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Air exchange solution?
Old 2 weeks ago
  #1
Gear Nut
 

Question Air exchange solution?

Trying to figure out best solution to this. Not sure if I'm correct in my thinking, but when it comes to simple air exchange (separate to hot and cold air), would this involve pulling air out of the room on one side via a fan, and letting it return through another vent (minus a fan)? You can't create a vacuum so I'm assuming I don't need a fan on the return here?

I am doing a garage conversion into a small home cinema, and it is quite petite, only 2.5m W x 4m L x 2.3m H

I'm not talking about a mini-split or AC solution, just getting some actual air in/out of the room via an in-line fan (which by building code in the UK I am required to do). I have seen people construct baffle/muffle boxes with pb/sound insulation, so that the air takes an indirect path, and place these in walls/ceilings. A baffle box seems to be the best solution to this, but as mentioned I do have limited space.

Rod's one caught my attention, but I wasn't clear if would be suitable in my case.

There's also a solution this guy did using acoustic flexi duct. Again, I don't know how suitable this is in my scenario. I found it interesting that this guy mentions he built a box like Rod's, and wasn't happy with the solution for several reasons. What to make of that, I don't know.

I am building a room within a room, stud walls, insluation, double PB etc, with the 3 walls behind these being all internal to the house. The far end wall is a garage door which must remain in place, so a new wall will be built behind this... additional to the room within a room that sits behind it.

This does present limited opportunities for ventilation/air exchange, so I am quite unsure what my best solution is, especially when wanting to maintain my sound insulating solution.

Any advice much appreciated.
Old 2 weeks ago
  #2
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Starlight's Avatar
 

Quote:
Originally Posted by McDuff View Post
... would this involve pulling air out of the room on one side via a fan, and letting it return through another vent (minus a fan)?
The air you extract should be expelled into the atmosphere and fresh air should be introduced from a vent some distance away from your exhast vent. Otherwise, you will just recirculate stale air with increasing levels of CO2.

Quote:
Originally Posted by McDuff View Post
Rod's one caught my attention, but I wasn't clear if would be suitable in my case.
Rod provides a good generic plan. Baffles are necessary to let air into and out of your cinema while attenuating the noise. Subject to your airflow requirements you may get away with a smaller baffle or need a larger one. 25 cubic metres per hour per person is the general recommendation. The requirements for a cinema will be similar to a library, far less than required for a fitness centre or a disco.
Old 1 week ago
  #3
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Quote:
Originally Posted by Starlight View Post
The air you extract should be expelled into the atmosphere and fresh air should be introduced from a vent some distance away from your exhast vent. Otherwise, you will just recirculate stale air with increasing levels of CO2.
Thank you. Am I correct in saying the intake does not need an intake fan? Only the extraction side? I cannot create a vacuum, so I am assuming this would be the correct set-up?
Old 1 week ago
  #4
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miguelmarques's Avatar
Quote:
Originally Posted by McDuff View Post
Thank you. Am I correct in saying the intake does not need an intake fan? Only the extraction side? I cannot create a vacuum, so I am assuming this would be the correct set-up?
It depends on the design of the system and your particular situation. There's advantages and disadvantages in your room being positively pressured or negatively pressured. That means pulling the fresh air in with a fan and letting it out passively, or pulling it out with a fan and let the fresh air come in passively.

I tend to prefer positively pressured rooms, as far as dust and overall cleaningness of the room it's the best way to do it.
Old 1 week ago
  #5
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I have a cunning plan ... I have been looking at the same thing. I am going to setup a positive pressure system, with a fan located underneath the studio blowing air into the room and the air passively being exhausted through a vent on the other side of the room. From that I have read, it seems a better idea than a negative pressure room, safer and easier to implement.

I am not using any baffles, as the air will flow in a wide areas between the two layers of floor, which should slow it down enough to reduce the air noise, and the sound escaping the room will be minimal (I am hoping).

For the fan I have an inline fan and filter, originally designed for hydroponics, it is heavy duty, good airflow and has a huge filter attached to it.

