Have you heard that a house needs to ‘breathe’ in order to avoid problems with indoor air quality (IAQ)? You may wonder if this is a good reason to not seal uncontrolled air leaks in your home’s structure. It is true that a house needs an exchange between indoor and outdoor air - but not at the expense of your budget, your comfort or your home’s durability! You can seal (or build) tight and ventilate right.
What’s the problem?
Most houses built in the mid 70’s and newer require ventilation. Even a leaky house can require mechanical ventilation because the fresh air for the home is coming in from the basement, crawlspace or garage and the stale, moist air escapes to the attic causing ice dams, mold or rot. This “natural ventilation” is not effective.
If a home is under-ventilated IAQ problems can arise:
- Mold & mildew
- Condensation on windows
- Lingering odors
- Allergies and asthma
- Accumulation of CO from stove, fireplace, etc.
- Chemical fumes from materials such as carpets, cabinets etc.
- Basic comfort issues
If any of these sound familiar, your home might be in need of mechanical ventilation.
Solving the Problem
A well-sealed healthy home needs two types of mechanical ventilation - Point Source and Whole House:
Point Source Ventilation
Bath and kitchen fans target moisture and air pollutants at their source and vent them from the home. They need to be powerful enough for the space and vented directly to the outside.
Whole House Ventilation
There are two options for providing continuous fresh air for the rest of the home:
1. A Continuous Run Exhaust Fan is the cheapest and easiest option for most existing homes, especially if they don’t have ductwork or a forced-air furnace/AC. However this type of ventilation can cause an imbalance between indoor and outdoor air pressure possibly resulting in safety issues with radon gas or combustion appliances such as water heaters. (Read more link)
2. More expensive Air-to-Air Exchangers vent indoor air and bring in filtered outdoor air thus maintaining a pressure balance and avoiding safety issues. They also can regulate humidity and reduce radon. There are two types: Heat Recover Ventilator (HRV), or Energy Recover Ventilator (ERV). (Read more link?)
How do you know if your home is under-ventilated? A Certified Energy Professional can test how much ventilation your home is getting and how much more it needs – both Point Source and Whole House. There are guidelines for calculating ventilation rates using national standards developed by ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) based on the home’s size and leakiness, number of occupants and existing ventilation.
The Energy Pro will work with you to determine specific problems and goals, and then provide prioritized recommendations Of course he can also assess your home for sealable air leaks, and return after ventilation is installed to be sure changes in the system result in a healthy and safe home.
- Learn more about energy audits and hiring certified energy professionals
- Find a certified energy professional
- Hire the appropriate professional(s) as recommended in the Scope of Work.
- Review additional resources to build your confidence:
- Read, Most Important Step
- Video - Indoor Air Quality - Improving Your Home's Performance
- Air sealing
- Moisture and mold
- Why air sealing and adding ventilation make sense
- EPA- Think about indoor air quality when remodeling
- Home Owners Guide to Ventilation - by New York State Energy Research & Development Authority (NYSERDA)
- ERV or HRV in cold climate. Serious research by the Cold Climate Housing Research Center
- ERV's and HRV's. More information from Building Science Corporation
- More Than A Beautiful Home www.morebeautifulhome.com