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Ventilation and Indoor Air Quality

According to the latest research, indoor air quality is considerably worse than outdoor air quality. It's critical to frequently remove polluted air and introduce fresh air to achieve and maintain healthy indoor air in a home.

Talking about an indoor air quality, we should take into account that there are a lot of sources of pollution: pets; off-gassing of building materials such as cabinets, carpeting and adhesives; everyday activities such as cooking and bathing; and remodeling projects such as sanding, painting and furniture refinishing. Outdoor pollutants near the home and pollution moving through the HVAC system can cause indoor concentration of bacteria, mold spores, pollen and dust. In hot climates, inside and outside humidity levels can even cause mildew or excessive condensation problems.

Airtight homes, nevertheless energy-efficient, tend to have poor indoor air quality because polluted air doesn't escape and fresh air isn't introduced.

There are some basic ventilation options for improving indoor air:

  • Don’t forget to open doors and windows
  • Operate attic fans, window fans or window air conditioners with the vent control open.
  • Install and operate kitchen and bathroom exhaust fans that vent outdoors (often required by code).
  • Install semi controlled ventilation.

Advanced Ventilation Options

Apparently the most useful and effective type of ventilation for a home is a mechanical, ducted, whole-house system that provides a steady supply of fresh, filtered, conditioned air from the outside while exhausting stale interior air. The pressure within the home remains balanced, which helps prevent backdrafting of combustion appliances because of the same amount of air is drawn into the home is exhausted. Mechanical ventilation systems can mechanically sustain 0.35 air changes per hour, the rate mostly recommended to maintain good air quality. A huge amount of sizes and configurations of mechanical ventilation are available. The most reliable system includes filtering, preconditioning and booster fans.

Here's a look at each feature:

  • Filtering. As it enters the system, fresh air passes through filters . It helps to control dirt that would unfortunately recirculate through the home. In other circumstances, homeowners need to clean or replace filters periodically.
  • Preconditioning. A heat recovery ventilator (HRV) uses heat exchangers to recapture 60% - 80% of the conditioned temperatures from the outgoing air to heat or cool incoming fresh air. Allowing conditioned exhaust air to raise or lower the temperature of incoming fresh air without contaminating it, the incoming and outgoing airflows pass through different sides of the unit but are not mixed. In climates with extreme distinctions between indoor and outdoor humidity, energy-recovery ventilators (ERVs) are recommended over HRVs because additionally ERVs exchange moisture between the two airstreams to control humidity. In hot, humid climates, ERVs are critical for drying out incoming fresh air; in cold, heating-dominated climates, ERVs can help hold in what little humidity may be indoors to control wintertime window condensation.
  • Booster fans. Small, severally switched booster fans can be located in bathrooms and kitchens to control moisture or heat generated by showering and cooking. While the energy used to condition the air is recovered through the HRV/ERV, odors and pollutants are quickly removed. There are several codes, which may still require stoves to be separately vented to remove grease or gas fumes.
    The biggest drawback to installing mechanical ventilation is the higher upfront cost to homeowners. In addition, homeowners must consider the complementary mechanical complexities of the systems, and be responsible for maintenance, especially in systems with filters.