# How do I cool the HT room



## chrapladm (Jun 17, 2009)

with a dead vent?

So the goal is to build a shed for my HT room. The shed will be 7.9m x 6m x 2.7-3m. In the shed there will be a HT room with the dimensions of 12ft x 16ft roughly. The extra space will be a half bath measuring about 3ft x 6ft, a media closet 4.5ft x 3ft deep and a spare bedroom measuring 12ft x 10 ft give or take.

Now I have been trying to figure out how to keep the rooms cool atleast. I was thinking ducted but every installer has said the smallest unit would be overkill for an area that small. Then after thinking about it some more I still wanted ducted but then the cost of $7500 put a damper on things.

I was told that I should just use a split system with a unit hanging on the wall. I dont like the look of those things and I really dont want to put one in the HT room. But with the cost being $4000 for one it seems alot cheaper. And one would be overkill for a 10x12 room but I am lost with what other options I have.


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## chrapladm (Jun 17, 2009)

I have been trying to figure this question out for a few months now. I have know idea what I can and cant do I just know what I would like to do. I emailed a member on here before and he said he would post our conversation but it didn't happen so I have to write everything I stated again. Here were the questions the member asked me.: 

Re: Dead vent I forgot two critical questions, which I added in red below. Please answer this email instead of the one I just sent. Sorry for the inconvenience. 

1. How many people (max.) are you planning to accomodate? 

2. What is the manufacturer/model of the projector? 

3. Will you have any other equipment, including powered subs, within the room? Think in terms of your ultimate (future) buildout, not necessarliy what you are going to put in now. I would need to know manufacturer/model for any power amps, but a general description of the other components (CD, DVD/BD, pre/pro) is fine. 

4. Will this be in a basement? Are any of the walls exposed to outside? Are there any windows? Is there a (conditioned) floor above this room, or is it a roof/attic? 

5. I would normally assume that all lights will be off while you are in the room watching a movie, let me know if that is not the case. 

6. If you have an A/C unit in the next room, why are you considering the dead vent for room supply? Are you just concerned about noise from the A/C unit? 

7. What is the desired maximum temperatue for the home theater room? 

8. What is the probable maximum temperature in the adjacent room from which you will be drawing air? Also, it would help if you can you draw a rough layout of the room.


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## chrapladm (Jun 17, 2009)

So to answer the questions:

1. 7 people max
2. Have not bought the PJ yet for the HT
3. I will have a media closet that will have all things electrical for the HT room. I might eventually do a Fibre sky ceiling but thats all

4.This is a shed that will be outside not attached to to the house. And yes it can be 45/120 degrees sometime here in Adelaide.

5. All lights will be off unless ceiling night sky is on for the rare occasion during a movie

6. I am wanting to use a register to suck the air from the cool room and distribute cool air into the closet and HT room.

7. 68-70 I guess. I have no idea. I like it cool and the wifey always likes to turn the temp back up in our old house with central air in the USA

8. I dont know what the max temp will be. With a shed roof, insulation then the 16mm gyprock/sheetrock I have no idea what the temp will be.

Here is a drawing I drew because my sketchup skills are vastly needing of improvemnt:










X = 15inches
And each square is a foot. It is not exactly correct in dimension but very close.


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## chrapladm (Jun 17, 2009)

So while I was trying to come up with something I was thinking of putting soffits all around the HT room except the screen wall.

I was thinking that I could use the dead vent sort of way to use a high velocity fan to pull the cool air from the spare bedroom and I could then route it where I needed it. And then I would also have some sort of exhaust vent to rid the HT room of hot air.

Sga2 stated this afterwards of me saying the last statement:

Hmm... What you are proposing is going to be very difficult to pull off. I would not recommend attempting to indirectly condition this room with a dead vent system unless you are willing to reset your expectations WRT temperature control. I’m not saying this can’t be done, but for this to be effective you are going to need to build a very efficient structure (high mass walls, lots of insulation, light colored walls and reflective roof) and put some serious (and creative) thought into the HVAC system.

