[Martin Pauly]

I need to decide what to do about cold air return in my home theater. My basement has two large air ducts going across the whole length, one for hot air and one for the return. The part that is about to become the theater has two warm air registers simply attached to the bottom of the warm air duct. However, there is no opening in the cold air return duct inside the theater room (there is one on the opposite side of the door into the theater, though).


I see three different ways to go, and I'd appreciate comments from you:

1. Not do anything, so the air would have to escape through the gap between the bottom of the door and the carpet. Not sure if building code even allows that for a room of this size (18' x 12').
2. Do what the builder already did for the warm air registers: basically just create an opening directly in the cold air return duct. Easy to do, yet the return would be very close to the two existing warm air registers. Plus it would return the warmest, not coldest air to the furnace since it is at the ceiling of the room. This may actually be a good thing for air conditioning: the cold air drops from the "warm air" registers, and the warmest air could be returned to the A/C. (I vaguely recall reading something about most theaters requiring air conditioning much more than heating.)
3. Add pipes from the cold air return duct to a location at the bottom of one of whe walls, like in all the upstairs rooms of my house. Most expensive solution, especially since our local building department doesn't allow individuals to mess with the HVAC system (only licensed professionals may do that).[/list=1]
   
   Any opinions? Any good fourth options that I forgot?
   
   
   Thanks,
   
   Martin

 

[patrickwebb]

Martin, there are numerous threads regarding HVAC work and options. A lot of people recommend adding zoning to your current HVAC system. What it will allow my HT is that when the HT is occupied and it needs to cool down, it closes the supply to rest of the house and only directs air into the HT. It is on its own thermostat and communicates with the main thermostat in the house. It will even allow the A/C to kick in the winter when the rest of the house is getting heat.

 

[Martin Pauly]

Patrick,


zoning would be a very good solution, no doubt about it. But it is probably not the low-budget answer that I need to find. I would like to live with what the builder has already installed in the basement, which I think is pretty complete - with the exception of the cold air return. Should the heat in the theater room become too much of an issue I'll have to think of something else, but I'd like to see if it's a problem in my basement before I spend money on it. Or should I take your message as a hint saying that it will be a problem?


By the way, I did a search on "cold air return" in this forum before I started this thread and found just one single thread. That surprised me; maybe I am not using the search function right? Lot's of other stuff about HVAC though, like you said.


- Martin

 

[patrickwebb]

The last thing that I wanted was to do all this work, spend $$$ on equipment, and then find that the HT gets too stuffy with 6 people in it. I have zero concerns about heat, i am concerned about cooling. What happens when the temperature outside doesn't warrant running the A/C in the whole house, but your HT gets too warm?

 

[usabrian]

Quote:

Add pipes from the cold air return duct to a location at the bottom of one of whe walls, like in all the upstairs rooms of my house. Most expensive solution, especially since our local building department doesn't allow individuals to mess with the HVAC system (only licensed professionals may do that).

Bingo! We have a winner.


Rant on...My biased opinion follows as a consultant in this industry: Screw your local building department. Since when is making sure your A/C works right a legitimate government function? This is not going to be a life safety issue and done right nobody would ever know anyway...Rant off.


This is beyond easy. Run flex duct one size larger than the supply serving your room to close to where the door is (typically) or opposite of the nearest supply ducts. Place it to the ceiling if you are in a cold weather climate. Place it to the floor if you are in a warm weather climate.


BTW, here is a great residential HVAC reference for anyone interested:

http://www.toolbase.org/docs/MainNav...ct_systems.pdf


Brian

 

[usabrian]

Quote:

The last thing that I wanted was to do all this work, spend $$$ on equipment, and then find that the HT gets too stuffy with 6 people in it. I have zero concerns about heat, i am concerned about cooling. What happens when the temperature outside doesn't warrant running the A/C in the whole house, but your HT gets too warm?

