There are 64 LEED-certified houses in Missouri, with 51 of these built by Habitat for Humanity in recent years. The director of the St. Louis office for Habitat says, “Actually, right now, we’re the largest LEED Platinum builder in the U.S. for single-family detached homes.” But within this discussion, the St. Louis director talks about why it would be difficult for larger homes to be certified as LEED Platinum:
Hunsberger said the investment for Habitat is fairly minimal. He estimates LEED adds about 5 percent to the cost of a standard home.
He said some of the organization’s costs are offset by partnerships with providers of energy-efficient products. Plus, there’s an advantage to Habitat’s houses — size. LEED applies a home-sizing ratio that makes Platinum certification easier to achieve for smaller structures.
“In essence, they don’t want McMansions,” Hunsberger said. “They don’t want 10,000-square-foot single family homes that may have two people living in them to reach LEED Platinum because it’s kind of anti what the movement is.”
This is interesting – so I did a little checking into LEED certification. According to “LEED For Homes Ratings” (a PDF file) from the US Green Building Council, the square footage of a home does factor into its ratings. There is a neutral home baseline and smaller homes have lower thresholds to reach certification levels (Certified, Silver, Gold, Platinum) while homes larger than the baseline have higher point thresholds to reach. The neutral home size is 900 square feet for 1 bedroom or less, 1,400 for 2 bedrooms, 1,900 for 3 bedrooms, 2,600 for 4 bedrooms, 2,850 for 5 bedrooms, and 250 square feet for each bedroom after this. The rationale behind this is explained on page 42 of the PDF file:
These data were simplified and generalized to the assumption that as home size doubles, energy consumption increases by roughly one-quarter and material consumption increases by roughly one-half; combined, these amount to an increase in impact of roughly one-third with each doubling in home size. Thus the point adjustment equates to one-third of the points available in the Materials & Resources and Energy & Atmosphere categories combined for each doubling in home size.
So it is not as if larger homes can’t be LEED certified but they have to meet stricter guidelines. Ultimately, I want to know whether a McMansion, say a home of 4,500 or 5,000 square feet, be LEED certified by making up for its size sufficiently elsewhere?
(I am also intrigued by this Habitat director tying the size of a McMansion to 10,000 square feet. That is not just a McMansion: it may very well be a real mansion. How exactly how large a home has to be in order to be deemed a McMansion is unclear but 10,000 square feet seems on the high end.)