Energy Vanguard Blog

I've written a couple of articles recently about the complexities of mechanical ventilation and the battles going on regarding when to install it, how much to ventilate, and whether ASHRAE 62.2 is worth all the resources we're throwing at it. (If you missed the debate between Michael Blasnik and Joe Lstiburek in the comments of the last one, you should go read it. It was the Building Science Super Bowl this weekend.) Those articles were aimed at pros in the building science/green building/home performance field. Today, it's time to step back and remember why we're even talking about ventilation.

With the help of people who know a lot more than I do, I'm slowly getting this stuff figured out. I wrote about my problems with using ACHnat a while back, and when I posted that article at Green Building Advisor (GBA) recently, Stuart Staniford wrote one of those comments that left me thinking, Dang, I should have known that.

I went to school with Cajuns in south Louisiana, and fights were a big deal. They happened frequently, and when they did, a small crowd would gather. The noise would grow quickly and soon everyone in the schoolyard would run over to where the fight was happening. One day in sixth grade, we exploited this tendency and staged a fight between two shoes at recess. Sure enough — our tight circle of boys banging two shoes on the ground and making a lot of noise brought the whole school to us.

You'd never settle for a recirculating toilet, would you? Press the lever and everything in the bowl just swirls around and around. Never leaving, just recirculating. That's the image Professor John Straube painted for us last week in his talk at the Building Science Experts' Session. He was discussing range hoods and indoor air quality (IAQ).

One talk at the 2012 Building Science Summer Camp stood out above all the others. The last speaker on Tuesday was Henry Gifford. (Yes, that Henry Gifford!) When he was done, the majority of the audience stood and applauded. The next morning, camp counselor Joe Lstiburek told us there have been four standing ovations at Summer Camp. Henry Gifford has gotten two of them.

We want our homes to be airtight. It saves energy. It helps keep water vapor from getting into places where it can cause problems. It keeps bad air from moldy crawl spaces and contaminated garages out of the house. It just makes sense. Tight homes, though, need a way to replace stale indoor air with outside air. That's the role of a mechanical ventilation system. Of the three types of mechanical ventilation systems, home builders in the Southeast have latched onto one that has a number of problems: the positive pressure system. (The other types are negative pressure and balanced.)

I've spent a lot of time in attics looking at problems with insulation, air sealing, HVAC systems, and ductwork. I've also seen why so many bathroom ventilation fans don't move much air. A typical bath fan is rated to move 50 cubic feet per minute of air when it's operating, but most actually move about half of their rated air flow. Here are 5 reasons why this happens.

Guest Post. Today's article is a guest post by Paul Raymer, one of the top guys I know on the topic of getting fresh air into homes.

Trade shows can be both educational and infuriating, and there’s one product I see at a lot of trade shows that fits easily into the latter category - power attic ventilators. The variety of this device that’s been popular lately is the solar-powered attic ventilator. Using the Sun to make the electricity for this fan, however, makes it only marginally better than its grid-powered cousin.

There's been a lively discussion going on in the RESNET/BPI group on LinkedIn. I posted my article about how infiltration occurs at the surface, not in the volume, and it's generated some good comments. In that article, I said we need to stop talking about infiltration rates in terms of air changes per hour because there are too many problems with it.