HVAC ideas & a few questions

[motown59]

OK, I'm getting closer to isolating the two room guest house turned studio. Two rooms 400 Sq. Feet. Pulled out the two window A/C units mounted in each room and sealed up the holes. Now there is nothing, but we're in winter here, soon enough I'll need to attend to the A/C situation.
My ideas:
1.there is a storage room on the back side of the two rooms where the extra gear/PA system is kept. I was thinking of framing a small enclosed "cold room" with a window unit vented to the outside and then ducting to the room(s) with appropriate twists and insulated ducts. I saw this idea from John in the archives.
2. for exhaust I was thinking of a Broan bathroom exhaust fan, also mounted in the back room. they have 'quiet' units capable of exausting 200-400 sq. ft. rooms.

Questions:
1. how big/small does the cold room have to be? would a 4'x5" cube room be enough?
2. what about condensation problems in the cold room? Mold
3.if the ducts go to both rooms I would have bad leakage from the tracking(drums) room to the outside? From the C.room to the T.room..
4.was thinking about exhausting only the control room and opening the door to suck out the air from the tracking room when needed so I don't have a path to the outside from the T. room. Bad idea?
5.what kind of insulation in the cold room box? I saw foil sided OSB at Home depot, looked really nice...and then
6.do I want to breathe gasses vented from some construction methods? Caulk, MDF, OSB fiberglass..
7. is there a way to put a furnace filter on the system for clean air?

thanks so kindly for any wisdom...

[rod gervais]

1. how big/small does the cold room have to be? would a 4'x5" cube room be enough?

This would be plenty big enough.

It isn't the size of the room - but rather the size of the AC unit that will be the deciding factor. If the AC unit can handle both rooms then you will be fine.

2. what about condensation problems in the cold room? Mold

Condensation should not be a problem - AC ubits dehumidify - they do not create humidity.

3.if the ducts go to both rooms I would have bad leakage from the tracking(drums) room to the outside? From the C.room to the T.room..

If the ducts are lined (or polymer lined fiberglass duct) - and take a few turns totaling more than 180 degrees - you should be pretty good in both respects as long as your cold room is well insulated from the outside world (In other words - you want to use the same isolating construction there as the rest of your studio - then the only weak point will be the AC unit itself.)

4.was thinking about exhausting only the control room and opening the door to suck out the air from the tracking room when needed so I don't have a path to the outside from the T. room. Bad idea?

I wouldn't do that, what I would do would be to duct both rooms - placing the exhaust fan inside of the cold room - then I would tie the AC Unit power swith and the fan switch - into a switch in each room.

When you turn the Unit on from room A - the fan for that room would run - and only that room would get circulated air....... and it would still work with both rooms at once if everything ties into the same leg of your power.

BUT - you have to make certain that you do not get a modern unit with the remote switch. That type of AC will not turn back on if you kill the power to it.

5.what kind of insulation in the cold room box? I saw foil sided OSB at Home depot, looked really nice...and then

Foil sided (which is just insulation with a vapor barrier attached to it) will work ok - but I prefer unfaced and then a continuos poly vapor barrier.

6.do I want to breathe gasses vented from some construction methods? Caulk, MDF, OSB fiberglass..

Once the room is finished and painted this should not be an issue.

7. is there a way to put a furnace filter on the system for clean air?

You can always put a filter on the return air to the unit right at your return air intake in each room.

This makes it easy to clean/replace - and will decrease the number of times per year that you have to clean the one on the AC Unit.

MAke certain you oversize your ducts so your air move volume without a lot of velocity - greater velocity = more noise.

Rod

[motown59]

Thanks so kindly Rod.
I think I get everything except returning the hot air into the cold room. I thought the hot air exhaust would go to the outside world. First, I'm thinking you must have meant a window unit that DOES recirculate the air, right? If I bring the return/hot air from the room into the cold box wouldnt it need it's own separate duct fitted to the face of the A/C window unit that normally sucks in the hot air from the room?
I get the switches in each room. But either one would send cold air into both rooms, right? Then a separate exhaust fan for each room maybe?
thanks for the info and clarification..[/i]

[motown59]

Been researching some more on this. I just need a few clarifications:

1. the A/C window unit does mount and vent to the outside wall and into my cold room(by the way, I mean t4'x5', not 5" on top my post)
2. 2 returns from each room into the cold room box?
3.both room can be ducted to from the same cold room box?

we'll be in springtime inventory soon at Home Depot and Lowes after January, what kind of unit should I look for?
thanks...

[knightfly]

1 - yes, just treat the cold room as if it were a bedroom and you were installing a single room AC unit.

2 - one supply and one return to each room from the cold room - try NOT to have the cold air inlet dump into the room between you and your speakers, this will cause some strange sounding effects relative to speed of sound in different air temperatures.

