for Cold Climate Housing and much more

Last Updated: , Created: Thursday, October 14th, 1999


Answer One

"Planned-holes-high-in-the-house" are part of buiilding science considerations as to how air moves in buildings creating pressure differences that can help to keep houses dry and mold free or can help to trap pollutants in the house or even in the walls.

A planned-hole-high-in-the-house creates a low pressure inside the house that helps keep the inside of the walls dry by raising the neutral plane.

Natural, or gravity, planned holes can be any ventilator which draws air high in the house, whose ducting rises or travels horizontally but not downwards, and which has no damper to block the air flow.

Power ventilators (i.e., bathroom vents and central exhaust systems) with rising or horizontal ducting will work as long as they have no dampers. A vent pipe found in the water closet of old houses will qualify. A plastic tube or vent duct run through the wall (high on the downwind side) or through the ceiling to the outside (and protected from the rain) will work.

Oddly enough, as long as these vents travel horizontally, or rise, and exit as near as possible to the upper most ceiling, it doesn't matter where they start. (The column of air inside the vent has the same rising effect as the air around the vent, and the end result on the pressure plane in the house is the same wherever the lower opening is.) Hence, fireplaces without dampers, be they on the ground floor or even in the basement, will work, as will furnace chimneys without dampers. A dummy chimney (a 7 to 10 cm PVC pipe run from the basement ceiling through the roof) will even work.

Click here for Answer Two.

Keywords: Condensation, Moisture, Neutral Plane, Exhaust Fans, Ventilation

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