Room in house is too warm, will adding a return air duct help the airflow in it?

[SA Development]

Hi,

I have a room in my house that I use as an office that I have to keep the door shut so the return air flow is very small. It has a 5/8" gap below the

2'6 door so I calculate this out to be around 18.75 sq.in. I have one air vent in it and my *theory* is that I think is fed by a 6" flexible ductwork of some type. This would be 28.27 sq.in. With my house set at 77 deg, this room with the door open is usually around 81 deg. If I close the door which is probably 12 hours per day, it rises to about 85 deg when the rest of the house is 77 deg. I have a computer and a couple printers in it, so a few things that generate heat.

The issue is that I am going to have to try and soundproof the room a little better. I have a toddler that makes considerable noise and it can be troublesome when I am working. I am going to get a solid core door and a sweep for the bottom to cut off all the places where sound can enter directly. This will however cut off the return air flow that I currently have which doesn't seem to be doing the job.

My house currently has two return air vents both located in the hall way. Each one is a 14x25, so 350 sq.in each or a total of 700 sq.in return air flow. My HVAC system seems to be ductboard or some sort of flexble ductwork. The ductwork that goes to all the supply vents is a round insulated flexible stuff. The two existing return air vents look a bit different in that they look like a constructed box tube. Silver foil on the outside. I'm not sure if it is ductboard or something else.

Here are the things I have thought of doing, please recommend which is best:

1. Put in a vent that has nothing to do with the HVAC system, but is sort of a room to room vent. I could pick another room that has decent enough open space to one of the two main return air vents in the hallway. The advantage here is that I wouldn't be doing anything on the HVAC system myself. I am also providing a way for air to exit the room when supply air wants to come in. I wonder however how well or not well this would work. For some reason, it seems to me that even if I put in a large enough vent/ductwork that it still wouldn't improve supply on my one supply vent.

1. Add a return air vent to my office. It looks like the smallest filter that I can commonly find on the shelves at Lowe's is a 10x20. This would add 200 sq.in. to my office for return air. Would this increase the airflow I am getting through my single supply vent with the door shut? Would more air being pulled out via the return vent push more cooler air in via the supply? This would a nice feature if it worked out well. Are there any downsides to this plan? I don't know if this is something I could do myself, or partially do myself and then have the HVAC company that put the system in come in and hook it up to the HVAC system.

2. Same as #2, but add a second supply vent in the office as well, doubling it from 28.27 sq.in to 56.54 sq.in.

1. Are there any more issues with sound with either #1 or #2? I wonder if #1 would be noisier because sound could come from the other room vent into the office vent. I will probably be using the flexible ductwork like they put in already so hopefully that doesn't transmit sound as well as something metal might.

Thanks for any advice and help,

Alan

[barry]

Before all the other stuff, could you tell us the fundamental stuff? Whether you're trying to heat or cool at the time of the problem. And your local climate.

TTFN, J

[SA Development]

Hi,

Sure, I am in Oklahoma, and the biggest issue is cooling during the summer. I usually shut the vent down to about 50% in the winter and it seems to run more closely to the house temp during those months.

Thanks for the help, I appreciate it!

Alan

[SA Development]

Hi,

Yes, the place I would add the office return air duct is only about 5 feet from the hallway return air duct, but that is a prime noise area, so I was thinking of running it from the office a little further down and join it up to the return ductwork where it isn't so close to the hallway return air vent.

I know what you mean, too much heat producing equipment! I had 180W in ceiling fan bulbs that I've replaced with some floroescents for now. I prefer the incandescent light, but these do product much less heat. Once I get the air vent put in I'll probably go back to the incandescent ones though.

I'll post how this all turns out when I get it done... We are still having

100 deg days here and there so hopefully I can get it done before it gets colder to see what the effect is.

Thanks,

Alan

[John Hines]

Then you want the return vents up high to return warm air to the air conditioner, assuming that you have central air.

You should be able to get a grill that fits between two studs 16" and use the air space between them for the vent, on an interior wall.

That is what I did, replace a single double stud wide grill with two half wide, one low and one high.

[No]

I would add a return air duct, tie into existing duct in hallway will make it an easy/inexpensive thing to try. This will increase sound infiltration though. If that doesn't work, and if its suficiently large enough of a return, then consider adding another supply. I am in same boat - 3 PCs, 2 LCDs, 1 21" tube monitor, 3 printers, 2 fax machines, scanner, incandecent lighting, halogen desk lamps, etc. All in 120sq ft room! Let me know how you make out.

[abi]

You also may wish to consider why the extra heat. Maybe you can cut down on the heat if a lot of it is coming from windows or underinsulated outside wall or whatever. I doubt the computers are warming it up 12 degrees. I agree the return vent is probably necessary, but there also may be air infiltration problems identified that may mean hot air is coming in from outside and into the wall cavities or from the floor (crawlspace or basement) or the temp of the outside wall and windows on the inside is way high.

