Central AC and Closing Interior Doors
- Thread starter mark_wpduet
- Start date
Help Support :
My home has air returns in all three bedrooms, the living room, the upstairs hallway and the kitchen. Only the bathrooms and the laundry (which contains the furnace) lacks return air. Ironically, the very HVAC company I now work for installed my HVAC when my house was built in 2004, nine years before I bought it and eight years before I started working for the company.
When my company does a new install, we insist on having multiple return-air inlets throughout the home, ideally in each bedroom in addition to the living room, dining room, etc. It really helps with efficiency, equalizing indoor temps, proper dehumidification when running the AC and much better indoor air quality.
We actually take the time to calculate for the optimal balance of supply and return. You want to have about the same CFM for supply and return. We factor in the blower CFM of the furnace or AHU, and even factor in frictional losses that system components impose (everything from registers to dampers to the air cleaner to the linear run of the system, including bends) to get the proper size of the trunks (the main run for supply and return).
Based on what I've seen in existing installs when doing a repair or replacement, a lot of HVAC contractors seem to only size the equipment, sometimes you're lucky if they even do that properly. The distribution seems to be an afterthought in a lot of cases.
When my company does a new install, we insist on having multiple return-air inlets throughout the home, ideally in each bedroom in addition to the living room, dining room, etc. It really helps with efficiency, equalizing indoor temps, proper dehumidification when running the AC and much better indoor air quality.
We actually take the time to calculate for the optimal balance of supply and return. You want to have about the same CFM for supply and return. We factor in the blower CFM of the furnace or AHU, and even factor in frictional losses that system components impose (everything from registers to dampers to the air cleaner to the linear run of the system, including bends) to get the proper size of the trunks (the main run for supply and return).
Based on what I've seen in existing installs when doing a repair or replacement, a lot of HVAC contractors seem to only size the equipment, sometimes you're lucky if they even do that properly. The distribution seems to be an afterthought in a lot of cases.
vacerator
Well-known member
air returns
in each room are most common in colder climates and houses with basements.
In the 80's, houses began being "prepped" for central a/c with a return near the ceiling in the main living space, and master bedroom.
Hot weather tip for basement houses; In the morning, open the air filter cover on the furnace for just a minute or so with the blower only on, and blow the cooler air upstairs. I also open my humidifier air damper slightly to recirculate some conditioned air into the blower plenum beneath the evaporator coil. Helps cool the blower motor too when it's running on high speed for a longer time.
in each room are most common in colder climates and houses with basements.
In the 80's, houses began being "prepped" for central a/c with a return near the ceiling in the main living space, and master bedroom.
Hot weather tip for basement houses; In the morning, open the air filter cover on the furnace for just a minute or so with the blower only on, and blow the cooler air upstairs. I also open my humidifier air damper slightly to recirculate some conditioned air into the blower plenum beneath the evaporator coil. Helps cool the blower motor too when it's running on high speed for a longer time.
My 3 bedroom 1400 square foot ranch (plus basement) has air return ducts in every room but the kitchen and bathroom.
For all that, one side of house is still a lot warmer than the other in the winter. I suppose I could adjust the airflow to even it out with enough effort and experimentation.
What the house really needs is more insulation in the walls.
For all that, one side of house is still a lot warmer than the other in the winter. I suppose I could adjust the airflow to even it out with enough effort and experimentation.
What the house really needs is more insulation in the walls.
Returns in each room surely improves performance (when doors are closed) but is not a common thing in this area.
I have two supply registers in the master BR, one in the master bath main area and another in the toilet "cubicle, one each in the split walk-in MBR closet. Two in the living room (or three), one in the kitchen (or two ... depends on where one considers the split between LR and K). One each in the dining area (which is almost part of the kitchen) and the laundry room and office room. One in each of the other two BRs, one of which has a larger walk-in closet with a register. One in the half-bath. Three (one in each section) of the jack-and-jill bath for the two spare BRs. Lacking registers are the kitchen pantry and the smaller walk-in closet for one of the spare BRs.
So that's 20 supply registers.
Returns in the small hallway between the LR and MBR, and in the longer hallway outside the two spare BRs. Both take 25" x 20" filters.
The spare BR wing is 2°F to 3°F cooler (or warmer) than the MBR end. The master bath is warmest (and coldest) due to three large glass-block windows and being the farthest airflow run.
mark_wpduet
Well-known member
Ok,
why have I never seen this? Maybe I just haven't paid attention. I just never remember being in a home that had multiple returns in every room like that. Then again, if I visit that's not really something I'm paying attention to. I'm imagining that's a pain too to change all of those filters. Hopefully, they are all the same size filters if there are that many intake or return or whatever they are called. I know in my hall where the 2 returns are, they are both differently sized returns so I have to buy 2 different sized filters. I'm trying to imagine that same scenario all over the house in each room. What a pain that must be.
why have I never seen this? Maybe I just haven't paid attention. I just never remember being in a home that had multiple returns in every room like that. Then again, if I visit that's not really something I'm paying attention to. I'm imagining that's a pain too to change all of those filters. Hopefully, they are all the same size filters if there are that many intake or return or whatever they are called. I know in my hall where the 2 returns are, they are both differently sized returns so I have to buy 2 different sized filters. I'm trying to imagine that same scenario all over the house in each room. What a pain that must be.
