Hot Bonus Room

[Tscott]

I've got a bonus room over my garage that stays a few degrees warmer than the rest of the house. It is the only upstairs room and there is no AC return but there are 2 supplies. The room is well insulated, but all the warm air in the house makes its way up there. It doesn't help that we have 2 PC's and a big screen up there either. I've been researching and I've seen a few options but I was hoping to get some opinions here as well. Would adding a return help circulate more cold air? Perhaps limiting flow downstairs via baffles could increase airflow upstairs? Zoning would also seem to be an option, but I'm afraid it will cause more headaches than it's worth.

Tom

Also, thermostat for the house is located downstairs directly under the return for the system right in the middle of the house.

 

[soob]

If the air has a path to return, go with baffles. Redirect more air up there. If not, add another return (or at least a "jump vent" that allows air to flow back downstairs, when, say, you have the door closed).

Alternatively you could add a mini-split to give the room its own heating and cooling. They are quite cheap and not too expensive to install. Might be cheaper to just lower the thermostat in the rest of the house, though.

 

[pseudorealityx]

If there's no return, step 1 is adding one.

 

[Syberia]

I'd go the mini-split (or window/wall AC) route personally. We had a similar situation, in that our house has an addition that was built well after the main house. It was tied into the HVAC for the house, but receives very little air flow. Instead of messing with it, we put in a 12k through-the-wall heat pump and were done with it.

 

[Charles (in GA)]

Ideal use for a mini-split heat pump. I'd totally remove the duct work from that room and use only the mini-split. Its never going to work correctly without a return anyhow.

 

[zmaxmotorsports]

Leave the door open so the hot air can be pulled out of there more easily.

 

[rburke65]

Air without returns in Fla? It dont sound correct to me, but what do I know.....

 

[DC73]

It wouldn't hurt to have a return if it's easy to install. At the least, you could install a return air pathway in the door of the room to help when the door is closed. http://www.tamtech.com/Return-Air-Pathways_c_20.html

I'm betting some type of return air path along with a 3rd supply will solve your problem. If there is an easy way to add some insulation to the room, that could help as well.

It might also be possible to increase the duct size for the existing supply vents to bring in more air.

DC

 

[6768rogues]

It needs return ducting or a good return path. How much air do you think you can shove into a box before the static pressure of the fan is met and no more air goes in?

 

[Tscott]

The room gets warm no matter if the door is open it not. It just happens faster if the door is closed. The room does cool off when the AC runs but the problem is that the thermostat for the whole house is downstairs in the great room area. So as long as the great room is at the correct temp, then the AC isn't going to run. The stairway leading to the bonus room is currently the only return path for warm air. But even if we put in a second return from upstairs, it will only draw air when the AC turns on, which due to the thermostat location, isn't often enough. Would making the upstairs a zone and adding a return be an effective fix or would it create more issues in the long run?

Tom


Sent from my iPhone using Tapatalk

 

[Tscott]

Found the below site while searching for information. Looks like a pretty slick system though I am a little concerned that shutting off all registers except those to the bonus room may over pressurize the AC system. I'm willing to bet that could cause fan failure and possible compressor failure if the system gets loaded up with too much cold air.

http://www.retrozone.com/oldsite/Packages/3 zone flex_damper_package.htm

Tom

 

[DC73]

Last summer I went through a similar problem with a hot kitchen/dining room in the house I bought. The rest of the house was very well balanced and temperatures were within 1 degree throughout. The kitchen/dining room was much warmer. I went with a 3 step approach and solved my problem. I added insulation above the kitchen/dining room. I added a 3rd supply vent to the kitchen/dining room by re-routing a small supply from the laundry room where it wasn't needed. I increased the duct size of the 2 existing supply vents and fed them from the main plenum instead of a junction box. This approach resulted in the kitchen/dining room being about 1 degree cooler than the rest of the house which is just fine. The cost was minimal and Home Depot carried everything I needed for the project.

I don't think you need to zone. Just get more air to the room and a decent return air path. If you can also add insulation, it will help.

DC

 

[Tscott]

I know insulation isn't the issue in this case. Our house has spray foam type insulation which means it is applied directly to the under roof area. My attic space never gets more than a few degrees warmer than the rest of the house.

I think my first step is going to be to try to partially close the downstairs vent baffles in an attempt to force more air upstairs.

Tom

 

[theoldwizard1]

Ideal use for a mini-split heat pump. I'd totally remove the duct work from that room and use only the mini-split. Its never going to work correctly without a return anyhow.

+1 !

Not cheap, but BY FAR the best solution !

 

[dougsey]

Would it help to set the fan to always on to help keep the air moving when you're using the problem room?

 

[Tscott]

Would it help to set the fan to always on to help keep the air moving when you're using the problem room?

I think it might. I should probably just make it habit to set it to run when I go up there.

Tom

 

[truckman5000]

cheapest..look into a modulating thermostat. the thermostat dosnt read the temp at location..uses 2 sensors that you can wire wherever. and thermostat averages the sensors..

 

[mpire]

Air without returns in Fla? It dont sound correct to me, but what do I know.....

My house was built in 2001, is 2 stories, has one 3.5 ton system, and has a single return. I can't help but wonder if I should install some air returns to help with getting hot air out of the room.

I'd go the mini-split (or window/wall AC) route personally. We had a similar situation, in that our house has an addition that was built well after the main house. It was tied into the HVAC for the house, but receives very little air flow. Instead of messing with it, we put in a 12k through-the-wall heat pump and were done with it.

My master bedroom was always hot, so I ended up re-directing the duct for the master bedroom to the dining room and then adding a mini-split in my bedroom to make up for it. Now I only run the mini-split when I am up there, and it cools down fast. I only run the whole house AC during the day, so it cuts the duty cycle in half and my power bill dropped around $70-$100 a month depending on the season.

Look into rebates for installing a high efficiency split system. My system was almost entirely paid for by my power companies incentives.

I think my first step is going to be to try to partially close the downstairs vent baffles in an attempt to force more air upstairs.

I may be wrong, but my AC guy tells me that closing down the vents in rooms I am not using just causes less airflow over my coil and makes my system less efficient. Granted my system is 15 years old now, and I don't need to stress it, but you get the point. Maybe consider a duct booster fan to get the same effect while increasing coil airflow?

 

[pseudorealityx]

Closing down registers can be a viable option, but it depends on what the current air balance is. You should easily be able to run down to ~325-350 cfm/ton, but you can sometimes run into coil freezing issues much below that on normal DX equipment. Depends on a number of factors.

In general, lowering the airflow through a unit increases the ability to dehumidify the space because the air is moving slower over the cold coil, so it's more likely to condense. However, total capacity falls a bit.

 

[Tscott]

So last night I went through the house and adjusted all the registers. The kids rooms which are right under the AC unit were always a bit cool, so I throttled those vents almost all the way shut. I partially closed most of the others except the master bedroom and the bonus room upstairs. Both of those locations have traditionally been warm. I'll run it like this for a week or so and see if we notice any improvements in the upstairs cooling. I am also going to look into tinting the bonus room windows to help keep the heat input to a minimum.

If all else fail, I'll look into a mini-split system but it has to be completely silent, that room is slated to get a projector and a movie screen in the next couple of years and I don't want a noisy AC ruining my home theater.

Tom