Hi,
I'm in a bit of a heating/cooling pickle. I have attached a look at my studio HVAC design from when I designed and built my VO studio. The HVAC is a mini split unit in the main building. In the attic, I have a duct line that pulls air from the ceiling in the booth to the main room. So, we are trying utilize the air gap to create an "air flow" by coming in my booth via the air gap and out the ceiling via the fan creating a sort of vacuum.
The air flow is not working as designed and the booth stays almost uncomfortably warm. I've added a fan to force air into the air gap but all it's doing is blowing the air up the wall and into the attic.
I'm hoping some fresh eyes can possibly help provide some ideas for us to try?
Some notes on my studio...
- This is an outside building and has it's own mini split unit. Its not tied into my home HVAC unit and was almost too small of a space for an HVAC unit.
- There is no way to add to my unit to create "zones". Also, the mini split unit is not made to be ducted.
- The walls are insulated, double drywalled with green glue in between layers of drywall.
- Acoustic panels are ATS Acoustic Panels thus adding another 2inch layer of insulation/sound absorption.
- There are no heat producing electronics in my booth itself.
Any ideas or help would be great.
Neil
VO Booth Cooling/Heating Issue
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neilwilsonvoice
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Soundman2020
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Re: VO Booth Cooling/Heating Issue
Hi there Neil. Please read the forum rules for posting (click here). You seem to be missing a couple of things! 
Second, the wall cavity is likely filled with porous insulation, such as fiberglass or mineral wool (if not, then it should be!). Moving air through that is not a good idea, as it loosens the fibers, and sends them flying out through the vents, spreading them around all over. HVAC ducts are lined with proper duct liner, which does not suffer from that problem at all, but ordinary insulation does.
And third, there's no reason why air would move through there at all! You are not creating a pressure differential, nor a even a temperature differential, which would at least drive convection a little.
Also, I see where the air is supposed to come in to the booth, but not where it is supposed to go out! There's a pair of vents in one wall, with one vent on the outer leaf and one on the inner leaf, and they are both marked as being part of the inlet system, but I don't see the other pair of vents for the outlet!
I also don't understand how air could be getting out of your isolation system, "up the wall and into the attic". That doesn't make sense. In order for that to happen, there would have to be a hole in the ceiling of your iso booth somewhere, so if that's the case, the first thing I'd do is to try to find that hole, and close it off! If there's a hole up there allowing air to flow out, then sound is also getting out, big time! So your isolation booth is not isolating at all.
So your first order of business is to find that hole in your outer-leaf ceiling, and seal it of completely.
What you need to do is to first ensure that both your inner leaf (all four walls and the ceiling) and also the outer leaf (all four walls and the ceiling) are absolutely air-tight. Then you need to do your HVAC calculations: you need to use the equations to first figure out how much air you need to move through that booth per minute (CFM), based on typical rates for that (room.changes-per-hour), then with that number in hand, and knowing that the maximum flow velocity for studios is about 300 fps, you can calculate what cross sectional area you need for your registers (assuming that only about 70% will be open area) and ducts.
With all that info in hand, you can then design the silencer boxes that you need to allow the air to move through the walls, while also preventing sound from getting through. A silencer box is just a big box, made from plywood, MDF or something similar, that has several baffles inside it, and has an internal cross sectional area at least twice that of the inlet and outlet ducts. It is lined on the inside with proper duct liner. You will need two such boxes in your case: one for the fresh air supply, and the other for the stale air exhaust. The actual registers inside the booth should be at opposite ends of the booth, as far apart as possible. For that size room, you'd probably want to have them both in the ceiling, with the supply register blowing straight down towards the floor, and the exhaust vent sucking straight up. So you should make your silencer boxes in such a way that they can sit on top of your outer-leaf ceiling, each with a "sleeve" that penetrates though both leaves without touching them, and with abundant acoustic caulk sealing the holes where they pass through, on both sides.
Finally, you'll need a fan of the correct capacity on one of the silencer boxes. Either a supply fan on the inlet box, or an exhaust fan on the outlet box. To figure out the fan capacity, you need to take into account the flow rate you originally calculated, and also the static pressure created by your silencer boxes and ducts: HVAC fans are rated at "xxx CFM, for yyy static pressure". If you get it wrong, then the fan will either move too much air too fast, thus making a lot of air noise and also not loading the fan motor correctly, or it will not provide enough air, as it will be overloaded by too much static pressure, so you'd be back to your current situation again, and you'd also be burning out fan motors due to them being overloaded.
So that's the outline of how to fix your problem. To summarize:
1. Find the leak in the ceiling, and seal it up.
2. Calculate your HVAC flow rates, speeds and pressures.
3. Build two silencer boxes, one for inlet, the other for exhaust.
4. Attach the correct size fan directly to the end of the silencer box furthest away from the iso booth.
5. Bingo! All done.
- Stuart -
You are talking about the air gap inside the isolation walls of the booth itself, right? If so, then that's not a good idea, on several levels. Firstly, by doing that you trash your isolation completely. A two-leaf isolation wall is a tuned system: the leaf on each side must be sealed completely airtight. Punch a hole in it, and you destroy that system. So no more isolation.So, we are trying utilize the air gap to create an "air flow" by coming in my booth via the air gap and out the ceiling via the fan creating a sort of vacuum.
