under bench in front of you so there are extra bends (static pressure) in calculations...

Also you refer to this as a alley with little air flow, this sets off sort of a alarm bell as even with the separation of exhaust and fresh air intake, system has a certain dependency on natural airflow's or drafts or breezes in alley way to ensure a supply of "fresh air"... IF area is to restrictive to air movement you will be drawing in the harmful things you are actually trying to expel...

Dale

blueburnsorange · #28 2013-10-08, 12:04pm

Thanks Dale and Lorraine!

I can adjust ducting sizes to match, I found some great 10" inlines on Grainger's site and I was planning on running the makeup air under the bench (both to minimize the outside cold and flu-reversal) but I'll consider my other options regarding the alley for makeup air - I do have a small window behind me but it's not an ideal location.

Regarding insurance policies - propane storage in the alley is legal, pretty much every house on the block has an alley and tucks their grills back there. My insurance agent said everything sounds fine as long as

1) no negligence in design/execution (follow all building/safety codes but there is nothing that says I CANNOT operate a gas-powered torch in a basement studio, at least in my 'hood which is zoned for both commercial and residential)

2) I'm not operating it as a business, else I would need an "umbrella" policy.

Lorraine Chandler · #29 2013-10-08, 2:45pm

Good deal, Don't forget to post pictures because they can help others.