Just a thought. No sense adding a return air duct if the drywall surface on the outside wall is 98 degrees, if you know what I mean... blowing foam or cellulose into the uninsulated cavity or sealing it from underneath if that's the problem will help tremendously.

One simple way to find out if heat is coming up through the floor and into the wall cavities and heating up the drywall, which heats up the room is to go into the crawlspace with incense stick or cigar or something smoke producing and run it along the sill plate or rim joist or whatever you want to call where the wall sits on the foundation, and if it's hot down there and smoke is sucked up or blown away from the plate, that's a problem easily addressed. If it's sucking in, it's better than blowing out. If it's sucking in, it's sucking in the air temperature in the crawlspace. If it's blowing out, you are sucking air from the attic. HOT!

Simply sealing off the bottom of the cavity stops the "chimney effect" so you don't have to seal off the attic side of the cavity.

Just a thought...

abi

[CL (dnoyeB) Gilbert]

I have the same situation, but I do have a return. Basically since this room is small and has essentially 2 space heaters + laser printer, it gets toasty. Keeping the door open helps a bit. I have a window exhaust fan that I can use and it helps a bit. But all in all I think I will need a booster fan. Plus a new computer desk that can vent the heat out the back instead of the front into me.

[trader4]

I assume you've verified that all the ducts are connected correctly, ie that none has fallen half apart from tape drying out, etc. Also make sure any balance controls on the ducts going to the warm room are fully open.

In addition to adding a return, which should help, there are several other alternatives. There are booster blowers available that can be inserted into a supply duct going to the area that is too hot. There are also booster fans that can be placed over the vents. This type senses when the air flow starts and turns itself on. I've tried the first type and it definitely helped, though it's not fully effective. Finally, you might want to consider adding a window unit to the room. Of all the solutions, that one is guaranteed to work.

Usually this problem is the result of incompetent installers who didn't run enough duct or return capacity to the farthest areas. And as you've figured out, completely fixing it later isn't easy.

[Anonymous]

I agree with the below a small window unit(thermostat controlled) sufficient to cool room with supply closed will keep room at a steady temperature and can be chosen for being quiet. A steady sound such as the ac fades into the background and also masks sounds from other areas. Cost and time would probably be less than installing return and possibly additional supply. Small efficfient acs don't pull much current so that is not likely to be a problen Stan

[SA Development]

Hi,

Thanks for all the good advice. A small window unit wouldn't be my first choice as the room faces the front of the house and wouldn't look the best, but thanks for the idea.

Thanks,

Alan

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[CL (dnoyeB) Gilbert]

Just one computer heats up my room. its toasty when I enter, but when I turn on my gaming rig, 10 minutes its much warmer. Like I said, equivalent to small space heater.

[SA Development]

Hi,

It doesn't take much with the heat that processors generate these days... I'm going to add a small return air vent to the room and see what happens, hopefully it will improve things.

Thanks to everyone for the help,

Alan

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[SA Development]

Hi everyone,

I added a return air to my office bedroom last night and it is working great so far. My office that had been running 85+ deg with the door shut is now between 79 deg with the door shut. I have the thermostat set at 76 so it is only 3 deg above the rest of the house instead of 9 deg above the rest of the house.

Thanks for all the advice,

Alan

[Cmc]

Can't believe this is 16 years ago, in having the same problem with my afternoon sun facing windows, it's hot and stuffy compared to rest of the house, how did you add the return vent and what size vent did you use?

[Dean Hoffman]

Retractable awning or outdoor window shade. Keep the heat out of the house in the first place.

[trader_4]

If you have to add a return vent, often the size is determined by what is possible to do without major work, rather than the ideal size. Even a pro is going to wing it. Look at the size for other areas of the house to get an idea. And inspect all the existing ducting looking for pieces coming apart, tape coming off, feel how much air is coming in and out or use a piece of paper as a flap, etc first. And if it's upstairs with the air handler in the basement, adding a return without creating an ugly undesirable chase somewhere may be impossible.

Another suggestion. Keep the blower going during periods when heat is a problem. I do that to keep my upstairs under control. I have an ECM variable speed blower, I just leave it on. It's very efficient, doesn't use much electric compared to a conventional motor and it also runs at a low speed when left on, but it's enough to make a big difference. The Honeywell VisionPro thermostats also have a "circulate" setting as well as "on". Circulate it puts the blower on low for about 30% of the time. That isn't enough here. And if you're going to replace your AC anytime, make sure you address all this with the installer.

[Ed Pawlowski]

The size of the return should be roughly the size of the incoming air. For the system to work you have to take out as much as you are putting in.