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Green Building Blog

High-Performance and Net-Zero Homes — Part 3

What does Code have to do with high performance?

For every unit of grid-supplied electricity, about 3½ units of fossil fuel energy needs to be burned at a power plant. Most of the other 2½ units of energy are lost as waste heat during the combustion process. That's why 1 unit of energy supplied by a PV array avoids the need to burn more than 3 units of fuel.

During the last month we’ve had a very stimulating conversation going about design – and how some important design opportunities for improving energy performance are often overlooked, and why. The dialogue started here and, thanks to fellow GBA Advisor Bruce King, continued on Facebook.

Now to continue the fun, we’re going to look at CODE – specifically, the energy code – and its role in high-performance and net-zero energy homes.

You might (understandably) be thinking, “My homes are way above code; where’s the conversation?” And if you’ve been at this energy efficiency thing for a while, there is no conversation. But what’s interesting is how often I see the code getting in the way, particularly for project teams that are relatively new to the arena of high-performance home design. Here’s how.

Code cultivates a mindset of compliance, not one of innovation and leadership

Folks in our industry have become accustomed to the unspoken mandate from builders and developers, “I just want the house to pass code at the lowest possible cost.” Instead, as I was harping on last month, everyone on the team should be asking the question, “What’s the most energy-efficient house I can build within budget?”

Ironically, here in California – where we pride ourselves on being so advanced from an energy perspective – our energy code has spawned legions who follow the “just pass” mindset. And, greatest of ironies, often among the legions we find even our energy consultants! Even on high-performance projects!

On more than one occasion, I’ve found myself in a conversation with one of these guys (or gals) when they’ve said, “No, we can’t do that, it will cost more.” Wait a minute – aren’t you the guy/gal who is supposed to be the most savvy, and most concerned about optimizing energy performance? And maybe first cost isn’t the only thing at stake here?

So why does this happen? It happens because this occupation has been beaten down by a steady river of clients whose principal interest in the energy code is scraping by with the bare minimum compliance. This means, as a number of my venerable colleagues have been known to quip, that if they built any more poorly, their homes would be illegal. Yet we can hardly blame those poor, beleaguered energy consultants for their uninspired mindset. Its genesis lies in the code, and in their mainstream, same-old-thing clients.

The code turns a blind eye to design decisions that may have substantial influence on energy use

In California (and elsewhere, if I’m not mistaken), energy performance is often expressed as a compliance margin, or “percent above code.” The energy models calculate this percent by comparing the predicted energy use of the home as designed with that of a minimally code-compliant home – i.e., one that incorporates a set of prescriptive energy features mandated for homes in that climate zone (e.g., R-19 walls, R-38 roof, etc.). This minimally code-compliant home is referred to as the “standard reference house.” The standard reference house has the same basic geometry, orientation, and size as the home as designed.

The standard reference house may be an energy HOG (meaning no offense to the very intelligent porcine species): poorly oriented, bloated, and excessively complex. This means that energy performance is benchmarked against something that – while it might comply with minimum R-values and so forth – is far, far away from anything that might be considered efficient. So you might design something that is 50 percent more efficient than an energy hog. Well and good. Does that mean it’s truly efficient?

Suppose you had started with an inherently more efficient geometry and a more modestly sized home? Ironically, you would find it more challenging to achieve substantial modeled reductions in energy demand; your design would show up as having a lower compliance margin, suggesting that its energy performance is inferior to the hog, when in fact the opposite is true. You would be penalized for having made good decisions from the outset. And worse, there is nothing in the code or the energy models that remotely suggests that the designer might want to tinker with size, geometry, or orientation; these critically important variables are completely ignored by the code and accepted by the models as fait accompli.

It’s no surprise, then, that these opportunities also are overlooked by design teams as potentially fruitful avenues to explore when seeking improvements in energy performance. It doesn’t benefit them (as viewed through the eyes of the energy model), even if they were to actually think about it … and they typically don’t.

In California, the code doesn’t incentivize the use of photovoltaics for on-site renewable electricity generation

In general, the highest energy production of photovoltaics (PVs) occurs at times of peak system loading – afternoon and early evening. This is a great benefit to the grid and hence to the state, utilities, and infrastructure as a whole. In the Sacramento Municipal Utility District, for example, there are certain power plants that are only needed at peak demand and therefore only operate for a few hours a year. (Yes, you read that right – a few hours a YEAR.) Needless to say, the cost of those few hours is extraordinarily high, and the power plants reserved for these periods of demand are often the oldest, dirtiest, and least efficient.

