A U.S. standard?

[Hayden Robinson]

The other night, I was having beer with colleagues. One characterized the conversation around PHIUS+ as occurring between one side that believed in rigid adherence to the Passive House standard and another that supported a standard adapted to U.S. conditions. I think there's something else going on. It doesn't look to me like PHIUS+ criteria have much to do with real conditions in the U.S.:

 

·        PHIUS decided that using real primary energy factors in parts of the U.S. with coal-fueled power plants would make PHIUS + too hard.¹ Instead, they decided to assume an average North American PE factor everywhere.  Since a North American power grid doesn't exist, the PHIUS+ PE values are a fiction. Half the time they underestimate CO2 emissions. Half the time they overestimate CO2 savings. In Seattle, PHIUS+ way overestimates savings. From a climate-change perspective, this is nonsensical. If you want to limit CO2, you have to put the plugs where the leaks are. Artificially raising PE values in areas with low-CO2 emissions cannot make up for artificially lowering them in areas with dirty power - the arithmetic doesn't work.

 

·        PHIUS+ underestimates energy demand by using German data on hot-water consumption and 80% of RESNET for plug loads. These inaccuracies combine with too low PE factors to throw PHIUS+ primary energy calcs further off.

 

·        PHIUS+ uses PV-cost parity as a yardstick for its heating energy demand criteria. This is said to make it financially rational. However, PHIUS+ uses national-average construction and PV-cost data. Of course, in reality, it costs more to build in Manhattan than it does in Oklahoma. A lot more. The outfall is that in places, like Seattle, with high construction costs and subsidized PV, PHIUS+ financial assumptions, and thus its demand criteria, have nothing to do with reality.

 

Most of this could be easily fixed - let's keep our fingers crossed for PHIUS+ 20. In the mean time, maybe we should put our heads together and create a PHNWplus? There are plenty of smart energy nerds here.

 

-Hayden

”In other areas where the grid is all coal-based and that have a very high source energy factor it would be impossible to meet the criterion without adding solar thermal systems." (Wright , Klingenberg, Pettit:  Climate-Specific Passive Building Standards, p.21, Building America Report - 1405,