A luxury home approaches zero net energy use thanks to extensive efficiency improvements, renewable energy systems, and a “dashboard” for tracking energy and water consumption.
Case Study Contents:
- Overview
- Energy Use and Greenhouse Gas Emissions
- Indoor Air Quality
- Natural Resources
- Water Conservation
- Community & Living Green
Project Stats
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Location: |
Tiburon, CA
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GreenPoint Rated Existing Home score: |
128 |
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Year built: |
1971 |
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Original size: |
5,500 square feet (Including a seperate 2-bedroom apartment) |
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New size: |
5,500 square feet (Including a seperate 2-bedroom apartment) |
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Project scope: |
Whole house remodel to reduce the home’s carbon footprint and |
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Architect: |
Mahoney Architects and Interior |
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Builder: |
Larwood Construction |
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GreenPoint Rater and green building consultant: |
Kevin Beck |
A Large Home Gets a Smaller Footprint
Frank Levinson likens the typical home to a car without a dashboard.
“When you drive your car, you drive it by looking where you’re going but you also have a dashboard that tells you how fast you’re going, how much fuel you have left, how many miles you’ve traveled,” he said. Like a car, “your house carries you forward in time, but without a dashboard.What I wanted is a dashboard that told me the performance of my house in real time.”
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| Home Control panel. |
After completing an extensive remodel of hisTiburon home, Frank Levinson now has that dashboard—a resource monitoring system that tells him minute by minute how much electricity, natural gas and water he is using, how much electricity and hot water his renewable energy systems are generating and how much water is stored in his rainwater harvesting system. This real-time data helps him adjust his behavior to reduce wasteful consumption, and helps Levinson pinpoint problems with systems and equipment.
These days, the resource monitor isn’t showing much waste, thanks to a major overhaul of the home’s energy-using systems and building envelope. The stunningly situated house, with sweeping views of the San Francisco Bay, was also updated with contemporary and green finishes, better lighting and changes to the floor plan to enhance flow and views.
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Levinson worked with architect Colleen Mahoney to substantially remodel both the main home and an independent apartment on the lower level. Mahoney’s design opened the main home’s kitchen and dining room to the living room, but for the most part she worked with the existing layout.
“That’s one of the approaches to making a project green—a careful assessment of how much of the existing home you can work with,” said Mahoney.
Mahoney, builder Don Larwood, and the rest of the project team were wowed by the lengths to which Levinson went to green his home, according to Mahoney. “He is absolutely committed to minimizing the home’s carbon footprint,” she said. “A lot of our clients want to go green but very few mean it to the level and depth that Frank Levinson has taken this home.”
In fact, Levinson so inspired Mahoney that she started a new company, Green By Design, a design center and showroom in Mill Valley.
GreenPoint Rated Adds Value
Mahoney and Mr. Levinson didn’t decide to have the home GreenPoint Rated until the remodeling work was quite far along. “Rating an existing home is quite complicated,” Mahoney acknowledged. “The time it takes to rate it is in proportion to how big and complicated the home is.” Still, the rating process “was a great experience,” she said. Although she is a Certified GreenPoint Rater for New Home, the program’s guidelines require independent verification, so she brought on board another rater certified to evaluate existing homes, Kevin Beck.
Meeting the program’s requirements isn’t a shoe-in. “You don’t just put green building products in a home and qualify,” Mahoney said. “It’s not about the points,” she emphasized. “It’s about making as much of a difference as you can.”
For Levinson, GreenPoint Rated is another type of dashboard, like his resource monitoring system.
“It’s not good enough to say you want a green house,” he said. “You have to put numbers to it. If you don’t monitor it, you can’t measure it. If you don’t measure it, you can’t improve it. When you improve, everyone likes to have celebrations. You can’t celebrate if you don’t measure. By doing those things we created an environment where we can get better and better.”
Energy Use and Greenhouse Gas Emissions
While the building footprint remained the same, the carbon footprint shrank as a result of the renovation. The original building had little insulation, so one of the first steps was to insulate the roof, exterior walls and the underside of the home with a soy-based foam insulation. The home’s single-pane windows and doors were replaced with double-pane, low-e products; argon gas between the panes of glass provide added energy efficiency.
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The home’s mainly incandescent lighting was replaced with energy-saving LED and fluorescent lighting. The house already had several skylights, including one in the kitchen that was reconfigured during the remodeling. “All the rooms have nice large window areas,” said Mahoney. “The house has deep overhangs. That’s an asset that helps us to have a bigger window area without the sacrifice” of too much heat gain.
