Uncontrolled air movement rarely provides the optimum amount of air exchange between the indoors and the outdoors to satisfy the needs of occupants: There is either too little or too much air infiltrating and exfiltrating. Too little air can mean health problems; too much air can mean high utility bills.
We do not strictly control Google ad content. If you believe any Google ad is inappropriate, please email us directly here.
Controlled ventilation by means of a mechanical ventilation system is the only way to consistently, reliably, and predictably exchange the air in houses. With a little forethought, incorporating a mechanical ventilation system into the design of a new house is relatively easy because provisions can be made for locating the equipment, ducts, controls, etc. during the design stage. In most cases, a mechanical ventilation system can be added to any house, whether new or existing, to provide the occupants with better comfort and air quality.
Exhaust ventilation systems
An exhaust ventilation system utilizes a fan to blow air out of a house solely for the purpose of ventilating. If there are no other pressures acting on the house, this results in an equal volume of air passively infiltrating wherever it can to make up for the air being exhausted. During this process, a house can become uniformly depressurized. The air that infiltrates into a depressurized house is often called make-up air because it makes up for what was exhausted.
Central exhaust ventilation removes low concentrations of pollutants that may be generated throughout the house. This can be done using a high-quality, energy-efficient, quiet exhaust fan designed to run for extended periods such as an inline fan. Keep in mind that the make-up air that infiltrates from the outside will also be the same temperature as the outside. Sometimes homeowner activities such as showering or cooking call for a “burst” of exhaust action. A bathroom exhaust fan or kitchen range hood are examples of products that can act as local exhaust systems, intermittently removing high concentrations of contaminants from specific locations quickly.
Heat recovery ventilation
Heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs) provide ventilation in a controlled, energy-efficient manner, bringing in air that is comfortable. During operation, both the incoming and the outgoing airstreams pass through the core. While the airstreams don’t mix or contaminate each other, the design of the core allows heat to pass from the warmer airstream into the cooler airstream. In the winter, the heat in the warm exhaust air is transferred to the cold incoming air. “Cool” is similarly transferred in the summer in air-conditioning climates.
Some people mistakenly believe that HRVs and ERVs produce heat. They don’t; they simply conserve some of the heat that would otherwise be lost during the process of ventilating. Therefore, they aren’t a substitute for a furnace. Their only purpose is to ventilate. Both systems transfer heat between the incoming and outgoing airstreams, while the ERV also retains some of the humidity from the indoor air to make it more comfortable in dry climates.
The bottom line
Natural and accidental pressures rarely supply the occupants of a house with the correct amount of fresh air. The quantity of air is either too small to be of much benefit, or so large that heating or cooling bills are exorbitant. Proper installation and use of mechanical ventilation products certified by the Home Ventilating Institute (HVI) in a tight house is the best solution. It is the only way to be sure that you have the optimum amount of air exchange at all times. The mechanical system also has the significant advantage of supplying air to and exhausting air from the right parts of the house. Fresh, clean air can be supplied to the living spaces, and stale air exhausted from the bathrooms, laundry and kitchen. Be sure to look for HVI-Certified products, which means the products purchased are in compliance with industry codes and standards.
Adapted from: Understanding Ventilation: How to design, select, and install residential ventilation systems by John Bower © 2010 The Home Ventilating Institute (HVI).
The Healthy House Institute (HHI), a for-profit educational LLC, provides the information on HealthyHouseInstitute.com as a free service to the public. The intent is to disseminate accurate, verified and science-based information on creating healthy home environments.
While an effort is made to ensure the quality of the content and credibility of sources listed on this site, HHI provides no warranty - expressed or implied - and assumes no legal liability for the accuracy, completeness, or usefulness of any information, product or process disclosed on or in conjunction with the site. The views and opinions of the authors or originators expressed herein do not necessarily state or reflect those of HHI: its principals, executives, Board members, advisors or affiliates.
