Rooms with doors closed too hot or cold
Got a nagging problem with our 5-ton Trane setup. It's a 3-zone system on an older split-level (three levels) cedar shake house. The thermostats are all in a hall area, which seemed like a good idea at the time of install. However, what happens is that when a bedroom door is closed, it'll get too hot because the thermostat is not in that room. My husband tells me that the only way to fix this is to install grills/vents in all the doors, but I'm thinking there has to be another way. After all, new homes don't have all the bedroom doors vented. I don't want the kids hearing what goes on outside the bedroom, nor do I want them to hear what goes on inside the bedroom. Are there any other options? Thanks very much.
Instead of putting vents in the doors you can have your hubby undercut the doors a 1" or so off the bottoms of the doors will serve the same purpose as putting vents in the door's. By doing this will allow the air to move out of the bedroom when the door is closed and not get too hot or cold.
Thanks, DanW13. I appreciate your reply, but to me, that's about the same as putting a vent in the door insofar as hearing what goes on in/out of the bedrooms is concerned. I'm really curious about what new construction homes do if they don't have the doors vented or cut too high off the floor. Guess I'm hoping that some cool stuff can be done with thermostats or something like that.....
"Jumper returns" can be installed from the ceing of the affected room to the hallway or living area.
Undercutting the door 1" would give you almost 30"s of free area ,with no grille restriction and less sound transmission then grilles in the door.
Done right. jumper ducts won't tranmit sound like an under cut door.
r a problem
New construction that i've seen have a return in every room , except kit & bath of course , can u use joist spaces for returns at all????.......Jack
Originally Posted by bhe
Thanks, rojacman, been there and dash.
There is a return air in two of the bedrooms, but I'm sure that's not the same as a jumper duct. That sounds intriguing. We have joist or attic space available for all three bedrooms in question. Can anyone give me a little more detail on what a jumper duct is so I won't sound like the newbie I am when contacting an A/C professional? The guy who installed ours would only tell us to install vents in the doors, and I just thought there had to be other options. Thanks again.
Do those 2 bedrooms also have trouble cooling when the doors are closed?
If so, the returns may be undersized.
A jumper duct. Is when you install a register in the room, and then run a duct out to(in your case) the hallway. And attach it to either a register cut into the hallway, or into the return box in the ceiling above the hall.
If the return in the hall has a filter in it, then your need to install return fiter grilles in the bedrooms.
Everything from Building Science Corporation is excellent, but here is another good report on the same problem:
Originally Posted by bhe
This is a corporate report designed to support sales of a commercial product:
Just wanted to show another alternative that looks valid to me, a homeowner in S.Texas. But if there is already a return in the bedroom, I would first look into whether the problem could be solved by a larger duct to that return. With the advice and consent of a pro who understands airflow of course.
Hope this helps -- Pstu
Wow! Thank you so very much, all of you, in trying to solve my problem. I really, really appreciate you taking the time out to help me.
I checked last night, and all three of the bedrooms in question have air returns. Two small - 10x10, and one larger 10x20. The one with the larger return has the pressurization problem; although I haven't put my hand by the bottom of the door to actually feel the airflow, having the door actually pull itself closed when the A/C turns on seems like a confirmation of that problem. Funny, the bedrooms with the smaller returns don't have that problem, although the A/C just blows you away when it's on - it's way too strong. I have no clue about the size of the duct; I'll have to check the attic this evening.
The thermostat for the room with the larger return is in the living room, (which faces West and has a huge picture window), under one zone, and the thermostat upstairs for the two other bedrooms is in the hall, under another zone. The hall thermostat is right by the stairs, so I know that it's getting air from downstairs, which exacerbates the problem.
I feel that the location of the thermostats may be the main cause of the problem, but if we move it to the bedroom, won't that just move the problem from the bedroom to the living room? Same thing upstairs - if we move it to one of the bedrooms, the other bedroom will have a problem, especially since one bedroom faces East and the other faces west, with large windows.
So, like davo wrote, was my contractor trying to solve the problem by putting returns in every room, but ended up making it worse because of the location of the thermostats? He didn't have any recommendations about where to put them.
Pstu - thanks for the link. I had no clue that a pressurization problem could lead to mold. The Building Science info mentioned that, but it was pretty technical and I didn't quite "get it". Luckily, we have no vinyl wallpaper, but still..... The product from Tamarack Technologies looks like something we need to look into. I especially liked the baffle to eliminate sound transfer, and the notion that only a 1" undercut, combined with the jumper ducts, will make a large difference.
Does everyone else agree this is the best way, or should we move the thermostat(s)?
I just thought of something else. We had new, high-end, windows installed last year, triple-pane with argon gas and Energy Star certified. They replaced 1952 super-leaky aluminum casement windows. They're a great sound barrier and I was also expecting a lower electricity bill, but there was absolutely no difference. Wonder if the inefficiency of the HVAC system is the reason......
Thanks a lot.
If you move the stat to one of the bedrooms. You will have the reverse at night time. But then no one will be in the other area to notice it. And aslo as teh doors are open during the day, the other area may be ok.
Let me reiterate, I never said returns were not required. I said it may not and probably is not her problem.
In Florida, many many zoned homes, have thermostats in the bedrooms.
I have a sensor in every single room, and even one in the master bathroom.
A door closing when the a/c turns on does not always mean the return is too small, although it could be a possibility. The room has to pressurize a little to cause displacement for the return to move air. It does not take to much to move a bedroom door.
My master bedroom has a 14" return with a 18"x 18" RHF type grill. More then large enough. My return static berfore my Infinity Air Purifier is .03 at full speed, 3 tons There is also a wall releif system I have not closed off yet.
My door closed when the zone calls and the door is left open about 2"-3".
Maybe I should add more returns? Could it be the unit is mainly drawing from all the closer returns, and a little pressure differential is needed to cause flow?
Remember, returns don't suck, air moves through them due to displacement.
When zoning, it is important to try and group areas with similar exposures and loads together to avoid this problem.
Adding returns will not hurt, but it probably will not solve the problem either.
Once the system is triggering on and off properly, air balancing becomes much easier.
Your house, your money, your comfort.
Last edited by davo; 06-10-2008 at 11:37 AM.
Reason: Added information
Davo, what is a sensor and how would it affect the thermostat / cycling on/off of the unit?
Regarding the return where the door closes when the A/C turns on: It just happens to be right next to the door, which is in a little alcove area, not in the main room. Perhaps the location is the problem.....?