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Gas furnaces were replaced with efficient dual-source (electric and gas) heat pumps, and the ductwork was tested by a home performance contractor to ensure that it the system was tight.
For Levinson, a venture capitalist whose company focuses on the clean tech arena, the house is something of a laboratory where he can try out systems and improve their performance. He has written at length about his approach to living in and remodeling his home on his company’s website, www.smallworldgroup.com.
Instead of relying on utility bill data that’s at least a month old, a state-of-the-art monitoring system gives them real-time information on gas, electricity and water use. Knowing exactly how much energy and water they are using—and when and where they are using it—helps them make decisions about how to conserve.
“This data allows us to make further changes from the initial design to improve its overall performance,” Levinson wrote in an essay on his website. “Sometimes the installed systems did not perform as specified and through the monitoring we were able to teach the installers and equipment suppliers how to improve their products or services.”
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| Rooftop solar PV and solar water. |
To ensure that most of the energy they use comes from sustainable sources, Levinson had a 12-kilowatt photovoltaic system mounted on the garage roof. The pitch of the roof was altered to improve its orientation to the sun. A solar hot water system serves the main house, the apartment and an endless pool, with a gas water heater providing supplemental domestic hot water during cloudy spells.
Levinson now uses 90% less gas than he previously used, and is making more electricity than he consumes.
“It’s a great example of just how far you can take a home to get it as close to zero as possible,” Mahoney said.
Indoor Air Quality
Throughout the interior, Mahoney specified healthier finishes, including low-VOC paints and natural stucco. Other healthy home features include high efficiency HVAC filters, bathroom and kitchen exhaust fans vented to the outside to remove moisture and odors, and insulation that gives off few or no indoor air pollutants compared to conventional insulation.
Resource Conservation
Products and finish materials were evaluated for their environmental attributes, with an emphasis on longevity.
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“Everything was chosen for durability,” Mahoney said. “We chose products like maple flooring that are less trendy and a little more classic so they can endure the test of time from a style point of view. That has always been a marquee of our firm in recommending finishes for our clients. We consider durability in everything we put into a home, so the next customer who comes in isn’t automatically going to remodel it.”
In addition to longevity, Levinson’s classic maple floor has another green attribute: it is certified by the Forest Stewardship Council to have come from sustainably managed forests. The new exterior cedar siding, as well as cabinets, new interior doors and the entry door are also FSC certified.
Mahoney and Levinson tried to work with local companies when possible. “The entry door is spectacular. It’s made by Liberty Valley Doors. They’re completely committed to being green,” she said of the company, which makes its FSC-certified doors in a solar-powered facility in Cotati, only 35 miles from Tiburon.
Water Conservation
Underneath the house, Levinson had two 7,500 gallon cisterns built to collect rainwater for landscape irrigation. Calling it “probably our most aggressive experiment,” he acknowledged that the water savings likely won’t offset the cost of such a large system, but he installed it in the spirit of using his home as a living laboratory of conservation techniques.
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| Bathroom water conserving fixtures include dual flush toilets and low flow faucets. |
To further reduce water use in and around their home, Levinson selected dual-flush toilets, an on-demand recirculation pump that reduces the time it takes for water to reach fixtures, and drought-tolerant plants for the gardens. The resource monitoring system tracks in real-time both household and irrigation water consumption.
Community & Living Green
The home has a number of design elements that accommodate diverse households, including a fully functional independent apartment and accessibility features such as a main floor with a zero-step entrance, doors and passageways with at least 32 inches of clear passage space, and bathrooms with blocking for grab bars. The home is within walking distance of public transit and neighborhood services.
Project Resources
Mahoney Architects & Interiors: www.mahoney-architects.com
Green By Design (green consulting and eco-friendly products):www.greenbydesign.us
Larwood Construction: (925) 299-1646
Earthcraft Landscape Design (rainwater harvesting ): www.earthcraftdesign.com
Liberty Valley Doors (FSC-certified doors): www.libertyvalleydoors.com
Sun First! (photovoltaic systems): www.sunfirstsolar.com
SoundVison (smart home controls): www.svsf.com
Anna Kondolf Lighting Design: www.kondolf.com
Kevin Beck, Certified GreenPoint Rater: kevinbeck@bigplanet.com
Suzman & Cole Design Asscoiates (landscape architecture): www.suzmancole.com
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