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    Polar Vortex in a Passive House? Fuggedaboutit...

    Below is the temperature and humidity data from a recently completed passive house (EnerPHit renovation of a brownstone rowhouse in Brooklyn, certfication pending) during last week's "polar vortex" cold snap. The heat, a Mitsubishi 2-ton minisplit system, was only turned on at the point noted - other than that, the temperatures are maintained within normal (albeit variable) comfort levels without any heating system (other than the sun and internal sources, ie passive house principles). It should be noted that the temperature was measured in the living room where the family spends a lot of time. But still... I'm amazed.

    Indoor temp & RH from a Hobo U14-001 logger, ambient temperature & dew point data from KNYBROOK22 via Weather Underground. Click image to embiggen.


    Retrofitting a Rainscreen Behind Cedar Clapboard

    Problem: despite best efforts with good primer & paint, the paint just keeps peeling off:

    Probable cause: water leaking in at windows was unable to dry out. Because this wall is south-facing, the sun heats the wall almost all day, which causes the moisture to evaporate and push its way out, any way it can - in this case, through the cedar.

    Solution: pull the clapboard and trim, install 1/4" vertical furring strips with insect screen looped at the bottom (creating a vented rainscreen), and reinstall siding. Sounds easy, right?

    Here goes nothin':

     The clapboard was face-nailed with ring-shanks, so there's only one way to get them off (by wearing a cool hat...and using an oscilating multi-tool with a good blade):

     The stains are probably tannins from the cedar, transported by high moisture levels. Fortunately, Tyvek and sheathing seem ok:

     The bottom vent - common aluminum insect screen rolled (not folded) around ends of furring strips:

    Normally this would be done at the top too, but we discovered that the soffit is vented already, and there's a gap the size of the furring to pass through (the roof behind meets the short parapet at the top, which is the top end of the roof deck vent). So we're hoping that's good enough. Fascia board was put back on with screws though...just in case!

     And then the siding goes back on:

    With an attempt to improve flashing at the windows:

    It took a solid weekend (two guys, except re-painting), but this ought to solve the problem. Check back in 5-10 years though!