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Ventilation for Designing Better Buildings

What is Balanced Ventilation?

Posted by Dustin DeTorres

Oct 28, 2015 2:23:00 PM

The air in a tightly sealed home can be up to 10 times more polluted than outdoor air. While a tight building envelope is important for energy conservation, ventilation is very important for filtering out the polluted air and infusing the home with fresh, unpolluted air. Unfortunately, systems that rely on exhaust-only or supply-only ventilation can throw off the pressure in a home and have limited ability to filter the air. A balanced ventilation system is much better at filtering pollutants out of the air and maintaining pressure.

How Does a Balanced Ventilation System Work?

A balanced ventilation system introduces fresh outdoor air into a home at the same rate that stale indoor air is exhausted from the home. If a balanced ventilation system is designed and installed properly, it neither pressurizes nor depressurizes the home. This allows the mechanical ventilation to control the flow of air within the home, rather than relying on natural ventilation to move air-and pollutants.

Keeping Ventilation and Temperature Control Separate

While some homeowners utilize existing heating and cooling ducts for ventilation systems, this approach can affect the balance of a ventilation system. When a ventilation system is set up to be balanced when an air handler is off, turning the air handler on can unbalance the system and cause supply air volume to increase. The reverse can be true if the system is set up to balanced when the air handler is on. Both issues can alter the pressure in the home and cause outside pollutants to be sucked into the home.

To maintain proper pressure balances and optimize both ventilation and temperature control, ventilation and air handling systems should be separated and use different duct systems.

Ventilation Energy Loss

One unfortunate part about most balanced ventilation systems is that they allow cooled or heated air to escape at a higher rate than usual while bringing in new air to heat or cool in order to maintain comfort. To mitigate this issue, an ERV or HRV can be purchased and installed. Whether an ERV or HRV would be best suited to preventing energy loss depends upon the climate in which the home is located. ERVs and HRVs allow heat to be transferred from incoming to outgoing air or vice versa in order to maintain temperature (and sometimes humidity levels) effectively.

Installing a Balanced Ventilation System

Balanced ventilation systems are often installed in attics, though the placement may vary based on the home design. A single exhaust point and a single supply point are part of the main unit.

Air that is piped into the home at the supply point is distributed to designated areas using ducts. Air is exhausted from differing designated areas in the home using a different set of ducts and is ultimately expelled through the main exhaust point. The ventilation unit and the ducts are strategically placed so that moist air is removed from rooms like the kitchen and bathrooms and fresh air is filtered into rooms that are often closed off, like bedrooms.

Topics: Heat Recovery Ventilators