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Supply and return location - Help me get started on the build !

post #1 of 15
Thread Starter 
I need some help finding out the best way to setup my ventilation for my future HT. I’m currently planning the build and I’m stuck because I don’t know if my ventilation setup is correct.

I live in Montreal, QC. The HT will be located in the basement. The basement is cool all year, without the need to have HVAC vents opened in the basement. As such, I plan to only exchange air with the next room which will be tied to the HVAC.

I only plan for 1 supply and 1 return. Room is 11.5’ x 19.5’ x7.5’. The room will have a fair amount of soundproofing (DD + GG, floating joist, double wall, sealant where needed).

I’ve attached a rough plan. As depicted, the entrance to the HT is in the back of the room. I believe the best would be to have the suplpy in the front and the return in the back.

Problem is, the soffit around the room probably won’t be big enough to hide a 6’’ isolated duct. With 89 inch of available height in the room and with a narrow room, I can’t have 12 inch high soffit. I plan to have them at 7 ¾ inch high. With some IC cans and speaker wires runs, there won’t be space to bring the supply in the front via the soffit. Width of the soffit will be 12''.

Another thing to consider is that I'll have floating joist between the current ceiling joist. As such, I can't pass anything in the celing either as the floating joist blocks the way.

So my other plan was to have the supply and return both at the rear of the room, seperated by 9-10 feet. Low supply and high return. Both would go through a shared dead vent in one corner (two separate section within one structure)

The HT will be used 90% of the time by 2 adults and 2 kids, with moderate equipement (7.1 AVR, cable, blu-ray) for movies and some TV show. We usually don’t do marathon session.

Can I have your opinion on this ? It would get me going on the actual build.

post #2 of 15
Read my build thread, there are over 100 posts on HVAC in the HT alone.
post #3 of 15
Thread Starter 
Thanks Dave,

I'll have a look at your thread.
post #4 of 15
For your duct run, if you cant fit the flex you could always use duct board to build the duct or a rectangular duct. I have no idea if that will allow for enough CFMs but its an option.

Two, need more information. Is it a zoned system. If it is, are the zones dedicated systems or zoned with dampers. etc.
post #5 of 15
Thread Starter 
Turning part of the soffit in a duct itself is possibly a very good idea to maximise the space availble. I know I've read about this in the forum, would need to dig the info again. Since most build recommend filling the soffit with insulation, not sure about leaving a portion of it empty to act as a duct. But I need to make some compromise with the space I have so it's worth checking out.

Regarding my HVAC system, it's not a zoned system in any way.

Thanks for the help
Edited by NicAVS - 8/1/12 at 5:50pm
post #6 of 15
HVAC over insulation all day. Much more important, IMO.
post #7 of 15
Thread Starter 
I agree with you, and I'm not suggesting leaving ventilation out of my plan. Even if cooling is not as important as it can be for people south of here, I understand the need to at least exchange the air considering the room will be sealed tight. Perhaps I underestimate the need for a true supply from the HVAC system. I've had a projector since 2008 but it's always been in a family room with big open space. A smaller room with the same equipement will perhaps feel hotter than I think.

Perhaps I need to contact a HVAC supplier to get some answers but the contact I had previously with local supplier doesn't inspire confidence with anything that isn't typical. Perhaps I should look again to find another contact.
post #8 of 15
Thread Starter 
I'd still appreciate if someone could chime in on the location of the supply and return at the back of the room.
post #9 of 15
I have had similar problems with local HVAC contractors. They just dont operate in the same arena as we do, as the needs for a HT are much different than what they are dealing with.

Did you say your supplies and return are in the back of the room?
post #10 of 15
Thread Starter 
Well my current plan would be to have them at the same end of the room, on the wall opposite the screen. The door would be in the middle of this wall, the supply and return would be placed on either side of the door. You can have an idea looking at the plan in my first post. Here's a capture of a sketch-up model I have with a crude location of the register. Missing on this plan is the soffit and the equipement rack which would be near the door. This plan present the room's shell, the DD+GG enveloppe.

post #11 of 15
I would strongly recommend moving the supplies to the front of the room. Much more efficient in heating/cooling of the room.
post #12 of 15
Thread Starter 
Just went to the basement to see if I could come up with different ideas. I was considering including taller soffit in the plan, in order to use them to pass 6 inch duct. The reason I wanted to keep the soffit height around 7.75 inch was that I wanted the soffit to run the entire perimiter of the room, even above the door. With 89 inch of height to spare and considering an 80 inch door, that was the limiting factor for my soffit height.

I could perhaps have the side soffit taller and either stop them at the back of the room or continue them on the back wall and above door but shorter.

Anybody care to comment on height of soffit in a 7.5 feet tall room ? My opinion was that with a small room, you can add lots of stuff but you need to scale it down a bit. I don't want the soffit to had too much "weight" to the side of the room.

Also any ideas how to frame a soffit in order to let as much room possible inside of it ? I thought of using steel angles instead of 2x4 for the framing.
post #13 of 15
at the very least use 2x2. Dont use 2x4's. If it is not holding anything with weight you could probably get by with 1x2
post #14 of 15
Quote:
Originally Posted by NicAVS View Post

Just went to the basement to see if I could come up with different ideas. I was considering including taller soffit in the plan, in order to use them to pass 6 inch duct. The reason I wanted to keep the soffit height around 7.75 inch was that I wanted the soffit to run the entire perimiter of the room, even above the door. With 89 inch of height to spare and considering an 80 inch door, that was the limiting factor for my soffit height.
I could perhaps have the side soffit taller and either stop them at the back of the room or continue them on the back wall and above door but shorter.
Anybody care to comment on height of soffit in a 7.5 feet tall room ? My opinion was that with a small room, you can add lots of stuff but you need to scale it down a bit. I don't want the soffit to had too much "weight" to the side of the room.
Also any ideas how to frame a soffit in order to let as much room possible inside of it ? I thought of using steel angles instead of 2x4 for the framing.

You might want to have a closer look at using the soffit as a rectangular hvac chase. Doing that vs a round 6" gives you more area to reduce your FPM without losing as much headroom. If you take that approach you should be able to get your supply ducts to the front of your room. I have a similar ceiling height to yours with a slightly larger room. I also live in the great white north so cool basements are common here also. Having supply and return in the back of room wouldn't give you the best airflow throughout the room. Take a look at my current plans maybe you will find it helpful: http://www.avsforum.com/t/1383183/235-build/60_60#post_21950547
post #15 of 15
Thread Starter 
Thans 235,

Terrific sketchup plans in your thread.
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