My house is 1565 or so sq. foot rancher. One air register per room. I have two air return "grills"--a larger one in the den next to the door into the entrance hall and that air return also butts up to the utility closet in the garage that houses the air handler and water heater. Then there's a smaller air return grill in the entrance hall perpendicular to the one in the den.
No air filters on all these return grills. Just a single "Aprilaire Space-Gard" filter that sits between the air return duct work and the furnace.
It takes one large 25" x 20" x 4" $30 filter that I change twice per year. These are fairly common around here.
It takes one large 25" x 20" x 4" $30 filter that I change twice per year. These are fairly common around here.
for me, there is only one filter, in the heater itself.....
there are little filters you can buy that fit behind the grill for even more filtering, I guess it would help keep the duct work cleaner...
theres also return air grill covers, their magnetic, never thought that I could close off return lines, and make the unit pull air from warmer rooms needing more cooled air...I wonder if that would put the system into havoc like when I closed off regular vents....
there are little filters you can buy that fit behind the grill for even more filtering, I guess it would help keep the duct work cleaner...
theres also return air grill covers, their magnetic, never thought that I could close off return lines, and make the unit pull air from warmer rooms needing more cooled air...I wonder if that would put the system into havoc like when I closed off regular vents....
jerrod6
Well-known member
I have a three story house with all of the bedrooms on the second and third floors but only one HVAC system. There are returns in each hall way on each floor. There is one return and two supply vents in the living room.
Every bedroom has a return high up over the door, and the master bedroom has two supply vents and two return vents. The return vents in the master bedroom are placed so that one is near the floor and the other is near the ceiling.
In the summer I have tried leaving everything open and also closing the bedroom doors. What happens is that if I close the bedroom doors, the bedrooms get very cool, but they end up the same temperature as the rooms on the first floor so this works out very well.
If I leave all of the doors open the entire house will level off to a temperature but because the the bedrooms are on the upper floors they become warm because the cold air is escaping into the hallways.
If you are in a single level house with few returns it is probably best to leave everything wide open to help with circulation.
I did another thing by accident but it turned out well. In the fall I opened all of the return vents as far as they would go to clean them, then I forgot about it. A few months later I turned the heater on and found that there is much more supply air coming out of the vents so it seems like if you have adjustable return vents it might be better to leave them wide open to improve the flow of supply air.
Every bedroom has a return high up over the door, and the master bedroom has two supply vents and two return vents. The return vents in the master bedroom are placed so that one is near the floor and the other is near the ceiling.
In the summer I have tried leaving everything open and also closing the bedroom doors. What happens is that if I close the bedroom doors, the bedrooms get very cool, but they end up the same temperature as the rooms on the first floor so this works out very well.
If I leave all of the doors open the entire house will level off to a temperature but because the the bedrooms are on the upper floors they become warm because the cold air is escaping into the hallways.
If you are in a single level house with few returns it is probably best to leave everything wide open to help with circulation.
I did another thing by accident but it turned out well. In the fall I opened all of the return vents as far as they would go to clean them, then I forgot about it. A few months later I turned the heater on and found that there is much more supply air coming out of the vents so it seems like if you have adjustable return vents it might be better to leave them wide open to improve the flow of supply air.
fan-of-fans
Well-known member
My house is right at 1400 sq ft. Have one vent in each bedroom, bathroom, two in the kitchen (one over the main kitchen and one over the dining area), two on the wall in the living room and one in the laundry room. The laundry room one is closed off all the time and the air handler is in there. The return grille is in the hallway, funny thing is at night, you can see a funny colored light through it because of the UV lights in the air handler. I always thought it was the LED night light we got reflecting off the vent louvers but it's actually those UV lights.
I haven't seen houses with a return in each room either around here.
I haven't seen houses with a return in each room either around here.
I think the placement of air returns depends on the individual HVAC contractor, and what they are used to doing if something else is not specified by the owner or architect. The house my cousins lived in (that I mentioned above) was custom designed and built, so every detail was specified as to how it was to be done. I know the place was very expensive when they built it in the mid 80's - over $500,000. I wouldn't expect houses built for the market to include anything that would add to the cost.
streakers
Well-known member
My home - built in 2004
two storey with a full basement - 4 bedrooms, has return air vents in all four bedrooms upstairs and two large return air vents in the living room and and the study on the ground floor.
Only one large filter which is in the basement on the return duct just before the blower fan itself. It's a Trane Unit both inside and out and keeps the house (over 2200 square feet not including the basement) comfortable both in heat and cool modes...
The return air vents upstairs in the bedrooms are however located up high, the returns downstairs are located at floor level. Upstairs, up high, I'm assuming to help draw the high, warmer air down back into the unit during the summer months to help improve airflow with cooling mode etc. - and I know that when in Air Con mode the blower does run at a higher speed. (Must be a two stage unit?) There are air vents in the basement as well - and has enough power cool the basement comfortably - but not necessarily heat it as the vents are at ceiling level only.
