Home Theater Help

[CJO4]

I am having a builder finish out my basement. As part of it, I am putting in a home theater. The HVAC guys that he is using are very accomodating, but are not familiar with what goes into designing a system for the home theater. They are willing to put in whatever I ask, but are looking for me to let them know what I want.

Here are the specifics- I'm in North Carolina and the theater is in a corner of a walkout basement. One of the exterior walls is approximately 70% below grade. The other exterior wall is on the walkout side facing the northwest and has two windows. This side is also fully shaded (under a deck and facing a heavily treed area). The room is approximately 24' long, 13' wide, and has 10' high ceilings. The screen will be in front of one of the 13' wide walls, with the seating on the other side of the room. I'm putting in seats for 8 people. All of the equipment, except for the projector, are in an adjacent room.

They ran two 6" supplies to the theater and one 10" return. The HVAC contractor has designed it so that each supply will push approximately 150 cfm. They used flex duct and the runs are approximately 50' long, so I don't think I'll get much, if any, sound from the HVAC unit. I am more worried with the sound of the air coming out of the vents and back through the return.

I am planning on running the supplies through a soffit to the front of the room, near the screen and will exit from the bottom of the soffit. The return is on the side wall, near the seating area. It's been recommended to me to keep the air velocity from the supplies (and return) at 250 fpm or less. This results in supply registers of approximately .6 SF or larger and the return at 1.2 SF or larger (which fits in well with the standard 14"x14" return box that they have installed). I'm comfortable with all of this so far.

I've also been told that I would want linear slot diffusers to keep the noise down. The contractor uses Hart & Cooley, so I was considering an LS200015x6W (LS series grill with control grid, straight bars, standard mount, 15"x6") for the supplies. For the return, I was thinking about an LS100014x14W (LS series with grill only, straight bars, standard mount, 14"x14"). I also wanted to put a filter cage at the HVAC unit rather than in the room to cut down noise.

Does all of this sound right?

Also, the HVAC contractor originally installed the return on the side wall, just below the soffit. I asked him to move it to approximately 8" above the floor for aesthetic reasons. Now I'm wondering if I made a mistake from a heating and cooling perspective. Since this will be a closed room with several people inside, I'm thinking that I'll do alot more cooling than heating. Any thoughts? I would appreciate any help or advice, even if it's to tell me to go away :)

Thanks in advance,
CJ

[Kevin O'Neill]

With 50' long 6" flex ducts I doubt you will get more than 50 CFM Each! How did he decide how much air you need? The 10 inch return may be adequate but I would recommend that you install a quiet mini-split in your situation. Tapping into your existing system will not give you the comfort you want. When the home theater is off in cooling season, you will likely freeze in that room. When all your home theater equipment is running, the added heat will roast you. The home theater will be its own climate zone, it needs its own system.

[jstjohnz]

With 50' long 6" flex ducts I doubt you will get more than 50 CFM Each! How did he decide how much air you need? The 10 inch return may be adequate but I would recommend that you install a quiet mini-split in your situation. Tapping into your existing system will not give you the comfort you want. When the home theater is off in cooling season, you will likely freeze in that room. When all your home theater equipment is running, the added heat will roast you. The home theater will be its own climate zone, it needs its own system.

He said the only equipment in the room is the projector, and it probably doesn't generate a lot of heat. I agree though that 150cfm from 50 ft of 6" flex isn't realistic.

[Kevin O'Neill]

He said the only equipment in the room is the projector, and it probably doesn't generate a lot of heat. I agree though that 150cfm from 50 ft of 6" flex isn't realistic.

8 people adds almost 1/2 ton. What is cooling the equipment in the next room? Some of that cooling load may transfer into the theater.

Perhaps a zone control might work.

[beenthere]

As others, those 6" supplies are under sized. Since its flex, they are really undersized for the CFM you think you'll get.

They would need to be 8" to get the 150 you want, and not have to high of a static pressure in the rest of the system.

Do you know the wattage of the projector.

[CJO4]

I appreciate the quick feedback. I had actually said that I wanted 8" supplies (and would pay for him), but the owner said something about the pressure not working out correctly. I haven't gone through the calculations, so I'm not sure that 150 CFM is what I want, but it sounds reasonable to me. This is with a new, 1.5-ton 13-seer system just for the basement. However, the theater is not on it's own zone. Also, I've taken lots of pain to make sure that the room is totally sealed, so I wouldn't expect any significant cooling from the other rooms.

I do not yet have a projector, so I don't know what the exact wattage will be. I'm considering the Panasonic PT-AE300U, which uses 240 Watts.