PV systems have the potential to delay or even eliminate the need for these plants, once widely deployed. And yet Title 24 dings PV homes for electric use – even at their peak production times. Let me explain.

Many net-zero and high-performance home projects on which I have worked are also all-electric homes, for the simple reason that the owners want their homes to be fossil fuel-free. They believe that natural gas will become increasingly scarce and expensive, as petroleum has become, and wish their homes to be capable of operating solely on renewable energy. This means that loads like water heating, drying clothes, and cooking are electric rather than gas loads; and some of these loads may be expected to occur at peak.

The code-based energy models take this into consideration and accordingly penalize these projects for those loads – in spite of the fact that those same homes may be cranking a very nice surplus amount of electricity from their PV arrays into the grid at exactly the peak time for which the homes are being penalized by the model. Not exactly incentivizing, eh?

Furthermore, every unit of electric energy supplied to the grid by a home-based renewable electric system typically represents a hefty multiplier effect, as shown in the illustration.

For every single unit of grid-supplied electric energy, roughly 3½ units of fuel energy need to be burned at a power plant (most of the other 2½ units are lost through combustion as waste heat). Correspondingly, 1 unit of energy supplied by an onsite PV array instead of by the grid avoids the need to burn more than 3 units of fuel. (The nationwide average site-to-source multiplier for electric energy is around 3.4.)

But the code is blind to this benefit. Go figure.

Regulation: friend or foe?

So there you have it – my beefs with the energy code. We’re due for a code update soon, though, so hold good thoughts that these things will change.

Don’t get me wrong – in general, I’m a proponent of regulating things, stopping environmental problems before they happen. Take the Clean Air Act and Clean Water Act: if we don’t let pollution happen, we don’t have to clean it up. If we didn’t let energy waste happen, then we wouldn’t have to worry about climate change or national security. (Maybe. You take my point.) But regulations, as I’ve now presumably persuaded you, have adverse consequences as well as positive ones. We can’t assume that code changes will fix all our problems; we have to remain vigilant, and pull the covers off the problems that codes fail to fix, or that they even create.

I hasten to add the footnote that there is much in California’s energy leadership to trumpet, and the code has been instrumental to much of the progress that has been made here. My point is simply that it behooves us to be aware of and to combat the unintended and unfortunate consequences of the energy code(s). Among the takeaways:

  • We need to be discriminating in our selection of energy consultants, ensuring that those we choose to work with are in fact not of the “just-comply” school of thought. Some can be quickly jostled out of that rut; others, not so easily.
  • We need to constantly examine the benefits associated with energy improvements, not just in terms of first cost but also in terms of operating energy savings, comfort improvements, and other non-energy benefits.
  • We need to benchmark our designs against more appropriate “reference homes” – homes that are smaller, more compact, and simpler in form.
  • We need not to be deterred by the blindness of the code to the benefits of what we may be doing in our homes. Just because the code models don’t reflect all those benefits doesn’t mean they’re not worthwhile or valid.

And finally, we need to look for opportunities to influence code development for the better, while at the same time understanding that we can’t rely on codes to do our job (of curbing home energy use) for us.


  1. kim_shanahan | | #1

    Codes vs good intentions
    Paradigms are not easy things to shift but codes are, and they are, on three year cycles. Because there will always be a vast majority building to the minimum, it is imperative that we keep raising the bar for code compliance.

    Percentage above "reference home" is a reasonable threshold because it at least offers a performance path as opposed to the severe limitations of a prescriptive code. Your notion of the "reference house" does not exactly match how RESNET does it for HERS ratings.

    "The standard reference house has the same basic geometry, orientation, and size as the home as designed." That statement is true. But your next statement contradicts that one: "The standard reference house may be an energy HOG (meaning no offense to the very intelligent porcine species): poorly oriented, bloated, and excessively complex."

    How do you square up the contradiction?

  2. wjrobinson | | #2

    When does one notice exponential growth?
    Where are the mathematicians? Who that posts blogs here understands exponential growth curves and what happens after such curves become unsustainable?

    This "green" subject needs the input of math PhDs that understand our possible predictable futures.

    global climate destabilization: 107 interesting videos

    Just a start to get you thinking... Albert Bart is quite good at explaining the arithmetic...

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