Without a zoned or separate system you are screwed. Now, you could just run the fan all the time which is what I do and it works for me but I do not plan on there ever being 6 people in my theater. Now, the best solution would be a separate system that pulls in the outside air when the temperature is low outside.


Brian

 

[Toxarch]

I usually just flip on the fan in the HT (zoned) while watching movies during winter. Last night I decided to leave it off and just see how much the room does warm up. It was 66 degrees in the theater when I started watching and I left the HVAC zone off. Two and a half hours later in a theater that is 19' x 30' with 12 foot ceilings, the thermostat (at around 5'6" high) read 77 degrees. I would have liked to have seen what the temperature was near the ceiling.


If you don't zone the HVAC system, then at least turn the fan on while in the theater to even out the air in the theater with the air in the rest of the house.

 

[nzkiwi71]

Martin,


Your basement HVAC situation is exactly the same as mine. I had the same question and was looking for a low cost, yet basically acceptable solution too. I never got to post my question on the forum and just went with my best guess.


In short, I went with # 2 - I simply cut a hole in the cold air return and connected an 8' length of flex duct (with the right connector thingy). I tried to run this as far away as I could from the warm air registers. Given my budget, it really was the only solution and it seems to work just fine.


Steven

 

[pauleyc]

I also opt'd to not to do a dual zone system. I'm doing a HT on a budget that would have double in price had I tried to do this (since I'm doing it myself).


Here's what I did. First, I located my equipment outside the room (easy solution to that heat source). Second, I located an 8" duct directly above my projector and use a inline duct fan from smarthome to exhaust the heat from the projector and provides a 'return' or negative pressure allowing the AC to enter the room (in the summer of course). If your room is leak free (like it should be), you will not benefit when the AC kicks on b/c it will follow the path of least resistance (not in a pressurized room). It also just pulls the heat from the ceiling (heat rises).


btw - I used a 110v switched outlet on a power conditioner to turn the fan on (fan is on when the HT in use). You could also use a switched outlet on a receiver to do the same.

 

[Marc Ye]

Martin,

This is what I decided to do. Our theater will be able to seat eight people total. With everyone seated and equipment going, it was calculated the heat produced would be roughly 9000btu's an hour. Heating won't be a problem. Cooling will be. I have been informed that during the winter months, I will be using A/C in the theater. So how do you run an your A/C system in the winter for just the theater while the rest of the house is demanding heat? You don't. Simply, the right way and probably the most expensive is to design a seperate system for the theater only. Besides, without a proper HVAC system, smells like popcorn, sweat or personal B.O my also linger well after the theater has been shut down!

 

[JasonATL]

I'll add my voice to the choir. The lower-budget option of tapping into the existing return is what I opted for. I strongly recommend AGAINST just leaving it as is and not having a return in the HT. My HVAC sub left it this way, saying it was to code and that air would easily flow (under the door). This was not my first indication that he was an idiot -- I had explained to him how sealed the room would be. In my case, to help with soundproofing, I used an exterior door, with gaskets all around. In theory, no air is getting in or out (so that no sound will get in or out). So, that eliminates the air returning around the door.


Despite my efforts, I'm afraid that my return was undersized. The theater definitely warms up. I leave the fan running full time to try to equilibrate the HT with the rest of the basement. It doesn't fully work. However, I'm sure it is better than if I had done nothing with regards to a return.

 

[Phil_Johnson]

Martin


I'm not sure how hard it would be for you but I'm putting my cold air return behind the projector to see if I can get rid of some heat. I can run a second one to my equipment rack pretty easy so I may do that too.


Phil

 

[Marc Ye]

Phil,

That is exaclty where my HVAC engineer decided to put my returns too. I thought it was an excellent idea since a lot of heat will be produced in these areas. Also, they would be concealed away from view.

 

[Phil_Johnson]

I don't pretend to know anyting about HVAC but it made sense to me to get rid of the heat. If it gets too warm I can run the furance fan or air exchanger. Since your HVAC engineer confirms it, I feel better about putting them there.


Phil