Help on HVAC

[tmix]

I have read everything I can findand all the stickies, but still have not found any definitive ideas on runnig quiet airconditioning to my studio rooms. Perhaps my searching criteria is all wrong.
If anyone can direct me to links on how to design quiet runs and returns I'd appreciate it.

I am building a new construction building about 950 sq/ft with 3 rooms that are acoustically sealed and quieted. I will have a standard 2.5 ton A/c unit mounted in a front breakroom area closet isolated from the other rooms by a double wall and about 6 feet of space,and need to figure out the best way to run sends and returns. The perimeter walls are 10 foot with trusses and the interior walls and ceilings are 8 to 9 foot high and not attached to the bottom of the trusses so there is plenty of attic space to run plenums and ducts. I just need basic construction ideas for thetype of ducts and what types of materials (flex or fiberglass ducts) that work the best.

Please aim me to some sources of info.

Tom

[sharward]

I've got a lot to learn about A/C myself, and I know there are threads here that cover A/C in quite a number of ways. (No time today to help you search though -- sorry.)

Here's what I do know:

• Larger ducts and registers with air moving in (and out?) at lower velocity will be quieter than standard ducts and registers with air moving in (and out) at normal velocity.
  
  Air movement can have an adverse affect on acoustics, so placement of your vents may be important (i.e., avoid blowing air directly across areas that separate sound sources and ears/mics).
  
  You need returns in sealed rooms in order for air to flow to them. Otherwise, a positive pressure situation occurs, and at a certain point, air will no longer enter the room unless a door is opened to equalize the pressure. This contrasts with typical residential construction, typically, because the air gap at the bottoms of doorways can allow a lot of air to escape the room -- although performance usually improves when doors are left open.
  
  For isolation purposes, you only want one duct per "run."
  
  To minimize noise from the air handler from entering the room(s), you want at least two 90-degree bends in the ducting, and a plenum may be desired to dampen the noise further.

There may be some other tips that people can add, and I welcome anyone to amend, clarify, or even correct anything I've written here.

[tmix]

Thanks,
These have been my observations so far as well.

I have thought about making a long trunk type plenum out of the rigid fiberglass ductboard going towards the rooms, then running some large dia ducts ( have sound dampening in them) run from the trunk to the seperate rooms. For the returns basically do the same back to the return base.
I figure as long as I have the same volume of air able to get back to the airhandler that is going out I should be safe. ? (that is more or less a question).

Any other input I'd appreciate it.

Here in Texas, we got to have our A/C!

Tom

[rod gervais]

Actually - you want a slight positive pressure within the room - this too helps to keep noise out -

So you want your return air to be less than your supply.

Rod

[sharward]

Ooooh, I hadn't heard that before, Rod! Just in time for me to incorporate that into my project, too!

[tmix]

Thanks Rod!
If you have any other thoughts you want to share or links to other info I can read, please feel free to post away!

I appreciate all the help I can get.
Around here in the Dallas area it seems all it takes to be an "Expert" in quiet a/c installation is knowing someone who has a friend , who helped somebody else install something similar to what you were talking about. (geeeesh!)

Thaks again.

Tom

[sharward]

Around here in the Dallas area it seems all it takes to be an "Expert" in quiet a/c installation is knowing someone who has a friend , who helped somebody else install something similar to what you were talking about. (geeeesh!)

Hey, that's better than "I once heard of a guy who knew a guy who I think worked on a project kind of similar to yours, and I think they said it worked, or maybe they said they thought it worked, or something. Anyway, yeah -- no problem... piece o' cake!"

[rod gervais]

Guys and Gals,

Probably the most important part of HVAC for any studio is that the design takes into account very accurately - the BTU output from the gear and what ever people will be in the space - and THEN the fact that these rooms are super insulated.

Standard calculations for residential or commercial HVAC systems will NOT work with these rooms.

Seeing as you have super insulated virtually air tight rooms - they will cool down very quickly - and maintain those temperatures a lot longer - than any standard construction. If the systems are designed properly - you will be pulling outside air into the space (nice to be able to breathe) and this generally adds to the moisture content of the space.

If the design is based on typical construction - this means you will super cool your space - get very little run time for the HVAC system - and thus will not properly dehumidify the space.

High humidity levels will play havoc with your instruments and gear - as well as run the risk of problems relating to mold.

I reviewed the HVAC design for a 15,000 sf movie studio that was over designed by 20 tons of cooling - I almost killed the engineer when I got him on the phone...........

I did get stung on my 1st recording studio with this problem - and it cost over 10 grand to add the dehumidification we needed to correct for this -

So make sure your designer gets it right the 1st time - you want just the right cooling capacity - with long run times for the condenser units.

Sincerely

Rod

[aschatzb]

Hello - I just recently installed HVAC in my space. I was totally paranoid about getting it right, so many factors to consider when creating the ideal environment...

One thing I can add to what has already been mentioned is the use of a multi-speed air handler. The advantage to a unit like this is there is virtually no noise when the unit turns on. It turns on slowly until it reaches max. fan speed. I've always found most HVAC to be the loudest when they first shut on until they stabilize. Units like this cost more, however in my limited experience thus far, I'm very satisfied...

take care,

andrew
[/u]

[tmix]

That is a great idea.
I have heard of the multispeed units , but I did know they varispeed up and down. I figure they had like 2 speeds( fast or slow) .

I'll check into that.