VAC - Ventilation and AC Supply Air

Howardk · Post by **Howardk** » Sat Jun 05, 2004 4:03 am

I am designing a studio for a teen drop in center, you know the story, hopefully make music instead participating in gang activities. I need to keep this whole project as inexpensive as possible. I am presently working on the HVAC design. The space is a concrete chamber within a large warehouse building. I know what I will do to route the return air (3 returns from rooms into control room and control room to central system), but I am looking for a simple but effective design for the supply air. I have a 13'6" ceiling and the AC unit will be in another room, on the other side of a concrete wall. There is already an opening we can bring the supply and return into the ceiling space of the control room. I believe we will keep the duct work behind a Gypsum bulkhead. I need to get the supply air into the control room, a live room, vocal booth, and instrument booth (acoustic guit). These rooms surround the control room. I want to retain as much of the ceiling space in the control room as possible and I am looking for sound isolation options to get the supply air to the rooms and also ideas on baffling to minimise sound transfer thru the entry points into the rooms. I have about $500 USD carved out in the budget for thhe ductwork, bulkhead, baffles, what-ever, mind you we are hoping for used and donation materials. We are not looking for perfect, just good enough. Ideas toward an effective low dough approach would be appreciated.

knightfly · Post by **knightfly** » Sun Jun 06, 2004 6:09 am

Howard, I resized your dwg to avoid so much sideways scrolling to read the text - I still have the original on my hard drive in case you didn't save it on yours;

Other than that, I'm going to wait to see if Rod has some ideas on this, it's one of my weaker areas (learning, but 'way too slow)

If you get no response in the next day or two, I'll see if I can embarrass myself a bit... Steve

Howardk · Post by **Howardk** » Mon Jun 07, 2004 5:45 pm

Thanks. . . the drawing is CAD and the graphic just a screen capture so no worries, I certainly have the original. I will go a little smaller next time I post an image. I look forward to any ideas and will keep thinking between other things myself.

rod gervais · Post by **rod gervais** » Wed Jun 16, 2004 11:42 am

Howard,

This has been bugging me since you 1st posted it - and I have wracked my brain to try and figure out a way for this to work.

The problem is that I just don't see it happening.

In order for this to work it would have to be an acoustic duct board or acoustically lined duct. That will handle the problems with cross talk.

Either way I do not see it happening anywhere near the budget you have in mind unless you know an HVAC contractor that is willing to donate all the labor and some of the parts.

It can work - with the materials I mention above - but you need to deal with fresh air (which right now you have no provisions for) and both the supply and the return will have to be lined.

The other thing is that studio situations really need some professional input - I would never presume to understand all of the requirements of you area of the world - and with the fresh air requirements (and the fact that we are talking a commercial venture here - with design requirements for permits a necessity) I am afraid I can't help you much more than that.

I am truly sorry.

Sincerely,

Rod

Howardk · Post by **Howardk** » Thu Jun 17, 2004 4:27 pm

What I am thinking may do the job is:

The separating walls between the isolation and control room are going to be 2x4 construction with a gap in between. The Return air will be directed into the cavity between the walls through an additional chamber that is lined with felt covered duct insulation. The air will follow between the walls and pass into a bulkhead located on the south side at the top of the control room. This will provide a number of 90 degree corners and insulation to reduce sound from transfering and no direct paths between any of the room. I should me fine sound transfer wise. The Return out of the control room can be a chamber outside the wall directing air into the same cavity between the walls. Basically the gap between the walls and the bulkhead will be the return air plenum, allowing the air to dump out. The supply air will be pushed in thru flexible insulated ductwork contained in the same bulkhead and separate runs directed out to each of the isolation rooms and studio. There will be one zig-zag duct with internal sound insulation at the transition point from the bulkhead into each of the rooms. We will use a residential furnace fan to push the supply air.

Keep in mind this is a small area and will not require that much ventilation to keep it fresh and achieve adequate air changes. The area outside the studio envelop is approx 75,000 cubic feet of open warehouse space so as far as I am concerned it is a source of fresh air.

What do ya think?

rod gervais · Post by **rod gervais** » Thu Jun 17, 2004 11:13 pm

Howard,

Let's begin with your last comment:

Keep in mind this is a small area and will not require that much ventilation to keep it fresh and achieve adequate air changes. The area outside the studio envelop is approx 75,000 cubic feet of open warehouse space so as far as I am concerned it is a source of fresh air.

The statement "so as far as I am concerned it is a source of fresh air" is meaningless - this due to the fact that THE CODE has no regards whatsoever for your opinions.

As I stated earlier - I am not familiar with Canadian COdes, but, in as much as it is a civilized nation - I would imagine it can't be that far off of the codes in the US.