A dead vent can work well for basement home theaters because (a) the home theater room has very little heat load since no walls or roof, (b) the adjacent space (also in basement) is usually very cool anyway and a good source for ventilation air, and (c) the slab, foundation walls, surrounding dirt, etc. provide significant thermal mass that helps keep both the theater room and the adjacent (source) room with minimal effort from the HVAC system. Once you go above grade you are in a different ballgame since you basically lose all 3 of the advantages I mention above, at least with conventional construction. You are now going to have to deal with loads from the climate and solar heat which are significant. Also, in order to keep the HT room at 70F, you will need to keep the adjacent room at ~65F or cooler which at least means you’ll be running at low efficiency but could also run the risk of freezing the cooling coil. One thing to keep in mind - no matter how efficient your HT room dead vent system, the air conditioning system still needs to reject all that heat to the outside to keep the building cool. If you are keeping the room at 65F, the unit will need to work harder and possibly need to be increased in size to handle the load.

Also, you will need to consider winter performance (i.e., providing enough heat to the room) as well. My gut feeling is that if you design this to handle summer conditions the winter conditions should be OK, but it still needs to be checked.

My recommendation is to provide a ducted HVAC system to serve the entire building including the HT room (with acoustic treatments on the supply and return duct, of course). This will be simple, cost-effective, and your best bet for maintaining comfortable temperatures.


Cost effective...... not in the beginning by having to shell out 3500 more. I was thinking there must be another way and yet not break the bank.

So for all those cost saving people out there what can I do?


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## bpape (Sep 14, 2006)

7.9m x 6ish m is hardly a small room. Something like a large mini-split would be an excellent solution for something like that.

Bryan


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## chrapladm (Jun 17, 2009)

I dont think I understand what you mean by large mini split. Is there a unit in the HT room?

Are there 2 units or just 1?


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## bpape (Sep 14, 2006)

Something like this

http://www.mehvac.com/UploadedFiles/Resource/Slim-M-Series.pdf

There are 2 pieces - 1 in room, 1 outside. Only a couple of small pipes/hoses between the 2 units. They're also quiet enough to easily operate in a home theater environment.

Bryan


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## chrapladm (Jun 17, 2009)

yah thats what the $4000 option was. I was trying to avoid puttin something like that in the room.

I wonder if I could put it behind the screen wall?

I cant remember if I could get 2 small units put in for 4k or not. I was trying to explore what other options there are without putting a unit on the wall. I think I will look maybe more at the idea of one behind the screen wall.

And what about noise transients? Wouldn't I have a week point where the unit is going through the wall?


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## bpape (Sep 14, 2006)

There would be some small penetrations in the structure - but they'd be to the outside world and directly covered by the unit itself

Bryan


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## sga2 (Nov 14, 2009)

I agree with Bryan. A mini split would be a good solution but it does need to be located so that it serves the room directly (not in the next room with a dead vent to this room). While they are not silent they are _very_ quiet and you'd probably not notice it running except during the very quiet scenes (even then would hardly be a distraction). Given your budget constraints, it would be hard to beat this option for the price. 

To hide the unit, you could build a removeable box (covering the front and sides but leaving the top and bottom open for airflow) that you could paint to blend with your decor. Or, as you suggest, hide behind the screen. Just be sure it is easily removeable so you can service the unit, change filters, etc. on a regular basis. If you're concerned about the noise, you can line the enclosude with 1" fiberglass duct board to help absorb any sound. You will want the enclosure to be tight fitting around the unit to miniize short circuiting of air, but leave the top and bottom of the enclosure as large as possible (no grilles) to minimize airflow resistance.


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## chrapladm (Jun 17, 2009)

Noise wise I think the unit will be fine.

I was told I couldn't put anything around the wall unit so that was the other reason I didn't want a wall unit in the HT room. If I could hide it then that would be a option I wouldn't mind.

