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Save Energy by Closing Heat Registers

It seems like a waste to heat unused rooms, but closing heat registers may actually increase heating costs, especially with newer systems.

By the DIY experts of The Family Handyman Magazine

Save Energy by Closing Heat Registers

It seems like a waste to heat unused rooms, but closing heat registers may actually increase heating costs, especially with newer systems.

Consult an HVAC contractor first

There are three good reasons to get an HVAC contractor involved before you start closing off heat vents, especially with today's high-efficiency furnaces and well-balanced systems. First, it might actually add to your heating bill. That's because with the heat vent closed, the suction from the return air duct can pull in cold air from the outside through any cracks around windows, exterior doors or exterior wall electrical boxes. Second, if the heat duct seams haven’t been sealed properly, the extra pressure from closed-off vents will force hot air through the leaks. That can be as much as 15 percent of heated air into basements, crawl spaces and floor cavities instead of into rooms. Finally, if you have a well-designed, finely tuned heating system, closing off too many rooms can damage your furnace because it has to work too hard to distribute the air. So, if you still want to seal off these rooms, consider hiring an HVAC contractor for advice.

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Comments from DIY Community Members

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December 05, 8:45 PM [GMT -5]

I closed two bedrooms and this is what I did. I think it overcomes all the objections of the article:.

1. I sealed the openings where the hot air duct and floor meet with aluminum foil tape, so that the pressure caused by the closed register would not force heated air through the openning back to the basement. I also stuffed insulation in the top of the duct to prevent hot air from leaking through the closed register.

2. I replaced the return register with two registers, an upper and a lower one, both of which have moveable louviers and keep them in the closed positon so cold air can not be sucked into the system.

3.I attached door weather strips to the bottom and weather stripping to the door frames, so a natural convection current would not occur.

4. Both bedroom areas are a relatively small percentage of the total living space. I have a two-year old, 95% efficiency furnace, and have run it from day 1 in this mode, It has run beautifully.
When my furnace or my AC is running,, the temperature in the upstairs rooms which are in use is identical to the temperature in the downstairs rooms. The installer said that in his 30 years of installing HVAC he has never seen or heard of any single zone heating where the temperatures are perfectly balanced.

When we have guests occupying the bedrooms, I remove the insulation from the heating register, open it, and during the winter, open the upper return register and keep the lower return register closed., and during the summer, I do the reverse , since hot air rises and cool air settles..

I hope this is of help. Guy Vacarro

January 30, 2:17 PM [GMT -5]

For new construction or major remodel, use the wall stud cavity as part of the return system and install two operable return vents in the stud bay, one 6 - 8 inches below the ceiling and the other 6 - 8 inches above the floor. For cooling, open the upper vent and close the lower, this pulls hot air from the ceiling. For heating, do the opposite, which pulls cooler air from the floor.

I did this when we built our house.

This avoids unbalancing the system as air flow doesn't change very much, but your comfort increases which may allow lowering the thermostat a degree or two, also saving energy..

Don Schmidt
Fargo

January 18, 7:56 AM [GMT -5]

Reponse to SRJ1957...I am not a professional but I think the concern is that the air throughout the house is not being filtered through the HVAC system. Thus, possibly making your house a sick house with all the that could be trapped in other areas of the house. Yet if the back door has leaks it could be bringing in fresh air which is good in limited amounts. I once had a modular home that had at the backdoor a forced air furnace the door to the outside was no more than 6ft away. However, the hallway was wide open to the rest of the house. If the mudroom has a door and it is closed off from the rest of the house that might be a concern.

September 08, 9:14 PM [GMT -5]

It takes more energy to heat 50 degree air to 70 degrees than it does to heat 60 degree air to 70 degrees.

January 20, 11:54 AM [GMT -5]

Can someone explain why it's an "issue" if cold air is going to the return vent...

January 19, 12:32 AM [GMT -5]

Hope this doesn't sound too dumb a question, but what does it matter if the air return is sucking in cold air in winter... I wasn't aware that it had to be warm air from insie the house.

The reason I ask is that our air return is in the mudroom about 8 feet away from the door to the back yard outside and it could be sucking cold air from the outside . I've put weather strip around the door but we all know we can't stop every spot.

Please help me understand how HVAC works with regard to the "air cycle":

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