I’ll be the first to admit that the basic building science details of a solidly built home aren’t quite as sexy as green features like bamboo floors and solar PV panels. Even so, we need to get away from the idea that a green home is just about the products. While new green products are great, they’re only “lipstick on a pig” if the home isn’t also energy efficient, built to last, healthy, safe, and affordable to maintain. Unfortunately, in my work with companies across the country, I see far too many “green” builders missing the mark. So, with a nod to David Letterman and his lists, I bring you my first “Top Five Mistakes” ranking in the hope of helping you avoid them and remind you to make these fundamentals the core of your green building efforts.

No. 5: HVAC Ducts Installed in Unconditioned Space

Where is the hottest place in your house on an 85-degree summer day? Where is the coldest place in your house on a frigid January night? In both cases, it’s the attic. So, if you were deciding where to locate a forced-air heating and cooling system, what’s just about the worst place you could put it? It’s obvious: Don’t put your HVAC system in an unconditioned attic.

What’s a better location? Put the ducts between the floors or in dropped soffits inside conditioned areas of the house. That way the conditioned air always travels through ducts at room temperature. Some builders are conditioning the attic by placing insulation near the roof deck rather than at the ceiling. This brings attic temperatures much closer to those inside the house, but it does add an additional energy load to the home. It’s a step in the right direction, which is getting HVAC systems located inside the living space of the home.