A poorly vented attic in summer can reach extremely high temperatures – and so will the ceilings of the rooms below. Unwanted heat results in discomfort and high air conditioning bills.
Ventilation doesn’t get nearly as much attention as its cousins, heating and air conditioning. Nevertheless, the “V” in HVAC is important to the health of your house, your family, and your budget. A poorly vented house retains excessive moisture and heat, reduces indoor air quality, wastes energy, and can cause all sort of costly damage. Dr. Energy Saver can help you identify and solve ventilation problems in your home.
Comparing a house to the human body is a reasonable analogy. After all, both entities have skin, circulation systems, plumbing, and methods for consuming fuel and staying warm. So it makes sense when we hear the expression that "houses need to breathe." But the subject of house ventilation is complicated and controversial. A good way to clear up this complexity and resolve some controversy is to go over some basic ventilation terminology. Here goes:
Uncontrolled vs. controlled ventilation. "Uncontrolled" ventilation refers to air that leaks into or out of the house. The pathways for this type of ventilation are numerous leaks in the "building envelope" that divides conditioned interior space from the outdoors. According to building scientists, uncontrolled ventilation is a bad thing, because it allows for conditioned air that you've paid to heat or cool to escape from the house (exfiltration), while unconditioned air (that's usually too cold or too hot) is allowed to enter (infiltration). This constant leakage makes a home less comfortable than we'd like it to be, and also makes it much more expensive to heat and cool.
The process of air sealing reduces the amount of uncontrolled ventilation in a house. But for healthy indoor air quality, we still need a way to get rid of stale or "bad" interior air and replace it with fresh outside air. That's where "controlled" ventilation comes in. Exhaust fans in kitchen and bathroom areas provide ventilation that we control on an as-needed basis. Opening a window is a low-tech method of providing controlled ventilation. Operating an air-to-air heat exchanger is a high-tech method of providing controlled ventilation. This appliance exhausts stale interior air while drawing in a balanced volume of outside air.
Controlled ventilation helps ensure healthy indoor air quality in a house that has been air-sealed to make it "tighter" and more energy efficient.
Active ventilation vs. passive ventilation. "Active" ventilation is accomplished using electrically powered vent fans. Small vent fans are installed in kitchens and bathrooms because these areas frequently need active ventilation to exhaust air laden with smoke, odors and moisture from cooking and bathing.
Attic fans and powered attic ventilators (PAVs) can provide active ventilation in attic areas. But this type of active ventilation can do more harm than good if your home has not been properly air-sealed. If oversized, negative pressure in the attic can suck conditioned air from the living spaces below.
"Passive" ventilation requires no electricity, so it's inherently more energy efficient. On a cool evening after a hot day, opening top floor windows allows the hot air to rise naturally and escape. Convection, also called the stack effect, draws cooler evening air into the house through windows on lower floors. In the attic, passive ventilation can reduce summertime heat buildup in the same way. Ridge and gable vents expel the hottest air at the roof peak. Cooler air is drawn in at the soffits, lowering the overall temperature of the attic. A cooler attic results in a cooler living space in the living space below.
For more on how to control ventilation and make passive ventilation work for you, talk to your local Dr. Energy Saver. Schedule a home energy audit or free estimate by contacting us today!
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