3 - Rod already answered this (I think) above - "If the ducts are lined (or polymer lined fiberglass duct) - and take a few turns totaling more than 180 degrees - you should be pretty good in both respects as long as your cold room is well insulated from the outside world (In other words - you want to use the same isolating construction there as the rest of your studio - then the only weak point will be the AC unit itself.)"

4 - look for a unit with a REAL switch on the front to turn it on/off, like a rotary knob (Freidrich units are inexpensive and at least some still use this - do NOT get a unit with "Membrane" type switches, these are the ones Rod warned against. IF in doubt, have the unit powered up in the store, turn it on, then unplug it - if it starts up when you plug it back in (and in the same mode as when you unplugged it) it will work... Steve

[motown59]

1 - yes, just treat the cold room as if it were a bedroom and you were installing a single room AC unit.

2 - one supply and one return to each room from the cold room - try NOT to have the cold air inlet dump into the room between you and your speakers, this will cause some strange sounding effects relative to speed of sound in different air temperatures.

3 - Rod already answered this (I think) above - "If the ducts are lined (or polymer lined fiberglass duct) - and take a few turns totaling more than 180 degrees - you should be pretty good in both respects as long as your cold room is well insulated from the outside world (In other words - you want to use the same isolating construction there as the rest of your studio - then the only weak point will be the AC unit itself.)"

4 - look for a unit with a REAL switch on the front to turn it on/off, like a rotary knob (Freidrich units are inexpensive and at least some still use this - do NOT get a unit with "Membrane" type switches, these are the ones Rod warned against. IF in doubt, have the unit powered up in the store, turn it on, then unplug it - if it starts up when you plug it back in (and in the same mode as when you unplugged it) it will work... Steve

thanks. Glad you mentioned where to bring in the duct. I was planning on dead center between my monitors..and I've heard this effect before. Not good. Thanks again. Wonder if I could sum together both returns into a single bathroom exhaust fan-into the cold room? That way the cold air won't try and go down the wrong way through the return without a fan on...

[knightfly]

NOT a good idea - for both inlets and both outlets, you need at least two 90 degree bends (180 degrees total) with lining for at least a few feet each direction from each corner; more is better. Also, each inlet and each outlet duct MUST be a separate run back to the cold room, or you will get bleed through the ductwork between the two rooms... Steve

[motown59]

Great advice again. Thank you.
When I get closer, and figure out how to make a drawing and post it, I'll make sure I get approval on the whole deal before I blow it, literally and figuratively!
So far I think I'm clear on these points:

1. I'm building an iso "cold room" with a window A/C unit vented to the outside. The cold room is built with the same specs and acoustic iso detail of the studio.
2. I'm running separate ducts to each room, tracking and control rm. Each duct has to take a series of bends equaling 180 degrees and be lined with insulation. note: Make the control room cold duct come in behind mix position.
3. each room has it's own return for warm air, also making 180 degrees worth of bends and only joining up at the cold room to minimize leakage between rooms.
4. A bathroom exhaust fan, at the entrance to the cold box sucks out the warm air from the returns
5. The A/Cond and exhaust fans power are tied together to a master switch. Only an A/Cond. unit that doesnt reset when unplugged is acceptable.
So far I think I have it. only small details I don't know about are how big the ducts diameter should be and what kind of registers go on the returns and cold air ducts.
kel

[knightfly]

It seems like quite a few bathroom exhaust fans aren't really very quiet; possibly since they're only intended to be on while YOU are on (on the throne, that is) - so listen before you buy, you will likely find a big difference in noise levels.

Duct size - make the cross sectional area at least TWICE what your standard ducting is, if they're round this will be 1.414 times the diameter. This will cut velocity in half with the same volume of air flow.

Registers - ask specifically for QUIET ones, look for ones with larger holes and less grating, along with more aerodynamic shape of the grill sections themselves (no sharp square corners, gradual softened edges instead)

Try NOT to use walls that need to be isolative for ducts; better to bring them in through the ceiling, but with earlier warnings taken into account on location relative to head/speakers, etc -

HTH... Steve

[motown59]

All the fans are hooked up at the Depot so you can listen..plus they have sound ratings from noisiest to quietest....seems the $80-120 ones are pretty quiet.
thanks for the info..Noted!
K

[guitarjim]

Have you checked into the Split type AC Units? They have the compressor outside, and a wall mounted unit inside. The only connection to the outside world is a 5 inch hole for the hoses and wires. I am thinking about using them in my new studio as it seems it will be easier to isolate.

I am also planning to use an air to air heat exchanger for fresh air, and a "cold room" may make isolating it easier.

Thanks for the ideas
Jim

[knightfly]

Jim, that's the downside of the splits - no fresh air. If you can fix that one, you should be good to go... Steve