From swapping in smarter lighting to installing solar panels, many homeowners are seeking energy efficiency boosts that can cut bills and lower their carbon footprint. But just how green can a home get? Julie Torres Moskovitz offers an answer in The Greenest Home, a just-released visual and practical guide to some remarkable passive houses around the world. (See related posts: “Green Fridays, Smart Lighting and More: How National Geographic Cuts Its Energy Use” and “A Model Net Zero Home by the Numbers.”)
What is a passive house? “Simply said,” Moskovitz writes, “a Passive House is a building that is very well insulated, virtually airtight, and primarily heated by the sun.” The interior temperature is designed to stay at 68 degrees Fahrenheit, and to bring in fresh air while removing exhaust air.
In order to meet the passive house standard in the United States, the book says, a home must be tested for airtightness, and caps are set on energy demand for heating and cooling.
The energy savings these homes can achieve are remarkable (reductions of up to 70 percent, according to the book), but what’s really striking about the homes in the book is just how modern, airy and inviting they look. Moskovitz answered our questions via e-mail.
How did the idea for this book come to you? What did you hope to achieve?
I was working on a Passive House retrofit project in Brooklyn and networking with people in the NYC Passive House scene. I realized that not only was there a lot of very current work happening that wasn’t yet captured in a book, but that it could be tremendously useful to collect information and present it in a way that would allow the public to better understand what Passive House is. I also insisted on adding an appendix with technical data, drawings, and construction photos that would help architects, builders, and students learn about meeting the Passive House standards.
I committed to writing a book that shows how integral the Passive House philosophy is through all stages of a project. I find that a lot of green design books are confusing for readers. For example, a text that describes an efficient technology in one sentence while dedicating the next to a concern like importing rare stone slabs from Italy for a kitchen counter, that runs contrary to green thinking. Passive House is green through and through and enables a homeowner to conserve energy without sacrificing comfort.
Is there a house (or houses) in the book that stands out to you in particular, either aesthetically or in terms of its energy-saving features?
My favorite project in the book is by BLAF Architecten in Asse, Belgium. I just love how congenial the design is with features like a basketball court in the yard, an ever-morphing chalkboard façade, and interior spaces that are so optimistic. It seems like a fun playhouse for a family to enjoy year-round. On top of all this, it’s Passive and Energy Plus that feeds power back to the grid with its 20 solar photovoltaic panels.
You display the latitude and longitude with each house listing in the book. Why is that?
This infographic came about when we were looking at how to order the case studies in relation to one another. Since location and performance are corollary in Passive House, we felt this to be a natural way to present the data. The coordinates reiterate that we are on one planet together and that orientation is integral to Passive House.
It matters how the sun affects each façade of your building, as windows and glass doors are part of the energy balance in the home. I combined the use of latitude with a graphic of Buckminster Fuller’s Dymaxion map, which envisions the continents as one island, and makes the point of how vulnerable we all are to climate change but also how interconnected.
What are some of the challenges one encounters when designing a passive house? Are retrofits harder?
The main challenge is getting buy-in from everyone involved so that there is comprehensive problem-solving at each phase of the project, especially during construction, when hasty decisions can negatively impact the stringent Passive House requirements, particularly airtightness.
Retrofits should theoretically be harder because you are working with elements that were inherited from the previous builder. However, I know it’s doable. Having completed a certified retrofit project, I know that the speed bumps are not likely to dissuade those committed to the Passive House model.
The book features homes from all over the world, but is there one country or region where you would say great progress is being made in green home design?
Well, I am going to give it to North America—precisely I am thinking of BC Passive House in Canada, founded by Matheo Durfeld. Passive House in Europe has a 15-year lead with established component manufacturing. In North America, the opportunities are limitless, as business-minded individuals begin to develop Passive House products for our market. For example, Durfeld founded a manufacturing plant that prefabricates building envelope panels that meet rigorous Passive House standards.
I noticed that many of the houses in the book have what seems to be a similar look: simple, smooth, a lot of dark wood on the exterior, irregularly placed windows, often rectangular. Is that just a function of the modern aesthetic now, or are there more practical reasons for this style?
It primarily speaks to a contemporary aesthetic but also to the fact that the homeowners aren’t over-doing it with materials and finishes that would contradict the greenness of what they created at the airtight thermal building envelope. In the book I was actually trying to highlight that these homes are inspiring modern designs, yet are super-high performance; they are models for 21st century living and show that green, formally speaking, can be anything.
What misperceptions do you think people have about passive houses?
The worst one is when people think that the windows don’t open and that there isn’t fresh air.
How does cost compare? Have you evaluated (or been asked about) payback times in terms of saved energy versus any additional cost required to make a house passive?
It’s very hard to do a cost comparison because there are so many varying factors. I have heard varying percentages but somewhere between 5 percent to 7 percent more for a Passive House is probably accurate. I am hesitant to give a definitive though because so many things factor in. If I am working with a client we work on other aspects of designing a comfortable and desirable home and this takes into account their programming needs. It’s very hard to separate those costs from what costs are the ones specific to a Passive House. Yes I am often asked about evaluating payback but it’s usually a developer wanting to know the bottom-line dollar investment. Clients realize there is more than a straightforward payback. For example, there is the stability of not being so dependent on volatile energy pricing, and the comfort of knowing that they have significantly reduced their carbon footprint.
How do you see the future evolving for passive house design and the market for it?
Well I am eagerly awaiting that tipping point where Passive House is in the vernacular and more people consider it for themselves. I hope my book will help familiarize the public about it. I am starting to receive calls from developers interested in Passive House. This is a good sign, as it suggests that they have market pressures to consider, not merely “green” design, but the deep potential impact of the Passive House model.
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This post has been updated from the original to remove references to energy consumption for the passive house standard, as cited in the book, and a misleading comparison with average energy consumption in American homes based on government data. Each figure was based on very different methodology.