Takeways from the 2016 North American Passive House Conference

We just got back from the PHIUS national conference in Philadelphia. It was quite well attended, with a broad array of topics covered.  These conferences are no longer focused simply upon how to do build one, but have become much more specialized and look at all the various aspects of what goes into a Passive House. They are also looking at other building types that are now employing Passive House design principles – multifamily housing, office buildings, schools, and even high rises. We have come a long way!

Takeaway 1: The biggest takeaway, I have to say, is Izumi’s: she went through the day-long training for the new PHIUS WUFI+ energy modeling software. Quite rigorous. She has immediately put it to work on a current project in the office. Matt learned this software when he did his PHIUS training. So that leaves me as only one who hasn’t made the shift to the new WUFI+.

Takeaway 2: Spray foams aren’t as bad as we thought. Several years ago Alec Wilson of BuildingGreen published an article positing that the global warming potential of the gases in the blowing agents far out outweighs the savings in CO2 emissions that these products give you. Bailes examined the assumptions of Wilson’s calculations and made a strong case that the issue is not quite so black and white. His argument is that the EPS and XPS foams’ savings in emissions actually exceed the environmental cost of the gases in the blowing agents when you apply it in thicknesses of roughly R-20 or less. This is based upon the declining increase in R-value with each extra inch you add. He did not address other issues around the foams: the lethal gases produced if they catch fire, and the fact that they are fossil fuel based. The takeaway for me:  yes, it is ok to use these products in small amounts where there is not another alternative insulation system that would work (such as some retrofit situations). The exception is XPS insulation (extruded polystyrene–eg: Styrofoam) for which one can always substitute the more benign EPS (expanded polystyrene) insulation. To learn more, read Allison Bailes’ article, which also references the Alex Wilson study.

Takeaway 3: … and cellulose insulation isn’t as perfect as we thought. Prudence Ferreira gave a very detailed review of the performance of different insulation types in various climates with regard to mold and wood rot. Her studies taught her that cellulose insulation—either loose or densepacked—tends to hold moisture longer than other insulations. This can become a problem at the outside edge of your insulation cavity where moisture can accumulate and remain if the surface bounding the outside face of the insulation (usually the building sheathing) gets cold enough. What it tells me for our climate is that we always need to have rigid insulation on the outside face of our sheathing to keep it from getting too cold and causing these problems. Luckily, that has been our practice to date. A wall that would not work well in our climate, for example, would be a double stud wall with nothing outside it. Even though the wall might be 10” thick and achieve tremendous R-values, it could develop moisture problems at the interior face of the sheathing.

Takeaway 4:Hybrid AC-DC microgrids are coming. Terry Hill, who sits on the board of both PHIUS and the non-profit EMerge Alliance, moderated a very interesting panel including  Brian Patterson, the founder of the the EMerge Alliance and Tim Martinsson, CEO of Power Analytics a leading firm in microgrid design. We learned of the latest  developments in microgrid technology and products and their application to individual buildings. We are working with both of these groups in trying to develop a case study project for a home powered by a hybrid microgrid. I’ll be blogging more on this later.