Toward a Zero Energy Home by David Johnston and Scott Gibson

I’ve been looking, apparently in vain, for a good book (that’s not in German!) detailing Passive House building and modeling techniques.  The best I’ve been able to do so far is Toward a Zero Energy Home, and it must have been pretty good, since I read it cover-to-cover in less than 24 hours.  It’s not particularly dense or detailed, but it was a nice quick overview of low energy building systems, with lots of pretty pictures, and a dozen case studies from all over North America, including a couple right here in Boulder.

Refurbished with passive house components, kindergarten in Estonia Valga

The goal that the authors have chosen to highlight — “Net Zero” — means that the buildings in question produce as much energy as they consume on an annually averaged basis.  This necessarily means that they all have some on-site production, wind, PV, solar-thermal hot water, etc.  However, to keep such projects reasonably cost effective, it’s necessary to focus first on energy efficiency measures.  Most important among these is a very tight building envelope, much more insulation than code requires, and appropriate glazing for passive solar gain.  Then the internal power loads need to be minimized, by using energy efficient appliances and LED or CFL lighting.  Only after doing all that is it financially worthwhile to start adding on-site renewable generation, capable of meeting the overall annual energy demands of the dwelling.  Financially worthwhile, that is, if you have already decided that you want to create a Net Zero building.

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German Passive House building robots

A short video from German home fabricator Hanse House.  They do both stock and custom homes, but both are fabricated off-site.  The video shows their production facility, and some of the techniques for putting together a building in pieces.  It’s pretty awesome.  Half robotic assembly line, and half humans, building to what’s essentially a CAD specification, with pipes and wires already laid in place within the structural elements before it gets loaded on the truck that takes it off to the building — or rather assembly — site, where the foundation awaits:

And here’s a time-lapse of one of their Passive Houses being assembled on-site:

I wonder if they do multi-family buildings too.  What it would take to get a facility like this operating in Boulder County?  Other than a rebound in the housing industry of course.

Boulder’s Passive Aggressive Building Standards

Usually when people say that “better is the enemy of good enough”, they’re pointing out that striving for perfection can be a distraction from just getting the job at hand done.  There are other dynamics that involve these concepts too.  As social animals, we tend to judge ourselves against those around us.  Once our basic needs have been satisfied, our relative wealth or deprivation often becomes more important to us than our absolute level of well being.  We have little concept of how much is enough.  This can lead to the familiar runaway acquisitiveness (keeping up with the Joneses) when there is a well established (or constructed…) social norm favoring consumption.  Less obviously, it can also lead to an inappropriate lack of ambition when faced with an objective task that is not supported by widespread social norms.

Over the last couple of years Boulder has upped its building energy efficiency standards.  The new permitting regime requires buildings to perform better — net of on-site generation like photovoltaics — than the 2006 international building codes (IBC).  Smaller dwellings (< 3000 square feet) have to use 30% less energy than the baseline.  Medium homes (3000-5000 sq ft) need to do 50% better, and large ones (> 5000 sq ft) have to beat it by 75%.  Obviously this is an improvement over the previous situation, but in comparison to what is possible, and what is necessary to combat climate change, it’s actually pretty unimpressive.  Homes of all sizes built to the Passive House standard use 80-90% less energy than the baseline code, and they do it without counting any on-site power generation against the building’s energy consumption, whereas the HERS index that is used in the Boulder code does count on-site generation.  This is an important distinction, because the atmosphere doesn’t cancel out your nighttime coal-fired emissions with the solar electricity that you sell onto the grid during the day.  All it cares about is the total amount of CO2 released.

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Links for the week of December 9th, 2010

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Links for the week of December 3rd, 2010

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