[dkcoop05]

My old house has no cold air returns on the 2nd floor. It's usually not a big deal but the guest room gets hot and stuffy in the summer when the temp is high -- like 85+. The room underneath the guest room (the dining room) has a cold air return on the outside wall. Is it possible to put a cold air return in the guest room on the 2nd floor that feeds into the cold air return on the 1st floor? Would that diminish the benefit of the 2nd or 1st floor cold air return? I've ordered a free standing A/C unit for the guest room and read that if you can vent the A/C unit to the cold air return it works much better to keep the room cool. So rather than install a completely new air return, could I tie into the 1st floor cold air return (and I'm not necessarily saying I as in I would do it--I just want to know if it makes sense).

Thanks,
Debbie

 

[user_12345a]

It's fine to have a common return if it's properly sized, otherwise it won't be effective on the second floor.

It should be near ceiling level to be most effective.

If you have another return on the main floor and it's open concept with no doors between rooms that close, you can close off that return downstairs and use the chase for 100% upstairs.

 

[beenthere]

Against code in most places to have the same return duct/chaise serve both floors, without a fire damper.

 

[dkcoop05]

Good to know about being against code. I'll probably end up venting the standing A/C outside and hope there are no leaks

 

[user_12345a]

Against code in most places to have the same return duct/chaise serve both floors, without a fire damper.

It's common to have some upstairs and downstairs returns share one wall cavity. Doesn't that count has using one return chase to serve both floors?

But if you're right, all the more reason to use that run for 100% second floor and add a new first floor return if there isn't one.

 

[beenthere]

It's common to have some upstairs and downstairs returns share one wall cavity. Doesn't that count has using one return chase to serve both floors?

Probably seen in older homes before the code. Or homes built in areas where code is not enforced.

 

[dkcoop05]

I kind of like the idea of running the cold air return to the 2nd floor and putting a separate one in for the dining room. What started this whole thing was that when my daughter's family visits they pick the absolute hottest week to stay. The guest room does get hot and stuffy because it gets a lot of sunlight. The forced air vent puts out very little air and my original thought was to figure out where the damper was for that vent and make sure it was completely open. That requires some drywall ceiling work which isn't too bad. A friend of mine said that since they only visit 1x a year why go to all that trouble--just get a window A/C. Except I got a free-standing A/C and am worried about the hoses and how effectively they will work -- whether there will be leaks etc. So now I'm back where I started. Thanks for all the help.

 

[roughneck]

A lot of those portable units aren’t that great, mostly disposable.
Make sure you get a 2 pipe model, the single pipe units pull air out of the space that it uses to run through the condenser then gets exhausted outside. This puts the space under negative pressure.

 

[user_12345a]

Adding return only won't fix the problem if the room has insufficient supply.

 

[beenthere]

Adding return only won't fix the problem if the room has insufficient supply.

But may reduce it, since the unit will have more air returning to it. Enabling it to move more air to that room.