In the US - code requirements are as follows (I quote now from the International Mechanical Code):

Section 402 NATURAL VENTILATION

402.1 Genral. Natural Ventilation of an occupied space shall be through windows, doors, louvers, or other spaces to the outdoor air.

402.2 Ventilation Area Required. The minimum openable area to the outdoors shall be 4% of the floor area being ventilated.

....402.2.1 Adjoining Spaces. Where rooms and spaces without openings to the outdoors are ventilated through an adjoining room, the opening to the adjoining room shall be unobstructed and shall have an area not less than 8% of the floor area of the interior room or space, but not less than 25 square feet (2.3m2) The minimum openable area to the outdoors shall be based on the total floor area being ventilated.

Please note that the bold and italics highlighting the middle of 402.2.1 are mine for emphasis.

The requirement of 8% translates to an area emcompassing 31.6 square feet in size for your space....... except for that you actually have 3 rooms here....... none with communication to the outdoors, and 8% of each of those small spaces is less than 25s.f. - so you can now make 3 cased openings of 25s.f. (just cut holes throught the walls) into the warehouse space..... and read carefully the the line that states these openings are required to be UNOBSTRUCTED....... and you will begin to see how your method of viewing this - and the Codes method of viewing this are 2 very different things.

Again,

Find an engineer that will donate his time for your cause........ there will be one I am sure....... and attack this the right way.

Sincerely,

Rod

Howardk · Post by **Howardk** » Fri Jun 18, 2004 4:33 am

I highly doubt this will be done with a Natural Ventilation method that related to the code in your exerpt. . . Most of the studios I am aware of have been forced air supply, with return air openings much smaller than the code exerpt, and also somewhat indirect paths to baffle sound (obstructed?). Cutting holes in 16" thick concrete/brick is extremely expensive esepcially when there will be structural issues and steel headers required. We have one existing opening available and I was hoping to share it for two main ducts, one to push in the supply air with a blower, and the other to allow the return air to escape out from the bulkhead. What am hoping for is clever and inexpensive ways to get the air in and out of each of the rooms, using baffled ducts, or insulated bulkheads, or cavities between walls or. . .? I can probably obtain free advice on sizing etc. . . from a local HVAC engineer to provide the required air changes, but it will be with semi-fresh-air in the large outside chamber and not outdoor air(we will not be to code). Also when it somes to practical sound isolation for a recording environment, it is not the area of knowledge they will possess. Also keep in mind, we are not going to the ultimate in isolation, just good enough, without any huge mistakes.

rod gervais · Post by **rod gervais** » Fri Jun 18, 2004 5:57 am

Howardk wrote: Most of the studios I am aware of have been forced air supply, with return air openings much smaller than the code exerpt, and also somewhat indirect paths to baffle sound (obstructed?).

Perhaps - but all of the studios I am aware of (and have been involved with) have had fresh air intake as a part of their HVAC design........ the outside air intake generally ties into the return air just before the air handler unit.. with a barometric relief located in the return duct upstream from that.

Fresh air is critical especially in anything constructed like a studio.

Cutting holes in 16" thick concrete/brick is extremely expensive esepcially when there will be structural issues and steel headers required.

You are missing the requirements of the code - it isn't that you have to cut through the walls - just that you have to provide fresh air...... it is when you plan on doing it the way you want to that you now have to provide the unobstructed openings through the walls to the interior space.

but it will be with semi-fresh-air in the large outside chamber and not outdoor air(we will not be to code).

And this is where we part company......... building any sort of a public meeting place - and knowingly violating code requirements - just goes against the grain here.

I wish you luck in your endevors.

Rod

z60611 · Post by **z60611** » Fri Jun 18, 2004 9:25 am

In Oakville Ontario Canada the city plans examiner will comment on any building code questions by email. I just send them to the city info desk, and less than a week later I get a reply.
For example, I found out that if I put an apartment into my basement (defined as any dwelling unit or bedroom) then I need an openable window. But if the room is for a home theater I don't need a window in my basement room.
So, what I'm suggesting is, ask your building inspector if you want to know about windows. They are also really good at keeping you from doing things that a previous coroners inquest decided were dangerous.
But they know nothing about soundproofing.

rod gervais · Post by **rod gervais** » Fri Jun 18, 2004 12:00 pm

Z,

I am not suggesting that he needs windows......... he doesn't...... but he does need fresh air - FRESH OUTSIDE AIR............ this is required everywhere - but is especially important in a studio that has any degree of isolation - this because isolation means close to air tight - otherwise the sounds just go in and out............

Rod

Howardk · Post by **Howardk** » Fri Jun 18, 2004 2:51 pm

The space exists now, is occupied now, and does not have fresh outside air delivered to that space. . . It will only be better than present by forcing air changes with a ventilation system. . . I have surveyed the building and fresh air is not going to happen on their shoe string budget so it is either do nothing or make it better with very low doe.