Second, the wall cavity is likely filled with porous insulation, such as fiberglass or mineral wool (if not, then it should be!). Moving air through that is not a good idea, as it loosens the fibers, and sends them flying out through the vents, spreading them around all over. HVAC ducts are lined with proper duct liner, which does not suffer from that problem at all, but ordinary insulation does.
And third, there's no reason why air would move through there at all! You are not creating a pressure differential, nor a even a temperature differential, which would at least drive convection a little.
Right. That's what I would expect.The air flow is not working as designed and the booth stays almost uncomfortably warm.
Where abouts is the fan in your diagram?I've added a fan to force air into the air gap but all it's doing is blowing the air up the wall and into the attic.
Also, I see where the air is supposed to come in to the booth, but not where it is supposed to go out! There's a pair of vents in one wall, with one vent on the outer leaf and one on the inner leaf, and they are both marked as being part of the inlet system, but I don't see the other pair of vents for the outlet!
I also don't understand how air could be getting out of your isolation system, "up the wall and into the attic". That doesn't make sense. In order for that to happen, there would have to be a hole in the ceiling of your iso booth somewhere, so if that's the case, the first thing I'd do is to try to find that hole, and close it off! If there's a hole up there allowing air to flow out, then sound is also getting out, big time! So your isolation booth is not isolating at all.
So your first order of business is to find that hole in your outer-leaf ceiling, and seal it of completely.
According to the manufacturer, those are basically mineral wool batts wrapped in fabric, so yes, they provide a lot of thermal insulation, and some acoustic treatment for the interior, but no additional acoustic isolation.Acoustic panels are ATS Acoustic Panels thus adding another 2inch layer of insulation/sound absorption
We are talking about the iso booth, right? So you have two layers of drywall with GG on the outside of the outer-leaf frame, and also two layers of drywall with GG on the inside of the inner-leaf frame? Is that correct? And that applies to all four walls, and also to the ceiling, correct? In other words, you havet wo layers of drywall with GG on the outside of the outer-leaf ceiling framing, and also two layers of drywall with GG on the inside of the inner-leaf ceiling framing? If so, that's probably over-kill for an iso booth, but it certainly won't do any harm, and you should be getting excellent isolation from that: Except for the vent holes, which basically destroy that, and the mysterious other "hole", where the air is escaping out the top...- The walls are insulated, double drywalled with green glue in between layers of drywall.
right, but when there is a person in there, you have a rather effective heat source that can put out anywhere between 100 watts about about 800 watts of heat. In a small space like that, the heat accumulates pretty fast, and it has nowhere to go. There's also the issue of no oxygen coming in, no CO2 going out, and no elimination of humidity, so it must get rather warm, humidy, smeyy and uncomfortable in there, quite fast.- There are no heat producing electronics in my booth itself.
What you need to do is to first ensure that both your inner leaf (all four walls and the ceiling) and also the outer leaf (all four walls and the ceiling) are absolutely air-tight. Then you need to do your HVAC calculations: you need to use the equations to first figure out how much air you need to move through that booth per minute (CFM), based on typical rates for that (room.changes-per-hour), then with that number in hand, and knowing that the maximum flow velocity for studios is about 300 fps, you can calculate what cross sectional area you need for your registers (assuming that only about 70% will be open area) and ducts.
With all that info in hand, you can then design the silencer boxes that you need to allow the air to move through the walls, while also preventing sound from getting through. A silencer box is just a big box, made from plywood, MDF or something similar, that has several baffles inside it, and has an internal cross sectional area at least twice that of the inlet and outlet ducts. It is lined on the inside with proper duct liner. You will need two such boxes in your case: one for the fresh air supply, and the other for the stale air exhaust. The actual registers inside the booth should be at opposite ends of the booth, as far apart as possible. For that size room, you'd probably want to have them both in the ceiling, with the supply register blowing straight down towards the floor, and the exhaust vent sucking straight up. So you should make your silencer boxes in such a way that they can sit on top of your outer-leaf ceiling, each with a "sleeve" that penetrates though both leaves without touching them, and with abundant acoustic caulk sealing the holes where they pass through, on both sides.
Finally, you'll need a fan of the correct capacity on one of the silencer boxes. Either a supply fan on the inlet box, or an exhaust fan on the outlet box. To figure out the fan capacity, you need to take into account the flow rate you originally calculated, and also the static pressure created by your silencer boxes and ducts: HVAC fans are rated at "xxx CFM, for yyy static pressure". If you get it wrong, then the fan will either move too much air too fast, thus making a lot of air noise and also not loading the fan motor correctly, or it will not provide enough air, as it will be overloaded by too much static pressure, so you'd be back to your current situation again, and you'd also be burning out fan motors due to them being overloaded.
