Passive Solar Design Is Changing In the Face of New Technology and a Changing Climate

© Not much has changed in 65 years: Frank Lloyd Wright Does Passive Solar

Alex Wilson of BuildingGreen has been playing with renewable energy and solar design for longer than he would probably like to admit. He writes about the mid-seventies, when he learned about passive solar design:

Those were heady times. We were at the leading edge of the future of energy design. We imagined, in our youthful idealism, that within ten years all new houses would be oriented on East-West axes and rely on south-facing windows and thermal mass for heating.

Then came Ronald Reagan, who famously ripped Jimmy Carter's solar panels off the roof of the White House, and interest in green design was relegated to niche status for almost two decades.

Now that green design has expanded from niche to specialty, what's changed? For one thing, insulation. Alex writes in Environmental Building News (behind a pay-wall, it is subscriber supported) that back then:

Almost no windows exceeded R-2; walls and ceilings rarely surpassed R-15 and R-35, respectively. It's a different world today, with triple glazing, low-e coatings, and gas fills pushing center-of-glass window R-values above R-8 and insulation levels commonly reaching R-40 for walls and R-60 for ceilings—at least within the green building community.

Basically one barely needs the passive solar heating any more; heating water often uses more energy. In fact, it is really easy to overheat. Now the definition of Passive has to be expanded; Architect Ken Haggard explains:

“It’s important not to define passive design strictly on the basis of heating,” he told EBN. He considers passive design to include cooling, ventilation, and daylighting as well.

Instead of Passive Solar, Alex introduces (at least to me) the term "Suntempering", with less glazing area, which "will result in smaller temperature swings and fewer periods of overheating." The age of Frank Lloyd Wright's floor-to-ceiling glass is pretty much over, even in Wisconsin.

Alex doesn't mention another thing that has changed since the seventies: The climate. As North America goes through an incredible record breaking heat wave, anyone who has unshaded or unprotected south facing windows is going to be cooking right now or running the AC on overdrive. Glazing becomes a huge liability in weather like this and right across the country we have to think about more thermal mass, smaller openings and better shading.

Read Alex's abbreviated introduction on BuildingGreen.

Tags: Green Building | passive house | Solar Energy