For the healthiest indoor air quality, choose the right ventilation strategy

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For home builders and contractors seeking to deliver healthy homes, installing powerful ventilation that assures good indoor air quality (IAQ) and energy efficiency is a must. In fact, at a recent IAQ conference for the building trade, many of the nation’s leading green builders ranked the indoor air we breathe as important to our health as the food we eat.

Stale, dirty indoor air from moisture and other pollutants can cause a home to become unhealthy and even toxic. A properly-ventilated home offers the many health benefits of improved indoor air quality and energy savings.

“New homes today are very energy efficient, which requires them to be built nearly airtight,” says Panasonic BPI Certified Building Analyst, Ken Nelson. “That’s great news for your utility bill, but not so great for the quality of air you’re breathing inside your home. The lack of natural ventilation can trap all kinds of toxins inside.”

Exhaust, supply or balanced ventilation. Which is better?

Enter mechanical ventilation into the building equation, which draws out pollutants and draws in make-up air in a controlled manner. But an effective IAQ solution requires more than installing a single exhaust fan in the bathroom. There are three primary strategies for controlled ventilation: exhaust, supply, and balanced systems. Let’s look at the nuts and bolts of each…

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Healthy homebuilding goals

The majority of builders today strive to create healthy, energy-efficient homes where families can breathe clean air and live comfortable, eco-friendly lives.

Exhaust-only ventilation

Exhaust ventilation removes pollutants at the source. An inexpensive and simple approach to ventilating a house, it works by drawing up and forcing air out of the home. A common example would be an exhaust fan in a bathroom or kitchen. Exhaust fans depressurize the home’s interior, which then gains make-up air through passive vents such as air leaks in the building envelope.

Because this strategy only actively exhausts air, it is not recommended in hot or humid climates. Since any make-up air is gained passively, that air may be humid, contain pollutants or be too cold, leading to energy penalties for the home and discomfort for its occupants.

Supply-only ventilation

Supply ventilation dilutes pollutants. Another simple and inexpensive approach, this strategy uses a supply fan to pressurize a home, actively bringing fresh outdoor air inside while squeezing out stale indoor air. Supply systems offer better control over pollutants present in incoming air, as they only obtain outdoor air through specified vents. Pressurizing the house more readily forces out combustion gases and other contaminants.

The downside? Supply systems struggle with conditioning or removing moisture from incoming air, and can raise heating and cooling costs due to leakage. This is particularly prevalent in older homes where building envelopes are more porous compared to today’s tighter sealed energy efficient structures.

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Guard against bad air & promote healthy living

Neglect from insufficient ventilation can stimulate dangerous indoor air pollutants and serious illness such as:
• Toxic molds
• Formaldehyde
• Carbon Monoxide
• Eye irritation
• Dizziness & nausea
• Coughing & wheezing
• Asthma & other respiratory issues
• Liver & kidney damage
Source: Introduction to Indoor Air Quality, www.epa.gov

A balanced ventilation approach

Indoor environmental professionals and air quality experts generally agree that a balanced ventilation strategy is best. Balanced ventilation works by both actively exhausting polluted indoor air and actively drawing in fresh, outdoor air in a balanced, controlled ratio. Because a balanced system uses more fans and ducts than either the supply or exhaust approaches, the price tag is higher. However, balanced ventilation is appropriate for all climate zones and will deliver the best indoor air quality.

By coupling a balanced approach with an energy recovery or heat recovery ventilator (ERV or HRV), incoming air can be conditioned and dehumidified, saving on heating and cooling expenses for the home, while simultaneously improving indoor air quality.

Contrary to popular belief, all ventilation fans do not perform the same. Testing by Lawrence Berkeley National Laboratory shows nearly half of all installed vent fans fail the required airflow standards outlined in ASHRAE 62.2.

Proper ventilation for today’s healthy home

Mechanical ventilation can take the benefits of a healthy home one step further by providing a controlled source of treated fresh air that balances indoor air quality with energy savings. This is more prevalent in today’s newer, tightly-built energy efficient homes. Your new home may look beautiful from the outside, but without a proper ventilation system installed by a professional HVAC contractor, invisible dangers lurk inside.