If I had the wall unit behind the screen wall I dont know what fabric I could use which would allow the unit to be usable and yet look nice still from the viewers view?

On the link there was a wall unit and mini ducted system. If I could duct the theater, media closet and entryway for around $5500 then I would be set but this is Australia. EVERYTHING is so expensive so I have know idea if this price is even possible.

I will contact someone later on about the price and see.


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## chrapladm (Jun 17, 2009)

And I forgot to mention wouldn't the wall unit allow the noise to transmit through the opeing in the wall?

In other words because there is a way for vibration to travel to both walls wouldn't that defeat the purpose of decoupling?


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## sga2 (Nov 14, 2009)

chrapladm said:


> And I forgot to mention wouldn't the wall unit allow the noise to transmit through the opeing in the wall?
> 
> In other words because there is a way for vibration to travel to both walls wouldn't that defeat the purpose of decoupling?


If the mini split unit is located in the room, it will be surface mounted on the inside wall. The only opening required will be one ~3" diameter holes in each of the inside and outside wall layers for the refrigerant and condensate drainage pipes to go outside. You can make this connection more flexible by offsetting the piping within the wall (go through inside layer, turn down 5-6ft, then turn back to horizontal and go through outside wall). If the penetrations on both sides of the decoupled wall system are properly sealed, I do not think this will do much to compromise the sound integrity of the room.


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## chrapladm (Jun 17, 2009)

Well I foound out that I can not cover the wall unit at all. 

And after checking prices a mini split duct/wall unit would cost closer to $8000 and 2 wall units would be about $5000. SO I guess I will be going with 2 wall units in the future.

I hope the wall unit wont have a bunch of parts that rattle at low hz when watching the movie.

What fabric allows for air to flow through it?

I wonder if the wall unit behind the screen wall will cause the screen to move?


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## sga2 (Nov 14, 2009)

chrapladm said:


> Well I foound out that I can not cover the wall unit at all.





chrapladm said:


> I wonder if the wall unit behind the screen wall will cause the screen to move?


Why can't you cover it? 



chrapladm said:


> What fabric allows for air to flow through it?


What do you have in mind?


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## chrapladm (Jun 17, 2009)

Because almost all models have to have the top and bottom exposed for air inlet and exhaust. Some models will allow me to put something small in front of the wall unit but not on top or bottom. And some models I cant even put anything in front of the unit.

So I was thinking the next best thing in my mind would be to either put the unit on the rear wall exposed or behind the screen wall. If behind the screen wall I would never see it and if the lower hz cause it to rattle it would be far enough away from the viewing position that hopefully I wouldn't hear it.

Regarding the fabric on the screen wall I dont know. I am not sure what material I could use that would be sturdy yet allow air flow. Speaker cloth, shade cloth.....IDK?


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## bpape (Sep 14, 2006)

If you made a 'cover' for the unit that matched your walls and extended above and below your unit say 6" but was open top and bottom (cover with a breathable cloth maybe???) - it could be made to blend pretty well. Can't help on the cost though.

Bryan


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## chrapladm (Jun 17, 2009)

I dont think I could cover it 6" below because of the angle of the air coming from the unit. It doesn't shoot air straight down, more like a 30-45° angle. I am thinking I could hide it behind the screen but that might be harder than just blending it in the viewer back wall.


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## sga2 (Nov 14, 2009)

chrapladm said:


> I dont think I could cover it 6" below because of the angle of the air coming from the unit. It doesn't shoot air straight down, more like a 30-45° angle. I am thinking I could hide it behind the screen but that might be harder than just blending it in the viewer back wall.


If the unit discharge itself is not adjustable, can you fabricate a baffle or turning vane which you could mount inside the screen assembly to direct the air downward? It would not take much to change the airflow direction, just a light gauge piece of sheetmetal that you could form and cut by hand.


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