Try the following since it is still the winter heating season.
Close ac vents in winter.
Although air should circulate year round through the attic your house will probably be more comfortable if you cover the foundation vents in the winter.
Open top return grill dampers and close bottom return grill dampers on all sets like this throughout the home.
In the winter you want the cold air to be drawn through the return registers leaving the hot air behind.
Why you should never close the vents in your home look at the nearest air vent in your room.
After all one of the purposes of attic vents is to help release some of the heat from the attic and prevent it from becoming super heated.
The popular notion has always been to shut off vents in rooms that you use infrequently.
It most likely has adjustable fins that allow you to direct the flow of air in the room and you can use the adjusting level to shut off a vent almost entirely.
It s not just the energy efficiency of your home that takes a hit if you close vents.
By opening the lower registers and closing the top ones you keep hot air in and draw the cold air out.
The simplest way to close foundation vents for the winter is to plug them from the outside with foam blocks made specifically for this purpose.
Don t shorten the life of your hvac system unnecessarily by closing off your vents.
Just remember to remove the plugs when the weather turns mild in the spring.
The pressure imbalance creates a suction effect that causes the cold air return duct to pull in air from cracks in windows and doors.
It appears set in first photo has high return grill damper closed with bottom open and the other set the opposite way.
Instead of blocking the flow of air in a room closed off vents simply create additional pressure within the ductwork.
So in a way the idea of closing those vents during the winter also makes sense because theoretically this would help prevent heat from escaping your home during the winter when you re trying to keep it in.
Since cold air is heavy it will automatically flow down to the lower register.
In extreme cold the lack of warm air in your duct work may cause freezing to occur.
Now most people close their crawl space vents in the wintertime to keep the cold out so that the cold air doesn t freeze the pipes under the house.
The warm air that s blocked from entering the closed off room will simply find other places to go through leaks and cracks in your ductwork or back.
You probably already know that attic vents are important both to your roof s longevity and to keeping your energy bills down during the summer.
You probably won t notice a temperature difference but your system will be happier without the closed vents and you will be saving money.
If you really want to save some cash on your bills keep your vents open and allow the air to flow freely throughout your home but consider lowering the temperature a few degrees.
But when you add humidity to the equation this is a very poor decision for the overall health of your crawl space and home because it doesn t have any effect at all on controlling humidity.
