The Passivhaus, or PassiveHouse building standard is really tough on energy consumption, and results in very comfortable buildings, but it is disinterested (in the impartial sense) when it comes to what the building is made of- it cares about the end result, not how you got there. There is a real logic and science to this, but I have noted before that it is only one aspect of green building. That’s why I proposed what I called the Elrond Standard, which also accounted for embodied energy, toxicity, and location.
A lot of Passivhaus buildings are made with plastic foam insulation, for one very good reason: it has a higher R-value per inch and doesn't absorb moisture. But as noted on TreeHugger many times, is made from fossil fuels and is often treated with toxic flame retardants.
An alternative way of building demonstrated at the International Passivhaus Conference was from Steico, seen on TreeHugger before for their wood fiber insulation that you can occasionally find in North America.
In fact, they make much more than that; they make almost everything you need to build a structure above the foundations. If you prefer really lightweight construction to their Cross-Laminated Timber option, they make a slick I-joist out of Laminated Veneer Lumber with a Masonite-type web, and wood fiber insulation to fill it.
LVL is interesting stuff, made up of multiple layers of 3mm thick softwood veneer, laminated together with all veneers going in the same direction, unlike plywood or CLT where they alternate. Because of its rigidity and resistance to bending, you can use 48 percent less of it than conventional lumber. That makes for a strong, straight I-joist with less thermal bridging.
I have joked before that you should be able to eat your home, that every material in it should be essentially a high fiber diet of cellulose, if not edible by me then perhaps by a neighborly cow or beaver. The only thing they sell that isn’t edible fiber is a roof membrane; perhaps they should start making wood shingles and we could dispense with that.
Well-respected people like Martin Holladay of Green Building Advisor have dismissed my edible building proposition but the more time I spend on this subject, the more convinced I become that we have to stop building out of the fossil fuels which are needed to make cement, to fire bricks, to make plastics and many types of insulation and that we have to substitute cellulose from trees whenever it is possible.
The traditional argument has been that embodied energy doesn't matter much over the life of a building and that it is much more important to save operating energy. But as John Ochendorf's graph shows, as the efficiency of a building increases, then the embodied energy becomes a much more significant factor. That's why the Steico products are so interesting to me; you can build almost an entire building with off-the-shelf low carbon, low toxicity, almost edible materials.
I know it is probably a fantasy, to imagine that architects would give up on the wonders of plastic. But when I was in Munich I saw Passivhaus standard housing made out of wood, and saw other projects built out of concrete and foam. In low rise residential construction it has become a matter of choice; both can do the job. Once you are building to such a high energy efficiency standard, embodied energy really matters, and I continue to believe that it should be part of every Passivhaus designer’s toolkit; I think it should be built right into their giant spreadsheet. The whole range of products from Steico makes it a whole lot easier.
I usually only say nasty things about companies that let employees park their trucks in the bike lane, but in this case I will make an exception.