Code for Dryer Venting

[molo]

I am installing a gas dryer and would like to know if I can vent it down through the floor and out a basement window. Any ideas?

Thanks for any replies

[jadnashua]

Not sure about codes, but you'd have a big problem if there was a leak, plus, I think you'd end up decreasing the efficiency by maybe a significant amount...hot air wants to rise, not be pushed down. Plus, if there was a leak, you could have CO, too. Having it rise, like in a flue, is both safer and more efficient.

[molo]

Not sure about codes, but you'd have a big problem if there was a leak, plus, I think you'd end up decreasing the efficiency by maybe a significant amount...hot air wants to rise, not be pushed down. Plus, if there was a leak, you could have CO, too. Having it rise, like in a flue, is both safer and more efficient.

This would be in a flu pipe (rigid) but it would go downwards about 2 feet and over about 5' before exiting.

Thanks for any replies

[jimbo]

Actually, I don't see a code issue with dropping down and over. True that heat rises, but air has mass, and can be pumped down more easily than up. Efficiency will not be affected.

Just exactly how you terminate needs to be worked out. You don't want moist air backfeeding into the basement through that window, or collecting in a poorly ventilated space.

[molo]

Actually, I don't see a code issue with dropping down and over. True that heat rises, but air has mass, and can be pumped down more easily than up. Efficiency will not be affected.

Just exactly how you terminate needs to be worked out. You don't want moist air backfeeding into the basement through that window, or collecting in a poorly ventilated space.

If this will work. I will probably eliminate the small basement window entirely to terminate the vent through.

[Ian Gills]

I installed a dryer vent window. So far so good.

[Dana]

Actually, I don't see a code issue with dropping down and over. True that heat rises, but air has mass, and can be pumped down more easily than up. Efficiency will not be affected.

Just exactly how you terminate needs to be worked out. You don't want moist air backfeeding into the basement through that window, or collecting in a poorly ventilated space.

A few errors in physical intuition model here...

*Heat doesn't rise, it moves from hot to cold.

*Less-dense fluids rise as denser fluids fall due to gravity. Hot exhaust gas has lower density than cold exhaust gas (or air), and will rise as the denser gas displaces it due to gravitational forces. (The cloud of less dense gas "floats" in the denser gas, rising.)

*It takes more energy, not less, to force a lower density gas downward, counter to the gravitational forces on the denser cool gases that it is displacing. (It's "easier" to pump it up, working with gravity.)

Thought experiment: Take a helium balloon at head height, push it to the floor, what happens? You've forced an equal volume of heavier gas (the air) upward against the force of gravity- that takes energy.

In the dryer vent gas case it's not a huge force if the drop is small, say 3-5', but at 20' you may encounter measurably lower flow (and not just due to duct friction.)

Can't help on the code issue though- no idea.

[Thatguy]

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