Here at the Clark household we recently had a debate about running the kitchen exhaust fan while cooking. Chef Haley (my wife) hates the sound of the fan so she prefers not to run it. But the smell of the gas range burning has me concerned about carbon monoxide poisoning.We have a carbon monoxide (CO) alarm that never goes off, so you might ask why I’m concerned. Here’s why: The CO alarm was not good enough quality for me to be 100 percent satisfied we weren’t getting low-level CO exposure. CO alarms only detect sudden and deadly levels of CO, not low and ongoing levels that create significant health risks in a home.

Many of our construction techniques have evolved by necessity due to how we live in our buildings. A great example of this is that 150 years ago in the warm South we started building elevated homes. This kept the house cool by allowing air to move underneath. We also began using high ceilings to allow the hotter air indoors to rise above the living space and constructed big wrap-around porches to shade the windows and keep direct sunlight out. All these changes helped create the Southern-style home most of us know and love.

Home energy efficiency is problematic when you have a ventilated crawlspace. Cold air blows in from the crawlspace and hot air rises, leaking through all your attic penetrations. Your home becomes a virtual chimney and loses all your precious conditioned air through the attic leaks. This means your heating and cooling systems have to run harder to keep up. At the same time, contaminated air from the crawlspace are circulated in your actual living space.

There is a catchy phrase right now that is growing in popularity among top builders: “Build it tight and vent it right!” We really need to change the conventional wisdom of ventilating houses. Vented crawlspaces are a very bad thing. Most good builders have switched to sealed, insulated, conditioned crawls…but that is just the beginning.When it comes to home construction, there really is no such thing as too tight. We want our homes to be airtight, then we bring in the right amount of fresh air through intentional ventilation rather than unintentional infiltration (air coming in through uncontrolled places like leaks in the crawlspace). We also want to control exhaust ventilation such as bath fans, range vents, and other exhaust when needed (i.e., radon control fans). The incoming fresh air and the outgoing exhaust air should be balanced.

If you have read anything I have ever written, you know by now that I preach about the “domino effect” that’s created when we make one upgrade to a home without accounting for how it affects other systems. Case in point: I recently visited a client in the Lexington area who said they had a case of “sick house syndrome,” meaning their house was making them sick. They would travel away for a few days and feel better, but immediately upon return, symptoms would reappear. There was also an off-putting odor in their home that they could not eliminate or identify that was making everyday living unpleasant.

Radon is a radioactive gas that leaks out of the ground. Outside, radon is found in such small concentrations that the air outside is able to dilute it enough so it becomes harmless. In our homes, however, radon gas can become trapped and build up to levels that can harm our lungs.

Sophomoric humor aside, houses that “breathe” through air leaks really do suck — they suck air from all the wrong places. We call this uncontrolled or unintentional ventilation, also known as infiltration.