CJ

PS- It's nice to get professional advice from another O'Neill, especially one who spells his last name right :)

[wahoo]

I agree with your earlier posters, you won't get anywhere near 150 cfm. from 50 ft of 6" flex. Go with 8" and you'll be a lot happier. Don't understand what the contractor could mean about "messing up his static" if he told you that he "could" get 150 cfm from 50 foot long 6" flex? One does not correlate with the other? You are gonna need at least 400 cfm into this room to keep 8 people, the projector, and the room cool. Any way you can zone it? That way you won't affect the remaining system, when the room is not in use.

[Kevin O'Neill]

I appreciate the quick feedback. I had actually said that I wanted 8" supplies (and would pay for him), but the owner said something about the pressure not working out correctly. I haven't gone through the calculations, so I'm not sure that 150 CFM is what I want, but it sounds reasonable to me. This is with a new, 1.5-ton 13-seer system just for the basement. However, the theater is not on it's own zone. Also, I've taken lots of pain to make sure that the room is totally sealed, so I wouldn't expect any significant cooling from the other rooms.

I do not yet have a projector, so I don't know what the exact wattage will be. I'm considering the Panasonic PT-AE300U, which uses 240 Watts.

CJ

PS- It's nice to get professional advice from another O'Neill, especially one who spells his last name right :)


:D

[andserco]

Hopefully...a non-smoking home theater, if not you better address that too.

[CJO4]

I agree with your earlier posters, you won't get anywhere near 150 cfm. from 50 ft of 6" flex. Go with 8" and you'll be a lot happier. Don't understand what the contractor could mean about "messing up his static" if he told you that he "could" get 150 cfm from 50 foot long 6" flex? One does not correlate with the other? You are gonna need at least 400 cfm into this room to keep 8 people, the projector, and the room cool. Any way you can zone it? That way you won't affect the remaining system, when the room is not in use.

It looks like I made a mistake on what I told you guys. I was posting from memory and went back to look. The supply is an 8" run that is split into two 6" runs when it gets to the room. So, the 8" run is approximately 30' long, while the two 6" runs are approximately 20' and 30' long.

As far as zoning the system, I had talked about this originally, but never really followed up with them. For the time being, I plan to use a poor man's zoning by changing the dampers at the unit.

Thanks,
CJ

[beenthere]

Still won't be getting 150 CFM for those 6" supplies.

If you let him install it that way.
Run the system before you close everything up. So it can be changed without too much fuss.

[CJO4]

Would it be sufficient to split the 8" run into two more 8" runs at the room, or should the initial 8" run be upgraded to a 10" run?

Also, back to my initial questions- I've also been told that I would want linear slot diffusers to keep the noise down. The contractor uses Hart & Cooley, so I was considering an LS200015x6W (LS series grill with control grid, straight bars, standard mount, 15"x6") for the supplies. For the return, I was thinking about an LS100014x14W (LS series with grill only, straight bars, standard mount, 14"x14"). I also wanted to put a filter cage at the HVAC unit rather than in the room to cut down noise.

Do these sound correct?

Thanks again for all of your help,
CJ

[beenthere]

I'd probably run 2-8" supplies to that room. Easier to damper down a large supply, then to replace an undersized one.

Slots are ok. But, you may not get the spread of air you want, depending on your ceiling height.

[CJO4]

Thanks. The builder is supposed to talk to the HVAC company owner on Tuesday to question him on the supply size. The ceiling height is 10', but the soffit, where the vents will be are only 8-1/2'. If not linear diffusers, what would you suggest?

Thanks,
CJ

[beenthere]

Probably A618's for side wall instalation.
They have adjustable fins to control spread.

[micdundee]

with a ten inch return and two sixes you will be sucking in the caulk from around the doors & windows. that wuold be called negative pressure.

[CJO4]

Probably A618's for side wall instalation.
They have adjustable fins to control spread.

I was going to have them installed on the bottom of the soffit, which would make them comparable to a ceiling mount? Based on the catalog, it looks like a pair of 12x12 A501's should work? Or, using 12x6 SV's appear to be quieter.

CJ

[beenthere]

A 12x12 501 won't have much throw at low CFM. Not really rated for the CFM you'll actually have.

An 8x8 would work better at CFMs from 90 to 105.
And a 10x10 for CFMs of 115 to 135.

Still has an NC of less then 20 at those CFMs.

[CJO4]

Great.. thanks!

CJ

[CJO4]

The builder talked with the HVAC guy on Tuesday. He thinks that we will be way too cold in the theater, but he will upgrade the supplies to 8" lines and 10x10 501's. I'm willing to adjust the dampers if he ends up being right. He is also going to install the filter box at the HVAC unit rather than in the room, though he doesn't think that this will make a sound difference.

In any case, thanks to everyone for all of their help!

CJ

[CJO4]

Just wanted to give an update. The HVAC system is in and running. It is very comfortable and I am having no issues with temperature differentials. The grill for the return is in, but the grills for the supplies are backordered. So far, it is silent!

I also wanted to thank everyone for their help.

CJ