depressurization

Exhaust-Only Ventilation Systems and Radon

Posted on January 30,2015 by user-756436 in bathroom exhaust

Articles on mechanical ventilation commonly warn builders that exhaust-only ventilation systems can pull radon into a house through foundation cracks. The warning makes intuitive sense: after all, an exhaust-only ventilation system works by depressurizing a house with respect to the outdoors, and it seems obvious that depressurization could pull soil gases into a basement. One thing I’ve learned over the years, however, is that just because an idea is intuitively obvious, doesn’t mean it’s true. Throughout history, many observers have speculated; far fewer have actually made measurements.

Makeup Air for Range Hoods

Posted on January 30,2015 by user-756436 in air sealing

Most homes have several exhaust appliances. These typically include a bathroom fan (40-200 cfm), a clothes dryer (100-225 cfm), and perhaps a power-vented water heater (50 cfm), a wood stove (30-50 cfm), or a central vacuum cleaning system (100-200 cfm). But the most powerful exhaust appliance in most homes is the kitchen range-hood fan (100-1,200 cfm).

Can a Kitchen Downdraft Fan Be Connected To an HRV?

Posted on January 30,2015 by Daniel Morrison in depressurization

Powerful kitchen exhaust fans do a good job of removing cooking odors and smoke. They also have the potential to depressurize a house, causing water heaters to backdraft and pulling ashes out of the fireplace and onto the hearth.

Return-Air Problems

Posted on January 30,2015 by user-756436 in commissioning

In homes with a single central return-air grille, return air often struggles to find its way back to the furnace. The result: room-to-room pressure imbalances that lead to uneven room temperatures, comfort complaints, higher energy costs, and even moisture problems in walls and ceilings.

Pinpointing Leaks With a Fog Machine

Posted on January 30,2015 by user-756436 in air sealing

In the last few years, energy consultants have developed a quick and easy way to pinpoint air leaks in a building envelope. The technique uses a theatrical fog machine — a small, inexpensive device that creates smoke-like fog for dances, Halloween parties, or theatrical events. Fog machines have heating elements that vaporize “fog juice,” a solution of water and glycol or water and glycerin. With the help of a blower door or a window fan, a fog machine can dramatically reveal holes in a building envelope.

Farewell to the Chimney?

Posted on January 30,2015 by user-756436 in backdrafting

For thousands of years, the chimney has been closely associated with our concept of home. Upon spying smoke curling from a distant chimney, the weary traveler ends his journey with lightened steps. When I built my house in Vermont, as a much younger man than I am today, I designed a house with two chimneys. The house has a cellar, first floor, second floor, and attic; because I wanted the chimneys to rise five feet above the ridge, they had to be 40 feet tall.

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