To close or not to close HVAC vents in unused space? (floor, furnace)

[Panu16]

We are moving into a bigger house next week. The basement is fully finished but we have no plan to use it except for storage. There will also be two guest bedrooms upstairs. I am getting conflicting information on whether closing HVAC vents in unused rooms is a good idea. Doing so may conserve energy but the HVAC system could be at risk for overloading. Is the risk for real? The house is newly built with two HVAC system (gas for 1st floor and basement and heat pump for second floor).

[MrRational]

Originally Posted by Panu16

getting conflicting information on whether closing HVAC vents in unused rooms is a good idea.

It's not. Avoid doing it ... even if your house is too big for you.
Especially not on the same level(s) where you actually live.

In YOUR case... closing off the basement supply & return... maybe.

[duster1979]

If we're talking about shutting half of your registers off completely you may put too much restriction on the blower motor, less that that and you're probably fine as far as that goes.

That being said, not heating your basement at all could cause cool air infiltration which would make your furnace work harder to heat the first floor so the idea that shutting the heat to the basement off completely will save you money on your energy bill false. And if you live in a cold climate you certainly don't want to cut off the heat to any plumbing down there.

A better idea would be to throttle the registers down to about half in the basement, that will keep your heating "envelope" intact while pushing most of the heat to your living space.

[btuhack]

You'll shorten the lifespan ($$$) of both the furnace and heatpump if you do what you're thinking of. Heating equipment, aside from hot water fan coils, rely on and are designed for specified air volumes to maintain efficiency and avoid problems. Same goes for A/C. Closed grills, undersized ductwork, and restrictive 1'' high efficiency filters all cause the same problems/symptoms.

Also, you could easily void any equipment and/or labor warranty.

[cvkool]

Originally Posted by Panu16

We are moving into a bigger house next week. The basement is fully finished but we have no plan to use it except for storage. There will also be two guest bedrooms upstairs. I am getting conflicting information on whether closing HVAC vents in unused rooms is a good idea. Doing so may conserve energy but the HVAC system could be at risk for overloading. Is the risk for real? The house is newly built with two HVAC system (gas for 1st floor and basement and heat pump for second floor).

Your not going to save any money by closing any registers, the system was designed to run with all registers open, closing them would only cost you in the long run. OPEN is the best option.

[RyanR]

Can't speak for gas since my house is all electric.

I have a 5-ton unit which is pretty big. Running it on the hottest days of the year where it's running almost constantly costs about $1 per day.

I'd leave all the vents open.

[HWTechGuy]

Depending on your location, there are other things to consider. A finished basement that's now going to be left unconditioned could develop mold/mildew issues.

[NJFillet]

Originally Posted by Panu16

We are moving into a bigger house next week. The basement is fully finished but we have no plan to use it except for storage. There will also be two guest bedrooms upstairs. I am getting conflicting information on whether closing HVAC vents in unused rooms is a good idea. Doing so may conserve energy but the HVAC system could be at risk for overloading. Is the risk for real? The house is newly built with two HVAC system (gas for 1st floor and basement and heat pump for second floor).

I was doing this with an unused bedroom and the HVAC pro told me to stop...so I agree with those here who advise against it. He said it's ok to close the door but not to block the system.