THE EXPERIMENT
Who: David Baker, an architect, and Yosh Asato, a design communications consultant, who live in Zero Cottage, a 712-square-foot loft apartment in the Mission District. It was designed by Baker and is LEED Platinum, GreenPoint Rated, Passive House and Net Zero Energy-certified.
How long have you lived here?
Baker: I purchased this property on Shotwell Street in 1999 and it’s been an ongoing project, starting with a remodel of the main house. There was also a storage shed at the back of the lot, but I’d always imagined a more substantial building. I decided to replace the shed with a loft dwelling above a flex space, and used it to compare the major green-certification programs and test what’s involved on a small scale. As with LEED (Leadership in Energy and Environmental Design) when it was first introduced, it can be hard to convince a client to be an early adopter of new standards such as Passive House. After the Zero Cottage was completed in 2012, we decided to live there part time to see what it was like to live in a net-zero house, but now we spend most of our time there.
What is the most significant difference
from a standard house?
Baker: The Passive House standard is quite challenging. The basic concept is that you need hardly any extra energy for heating or cooling, because the house is so well-insulated. You use an HRV (heat recovery ventilation) system to extract heat that you generate — taking a shower, cooking, using your computer — from exhaust air and use it to warm fresh, incoming air. It’s an amazing system. I would never build a house without an HRV now. It’s so quiet, you can’t tell you are in the middle of the city.
What other aspects of the house do you
like?
Baker: I got to prototype an experimental facade with metal shingles. It’s inexpensive to produce using digital fabrication, easy to install, and the shingles can be swapped at any time. In fact, we replaced some with planters, so there are succulents and herbs growing on the side of the house. We also incorporated wood flooring salvaged from a pasta factory. We didn’t sand the wood at all; we just treated it with a natural flaxseed-oil finish, which lets all of the history show through. The reclaimed wood flooring also appears on the exterior, but there we charred it for a different natural finish. On the roof, we have a part-cactus and part-vegetable garden, complete with composting. The gardens coexist with the solar electric- and hot-water-generating panels — it’s a very intensive multiuse space.
Asato: The Passive House standard limits the amount of window area you can have. This runs counter to current tastes, but it worked to our advantage in the cottage. The windows are carefully placed so we have light and views — a sense of being in the city — as well as privacy.
Have you had to make any compromises in
your lifestyle to get to net-zero?
Asato: The idea of net-zero does make you more mindful. We already were pretty resource-conscious, but here we go further. We found some great LED lighting by Pablo Designs, rarely use the dryer, and “work” the house — opening or closing windows — to keep the house comfortable year-round. We’re also trying to see how little water we can use.