Will this work for a cellar vent?

[Dexter]

The cellar (concrete walls and roof), is 8' x 10'.
Completely buried. Walls have been poured, roof gets poured tomorrow.

Because I could not find a 6" roof vent (for outgoing warm air) I purchased two 4" pipes. Bubel suggests 6" for this size cellar.

So... the 'cold air in' vent will be on the door, near the floor. (does that even make sense with a double door?? I got the idea from the Bubel book I believe)

Then, there will be one 4" vent on the roof, furtherst corner from door.

Where would you put a second 4" vent? Or maybe have the two 4" vents side by side? Aghh this is tough!!

I bet this is NOT clear but I can't scan a sketch....from here.

Thanks agaoin for any tips. Help from my previous cellar posts have been very helpful. I will post pics when it is completed!!!

[Katey]

The area of one 6 inch pipe is roughly 27 sq inches. The area of two 4 inch pipes is about 24 square inches, total. I'd put the two 4-inchers side-by-side. I'm assuming that you have a 6" floor-level input?

[Dexter]

I hadn't guessed that the 2 four inchers would be less! Thanks for this! I will try to get one more before the pour.
Thanks!

[Katey]

The formula is :

Take half the diameter
square it (multiply it by itself)
multiply the result by 3.