Kinetic River Cinema - Page 9

The only thing we disagree on is that I don't see it as a first-choice option, particularly when everything is being built. If two fans, one or two controllers, flex duct, the additional electric, Green Glue, lumber, duct board, etc. is $600 of total materials (about 55% of which is the cost of the fans) and is able to cool to roughly ambient, I do not disagree that it is fairly cheap and fairly effective. But if it is $500 more to hire professionals to engineer the system and buy / install the materials then it is probably a worthwhile expenditure to have the engineered forced air system handle 100% of the room's conditioning without the need for a secondary or supplemental dead vent system, then that saves a lot of construction hassle and brings everything into a common, controllable system.

@DAVID - you may want to call these guys: http://www.hvacpartsoutlet.com/ or these guys http://www.bestbuyheatingandairconditioning.com/ Either may be able to help you with your system design (typically for free) and ship all the parts you need to your doorstep. They also offer advice on proper installation as service for their sale. You will still have to do some of the legwork in being their eyes and ears, but it could be another option for you.

The AC and condenser would operate in the winter? Meaning no snow on the outside unit? I'm interested in this, as I would have deemed this a real long shot to implement.

The Dead Vent is simply a muffler. Can be used in conjunction with the main HVAC loop or independent of it, though it is often (incorrectly) exclusively associated with stand-alone systems.

Most often these are considered during remodels. If the whole house is being built new, then we have many more options avilable, obviously.

Ted - this may answer a few questions regarding low-ambient startup: http://www.midtninspections.com/low-ambient-start-up.html

You are correct - the unit must be free of most snow and debris prior to running. Snow fences and other temporary barriers around the unit can also help.

@Ted - If you have been following my posts on this thread you will see time and time again that I think the dead vent is a great idea to use with forced air HVAC systems as a relatively soundproof way to get large duct openings through the soundproof shell. I just dislike it as a standalone or supplemental system unless it is the only option (i.e. after-the-fact or "quick fix" approach). As many of the theaters in this thread are from the ground-up with rough space being converted to finished space, there is plenty of opportunity to engineer and implement a 100% forced air HVAC solution correctly as the preferred option over all others.
Edited by TMcG - 7/26/12 at 5:59pm

In the winter - while the main level of the house is calling for heat, but the theater needs cool - a separate thermostat in the theater will close the dampers for hot supply to the theater from the main system, then open and power fresh cold supplies of outside air - do I have that right? What balances this airflow? return to outside or return into the main return (back to the main level of the house)?

Like you said, you'll need a little experience with it to get it set to the right levels, but overall, it sounds solid to me.

I'm interested to see what equipment you decide on.

You had me right up until this point above. I thought you said that your upper floor is on one zone and your basement is on a second zone and that you have motorized dampers allowing for control of which zone (or both) gets the conditioned air at any one time. Second, isn't the rest of your basement going to be finished out and conditioned space so ambient temperature will be way above 55 and at "normal" indoor household temperatures? I thought the goal was to zone off the theater separately but tie it in to the primary HVAC with the right "brains" controlling the system and giving zone priority. Is that not the case?

Third, and most disturbing, is this guy's recommendation to pull outside air into the room via Dead Vent. How is this air brought in under a controlled fashion? Devices called EVHR (Energy Ventilation Heat Recovery) are designed for fresh air exchanges with the outside and provide a sealed, filtered method for air exchange. But these are pricey to have put in and installed - about $3k at minimum depending on the unit. If it is truly just a pure vent, you will be introducing humidity, dust and bugs into your theater environment - guaranteed. How will this be handled with the HVAC guy's recommendation?

I am a bit confused and should probably go have a beer now....

OK, so I take it that you have three floors to your house . . . a second floor that has its own unit and a main floor and basement that share one unit but have no dampers - correct? This is different from the way I thought you were explaining it before.

Assuming the area outside the theater is conditioned, you might as well just ventilate to ambient with a separate dead vent system (as per Ted's instructions) vs. pulling from outside directly. Although the outside air may be dry, wherever cold meets warm you will have condensate....and this will either drip and run somewhere or pool and collect. Both will cause mold over time. That's where an EVHR comes in to do fresh air exchanges with the outside without actually venting directly to the outside.

I just don't understand why they can't zone out the theater with mechanical dampers and be done with it. It could be programmed to NOT put heat into the theater by keeping the dampers closed and opened when you are either cooling or wanting to force ventilate with the HVAC system. This seems simple and straight-forward to me.

