HVAC and Ventilation

[xaMdaM]

While I've kinda' got some time here, I've been thinkin' about all the different issues I need to cover. HVAC being one of the biggies...

I'm attaching a pic of my truss system for reference.

In thinking about room w/in room construction; Here in the southeast US, we get pretty darn hot in the summer, so I'm thinking about how to get the hot air out of the structure AND keeping cooling costs down.

If the AC unit is supplying cooled air in sealed rooms, does it make sense to try to "vent" the ambient "dead" air space around the rooms?

My thinking is to mount intake and outtake plenums in unused portions of the air space... The out-take high (In the truss roof at one end) and the in-take low (At the opposite end of the studio... probably in the lounge area)

By using a double plenum system and putting a thermo-couple midway in the air cavity, I should be able to exhaust the excessive warm air and reduce the overall stress on an AC unit shouldn't I?

I'd use a large, low rpm squirrel cage unit mounted on a vibration isolation pad. The fan would be attached to the plenum via flex duct w/ at least 2 sweeping turns to the fan. The fan would be attached to the external vent grill with flex duct. The grill would be angled out at the top so as to avoid using a "flapper" type of louver and avoid mechanical clanking running back into the system.

Am I stupid for thinking about this? My guess is yes. The air cavity needs to be air tight, right?

ALSO...

I already have a propane heating unit that will attach to my existing tank with no problem. The unit is good for 1200 sq. ft. It's a bit oversized for the amount of finished square footage, but at the price... (free!) I couldn't complain too much.

Does it make sense to use two completely seperate systems for heat and cooling? That makes for double the amount of penetrations into the rooms, double plenums and double ducts.

Should I use a common return? Common ducts?

Thanx,
Max

[knightfly]

Max, you've found one of the areas I know not quite enough to be even slightly "dangerous" in - I'm still trying to find a way to get up to speed on AC without quitiing my job and apprenticing to the local Trane guy (bit late for that anyway) - Rod Gervais is extremely knowledgable in this (as in all other construction details) - maybe he will see this and chip in... Steve

[rod gervais]

If the AC unit is supplying cooled air in sealed rooms, does it make sense to try to "vent" the ambient "dead" air space around the rooms?

No it doesn't - your later comment about the area around the inner assembly needing to be "air tight" is spot on - violating that with additional venting that would essentially destroy that - would not make sense.

By using a double plenum system and putting a thermo-couple midway in the air cavity, I should be able to exhaust the excessive warm air and reduce the overall stress on an AC unit shouldn't I?

Actually - the lowering of the work on the unit is accomplished through the fact that in order to construct rooms which have good sound isolation - you effectively end up with spaces that are super insulated. Thus you generally have lower run time with AC than in normal construction.

By the way - be carefull that the unit is sized properly - you need long enough run time to dehumidify properly - over sized units create nightmares you don't want.

I already have a propane heating unit that will attach to my existing tank with no problem. The unit is good for 1200 sq. ft. It's a bit oversized for the amount of finished square footage, but at the price... (free!) I couldn't complain too much.

Does it make sense to use two completely seperate systems for heat and cooling? That makes for double the amount of penetrations into the rooms, double plenums and double ducts.

Should I use a common return? Common ducts?

Everything should be common even if the units are seperate - it makes no sense to have double the duct runs and penetrations.

Rod

[xaMdaM]

Steve and Rod,

Hey THANX Guys! It's help like this that makes this site such a GREAT resource... Killing myths and slaying mis-information!

I will definitely wait until I get a final studio design before I go looking for cooling units so that it's sized properly.

... and Steve, I personally appreciate what you mean about it being a bit late to hang in the "back pocket" of a Trane guy... about like me and plumbing!!

Max

[Sen]

Rod, while you're at it...(sorry to just jump in like this guys)...
What do you think of the split systems..(comp. outside, the head unit inside).There's some new models that use "plasmacluster" technology which claims it purifies the air and supplies the rooms with fresh, clean air.
How would this work in the "no window" studio environment.
My main concearn with the evaporative ducted system is the loss of sound isolation. Anyone that has these split systems installed in their rooms(STUDIO)??

thANKS

[rod gervais]

Rod, while you're at it...(sorry to just jump in like this guys)...
What do you think of the split systems..(comp. outside, the head unit inside).There's some new models that use "plasmacluster" technology which claims it purifies the air and supplies the rooms with fresh, clean air.
How would this work in the "no window" studio environment.
My main concearn with the evaporative ducted system is the loss of sound isolation. Anyone that has these split systems installed in their rooms(STUDIO)??

No - that is not their claim - here is their claim:

Sharp’s new air purifier using Plasmacluster technology helps clean indoor air by treating it in a manner similar to the way nature cleans the outdoor environment. "It creates positive and negative ion clusters, which we call Plasmacluster, that spread throughout the room, effectively cleaning the air by breaking up airborne particles," added McKinnon. In addition, Sharp’s air purification products go beyond conventional systems by employing three different filters to remove airborne irritants and allergens.

No where do they claim that it provides "fresh air".

There is nothing on the market that takes carbondioxide and turns it into oxygen.

And that is the reason we need fresh OUTSIDE air....... so we duct it and draw it in - and figure out ways to handle the system so we still have isolation.

Rod

[knightfly]

"There is nothing on the market that takes carbondioxide and turns it into oxygen" -

Sure there is, Rod - it's just not very practical

http://www.madsci.org/posts/archives/Ju ... .Bt.r.html

I actually looked this up several months ago due to the curiosity of someone on one of the boards, and saved it in case this ever came up again - kind of interesting, but not too useful... Steve

BTW, Rod, can you find time to answer my last email? Either that, or a time I could call and discuss a couple of things? Thanks...