[MollieW]

I have two extra bedrooms that we are not using, except for company. Would it be better to shut the vents and close the doors when not in use or will that make the rest of the house hotter with the build up in heat in them. Should I remove TV's and things if I close them off?

[luckpants]

I would. Just unplug the TV, It's not like it will get that much hotter in there.

[observer53]

Just two rooms should be okay, but closing registers and doors can increase the pressure in the rest of the system, which is not good.

[Scott456]

I would say it's ok to shut the vent and close the bedroom doors. But make sure your bedroom doors are sealed. Use weather stripping around the doors. Just treat these rooms as exterior space. You may want to open the windows in these rooms at night when it's cooler outside.

[PinkString]

I keep wanting to close off vents to some rooms we do not need cooled during the day or night. But I always keep hearing that it is bad for the ventilation system. It would save more money to close off the unused spaces, but we definitely do not need problems with the system. I swear we can't win in some things.

[Willy702]

Savings are minimal really, but doesnt hurt to spend 10 mins in covering the vents and putting towels in the door gaps. Blackout curtains and shutters are far more effective so make sure you have those in first.

[Scott456]

I am in a two story house, and have 2 ACs. I only live downstairs, so I plan to use thick curtain to close off the stair way, and only use downstair AC.

[Willy702]

Originally Posted by Scott456

I am in a two story house, and have 2 ACs. I only live downstairs, so I plan to use thick curtain to close off the stair way, and only use downstair AC.

I highly doubt that will be very effective. Heat will rise despite your curtain efforts, wood frame houses were designed for fairly easily heat exchange.

[cBach]

Originally Posted by Willy702

I highly doubt that will be very effective. Heat will rise despite your curtain efforts, wood frame houses were designed for fairly easily heat exchange.

Heat will rise, the downstairs will remain cool, so putting A/C for downstairs and leaving it off upstairs works fine. I work from home and the A/C is off upstairs and I work downstairs. In the evening the A/C is cranked back on upstairs to cool the upstairs for the kiddos at night.

[ScoopLV]

Minor point, heat doesn't rise. It radiates. Hot air rises. And the only reason it rises is because it's less dense than cooler air. Heat is quite happy to radiate in any direction.

For instance, because of the orientation of our house, the billiards room is the hottest room in during the summer. It sits directly over the garage, which takes a pounding from sunup until around 2 pm. Even with insulation, the metal door will burn you if you try to touch it, it's so hot. Most of the hot air pools near the ceiling, thus making the billiards room warmer than the rest of the rooms. But heat also radiates through the first-floor walls, making the kitchen, living room and entertainment areas hotter as well. If heat only moved in one direction (up), mitigating the effects would be easy.

The best way to fix the garage heat problem was to install the same gable fan we have in the attic. It's near the ceiling, away from the garage door, to vent the heat. This is mainly for the lower level rooms. The billiards room typically only is used at night, when the garage heat is no longer a factor.

The trick is to vent what you can, and put a barrier between the sun and the rooms it will affect the most. Shade trees, pergolas, solar screens are the most effective. Black-out shades are good, but they aren't nearly as effective because the heat has already entered the house through the window. The black-out shade simply slows the transfer of heat. It's better to keep the heat out in the first place, if at all possible. It has been my experience that it's a good idea to think like you didn't have AC at all, and make improvements that would make your house somewhat comfortable. That will save the most money in kwh and wear and tear on the AC unit(s).