How Should We Really Measure Green Building?


"One of the greenest homes ever built"

Katherine Salant writes in the Washington Post:

Can a big house be green? Yes, but a smaller house will always be greener because fewer resources were used in its construction and less energy is needed to heat and cool it.

It is certainly a point we have been discussing on TreeHugger for years, and it is great to see it in the Post, even if we would have answered no to the question. But it also raises another important question: how do you measure green, and how do we determine our fossil fuel footprint?


Energy Star: A Relative Measure

Most rating systems measure relative performance. They define it:

To earn the ENERGY STAR, a home must meet strict guidelines for energy efficiency set by the U.S. Environmental Protection Agency. These homes are at least 15% more energy efficient than homes built to the 2004 International Residential Code (IRC), and include additional energy-saving features that typically make them 20-30% more efficient than standard homes.

But it could be any size; any McMansion or Monster can be Energy Star. And there is no dsiscussion at all of how it is made, what the embodied energy of its materials are. It's just energy consumption.


LEED for homes has an adjustment for house size; you lose points for being bigger and gain them for being smaller. So the bigger the house is, the more you have to compensate in other ways to make up the points. According to Building Green, The National Green Building Standard awards points to all houses smaller than 2,500 ft2 (230 m2), regardless of the number of bedrooms, and penalizes homes over 4,000 ft2 (370 m2).

But with both systems, building size is only one of many components.


Lumber in driveway
Measuring Energy and Materials Per Occupant
The Washington Post article offers another way of thinking about the issue.
Michael Horowitz of Sustainable Solutions, a Vermont green builder, suggests:

A better way to rate houses -- and one that would illuminate the gross differences in material and energy consumption between large and small houses -- would include occupancy in the formula, Horowitz said. He proposes a scoring system that rates the greenness of a house by the amount of material and energy used per occupant, which is assumed to be the number of bedrooms plus one.

Graphically describing what this might look like, Horowitz compared his own modestly sized, 1,800-square-foot, three- bedroom house with four occupants with another home that is three times as big, carrying a higher green rating and housing the same number of occupants. "First," he said, "divide all the materials used to build my house into four piles in my driveway and then added a visual to each pile that would show how much energy each of us used per year. The size of the piles would be impressive. But when you do the same thing for the bigger house, the size of its four piles would dwarf mine."

It is an interesting idea. Last year Horowitz had a debate in Green Building Advisors with Kim Calomino from Colorado, where they build a lot of so-called "green" big houses. She said:

When I hear the question, "Can large homes be green?," I think the questioner is really asking, "Is it right for some people use more resources -- live in big homes -- when they could live in smaller homes like the rest of us?" That question is not really about green building; it's more about moral or social equity, and I don't think the green building movement should dilute its focus by debating the issue.

No, it is not about moral or social equity, it is about consuming less energy. As houses grow they consume proportionately more; the ceiling shouldn't be on area but on consumption.


Avid Home Studios
Although they have dropped a bit in the recession, the average house size is a lot bigger than is used to be.
Make Efficiency Absolute, not Relative

Three years ago I made a proposal for a rating system that addresses both issues: Make the energy efficiency of a building absolute rather than relative. What if instead, one took the energy consumption of the average, say 1800 square foot house built to code, and said that's all you get. So if you want to built 3600 square feet you have to use twice as much insulation and be twice as efficient. To build 7200 square feet you are into Passivhaus territory.

Kim could build her Colorado mansions as big as she wanted, as long as they didn't use any more energy than the base1800 square footer. Not at all impossible.

But it is still a problem, for my approach actually increases the embodied energy of the house from the extra materials needed to insulate it. Horowitz's pile of building materials in the driveway just got even bigger.


Embodied Energy

Another issue that none of the current standards take into account is how much energy it took to make the building materials, the carbon footprint of each. So a house built of insulated concrete forms will have wonderfully low operating costs, but starts off with an embodied carbon footprint that will take years to pay off.


21 Nottingham St. Guelph; 150 years old and still going strong
Durability

As I noted in The 50 Year Toaster vs the Five Dollar Toaster, the flip side of embodied energy is durability; you almost have to divide the embodied energy by the projected life of the building to calculate the embodied energy debt used up each year. So perhaps those insulated concrete form houses that I complain about so much come off better in a complete calculation because they will last a long time.


Abogo

Transportation Efficiency trumps Building Efficiency

Furthermore, none of the rating systems take transportation energy intensity into account; the big Colorado house is on an estate lot and probably has an SUV in front of it. There's a new sort of walkscore for transportation costs and carbon footprint out called Abogo, that "lets you discover how transportation impacts the affordability and sustainability of where you live." Perhaps an Abogo score should be a major part of the green rating system, so that it becomes almost impossible to get your green McMansion in the middle of nowhere.

Because in the end, the transportation efficiency is a far bigger indicator of how much fossil fuel we are using in our lives. A green building standard that doesn't take it into account is ignoring the single most important thing that we have to do to get off oil, and that is to get out of our cars.

Personal Cap and Trade?

A logical extension of the absolute energy consumption concept combined with the issue of transportation efficiency is a sort of carbon ration. One commenter on my earlier post on absolute vs relative suggested a sort of personal cap and trade:

Why not give every household a yearly energy budget that includes all energy use? Want to drive a Hummer? No problem- better have a super efficient house with photovoltaics. Want a 6,000 SF mansion? Better start riding your bike to work.

People should be able to buy and sell energy credits as well. That way a low income family living in a one bedroom apartment with no car can earn some extra money selling energy credits to the wealthy.

That may be going too far, but there is no question that a real green building standard should take into account the Energy Efficiency + Building Area + (Embodied Energy / Durability) + Transportation Efficiency. That's a green building standard that would mean something.

More in our Minus Oil Series:
Is the Electrification of Transportation a Good Thing? (Part 2)
If You Really Want To Get Off Oil, Move To Buffalo
Minus Oil:Three Ways Technology Can Curb Our Consumption
How Can Technology Reduce Global Shipping's Fuel Consumption?
Stop Eating Fossil Fuels, Start Eating Food
How Can We Detox Our Cars From Their Oil Addiction? (Part 1)
How Can We Reduce Oil Consumption & Still Ship Goods and Ourselves Around the Globe?
Do We Really All Have To Live Like New Yorkers? Does Density Matter?
My Other Car Is A Bright Green City: A Second Look
Setting a Price on Carbon Will Help US End Oil Addiction - Not Just Combat Climate Change
Minus Oil: Forget Hybrids And Solar Panels, We Need Active, Exciting and Vibrant Cities

Tags: Energy Efficiency | Energy Star | Green Building | longreads | Minus Oil | Oil

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