Net Zero/Sustainable/Green Building
“We are dedicated to environmentally sustainable and healthy construction and we
incorporate these principles into every step of our build process.”
NET ZERO BUILDING
What is Net Zero?
Net Zero is, put simply, the process of end-using – or “netting” – zero fossil fuels. To achieve net zero, a home must have the ability to generate power (typically through photovoltaic solar cells), and must consume the equivalent or less of what it generates. Most net zero homes today remain connected to the local power grid, such that they may feed surplus electricity back to world, and likewise obtain power during long stretches of cloudy weather. At the end of the day, you’re running a fair and balanced operation (with no oil or natural gas expenses, to boot)!
Batteries are coming down in cost, and are starting to make sense to replace generators for power outages, and will make sense soon for completely off-grid homes. Note that the largest problem with being off grid is heating the home, which is an excellent reason to build based a Net Zero Ready home.
What Does Green/Sustainable Mean?
Basically, these terms refer to the use of natural resources that are replaceable, that don’t damage our environment and that don’t make people sick. Many of today’s health problems come from or are aggravated by poor indoor air quality and exposure to toxic substances released through commonly used building techniques and products. Green products and methods are designed to minimize or eliminate these problems.
Our construction techniques are based on techniques developed by Passive House – the highest proven building standard in the world.
Passive House is a comprehensive approach to designing and building affordable, sustainable and healthy homes which use up to 90% less energy than comparable homes built to current building codes. Passive House is different from most of the “standards” in that the goal is not a particular insulation level or a particular HERS rating, but a defined level of very low energy use (4.75 kBTU/SF in the living area) without or prior to the use of site generated energy. Thus, the Passive House concept is today’s highest energy standard for home construction. These standards are more energy efficient than the programs and ideas listed above, and the extensive proliferation of the Passive Houses in Europe shows that they can be built economically. At least two European nations are using Passiv Haus standards as the minimum allowed under their building code.
The Passive House is designed using a computer modeling program called the Passive House Planning Program. When a house is completed to specifications and passes the required tests and inspections, it can be labeled a Certified Passive House.
OTHER ENERGY STANDARDS
LEADERSHIP IN ENERGY AND ENVIRONMENTAL DESIGN
The U.S. Green Building Council (USGBC) developed LEED certification to help promote green building practices and sustainable development. It rates construction projects by awarding points for green building practices in four separate areas: sustainable sites, energy and atmosphere, materials and resources, and innovation and design process. Points are awarded for each sustainable practice. When the points are added up, a structure or project is assigned a LEED rating of Certified, Silver, Gold, or Platinum.
In energy use, LEED accreditation requires the building to attain Energy Star as a minimum, but increased insulation values will add points, as will adding renewable energy generation such as photovoltaics or wind generation.
In addition to the added cost of necessary upgrades, the cost for LEED accreditation includes a fee to the USGBC, the cost to document each green or sustainable product, the cost for several meetings of the design team, and a fee to the rating agency.
HOME ENERGY RATING SYSTEM
HERS is a Home Energy Rating, established by the Residential Energy Services Network (RESNET). It is a measurement of a home’s energy efficiency. It allows buyers to compare the energy efficiency of different homes. With the HERS index, the lower the score the less purchased energy is needed.
The HERS Reference Home has a HERS Index of 100, representing the energy use of a home built to current energy codes; an Index of 0 (zero) indicates that the home uses no net purchased energy (a “Zero Energy” home, (ZEH or ZEB). A home we completed in May 2009 received a HERS index of 52, and we have identified changes that will help us achieve an even lower index.
Each 1-point decrease in the HERS Index corresponds to a 1% reduction in energy consumption compared to the HERS Reference Home. Thus, a home with a HERS Index of 85 is 15% more energy efficient than the HERS Reference Home, and a home with a HERS Index of 80 is 20% more energy efficient.
In climate zone 6, a HERS index of 80 is required for Energy Star accreditation.
ZERO ENERGY HOMES
Although not an official standard, a ZEH home (or ZEB) must obtain a HERS index of 0. This level indicates that the home has increased insulation levels and uses only site generated energy such as photovoltaics or wind generation.
Passive House is based on pioneering work by Americans and Canadians who built super insulated houses in the 1970s and 80s. In 1990, a Swedish professor and a German physicist fine tuned the previous research and developed a mathematical model for building extremely energy efficient buildings. They named this method Passiv Haus (sp) and built the first prototype in Germany. The concept caught on and this home and others were monitored extensively and the resulting information used in computer simulations to develop ideal construction parameters
Today there are tens of thousands of Passiv Haus buildings, both residential and commercial, throughout Europe. The Passiv Haus vision is that every family has a green home that is energy efficient, durable, comfortable, healthy and safe.
In 2002, a German architect hired by the University of Illinois built the first Passive House in the US and has subsequently founded Passive House Institute US as a clearinghouse for information and certification. At this time there are around a dozen Passive House homes in the US, but the interest is growing rapidly so that number will grow quickly.
How It Works
The Passive House concept includes superinsulation, airtight construction, mechanical ventilation, passive solar where possible, elimination of most thermal bridging, and choosing home appliances, heating and ventilation units that use minimal electrical energy. A Certified designer uses the Passive House Planning Program (PHPP) to develop a computer model of the project and tests the completed house to verify that it meets the standard. Houses that meet the standards are allowed to use the term Certified Passive House.
Style & Size
Passive House techniques lend themselves to any style and any size house, using a variety of insulating materials.
Indoor Air Quality
The key to indoor comfort in Passive House is a quiet central ventilation system that is widely used in Europe but still relatively unknown in the United States. As warm, stagnant air is expelled through the energy recovery ventilator, it passes by incoming streams of fresh, cooler air, allowing up to 90% of the heat to transfer without mixing the two streams of air. This system provides superior air quality 24 hours a day. Some European ventilation units not yet available in the US can provide all necessary heat for the house. As a result, says Passive House advocate Tad Everhart, “a passive house loses very little heat and then recycles it.”
Heating and Air Conditioning Systems
Passive House is designed so that typical heating and AC systems are not needed. The actual system, which will vary by house, might be a small heat exchanger or point source heater. These savings help offset the investment in added insulation, air sealing, better windows and other upgrades to the building envelope.
Passive House uses only triple glazed windows with ultra high efficiency glass and insulated frames. At this time there are only a few US manufacturers who make windows that will qualify, leading some builders to use imported Canadian or European windows.
Passive House standards recommend the home be sited to provide southern light and passive solar heat where possible, with wide overhangs used to shade the windows in the summer. The Passive House design program takes the size, placement and shading of all the windows into consideration.
Passive House standards were designed to minimize the carbon footprint of the house.
In the United States, buildings are the largest contributor to global warming, responsible for 48% of greenhouse gas emissions. Passive House standards are the single most powerful proven building concept for reducing greenhouse gas emissions.
Soaring energy costs, rapid climate changes due to greenhouse gas emissions, and the demand for high indoor air quality all call for effective solutions from the building sector. With unparalleled super-energy efficiency and superior air quality, Passive House design also provides a solution that puts true carbon-neutrality within reach.
Aside from one house on Martha’s Vineyard, there are as yet no Certified Passive House homes in New England. Therefore, the cost of meeting the standard in our region has not been determined. In Europe, the cost is estimated to be 10-15% higher than a code built home, but total cost of ownership evens that out within five to seven years, based on fuel savings alone.