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how renovate air without losing the isolation?
Posted: Tue Oct 07, 2003 8:24 pm
by jtvrdy
Imagine that you have a perfectly isolated room,how renovate air without losing the isolation?
I suppose that it will be necessary to build a special conduit, but how should it be?
thanks,
Posted: Wed Oct 08, 2003 12:34 am
by laptoppop
John's info at
http://www.saecollege.de/reference_material/index.html
has a section on air conditioning under the "fitting out/electrics" section.
Another thought - I don't see the exact source offhand - but you can build a couple of boxes to isolate the sound from the air conditioning. One box for air in, one box for air out. Each box should be big enough that they don't restrict the airflow. The air in for each box should NOT be in line with the air out. Line the box with rigid fiberglass covered in cloth, such as Owens-Corning 703 covered in cotton muslin.
For my little room, I built a lined box to isolate the air conditioning. The air comes in the side, and exits out the bottom. You can see pictures at
http://johnlsayers.com/Studio/Mainpage/MP-laptoppop.htm
if you press the update1 button on the left.
Hope this helps,
-lee-
Posted: Wed Oct 08, 2003 2:15 am
by rod gervais
Well,
A lot depends on what you're using for a system........ if you're doing this at home and are ducting off of a through the wall (or window) unit - as long as it is set up in the "fresh air mode" this is already taken care of for you.
If you are talking about fresh air intake for a standard commercial split air system.........
then typically a fresh air duct is installed and connected to the return air duct directly before it's connection into the air handling unit - the flow of air through the return then pulls fresh air into the unit.
This also puts the fresh air passing through the condenser coil prior to being introuduced into the space- which will help reduce the humidity level during the cooling process (very important for the hot humid summer air).
However - this is only half of the process.
If all you have is fresh air intake - you will pull air in until the room pressurizes and when the pressure reaches the maximum static level of the unit no more fresh air will enter until someone releases the pressure.
Thus you also have to install a pressure relief to get air back outside.
This also is typically placed on the return duct - but downwind from the unit - this is a simple duct running to outside air that only needs a barometric pressure relief on it - when the inside room pressure exceeds the setting of the barometric relief - it slips open and releases the return air to the outside.
Very simple to explain in theory - simple to understand - but it is not as simple as just doing it - seeing as it is a passive system - relying on the AHU fan move the air - the ducting has to be sized correctly to create the proper air flow.
As far as materials I personally always reccomend the use of John Manville Super Duct (or it's equivilent) for any ducting moving air in these spaces. It is a polymer lined fiberglass board. Has excellent acoustical properties - and the polymer lining help to stop the glass fibers from entering the air-stream.
A few other notes - be very carefull with the sizing of HVAC systems for studio use.
A lot of engineers end up over designing these systems - due to the fact that they do not properly account for the super insulated structure - for example - a unit sized for a typical 900 s.f. apt - ( say 2 tons of cooling) would be oversized for a 900 s.f. studio. It would not get enough run time due to the studio design and thus would not dehumidify properly during hot sticky summer months. Run time is critical for humidity control.
Also very important -
If - when everything is said and done - you still find that humidity is a problem in your studio - always install humidifiers on the supply side of the Air Handler Unit (AHU) and dehumidifiers on the return side of the AHU. They work better in concert with the unit rather than fighting it.
Rod
Posted: Wed Oct 08, 2003 4:29 am
by jtvrdy
thanks,
my idea is to install two split systems one in the control room and the other in the studio but I need to refresh the air from the exterior so I need to do some circuit with conduits and a fan from outside to inside and vice versa.
Posted: Wed Oct 08, 2003 7:01 am
by rod gervais
HI,
you do not need seperate fans - and if you take the ducting to the unit itself - then the isolation the unit gives you already exists..... PLus you then have one less piece of gear to maintain /replace/break down. You can take one inlet into the building and then branch that off to connect to the 2 air handlers. The same thing can be done with the release for the interior pressure - seperate outlets joined to a single outlet with a barometric damper. As long as the design is correct - it will work perfectly.
If you use the duct board i refer to - this will essentially maintain your isolation. It's the duct board i used to connect to the through the roof units i installed at the movie studio i constructed (15,000 s.f. in CT)
The trick is to make certain to connect tightly to the inside face of the roof (or wall) sheathing you install - caulk those joints well - and then let the air flow run through the unit. this again creates a longer pathway for the air (when i say air picture noise - cause that is how it's going to travel) to run - thus increased isolation.
This also tempers the air for your room prior to it entering the space...... so you are not pumping cold air in during winter months or hot air during summer months.
If however - you are determined to do this with a seperate system - you have to make certain to either interlock the fan for the fresh air to the Fan Coil Unit - or should install an alarm - to show you if the fresh air unit goes down. Although you will figure out real soon if the AC is off - heat may not be quite as noticable, so the alarm would probably be the better choice of the 2.
The reason for this is so you will be aware of the lack of fresh air - which could cause some real health concerns if you were to lose it. Or at least in the long term sense.
Rod