I have installed a NEST thermostat so I can have some more flexibility when I'm not at home and for scheduling etc.
But larger rooms have more than one vent - master bedroom has three in total for example, living room has multiple etc...
Does the trick! I just figured most newer build homes would be all like this? Seems logical to me with convection from heating and and cooling modes - hot air rising and cold air sinking etc??
Those that don't have return air vents in those rooms - do you have trouble with hot/cold rooms - and if you do - how do you combat that?
two storey with a full basement - 4 bedrooms, has return air vents in all four bedrooms upstairs and two large return air vents in the living room and and the study on the ground floor.
Only one large filter which is in the basement on the return duct just before the blower fan itself. It's a Trane Unit both inside and out and keeps the house (over 2200 square feet not including the basement) comfortable both in heat and cool modes...
The return air vents upstairs in the bedrooms are however located up high, the returns downstairs are located at floor level. Upstairs, up high, I'm assuming to help draw the high, warmer air down back into the unit during the summer months to help improve airflow with cooling mode etc. - and I know that when in Air Con mode the blower does run at a higher speed. (Must be a two stage unit?) There are air vents in the basement as well - and has enough power cool the basement comfortably - but not necessarily heat it as the vents are at ceiling level only.
I have installed a NEST thermostat so I can have some more flexibility when I'm not at home and for scheduling etc.
But larger rooms have more than one vent - master bedroom has three in total for example, living room has multiple etc...
Does the trick! I just figured most newer build homes would be all like this? Seems logical to me with convection from heating and and cooling modes - hot air rising and cold air sinking etc??
Those that don't have return air vents in those rooms - do you have trouble with hot/cold rooms - and if you do - how do you combat that?
gusherb
Well-known member
It’s standard practice around here in the Midwest to install a return in each room. Down south it’s standard practice to have one central return in the hallway, primarily to cut costs, reduce amount of ductwork in the hot attic and I suppose a return in each room isn’t as crucial for cooling as it is for heating, though I find that arguable. We have two systems here, one for upstairs and one for downstairs. Downstairs system has sheet metal ductwork in the basement and upstairs system has flex duct in the attic. Both levels have high/low returns in the walls, plus I had a return added to the ceiling in each room when the upstairs system was replaced because the return side of the system was starved for air.
Photos of my return vents
1047 SQ slab-on-grade home with 2 Ton Goodman AC and 60,000 BTU Goodman furnace.
In living room photo with TV, the bottom return air vent is to the left of the fan.
Attached vid of the Goodman running in August of 2015
1047 SQ slab-on-grade home with 2 Ton Goodman AC and 60,000 BTU Goodman furnace.
In living room photo with TV, the bottom return air vent is to the left of the fan.
Attached vid of the Goodman running in August of 2015
vacerator
Well-known member
I guess apples
and oranges for heating with the air returns near the ceiling. Heat rises, so the furnace gets warmer air rather than colder off the floors. Reaches heat exchange temp. faster?
You can tell when a guy is single when a wire or cable is in plain sight on a wall. Not that it's second class or anything. A friend once strung Christmas lights on his Nordic Track. He's not the best house keeper though. Says no one see's his mess. But after remodeling with nice Kitchen Aid appliances, and antique brass light fixtures and all?
and oranges for heating with the air returns near the ceiling. Heat rises, so the furnace gets warmer air rather than colder off the floors. Reaches heat exchange temp. faster?
You can tell when a guy is single when a wire or cable is in plain sight on a wall. Not that it's second class or anything. A friend once strung Christmas lights on his Nordic Track. He's not the best house keeper though. Says no one see's his mess. But after remodeling with nice Kitchen Aid appliances, and antique brass light fixtures and all?
If the single person is living in a rental place-than the wires in sight are really OK-he or she doesn't want to damage building walls that don't belong to them.The habit carries to this day with me!
I would assume it very much depends on how your system is designed. A proper system should be able to function with the doors closed by having air inflow and outflow in every room.
I remember working in a university where a room had been divided up with partition walls to create lab spaces, without any reference to the air conditioning design. It ended up with one room barely getting any flow and the other two were often freezing as it screwed up the system's ability to pick up temperature readings. So it was opening dampers and flooding one partition with very cool air all the time.
After a lot of complaints to facilities they eventually added the necessary ducts and stats.
I remember working in a university where a room had been divided up with partition walls to create lab spaces, without any reference to the air conditioning design. It ended up with one room barely getting any flow and the other two were often freezing as it screwed up the system's ability to pick up temperature readings. So it was opening dampers and flooding one partition with very cool air all the time.
After a lot of complaints to facilities they eventually added the necessary ducts and stats.
Steve, is your heat source natural gas and not electric or heatpump? All 3 houses I've owned (gas & heat pump systems) the blower was specifically set to run slower when heating vs. higher speed in AC mode. It's probably not a 2-stage system. If it were, the blower would be more variable in speeds than just the 2 you've noticed.
Similar threads
