Concentration of CO2 in the Atmosphere

How Safe Is Your Indoor Air?

Barbara and Greg Whitchurch

Indoor Air Quality (IAQ) refers to the quality of the air within buildings, especially as it relates to the health and comfort of the occupants. A home that’s healthful for the occupants has the proper moisture level, is pest-free, contaminate-free, and well-ventilated with filtered outside air.

Health effects of formaldehyde. Image:

IAQ is affected by building design, construction practices, materials, and by the furnishings and finishes; also by having a tight building envelope that keeps undesirable outside pollutants out of the building, such as mold, pollen, and smoke. All this is consistent with what we now know about energy efficient building practices: a tight, well-insulated building gives one control over the quality of the inside air, while leaky, “breathing” buildings are at the mercy of outdoor pollution, wind, and temperature swings.

In the past, we relied on air leakage to ventilate homes. The old myth saying “a house has to breathe,” has been debunked. Improved construction methods achieve airtightness with continuous vapor and air barriers and airtight windows.

One common problem is formaldehyde (, a chemical that is used in pressed wood products, plywood, paneling, foam insulation, carpets, drapery, glues, and gas ranges – even paper towels, dryer sheets, and baby wipes.

To cut down on formaldehyde in your home, avoid the products that contain it. But what if they’re part of the building itself? Certain plants (e.g. ) and materials (e.g. can assist in scrubbing specific pollutants out of indoor air. But once the toxin is in that air, the simplest answer is ventilation.

Why ventilate?

Ventilating a building brings in air with the oxygen we need to live. As we breathe, the oxygen is replaced with carbon dioxide (CO2). Without proper ventilation, oxygen levels in your building can be reduced and cause headaches, fatigue and concentration difficulties.

Front panel display of CERV showing temperature, humidity and indoor contaminant level. Image: Build Equinox.

Ventilation controls humidity. Human activity creates humidity (breathing, taking baths or showers, cooking, laundry). A family of four can release about five gallons of water vapor into their home each day. Excess moisture can cause odors, oxidation (e.g., rust), mold, rotting and condensation. And, in cold climates, the typically very low humidity in winter causes reduced resistance to colds and flu. Proper ventilation can keep the humidity levels from dropping too low.

Ventilation is important to eliminate pollutants. Smoke, paints, solvent and glue fumes, pollen and mold spores are all pollutants that increase the risk of contracting respiratory allergies, rhinitis, asthma, and bronchitis. Ventilation reduces the risk of exposure to radon gas, considered the second leading cause of lung cancer – after tobacco smoke.

The simplest ventilation technique is to open your windows. Obviously, this is hardly any better than depending upon air leakage from the construction materials and methods of older buildings. In most homes, the leaky places where air comes in are where bugs and vermin travel, hide food, die, and deposit their wastes and dander.

Addressing leaky houses, Allison Bailes III, PhD, of Energy Vanguard says, “Probably the most common type of whole-house mechanical ventilation system in homes is an exhaust-only system. The problem is, this type of system sucks. Literally. And if your house is sucking from an attached garage, a moldy crawl space, or dirty attic, you could be making things worse. The way to avoid having a house that sucks is to do balanced ventilation (

Balanced ventilation with a heat or energy recovery ventilator (HRV or ERV)

These devices push stale air outside and bring fresh filtered air inside while saving most of the thermal energy (heat or coolness) already invested. The HRV just saves temperature; the ERV also saves the moisture difference. If you wish to go beyond the ERV by including a small heat pump for heating and cooling, consider the Conditioning ERV (CERV or the Minotair ( — both devices can also control other heat pumps throughout the home.

The CERV shows a continual readout of parts per million (ppm) of CO2 and ppm VOCs throughout the day – the tolerance levels for those pollutants can be adjusted by the homeowner. It is used in Efficiency Vermont-related projects ( We have a CERV in our own award-winning Passive House (

The U.S. EPA ( and Efficiency VT ( provide information and links to research regarding IAQ effects on cognitive function, quality of sleep, and frequency of employment sick leave.

Superior indoor air quality is one of the many benefits of a high performance home. But even if you have an older home, you can still improve your IAQ, perhaps while you improve its energy efficiency; for help, contact Efficiency VT

Barb and Greg Whitchurch own a net-zero Passive House in Middlesex, Vermont.

Learn more at

Leave a Reply

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>