We have two heating units in a single level house. One heats the den, kitchen, living room, dining room and two baths. The other unit heats the 4 bedrooms and one master bath. Return #1 is in the den beside the hallway. Return #2 is in the same hallway centered among the doors to the bedrooms. For Unit #2 the vents to the master bedroom and bath are closed. The vents in the other three bedrooms are open. Only one of these bedrooms is being used. It's my mom's who leaves her door closed all the time.
My mom says we are wasting money heating the two empty bedrooms. I say we have to leave them open so the unit will get circulated air. If I close off the two empty bedrooms, the only one with an active heat vent has the doors closed which will cause the unit to run unnecessarily costing even more money.
I say both units have to be running.
So who's right????????Settle a debate. Re: Closing heat vents to save money works in all cases?
Each register if open must have a path to a return air. It would be different if each bedroom had a separate return air along with a heat register in the room. As far as heat loss is concerned, you must first realize that the bedroom outside walls are insulated thus minimizing heat loss to the outside. Now if you shut heat off to these rooms, and the rooms cool off enough, remember that the interior walls to these rooms are more than likely not insulated, so now these walls can be concidered cold partions which will add heat loss to the smaller space being heated. Overall, it is probably a wash as far as which method will use less btu's to heat the house. The problem I see is that once you start shutting down too many registers, you cause a larger static duct pressure on the supply ( heat side of the system), thus creating more air velocity in other registers but overall, causing a drop in cfm over the heat exchanger in the furnace. A PCM ( ac motor ) is designed to work properly or most efficiently with a .5 static duct pressure. shutting off registers increases the static duct pressure.
now you create more expensive problems.
1. more static duct pressure means larger current draw on the blower motor.........meaning costs more electricity to maintain motor rpm.
2. with less cfm over the heat exchanger, you now have a higher heat exchanger operating temperature perhaps outside of the designed temperature differential. If a furnace is designed for a 40 to 80 degree rise from the return air to the supply air, this must be within these limits.
over time, too high operating temp causes cracks in heat exchanger.
too high exhaust temp if a 55% efficient furnace will cause poor natural draft and premature condensation as well as if the exhaust gas were too low a temp.
Same situation in a 80% design furnace, except that now you have a combustion fan to fail now as well or cause the temp limit control on the combustion fan housing to trip.
Bottom line is that if the duct system was initially designed by a heating company or a competent contractor, changing the airflow of the system in the long run only causes damage to the equipment.
Its hilarious when people shut off registers to bedrooms and shut the doors and I go find a cold air return in the room also that was drawing in cold air to the furnace on every cycle, and they wondered why the heat didn't feel as warm elsewhere in the house. All this does is mix cooler air back into the system when they thought they were saving heat loss.Settle a debate. Re: Closing heat vents to save money works in all cases?
The exterior walls of your home are insulated to keep out the cold. The interior walls are not. If you allow one segment of your house to become cold it will cause the rest of the house to be colder.
Instead, insulate and weatherstrip everywhere. Put up double glazing on the windows and anything else you can do to improve the barrier against air infiltration.
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