So that's the outline of how to fix your problem. To summarize:
1. Find the leak in the ceiling, and seal it up.
2. Calculate your HVAC flow rates, speeds and pressures.
3. Build two silencer boxes, one for inlet, the other for exhaust.
4. Attach the correct size fan directly to the end of the silencer box furthest away from the iso booth.
5. Bingo! All done.
- Stuart -
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neilwilsonvoice
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- Joined: Mon Oct 20, 2014 5:39 am
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Re: VO Booth Cooling/Heating Issue
My bad - I think I got all the requirements taken care of via your link.
Since I don't need 100% isolation (I'm doing spoken word voice over) I wanted to utilize the air gap as a passage for cool air to come in. Then hot air is pulled out as return via the fan in my ceiling.
The issue here is that I'm using a mini split system outside of the booth in the main room. It has no way to be ducted, zoned or any other way to get air from it to the booth without somehow forcing the air from the main room into the booth via a ducting or fan type system or setup. I'm trying to figure out that system now as my intake via the air gap (yes, I know it disrupts the complete iso) as that is not working as originally planned.
My main building, a 12x18 building outside of my main house, is too small for traditional ducted type systems.
I'll try your suggestions. If anyone else can add anything that I may also want to try that would be most excellent.
Neil
Since I don't need 100% isolation (I'm doing spoken word voice over) I wanted to utilize the air gap as a passage for cool air to come in. Then hot air is pulled out as return via the fan in my ceiling.
It is in the far back right corner. The fan is in the ceiling. It is a Fantech FG6 and is speed controlled by a dial on the wall next to me. I didn't have a picture to post of it.Where abouts is the fan in your diagram?
I added a fantech FADE 10-4 on the outside wall to push air into the air gap and into the booth via the air intake as shown in the diagram.I also don't understand how air could be getting out of your isolation system, "up the wall and into the attic".
Only the inside layers of my booth are double drywalled with GG on walls and ceiling. The outside is single layer drywall.We are talking about the iso booth, right? So you have two layers of drywall with GG on the outside of the outer-leaf frame, and also two layers of drywall with GG on the inside of the inner-leaf frame? Is that correct?
The issue here is that I'm using a mini split system outside of the booth in the main room. It has no way to be ducted, zoned or any other way to get air from it to the booth without somehow forcing the air from the main room into the booth via a ducting or fan type system or setup. I'm trying to figure out that system now as my intake via the air gap (yes, I know it disrupts the complete iso) as that is not working as originally planned.
My main building, a 12x18 building outside of my main house, is too small for traditional ducted type systems.
I'll try your suggestions. If anyone else can add anything that I may also want to try that would be most excellent.
Neil
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Soundman2020
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Re: VO Booth Cooling/Heating Issue
As long as you do the math correctly, and size your registers / silencers / ducts / fans correctly, then it will work. The fact that it isn't working, indicates that something is not sized correctly. There are not other possibilities.
With high static pressure, the fan blades will be stalled, so all they will accomplish is generating lots off turbulence, making a lot of noise, overloading the motor, but not moving any air.
Adding another fan on the inlet won't help either, because that does not change the static pressure at all.
That's why it isn't working.
That's why it is important to do the math.
So once again, the solution is to work through the math, make sure you have the right flow rate and flow velocity for your room, then choose the right fan to handle that at the static pressure presented by your system. If the static pressure is too high (as seems to be the case), then you'll have to reduce it. There are a couple of things you could do to achieve that.
- Stuart -
Have you measured or calculated your static pressure? The FG6 fan is rated at 303 CFM with no load, but with a load of 0.5"W, that drops to only about 210 CFM, and at 1"W its down to about 130 CFM (less than half the full rated capacity). At 2"W static pressure, it is rated at zero CFM. So if your static pressure is very high (as it certainly will be, with tiny little registers, a thin tortuous path through the wall, and many feet of insulation), chances are you'll get little to no flow at all from that fan, and you'll also be overloading the fan motor. Anything above 1.5" of static pressure, and that fan won't be doing anything at all, except burning out frequently! At 1.5", it only moves 19% of its full rated capacity: just 58 CFM...It is a Fantech FG6
With high static pressure, the fan blades will be stalled, so all they will accomplish is generating lots off turbulence, making a lot of noise, overloading the motor, but not moving any air.
Adding another fan on the inlet won't help either, because that does not change the static pressure at all.
That's why it isn't working.
That's why it is important to do the math.
So once again, the solution is to work through the math, make sure you have the right flow rate and flow velocity for your room, then choose the right fan to handle that at the static pressure presented by your system. If the static pressure is too high (as seems to be the case), then you'll have to reduce it. There are a couple of things you could do to achieve that.
- Stuart -