I need to move around some duct work in my house to make way for a closet and to rebalance the system. The side of the house far from the furnace is much colder. I’m just hoping for some basic guidelines such as:
1) Is there any negative circulation effect to move registers from the wall to the floor. I could eliminate a 90 turn, but the heat/cold air would blow up instead of across the room.
2) To force more air to the far side of the house, is it better to partially close registers in the hotter side of the house, or is it worth it to disassemble ducts and install dampers near the furnace.
3) My second floor only has two returns (1 each bedroom) but there are two supply vents in each room and one in the hall and one in the bath. That’s 6 supply vents for 2 returns. I suspect it makes sense to stick a return at the top of the staircase. Thoughts?
Replies
1. Do you have attic access? Maybe a ceiling vent might be a better option
2. Ideally there should be butterfly valves in the duct near the HVAC supply plenum that would allow you to tune the air flow. Closing the registers may have limited success - one register would be blown off the hole when the AC kicked on in an old house I had.
3. More returns are always better, in my book - but what kind of house do you have? A colonial with an open stairway? McMansion with 2 floor great room and balcony hall? How many sq feet?
Returns are only usefull when the fan is running. Sometimes the answer ti to run the ventalation fan more to balance the hot and cold air pockets around th house.
Tu stultus es
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
Thanks Paul: I dropped in answers after your questions:
1. Do you have attic access? Maybe a ceiling vent might be a better option .A -- I don't have ceiling access. It's a cape code with all kinds of weird dormers.2. Ideally there should be butterfly valves in the duct near the HVAC supply plenum that would allow you to tune the air flow. Closing the registers may have limited success - one register would be blown off the hole when the AC kicked on in an old house I had.A -- Butterfly valves sound good to me.3. More returns are always better, in my book - but what kind of house do you have? A colonial with an open stairway? McMansion with 2 floor great room and balcony hall? How many sq feet?A -- Its a cape code with an openish stairway, Its only about 1400 sq ft. Returns are only usefull when the fan is running. Sometimes the answer ti to run the ventalation fan more to balance the hot and cold air pockets around th house.
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Something like this describes your house (stylewise)? You might have access upstairs through kneewalls (about the height of your knees!) along the edge of your roofline on your upper floor for new vents.
If you have flexible vent pipe, adding a valve if it isn't there already is a cinch. If you have solid metal pipe, it's still easy though moving the pipe enough to get it in might be hard.
Onehing about ALL of this is very conditional - how old is your furnace? If it's more than 10 years, you should have a pro look at it. Cracked heat exchangers are pretty common, and those let carbon monoxide into the air you breath.
I just replaced ours ($5700) with new furnace and all new duct for our 1700 sqft ranch with added 2nd floor. If you need to look this way we can talk about how to pick a good HVAC contractor.
Tu stultus esRebuilding my home in Cypress, CAAlso a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
Maybe your old system wasn't designed for efficiency in air circulation or energy. So the notion of installing balancing dampers near the furnace is a reasonable thing (surprisingly, I had them in an OLD house I had). They may be easy to install. Operable registers work fine ... open them in the summer ... easy to adjust.
Reconfiguring registers wall to floor, etc. sounds like a big effort. In the floor is typical ... throws air up and allows it to wash the wall and circulate in the room (if on the outside wall which is also typical).
Number of returns means little ... it is the size that matters. I can have 2 returns in a space or one large return. Location counts more than anything. Good distribution provides a better balance and helps prevent pressure imbalances and ensures good circulation/even heat/cool. Often supply air is at the perimeter, returns near the center of the house .... this means returns can be relatively smaller due to the lower pressure drop due to the more direct return air to the furnace (i.e. shorter run, fewer 'turns'); a little smaller duct will do the job.
I wouldn't put a huge amount of effort into your return unless you identify a specific significant problem. On the surface, you didn't indicate there was a problem.
I do think an extra return makes sense. The upstairs returns are the same size as the supplys. And when you stick a piece of paper in front of a return with the fan on, it really slaps into the return and sticks there. The supplys don't seem to have as much pressure blowing out. But who knows.
Just covering bases that you may not have. Someone has to do it! I've generally seen returns larger than the supplys. So your statement may be correct to add a return. A smaller return may flow the same air ... just at a higher (and noisier) velocity. Again a shorter return will be lower static pressure. It's hard to determine if the suction of your paper is as hard as the supply side since you can't really do the same test on the other end. A flow hood would tell that story.
If you are inclined to pursue the extra returns ... consider borrowing (if you can) a flow hood and testing the air flow to see where you are lacking balance. Might even be worth having a technician come out and read all supplys and returns to show you where the imbalance is. A guy should be able to read out all of them inside an hour easily, I would think.
Thanks Clewless:I think by adding some dampers in the shorter supply runs that blow hard and adding one return to help balance the upstairs, I might make some progress. The return will be pretty easy as I got some other remodeling to do anyways.
Is this for heat only or air conditioning too? With air conditioning, you want plenty of returns upstairs with the grills as close to the ceiling as possible to pull the heat out and supplies blowing upwards is likewise beneficial. If it is for heat only, the cooler return air from the hall and bath areas can "fall" down the stairs and find its way back to the furnace through a first floor return unless this causes a draft problem.
Its both AC and heat in Maryland. So they are both used equally.
basically i have always been told that you need 10% more capacity in the return ducts to stop the hot air from meeting resistance in a room because the cold air cant get out
often doors are cut too close to the floor and the room becomes pressurised due to inability of return air to get out
what your after is a balanced system for heating
check no ones dumped clothes on hot air registers or on cold air returns & check furnace filter on a regular basis and change it , their cheap compared to fuel