Remember those old “tin can” phones connected with a string that we all played with as kids? “Can you hear me now” was always the question and the answer was seldom related to that question. Communication was mostly noise, and we all pretended that we understood. It’s a lot like “green” conversations that we hear so much of today. Everybody is talking a lot, but all too often the full point is missed.
From one end of the “tin can” phone line we hear, “We must make our homes tighter…” The one on the receiving end agrees, but really did not hear the rest of what was said, “… and keep proper ventilation in place.” So off we go, building these phenomenally well-insulated houses with every crack and penetration caulked and sealed, resulting in minimal utility bills from an almost air-tight envelope. But unlike play as children, what we did not understand or hear can come back to haunt us.
It is estimated that most Americans spend 90% of their lives inside a building; the majority of it is in their home. Air quality was built-in by the “old way” we assembled houses. The majority of older homes have a complete “air change” every hour or so. Excess moisture, toxic chemicals, radon, odors, pet dander, mold spores, and anything else we don’t want to breath is carried out by the “built-in” leaky construction techniques. Without proper ventilation in our “air tight” houses, all these bad things just hang around and keep circulating, growing in quantity and amplifying possible health issues.
The part of the “green conversation” we did not hear was that good ventilation is easy. Building science and the resulting codes and standards are well developed and simple to apply. One of the results of a Blower Door test is to see how much ventilation is needed. The goal is about .35 ACH (air changes per hour). That means all the air moves through a house in about three hours. In many of the homes we build today, this exchange takes 10 and up to 20 hours; great for utility bills, but bad for air quality.
ASHRAE 60.62 gives us the math, and we can solve these issues with an amazing ERV (energy recovering ventilator), affordable ENERGY STAR Certified exhaust fan or an intake fresh air fan. Each method has advantages and disadvantages. The choice is based on cost, and what the house needs.
Those who avoid these solutions are at risk of many heath issues. But, ventilation is often ignored because it is perceived as too expensive. Funny thing is that a proper ventilation system saves on utility costs also. For example, when you exhaust the humidity from the baths and kitchen with a correct fan, you make your air-conditioner’s job much easier. In our moist and humid zone 4, the main job of your AC is to remove humidity from your house. That’s right, proper ventilation can save you money. And that’s something we all can hear loud and clear.
Jim D. Baker, B & G Drafting—HERS Rater, and NAHB Verifier, LEED AP for Homes
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