What I have learned about HVAC

Hello Eveyone, I just wanted to share with you all my findings on HVAC. I am by no means an expert and this is just a culmination of what I have discovered in my quest to supply air to my Basement Studio. I will try to abstract what I have learned and apply it to different studio situations, but again this is just to get it all in one place and is by no means definitive. Just to give you an insight into my application.. 1 room 10'w x 12'l x 7'h very small basement. I choose to go with my pre-existing furnace/air-conditioning system. I will cover the following in this thread. I strongly encourage anyone who knows more or has heard anything different then what I propose to chime in here. Vent Locations Air Change Units Air Change Calculations Duct Silencers Vent Locations One of the most common questions that I have seen is 'where should I put my registers'. Well the simple answer that I have found is, it really doesn't matter. The ducts 'in theory' will be connected to silencers and should provide limited background noise. Now in a real world situation like mine, I am dealing with low ceilings and only a 10x12 space.. I have chosen to place my registers as close to the floor as possible for the supply and in the ceiling as far to a corner as possible. I choose these locations on 2 common sense principals. 1. Heat Rises. My studio has low ceilings, and is in a well insulated basement. If I were to put the return on the floor/lower wall, the heat would stick around in the space. We all know drummers are heat machines, so this would not be optimal. 2. Supply is generally louder then return. I placed my registers on the floor because most of my microphone placement in this room will be above the middle of the room height. If the supply was on the ceiling, this would theoretically waft air across my mics causing additional background noise. If this is a proven theory or not is beyond me, but it made sense. I choose to bury these as far to the corners as possible just to keep them as far from the mics as possible and to keep as little duct work in my walls as possible. The locations I choose were places that I could run no more then a few feet of duct work directly between my 'room in a room' walls. My finding here was the more duct in the walls the greater the chance that the ducts would capture sound and transmit it throughout the house. Air Change Units This has been a great topic that I have found a lot of product info on. There are these great units which seem to be preferred in many studio applications, but require a bit of knowledge and work to install. http://www.mini-split.com/ These units are great for an application where you can install them, but they didn't make sense in my space. They provide enough fresh air and circulation to get the job done right, but cost a bit more then tapping into existing HVAC. Air Change Calculations Ok well here is something I definitely didn't find on this forum. This is the formula to figure out if you need more fresh air in your studio or not. CFM = Cubic Feet Per Minute Area = cubic feet of a given space Get the CFM of your air mover (blower speed) there is a tool to measure this if you don't want to do the math or if its not provided in the specs from the factory. I have a formula, but i am not sure its accurate so I don't want to post it. I went with the tool. Here is a link to the type of instrument you will need. Anemometer This will measure the FPS of air flow then, you need to put it against this formula to get your CFM.. FPM * area(of the duct) = CFM Link to the article I found this on Fan Calculations - Measure Airflow with CFM (CFM * 60) / area (of the room) = Air Change Rate Per Hour Link to article Learn the Air Changes Method of Calculating CFM So now you should have your air change rate per hour... well this doesnt help you yet. Now you have to figure out your optimal air change rate for your space. This to me seemed a bit over my head. You would have way to many measurements to figure it out exactly, this is better left to professionals. What I did find was a rainbow chart giving you some averages for common spaces specifically mentioning recording studios (10-12 ACH) Link to Rainbow chart. Typical Air Changes Per Hour Table Now on to fresh air...Fresh air changes for comfort should account for 20% of your total air changes. So if you calculate down to 10 changes per hour 2 of them should be fresh air changes. So now you can figure out if you need to add that air supply, and how big it needs to be by reversing all the math above. So how much fresh air am I getting? Well the answer to this is a little more difficult and requires a tool for measuring C02. What I suggest doing, which was what I did, was make sure you have a fresh air intake that provides the required air changes as calculated above. I piped this to a basement window and connected it directly to my return trunk. You don't want to go too large of a pipe, because then you affect the static pressure of the house and your fan might need to work overtime and wear out faster. I suggest doing the calculations and putting in the exact size of what you need. Again this is all for using your central air system.. If you are using dedicated system, like the mini-split, you won't need to worry about this, but instead you would need to still do the calculations to make sure your system is big enough. Here is a link to the article that explains more on C02 consumption and how to figure out how much fresh air supply you have in your home. Duct Silencers Ok, so here is the fun part for people like me.. building stuff. A few basic rules on these, (which is all I could really find) 1. The more 90 degree turns the better 2. The silencer should be twice the volume of your incoming pipe. Brad built one that seems to be on par with the suggested way to do this. viewtopic.php?f=2&t=9756 Anyone else have links to duct silencers? I'm tired of typing... So in conclusion, I know more about HVAC then I did a week ago, but I still dont have all the answers.. but this helped me decide what to do with my system and feel better that a drummer or vocalist wouldnt pass out for C02 poisoning in my studio... Cheers!

Wow! Great stuff! Thank you!