Whole-House Green

Back in 1971 when this modest, split-level home in Cupertino, Calif., was built, very few people could have envisioned the changes that technology companies would bring to the area over the following 36 years. Today Cupertino is part of the Silicon Valley.

This same house that initially sold in the neighborhood of $20,000, now exists in a zip code where the average home value is $1.14 million. So it stands to reason why the couple who owns the home felt free to invest $467,153 in a whole-house remodeling project. It is also not very surprising—considering the growing interest in sustainable design and green building—that the couple chose to embrace a green approach, and why they ultimately selected Spectrum Fine Homes Inc. of Mountain View, Calif. to design and build the project.

According to Susan Davis CKBR, CGBP, the design principal at Spectrum, the company is well known for sustainable design and green building. Green is not just something they offer as a special item. It is a way of doing business.

“We have been remodeling homes for about 20 years now, and to really make green a focus company wide—in everything that we do and everything that we think—it started about four or five years ago with a project we were involved in,” says Davis. “It got us a lot of attention and everything we have done since has been green.”

Goals and Objectives

Within the spectrum of green colors, this project qualifies as a very dark green. Almost every aspect of the project took on a sustainable design or green building aspect. For the busy couple who own the home, the primary objective was to make the home comfortable and energy-efficient. They wanted healthy indoor-air quality. They also wanted to update their kitchen and bathrooms; to open and update their main floor living space; re-configure their lower-level spaces, which were dark and cramped; and, above all, they wanted use “technologies, materials, and building techniques that did not adversely affect the environment and natural resources.”

With these goals in mind, Spectrum brought in a consulting firm, Sustainable Spaces Inc. of San Francisco, to run a battery of diagnostic tests on the home. In fact, this type of diagnostic testing is now standard operating procedure for Spectrum. Sustainable Spaces gathers air flow and other metrics on the home and compares them with a set of targets established by Energy Star, and the California Home Performance Program.

“With sustainable design, it is different than the traditional way of thinking,” says Davis. “Part of it is a commitment to respect collaboration, and to bring in outside experts. So, when we first begin to design a project, the first thing we do is perform an audit on the home so we can get the right information for designing.”

Sustainable Spaces begins by analyzing energy-bill data from local gas and electric utilities. From this, they map the home’s monthly energy use, specifically the amount of kWh (kilowatt hours) and therms consumed. This analysis showed that prior to any changes, the home consumed 8,537 kilowatt hours and 733 therms each year. From there, Sustainable Spaces measured temperature loads in each room and determined where the home’s energy was used. The tests determined that air leakage consumed 29 percent of the home’s energy: walls, 25 percent; duct leakage, 18 percent; attic, 16 percent; and windows, 12 percent.

Next, a blower-door test was conducted on the home to put some specific numbers to the home’s leakiness. The blower door pulls air through the house and measures the rate of air exchange in the home. By determining the rate of air exchange, a baseline level of efficiency or inefficiency is determined. The lower the rate of air exchange, the greater the home’s efficiency because that reduces the amount of energy used to heat or cool outside air that is coming into the home. This test found a “natural air exchange per hour” of .71. This means that each hour of every day, 71 percent of the home’s air is exchanged with the outside. According to Sustainable Spaces, the maximum recommended level of air change per hour is .35 or 35 percent. Thus, a target leak reduction of 50 percent was established.