I have a finished basement with an open stair well to the 1st floor which even in the middle of the summer needs to be heated to stay at 69F degrees. There's also a large open foyer leading to the 2nd floor. I'm thinking of moving hot air on the 2nd floor down to the basement. Would this help?
Some house details:
- Basement (1500 SQFT) is open to the 1st floor through stairwell
- 1st floor (2000 SQFT) is open to the 2nd floor through foyer
- 2nd floor (600 SQFT) has some common space and two bedrooms
- Every room and a common space has individual returns
- Basement is walk-out and there's no radon
There are 2 HVAC systems (both sitting in the basement):
- The larger (100kBTU) system is zoned for the 1st and 2nd floor.
- The smaller (40KBTU) system is zoned for a large south-west facing 1st floor office with many widows and the basement.
In the summer, the cool air sinks to the basement, and the heat must run to keep it at 69F. If I turn off the basement zone, the basement eventually settles at around 64/65. Heat seems to rise to the 2nd floor open space, where it's usually at least 80F at the ceiling when the AC is set to 75F.
This 2nd floor common space has a return at the top of a wall near the ceiling (conveniently right near the attic entry), and seems to be the hottest place in the house. I'm thinking of disconnecting this return in the basement, and using a Tjernlund M6 duct fan to move that warm air down dispersing it through the basement near the floor.
I'm hoping this would essentially circulate the hot air to the basement, pushing some of the cold air up. Or, potentially it could be done in reverse (move the cold air near the basement floor to the 2nd floor ceiling). Would this help? I don't want to have to run the heat in the summer, it seems like a waste and there's plenty of hot air around.
The Tjernlund M6 moves 500CFM and even at a higher static pressure (say moving 200CFM) it would exchange the entire basement volume throughout the house in 60 minutes. There's also a Tjernlund through floor (ASLL) fan, but this would move 75F degree air from the 1st level floor to the basement ceiling and only provides about 50CFM. It seems moving the 80F degree air from the 2nd floor ceiling to the basement floor would be a better choice.
Best Answer
I live about 30 miles north of Pittsburgh, Pa. so I am familiar with some of your problems. First: the office and basement should not be on the same zone. Since it is installed this way it may be impossible to change now. In summer the office needs lots of cooling to offset the southwest facing windows and the basement needs none or even some heating. Add returns, 2 or more, or as many as you can at the floor level in the basement, connected to the 1st. and 2nd floor unit. Do not disconnect the high wall return near the attic access, but add more if you can to take the hot air off the ceiling. Run the fan for this unit continuously, 24 hours a day on a low speed when the unit is not calling for A/C, to help recirculate the cold basement air. Close any basement supply registers in the summer when the A/C is running. Consult a roofing specialist to see if it would be advantageous to add a roof mounted, thermostatically controlled, attic fan, to vent the excess heat from the attic area. You said that every room has cold air returns. Are there both high and low returns in each room? If so, the highs are used in the summer and the lows in the winter except in the basement. Multiple story homes with open stair wells, open to all floors are very hard to heat and cool. All the heat rises and the cold air falls, as you well know. In my experience adding Tjernlund fans to circulate air is just another noise you will have to contend with. Hopes this info helps. Good luck, in solving your problems.