I am in a five year old cookie-cutter home. Its a two-story home on a walkout basement, and the two finished floors have separate HVAC zones. The first floor gas-furnace & AC is in the basement, and the second floor gas-furnace & AC is in the attic.
During the warmer months, there is a big difference in temperature between the Master Bedroom/Bath suite and the other three bedrooms on the same floor. One of these other bedrooms is converted into a media room with a ceiling-mounted CRT projector (three-eyed monster) and a bunch of electronics in the bedroom closet.
As you can imagine, this converted bedroom is already operating at a handicap being that it doesn’t get as cool as the master bedroom. Now, add to this handicap about 1500 watts of energy from electronics when in use. So, instead of the 5-7º temperature differential between the master and other bedrooms, there is a 10-15º temp difference between the master and converted media room.
I am looking to explore ideas on how to handle this situation without installing another one-room zone AC unit, but I am not an HVAC person. Any enlightenment would be helpful. Previously, the only suggestion was a Mitsubishi two-part system, but that would have a fan inside the room (pretty much like a window AC unit). This is something I am looking to avoid as I’d rather not want to spoil the audio of the media room.
Replies
You did not say which floor the "hot" room is on.
You have a couple of options if you can get to the ducts easily.
First is add a another return air vent near the top of the wall. This will pull the heat out of the room and to the HVAC unit for conditioning. You may also need to add another supply run to balance the air, but maybe not.
The second option is just the addtion of an exhaust fan. Something as simple as an attic mounted exhaust fan will keep the noise out of the media room, and provide enough negative pressure in the room to exhaust loads of heat. It to should be in the ceiling or as high on the wall as possible.
Dave
Sorry. On my two-story home all bedrooms are on the same fllor, and this would be the second floor. I should also add two pieces of information as an after-thought:
All returns for all rooms on the second floor (where the hot room is located) are individual-returns in the bedrooms and mounted to the ceiling. Also, this particular bedroom resides directly above the garage, but the floor of this bedroom is insulated and the garage (below) is finished.
Since the returns are ceiling-mounted, I presume your first suggestion still applies, but I wouldn't be sure how this would get tied into the existing flex-duct. If I tie it into this room's existing return line I'll need to increase the size of the flex duct beyond the joined location, right? For instance, if I add another 6" return line and tie it into the existing 6" return line I should upgrade the return line beyond the point where they are joined to something like an 8" return duct, right?
You may have already done this, but have you had an HVAC person "tweak" your system? Some simple adjustments may help and eliminate (or at least reduce) the need for more drastic modifications.
I wonder if adding another duct or 2 in that room would make a difference. When the heat is on, you could close most or all the registers. And when the AC is running, open 'em all up. Adding a 2nd air return or enlarging the current one could also help..Another idea came to mind, but I don't know if it's kosher or not. They make bathroom exhaust fans that move a lot of CFMs, and are remotely mounted. They cost about $200, but more a lot more air and are quieter than the cheap ones that mount in the ceiling. I wonder if you could mount on of them in the ceiling, and run the exhaust into the return air duct. That way you could turn it on whem the temps outside were moderate and the heat or AC weren't running a whole lot. Another really ewasy solution might be to set your furnace fan switch in the "on" position when you're using the room. That would keep some air circulating all the time.
The truth is more important than the facts. [Frank Lloyd Wright]
A) it sounds like this is a "so called" bonus room**. It is common for those to be at the end of the HVAC and have this problem even without the electronics.
B) you really should have it checked out by an HVAC pro. Lots of time ducts are just "stuck in" without an reqard to the lenght or the amount of air needed. Also with flex duct it is easy to make mistakes and to crush it, etc.
C) you can have zoning without another system. It consists of motorized dampeners that control the air flow.
** I have never heard of a builder selling a 2500 sq ft house and after you sign the papers saying that they are giving you a "bonus" of an extra 300 sq ft at no addiontal charge. That would be a BONUS ROOM.
Bill, you are right. About ten or so years ago I started seeing bonus rooms above attached garages in an unfinished arrangement. Now there are tons of builders around me that make these 100% bedrooms to skirt costs of building a real bedroom. How else could they sell a 3-bedroom five years ago for so much?
They simply followed necessary code and added a closet and window and viola!
I think I might have insufficiently mentioned I did have an HVAC person take a quick look the last time they were out here replace a capacitor (kicker, for the second floor AC unit). They suggested double-runs to/from room and AC unit, then suggested a dampener in the Master bedroom leg to squelch that room from overcooling when attemptinto to cool this media room.
The one thing I want to avoid, if at all possible, is expense. $1000-1500 to cool one room is absurd--yet I know of some that have spent more for the same thing. Let me call these people back out here again. Its been about a year since they were last out here. Thanks all for the replies.
Hmm, one other option, a frequently overlooked one, is moving the thermostat. It's the "switch" that controls how warm or cold it gets. It can be easier to move the stat to closer to the "problem" area (it's undercomplicated wiring, to boot). You might then need to "throttle" down registers in the other rooms to hit a good balance.
"Bonus room" raises some flags for me--I've seen some that were less-than well insulated (like cheap 3.5" batts in 7.25" bays). The ductwork is likely undersized for 1500W of a/v equipment in any event.
I would not put an exhaust fan in the room without knowing where the make up air would come from in the house (no need to create, or worsen, an air leak elsewhere). Also, unless you are in a very temperate clime, you will have attic-temperature (or near-to) air sitting against the exhaust fan's register until the fan goes on. That's just adding heat where you already need it least.Occupational hazard of my occupation not being around (sorry Bubba)
Air leak, you say? Now that's a topic of disgruntled concern.
How would moving the thermostat closer then what I am already doing, which is to turn down the temostat and close the source vent in the master bedroom?
moving the thermostat closer then what I am already doing
Well, it would "respond" to the heat loads generated in the room more directly, rather than lagging until the warmed air reached the tstat.
The flip side of that is just putting a stat in the media room (get a programmable--you'll be much happier). The stat would respond to people in the room (person at rest gives off 350 btu/hr); and to the heat of running equipment. Ok, so the rest of the zone gets more a/c than it needs--but you're not sweating through half your movie, either.
The mechanically elegant answer would be a duct valve box on the zone, feeding directly to the media room, and an exclusive stat. That way, only the media room gets conditioned air on need. That's not as elegant in the attic--what with the extra ductwork and all.
The other answer might (stress might) be a single room compact unit. This would be a unit designed to run just for the media room. Wow, there's bunch of hits googling.
Occupational hazard of my occupation not being around (sorry Bubba)