Spot the Passive House!
There is a wonderful demonstration of different approaches to green building on Bergen Street in Brooklyn. To the right in the photo above is a house we covered two years ago, complaining that its facade of solar panels was not going to generate much power and that it was really just shouting "look at me, I'm green!!!"
Lloyd Alter/ Jane Sanders/CC BY 2.0
Meanwhile, two doors to the left, is what looks like a normal Brooklyn townhouse, totally inconspicuous. In fact, the 1870 row house has been renovated to Passive House EnerPhit (the renovation standard) by Jane Sanders, who wears three hats as the architect, Passive House consultant and owner. She describes it:
© Jane Sanders/ Living and dining
The house is air tight and well insulated, and has a constant supply of fresh filtered air through its energy recovery ventilator. Other energy saving components include triple glazed windows, solar hot water, induction cooking, and an ethanol burning fireplace. Original features such as stair railings, a marble mantle, and plaster moldings were restored. Usable space in the cellar with increased ceiling height was gained by installing a new insulated slab and drainage system. A new stair links the family room in the cellar to the main living space above.
Lloyd Alter/CC BY 2.0
The design is economical and sensible; the basement has a ledge around it to get the extra height, which is cheaper than underpinning the walls. That means that the new stair to the cellar cannot be under the old one, which creates a bicycle storage space on the ground floor under the stairs.
Lloyd Alter/ Utility closet/CC BY 2.0
This is not an over-the-top lavish renovation; it is a comfortable family house. The only way you would even know that it is built to Passive House standards is by looking in the third floor closet, where you find a giant heat recovery ventilator that delivers fresh air year round, plus a big hot water tank connected to the solar thermal collectors modestly and inconspicuously put on the roof. This post is light on the technical details, but Cecil Scheib of Urban Green visited it during construction and reported:
Construction entails no fewer than six different types of insulation (XPS, EPS, dense pack cellulose, spray foam, polyisocyanurate, and rock wool) and three different types of air barrier. There’s a reason for this range of products, and each material has its place. Take spray foam; it’s often the easiest way for semiskilled personnel to add insulation, especially in rough or irregularly shaped cavities. But project contractor Jeremy Shannon (Build with Prospect, Inc.) advised not to rely on spray foam as an air barrier as it can pull away from masonry and wood studs, even on prepared surfaces. Instead, he recommends non-foam air barriers such as membranes and tape.
There is a great video by 475 High performance Building Supply that shows how this all goes together. On the front and back walls the windows are boxed inwards to provide room for densepack cellulose. It's then lined with an Intello, a "smart" vapor retarder. Then there is a layer of framing to provide space for electrical wiring so that nothing penetrates the membrane.
© Jane Sanders
Being a townhouse saves some money and a lot of space because the fancy thick blanket of insulation doesn't have to be on the side walls. In fact, Jane notes that they don't need any heat at all in winter because their neighbors are so generous in sharing by warming up the party walls. However the walls are rather elaborately sealed against air leakage, which also reduces noise transfer.
© Jane Sanders/ Office
In fact, for someone living in New York City, perhaps the biggest benefit of building to Passive House standards is that it is incredibly quiet inside. Bergen is a busy street, with buses and trucks going by at all hours. However the high quality triple glazed windows plus the thick blanket of insulation really cut the noise; You could see buses go by and really could not hear a thing.
Lloyd Alter/CC BY 2.0
There are many people who now say that solar panels have got so cheap that it's not necessary to build to Passive House standards, that offsetting energy consumption by going net zero is just as good for the environment and our carbon footprint. It is a reasonable argument, but the fact is, Passive Houses really do have the added benefits of comfort and quiet. And they certainly fit into a neighborhood more comfortably than a facade of solar panels.
Thanks to Jane Sanders and the North American Passive House Network for organizing the tour.
UPDATE: with regard to how quiet Passive Houses are, I am reminded that we wrote about this last year in Another great reason to build Passive House: They are really quiet (video)