In 2010, I’m taking a room-by-room approach to green building. My columns will examine specific rooms and how to make them as green as possible. To begin, I’m compelled to address the largest “room” in a home, and that’s the building shell itself.

Way beyond VOCs, recycled content and driving hybrids, by far the greenest thing you can do is design a high-integrity thermal envelope so your structure consumes as little fuel as possible for heating and cooling. This kind of “at-scale” application of green principles really makes a difference. All the recycled coffee mugs, reusable grocery bags and other recycling contribute positively to the green effort and I don’t want to diminish that. However, the benefits of someone recycling, say, a ton of old magazines is environmentally negated hundreds of times over if the structure is bleeding heat/cold, guzzling fuel and pumping out CO2.

Greening of the building shell should improve the thermal performance of the building using materials that: A) are nontoxic/low-toxicity; B) are harvested and/or manufactured in a sustainable way, and; C) don’t consume a great deal of fuel when shipped. Let’s take a category-by-category look at the principles driving your options, starting at the top.

Roof. Reflective or even light-colored roofs lower cooling loads, sometimes dramatically. (Black shingles reflect about 5 percent of the sun’s heat; gray shingles 20 percent, and white shingles 25 percent.) Look for an Energy Star roof, which meet baseline reflective qualities. Note: They are not all metal. Some three-tab products are Energy Star-rated, which feature reflective granules that turn back sunlight. MIT is experimenting with roof panels that change color with temperature to match reflectivity to conditions (http://web.mit.edu/newsoffice/2009/madmec-roof.html). When sheathing, note that radiant barriers or insulated sheathing are key to any good system.

Certified wood. For framing and sheathing, use certified lumber. Frankly, it’s difficult to purchase lumber in North America that isn’t sustainably harvested. For political reasons, USGBC’s LEED standard accepts only FSC certified lumber, while ignoring other good standards. But NAHB’s National Green Building Standard recognizes both FSC and SFI. Nonetheless, look for a label and learn its background.