Your HVAC tech is right and wrong. The human body will produce about 250 BTU while sleeping, about 400 BTU at idle, 650 BTU doing light work, and 2400 BTU with heavy work / exercise. The typical cooling temperature from a forced-air HVAC system is in the 52 to 56 degree range. Assuming there is no equipment on in the room and there is nobody in the theater, the room will eventually match the ambient temperature of the room next door if you used pure ventilating dead-vents. However, even just one person at idle and the exhaust output of a typical projector (if the exhaust is released into the room) will overwhelm an independent ventilation-only dead vent system which is why I personally don't like them. Having more people will make the problem worse, of course. Another reason NOT to do separate dead vents is because you will have full-fledged supply and returns through the forced-air HVAC system which will allow you to ventilate with ambient air through the HVAC system. You could then have the system's fan on 100% of the time and have the dampers closed when the upstairs calls for heat.

As for cooling, I have never heard of direct ventilation from the outside - ever. Why couldn't he advise slight modification to your outdoor condensing unit (if needed) for running in low ambient conditions. I think the refrigerants boil at something like minus 60 degrees Fahrenheit, so even if it was 10 degrees outside you are 50 degrees above the boiling temp of the refrigerant. This will obviously involve a few more dampers to prevent the cool air from going upstairs, but it also cannot be 100% dedicated for the HVAC system as the amount of CFM your system can produce cannot be accommodated by just the two 6" supplies going to the room. You also must have a minimum CFM moving across the A-frame coils to keep them warm enough to prevent them from icing over.

If you think about the size of supply you would need from outside to cool your room, just look at your return - I'll bet you he spec's something like an 8" feed or a single 6" at minimum. That's a HUGE opening to the outside and you will have all kinds of critters, dust and condensate. I can't believe he would even suggest direct ventilation from the outside IMHO.

As I said above, you could simply use the HVAC system's fan to ventilate the room using ambient temperature air. Why use a separate dead vent and fan when you have the forced air system already on-tap. Just have the supply dampers close if heat is called for. The HVAC fan is very cheap to run the fan from an electric bill perspective.

Right. Nothing only during the time the rest of the house is receiving heat. Given a normal cycle time of 10-12 minutes 2 or 3 times per hour, about half the time the theater would not be receiving heating supply with the dampers closed. The remaining time it will be ventilating with the dampers open.

Anything you do without investing in the system will be a sub-optimal work-around, but livable.

That's where the communicating thermostat comes into play which will integrate with your control system. The HVAC guy will spec the zone controller for automated control of the dampers. All you should be concerned with is with thermostat control through your control system, that's it.

Correct. The HVAC guy you hired should be spec'ing all the necessary hardware you require to make it work with your system. Did you contact either of the two online companies I sent you?

Dave, I was away from my computer for a few days, so I dropped out of the discussions. I agree that untempered outdoor air would be a bad idea to dump into your room for the reasons already stated.

As you have realized by now, its kind of hard to retrofit an existing furnace to do what you want. By the time you spend the money to make it work correctly, you could have just bought a separate unit for the theater.

This is probably why you see most people do one of two things:
1. Install a split sytem (cheaper than a new furnace system)
2. Use inline fans and recirculate tempered air from the adjacent space.

For my room I went with a ductless split system, and I am pretty happy with the results. For $700 it was an affordable option for me (I installed the unit myself and had a buddy help me pull a vacuum and start it up). If I were to do it again, I would probably do a ducted split system (purely for asthetics).




If you do inline fans tied into the supply and return air mains the problem you run into is getting the correct amount of airflow required - this will vary depending on the season:
-in the summer, you are supplying about 57 degree supply air (so you would need 100 CFM)
-in the winter, the condensing unit is not cooling so you would be providing 70? degree air (so you would need 500 CFM)

I am totally guessing on those airflows, but guessing you would need 5 times the airflow when not cooling the air (calculations would be required). You would also still need to keep heated air out of the room in the winter, so controls would still be required (dampers to block hot air from entering and to turn off the inline fans).

If it were me, and I didnt want to do a split system to save money, I would probably do inline fan(s) with dead vents pulling air from a conditioned space and blowing the air back to a conditioned space. It would be nice to maximize the distance between where you getting the air from, and where you are putting it back. This option allows you to size your inline fans once because the airflow requirements stay about the same (the conditioned space temp is usually around 70 degrees). You will have to calculate the required CFM based on what temperature you want the theater room, and what temperature the rest of the basement is at. Once you get that CFM, you can size your exhaust fan/supply grilles/return grilles/ductwork.

I need you to clarify your question. If you tie the return back into the HVAC system, where are you planning to pull supply air from? The supply air main, or the tempered adjacent room air?