Building With the Future in Mind Since 1955

Rick Dubrow’s “On The Level” Column in the Cascadia Weekly; Published 5-9-07

Twelve seconds.  That’s how long it takes to completely replace the air inside your body when you’re at rest. One inhalation and one exhalation.

But how’s the health of the very air you’re inhaling?  (Since we spend about 90% of our time indoors, I’m assuming that you’re inside a room at this moment!) How long does it take to completely replace the air enclosed by your building’s envelope? How long should it take for your building to breathe to guarantee that the air you breathe is fresh and clean?

You can generally figure that the volume of air in a typical house ought to be replaced every two or three hours in order to secure a healthy amount of fresh air.  In building science we refer to this as .33 to .5 air changes per hour (ACH).

How often your home or office breathes affects far more than your health.  If your home is too loose, thereby allowing an overflow of air movement, you’re re-heating or re-cooling this additional volume time and again, painfully affecting your spending, your planet’s health and your home’s heating/cooling equipment.

Too tight and your air stagnates.  Toxins and moisture can accumulate to unsafe levels. Molds and mildew can party. Oxygen can be depleted by combustion equipment.

Older homes tend to suffer from being too loose while new construction can tend towards too tight.

“Build ‘em tight and ventilate ‘em right’ is the psychology of the energy code.  In order to honor our planetary needs the building codes have tightened up our building envelopes, thereby relying upon mechanical ventilation to furnish the proper amount of fresh air.  Yet I’ve personally overheard heating contractors tell their clients to disconnect their seemingly complex control systems because it’s, uh, too complicated!

Too loose?  Too tight? .33 to .5 air changes per hour?  How can you tell?

Energy auditors perform simple visual inspections for about $75 to $100, but can also perform more sophisticated and expensive tests on your home, such as a blower door test, duct leakage tests and comprehensive computer energy analysis.  Costs for the complete energy analysis can typically run $300 to $400 but the payback, assuming you follow up on the auditor’s recommendations, is short lived.  The auditor literally arrives at the air changes per hour (ACH) for your home and, from there, can suggest the means to achieve the proper balance.

Thankfully, an auditor’s suggestions are often easy to accomplish.  Caulking and sealing if you’re too loose; adjusting existing equipment if you’re too tight.

You can find energy auditors by:

  • Referring to “Energy Conservation Products and Services” in the phone book
  • Go to www.natresnet.org/directory (Residential Energy Services Network)

Without knowing your home’s ACH it’s very difficult to know whether your own, personal 300 ACH, at 12 seconds per breath, are healthy air changes.

We just don’t want any 300 ACH.  We want good, clean air changes.  We want you to party instead of the molds and mildew!

“Build ‘em right and party all night!”  Wouldn’t that be quite the energy code?

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