There is the particle board of the original floor, then a layer of acoustic underlay, then I am using some thick wooden square boards which have had nine small squares attached to the underneath of them, they were originally used for a trade show to run cables underneath them. I will attach a picture. Anyway, so I create a airtight divide between the two sides of the room and the edges of the floor, except where the inlet and outlet vents are located, this will force the air into the room and air pressure will force it out the outlet. I think this will work? anyway still figuring out the logistics. Maybe you could do something similar if you are building a second floor? I will attach a VERY rough sketch, not to scale.( I am having trouble posting with image tags, so hopefully you can follow the links...)


Old 1 week ago
  #6
Gear Nut
 

Quote:
Originally Posted by miguelmarques View Post
It depends on the design of the system and your particular situation. There's advantages and disadvantages in your room being positively pressured or negatively pressured. That means pulling the fresh air in with a fan and letting it out passively, or pulling it out with a fan and let the fresh air come in passively.

I tend to prefer positively pressured rooms, as far as dust and overall cleaningness of the room it's the best way to do it.
What would be the advantages of positive pressure exactly? I have experience with PC building and am aware of dust often being less of an issue in positive pressure PC cases, but it doesn't eliminate it entirely. My main concern was the potential of stale air building up in the room, as it won't have any windows, just the doorway (actually x2 doors). It could be that passive exhaust will deal with this just fine though, I don't know.

Is there any merit in setting up equally powered fans on BOTH intake and exhaust and trying to achieve a neutral pressure system?


Quote:
Originally Posted by Doogstar View Post
I have a cunning plan ... I have been looking at the same thing. I am going to setup a positive pressure system, with a fan located underneath the studio blowing air into the room and the air passively being exhausted through a vent on the other side of the room. From that I have read, it seems a better idea than a negative pressure room, safer and easier to implement.

I am not using any baffles, as the air will flow in a wide areas between the two layers of floor, which should slow it down enough to reduce the air noise, and the sound escaping the room will be minimal (I am hoping).

For the fan I have an inline fan and filter, originally designed for hydroponics, it is heavy duty, good airflow and has a huge filter attached to it.

There is the particle board of the original floor, then a layer of acoustic underlay, then I am using some thick wooden square boards which have had nine small squares attached to the underneath of them, they were originally used for a trade show to run cables underneath them. I will attach a picture. Anyway, so I create a airtight divide between the two sides of the room and the edges of the floor, except where the inlet and outlet vents are located, this will force the air into the room and air pressure will force it out the outlet. I think this will work? anyway still figuring out the logistics. Maybe you could do something similar if you are building a second floor? I will attach a VERY rough sketch, not to scale.( I am having trouble posting with image tags, so hopefully you can follow the links...)
That looks good actually. I see quite a few people using hydroponics stuff for this kind of thing. Either that or bathroom extractor in-line fans.

When you say 'safer' for positive pressure, how is that exactly? Just so you KNOW for sure you're getting adequate air in there?

Can I ask what fan and filter you're using exactly? I am in the UK though, so same products may not be available.
Old 1 week ago
  #7
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I was thinking that in a negative pressure, if there is a blockage in the passive inlet, the air will be sucked out of the room. In a positive pressure situation if the passive outlet gets blocked the air pressure just increases but you will still be able to breathe. In a negative pressure situation you don't know if the bad air is being extracted, at least in a positive pressure room you know for sure that fresh air is coming in.

Here is the fan setup I am using...
It is strong and quiet, you can even get a speed controller for it. You should be able to find this or something similar.

In a positive pressure system you wouldn't need a fan on the exhaust as the pressure in the room will force it out of the exhaust no matter where it is.
Old 1 week ago
  #8
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Quote:
Originally Posted by McDuff View Post
What would be the advantages of positive pressure exactly?
Positively balanced rooms actually have a higher transmission loss (isolation), as I understand it not by a lot, but when you spend as much on each dB as we do it seems pretty worth it.

Ventilation Question? Push or pull?

The other thing you hear is that if the room isn't super tight, and you have a lot of fiberglass insulation, a negatively balanced room can have more of a tendency to pull those fibers into the room...

Are you looking to exchange with another heated/cooled space that has ventilation? A proper studio/isolated build will have no infiltration, so unless you have an economizer or other active fresh air source, it's probably best to look into intake and exhaust directly from the outdoors- and then avoid too much heat/cold loss with either an ERV or HRV- which also provide some filtration.

Then you can use inline dampers to positively balance the room- Dampers will make noise as they get closed off (and velocity increase in a smaller effective cross sectional area) so best not to have them on the actual registers.
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