High-performing home showcase 2017
What makes a high-performing house?
By Chris Briley & Heather Chandler
Photo: Trent Bell
THERE ARE A LOT of loosely defined terms used to describe how “green” a house is. Luckily, some professionals in our industry have worked very hard to find ways to quantify this almost intangible quality, and in so doing, have generated new nomenclature that can often sound foreign to those outside the industry.
Net Zero refers to the building’s energy consumption and means that the building produces as much energy as it consumes. This is achieved through the use of renewable energy systems, most likely in the form of photovoltaic solar panels. It is also very likely that the home’s energy demand has been reduced by increasing the building’s insulation, system performance, and air tightness values. If a home produces MORE than it uses, it is said to be Net Positive.
Net Zero Ready is a term that is applied to a home or building that has done everything necessary to become Net Zero except add the renewables. One might think that solar panels are the most important part of this equation, but in fact, it is the act of reducing the energy demand of the house that is far more critical. Skimping on insulation or air leakage, or reducing the performance of the windows, could mean one would need to double the amount of solar panels on the roof.
The term Passive House or Passivhaus (not to be confused with passive solar design which refers to a design strategy) is an international standard focusing on the building’s energy demand, or how much energy a house uses. A certified Passivhaus uses about 90% less energy than a typical code compliant house, meaning in essence that it can be heated in the dead of winter with the same amount of energy a single hair dryer consumes, or about the same amount of heat given off by a small dinner party. Impressive indeed!
When a home is EnergyStar certified, a series of energy modeling, inspections, and testing provide the completed home with a score on the HERS (Home Energy Rating System) index. The U.S. Department of Energy has determined that a typical, code-compliant, well-built home has a HERS score of 100. So if you hear of a house having a score of 80, that home uses only 80% of the energy of the typical home. The lower the score, the less energy it consumes. If a home has a score of 0, then it is a net zero home. A HERS score below zero means the house is net positive.
An energy efficient house is also a tight house, meaning that it has very few leaks where air can pass from the interior to the exterior (or vice versa). Air sealing is one of the most costeffective measures one can take to deliver high performance. This is achieved by careful planning of the construction details and also by vigilant building professionals armed with an assortment of tapes and sealants, who patch every hole and seam in their path.
But how is air tightness measured? A blower door test is performed by removing an entrance door and replacing it with a special door with a large fan in it that then depressurizes the house. It also measures the rate at which air flows into the house to replace the air being displaced by the fan. This metric is known as ACH50 (air changes per hour at 50 pascals of pressure). The lower the number, the better. The average home for sale has an ACH50 of 3.9; for new homes it’s 2.5. To be a passive house, however, a building must have an ACH50 of 0.6!
Of course, many homes do not seek certifications or third party verification, but they do implement many of the same strategies as those that do. Often their proof is evidenced in their low utility bills or in their ease of comfort on those brutal Maine winter nights. These homes fall into the category of Pretty Good House, a popular colloquial term.
The homes featured on the following pages all address sustainability and deliver high performance as compared to a typical home. Whether they pursue certification or not, a high performance home is one that implements the same strategies: they reduce energy demand by insulating; air-sealing; choosing well-insulated, climate appropriate windows; choosing efficient mechanical systems; balancing air ventilation; choosing efficient fixtures and appliances; and incorporating renewable energy systems if possible.
Every home has an impact on our environment: some great and some slight; some negative, some positive. A high performing home is one that is leading the building industry in a positive direction.
Editor’s Note: The submissions for homes featured in this article came from home owners, builders, architects and renewable energy professionals across the state. We reviewed data for the submissions received and selected the six homes that you will see featured in this issue. As you will see, they represent a diversity of size, style, geography, methodologies, price and performance, showcasing a variety of options for Maine homeowners.
Five of this year’s submissions are newly constructed properties and one is a re-build. In every case, energy and performance was a goal of the design and build from the start. For each project, you’ll find an overview of the home, a summary of what we like about it from a technical perspective, details about the approaches implemented in the house and the performance it has achieved.