I have seen a lot of these “Your Speed” Police displays around the Twin Cities lately, and while I think that they are a good idea, I feel that we are in desperate need of displays that tell us what our “environmental speed” is. 

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Now I know, some people think that we are scolding people by showing them how much gas their vehicle burns or how much CO2 comes out of the tail pipe. Nevertheless, how is one to conserve if he or she has no comparison, no number that tells him or her what a “good” number is and how to get to it.

For vehicles, I propose to start with a gallon per mile rating system. This captures the idea of consumption much better than miles per gallon, which sounds more like an achievement. I wonder what marketing genius ever came up with that ;).

Once we establish those numbers, we can look at buildings and compare their energy use in a similar way—gallons per square foot for example. The Germans are already doing that. First, there was the 3-liter-car (3 liters of fuel per 100 kilometers) and now there is the 3, or even the 2-liter-house (2 liters of fuel equivalent energy per square meter and year). The good news here is that the Passive House comes in at about 1.1 liters. Converted to gallons per square foot, that equals about 0.03—not an easy number to remember. How about a half a cup per square foot? Any cooks out there to verify my math?

What does this mean for an average home in urban Minneapolis?

Now, just as a comparison—my own house, which is a remodeled 1927 2X4 stud-framed building with roughly 2,400 square feet of living space (including a finished basement and low-ceiling half story). The walls are filled with cellulose insulation, the roof is also 2×4, furred down to 2×6 and filled with batt and reflectix insulation. The basement is insulated with EPS foam on the inside. All-in-all a fairly average case for urban Minneapolis I would say. I tracked gas usage for 6 years and averaged 44,500 BTUs per square foot and year, not including energy for cooling. Just for comparison: Passive House standard allows for a maximum of 4,750BTU per square foot and year for space conditioning energy. So in comparison, my house would be the perfect example where a Passive House in its place would use 90%+ less space conditioning energy. This fact aside, the “gas-mileage” of my house breaks down to about 0.36 gallons per square foot and year (Remember, Passive House is at about 0.03 or a half cup). Over the course of a year this equalsthe energy of well over 850 gallons of fuel. The average American uses 500 gallons of fuel per year for transportation according to the Department of Energy. I think if we tweak this a little bit we can come up with meaningful numbers that make the performance more transparent to the user or owner. I believe this would be a useful first step in visualizing environmental impact. This of course only looks at performance in regards to operation, not the environmental impact of construction or demolition, which technically should be figured into the equation as well. I think, for arguments sake, we can agree that the energy used to construct, remodel, or demolish a building will add significantly to the operational energy use, so if anything, the building gas mileage will go down from where we started in this exercise.

Big picture please!

There are two things that I find important here. First of all, conservation is a huge resource that I feel needs to be tapped into. I should mention that when I purchased my home it was not insulated and consumed roughly 40% more natural gas yet! On the road to a Passive House there are many stops worth considering that can make a building better and cut consumption—all of them are better than doing nothing.

Secondly, I believe that the comparison with the MPGs (or better GPM, gallons per mile) in a car can help us visualize impact of buildings. We are so used to gas mileage since it gets so much media coverage these days. I think a discussion is needed that puts that much emphasis on the gas mileage—or should I say gas footage— of our buildings.

Practical Solutions

One practical solution could be a performance meter of some sort that gets installed in a central location inside a building, or can be connected to on a website. I don’t even think that we need a high accuracy read-out at all times. A simple color indicator could be enough to tell us we are using little or a lot.  This could also function as a “reward meter” for owners, who can witness less consumption after a remodel project for instance. 
The Germans recently started using what they call the “Energy Passport”. This is a static indicator of a building’s performance much like the “Energy Star” label one will find on a refrigerator at the local appliance store. 
In the end, it doesn’t matter whether this is tricked out live performance meter or a static sticker one receives upon purchase of a home. And while the offer different levels of interaction, both of them can help visualize performance and environmental impact, which brings me back to the beginning of this post and the Police’s “Your Speed” display. If only we knew, I think more of us would be inclined to make a difference. 


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