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Passive House in Derwood, MD takes form

It was a gorgeous day to bike out and visit this Passive House project, located in Derwood, MD.  The site is surrounded by forest, and abuts Lake Bernard Frank.   The bike trail passes over the earthen dam, where I saw great blue herons sunning on the berm, and a banded kingfisher perched in a branch near the water.  When I arrived at the site, a red tailed hawk was wheeling right above the house.

passive house rough framing

Here’s a view of the west elevation.  What has been erected so far is the first layer of the wall and roof assemblies, which will function as the structural shell of this Passive House.  The yellow membrane–which extends under the slab–will be lapped over the green sheathing, and taped together with an aggressive, waterproof tape.  Similarly, the reddish brown sheathing on the roof will be sealed to the walls with additional membrane and tape.

Over all that will nail base–a sandwich of foam and plywood.  The walls will get a 3 1/2″ layer, and the roof will get a 6″ layer.  The roof layer will extend about 30″ beyond the outside walls to form the eaves.  This projection will not only protect the walls from the weather, but will also shade the windows from the summer sun, while admitting the winter sun.

Then, a second set of framed walls will be built inside the walls shown in the photo.  they will form a 10″ deep cavity that will be filled with cellulose insulation.  According to PHPP, the walls will achieve R-52.1, and the roof will achieve R-66.1

passive house framing the structural shell


This is a view from the south west.  When complete, the low sloped roof on the left will continue across the porch (defined by the block piers), and wrap around to the right and join the roof where the carpenters are working.


Here are views of the southeast (above) and northeast (below).  A small screened porch will fill in the recess on the right.