Two or Three floor vents

8 years ago

We are building a morning room addition that will be 12 X 12 room. On all three sides we will have windows and it's south facing so we get a good amount of sun. My question is with the size of the room do you think two vents would be fine to cool / heat the room or should I go with three.

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Mark Bischak, Architect

8 years ago

"On all three sides we will have windows and it's south facing so we get a good amount of sun."

Wait a minute; you have a three sided room and it faces south?? For that to happen it would have to be located at the north pole.

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Comments (10)

Josie23: Zone 5: WI
8 years ago
Um where are you? Heating/cooling needs are different depending on your location. Are you in Alaska or Florida?
Sami
Original Author
8 years ago
I'm in illinois
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Sami
Original Author
8 years ago
Most our rooms that are bigger than 12x12 or close to that size (master and family room) all have two vents in those rooms. I'm just worried that all the windows in the addition and sun coming through will warm it up fast.
drbevdc
8 years ago
Your HVAC guys should be able to properly calculate the number and size needed.
chisue
8 years ago
A professional should be looking at the exposures and the total volume of space to be warmed/cooled. What's your ceiling height? Are you planning air supply vents in the floor or on a wall? Where will the air returns be placed? Will you be able to adjust the amount of supply airflow -- at the vents or in the ducting?

I have air supply in the floor and return systems in the wall -- one set of returns for summer (high on the wall to draw the cool air up through the room) and one for winter (low on the wall to draw the heated air down through the room) .
mike_home
8 years ago
Two vents would be fine for a typical 12 X 12 room. But you have a lot of south facing glass so I would suggest you go with three vents if it is not too difficult. The windows also increase the heating load so you will also appreciate them on a cold winter night.
Sami
Original Author
8 years ago
The air supply vents will be on the floor and their will be no return in the addition. Our ceiling height is 9ft. In the plans they have 3 air supply vents on each side. With energy efficient windows and I feel like 2 vents will be fine I just don’t want it to be too cool or hot.
User
8 years ago
No return? What's the connection to this addition, a door? If so, consider at least a jump vent.
David Cary
8 years ago
Variables - register size - they differ.

Duct size - big difference between 6 in and 8 in

Energy efficient windows? - ok - what is the U factor and the SHGC? Air leakage rate?

In the winter - even the most energy efficient window is not nearly as good as a wall and it sounds like this has 3 exposed walls - like no other room in your house. In the summer - even the best windows let in more solar gain by a factor of 10 or more than your walls.

That being said - I have a 20x20 room with 14 ft cathedral ceilings fed by a single duct.