More on Measuring Energy In Green Building: Absolute vs Relative


heat loss from Passivhaus. Source: wikipedia

Defining green building is not easy; for many, all that matters is energy consumption. One of the major ways of reducing consumption is to increase the amount of insulation, but that is only one component, and not necessarily the most important one.

Earlier this week I wrote a post about "a strange debate going on at Green Building Advisor, where a writer thinks "home buyers have been "brainwashed" into thinking only about R-values, as energy codes give short shrift to the importance of airtightness."

Scott Gibson was, I think, saying that there is not much point in worrying about R value if you don't ensure that the building is properly sealed. I used the post as a springboard to write Which Is Worse, Air Leaks or Heat Loss? Neither. It's Energy Consumption That Matters and discuss my favourite argument:

The debate goes back and forth, but not once to they address the real point: How much energy is being consumed over all. They are preoccupied with relative efficiency when they should be concerned with absolute consumption.

I then received an email that included the following:

Your editorial piece on the Green Building Advisor discussion reminds me of the environmental thinking and writing done in the 1970s & 1980s as well as ideologues who propose simplistic solutions with no proof or evidence that they could work or have worked. You not only ridiculed the web site and its mission but also misrepresented this particular discussion. In my opinion you owe the web site and the participants in this discussion an apology.

You propose that the building code should accomplish energy efficiency by mandating a top level on absolute energy consumption without proposing any means to accomplish it other than reduce building size and/or implement photovoltaic solar panels.

Well, that is not entirely true; there are lots of ways to achieve a fixed cap. So I responded:

Frankly, I thought it was silly argument in the first place, since R-value is a design decision and air leaks are an execution issue. I thought then that it was a comparison of apples and oranges. Siting, windows area, building form and most importantly, size, all play important roles. Just discussing these two items in the absence of the larger discussion is what I would call simplistic.

My correspondent responded:


You have also set yourself up as the authority and judged them ignorant of the real issue and it comes through strongly in your writing. This is why I reacted.

You continue to hold that the only important thing is to reduce absolute reduction of energy consumption by reducing the size of the homes and using less insulation in smaller homes especially for the poor. The latter does not make any sense to me. Regardless of how much insulation they have most buildings, condos and houses built in North America today leak energy like a sieve and our worldwide population continues to grow at an alarming rate so clearly just making them smaller is not going to work. Without dealing with how to make them energy efficient you are riding a one trick pony.

More importantly very few agree with your viewpoint especially in the real world in which we live.... It is simplistic and doesn't work.



How Should We Really Measure Green Building?

At this point I did not know what to do, other than turn this into a post and open it for discussion and reiterate my points.

I have never said that the only solution is to make things smaller. There are lots of solutions, including more insulation, better windows and both passive and active solar. My point is that if you regulate absolute consumption rather than rates through each component, then people have options and flexibility in how they build. It also gives a nice inducement to build smaller and to build multifamily. We got the McMansion because pumping up the volume of a house was cheap; if a builder had to pump up the insulation or reduce the window size to maintain the same energy use, they might never have been built.

You do not need to build R-50 walls with passivhaus standard windows if you are living in a multifamily dwelling or a thousand square feet; we should have a progressive scale so that the standards are appropriate to the type of dwelling. One size does not fit all. That is why I think an absolute energy consumption target remains best way to deal with it. It should obviously be a high enough target to eliminate condos and houses that leak like sieves.


Forget Energy Star and LEED, Green Building is Passivhaus

My correspondent complains that I am "alienating many of the very people who working on creating solutions including those in the Passive House/Passiv Haus movement." I sincerely hope that this isn't so, I think it is the future of housing and the best standard we have. I agree with Alex Wilson that "Passive House is one of the most exciting things to come along in decades." (quoted from Katrin Klingenberg complaint about my post here)

But I am not the first to note that when you are measuring kWh/m2 like they do in Passivhaus, it is harder to build small; the calculations work out almost universally that a larger home will use more energy than a small one, but will use less per square meter. As one designer on the Passivhaus bulletin board noted, it "begs the question of why small buildings need to (should have to?) perform better than larger buildings to qualify."

I think the opposite should be true. I really do believe that small buildings should not have to perform as well as big ones. They will ultimately use less energy, and the mathematics almost demand it, since there is more surface area per unit volume and some energy consuming components, like a fridge or a heat exchanger fan, are the same in a big house or a small one.One way to make it work is to use an absolute consumption cap instead of a relative standard.

In the end though, there is a much simpler way to look at it. I use a lot of analogies to the food movements, and come back to Michael Pollan's Food Rule #44, Pay More, Eat Less. Substitute building for food:

The American food building system has for many years devoted its energies to increasing quantity and reducing price rather than improving quality.

We have to pay more, and build less. Simple, yes. But not simplistic.

More on relative vs absolute:

Big Steps in Building: Change our Building Codes from Relative to Absolute
How Should We Really Measure Green Building?
5 Building Code Changes That Absolutely Cannot Wait Until 2030
Stop With the Glass Façades Already

Follow me on Twitter! @lloydalter and friend me on Facebook

Tags: Designers | Green Building | passive house

Best of TreeHugger 2014

WHAT'S HOT ON FACEBOOK