Certified green, sustainable building design is becoming a reality across the country, for all kinds of markets and at nearly all price points. The industry is abuzz with questions about how a green building code may change their business outlook, change the laws or even change the world. There’s no doubt that broadly-applied minimum regulations for better, healthier, more efficient and environmentally sensitive building practices are changing the high performance building landscape. Like it or not, green building affects how builders, contractors and adjacent businesses like ours will do business in the 21st Century. Here’s what you need to know.
What is Green Building?
The U.S. EPA says “Green building is the practice of creating structures and using processes that are environmentally responsible and resource-efficient throughout a building’s life-cycle from siting to design, construction, operation, maintenance, renovation and deconstruction. This practice expands and complements the classical building design concerns of economy, utility, durability, and comfort. Green building is also known as a sustainable or high-performance building.”
There are a number of features which can make a building ‘green’. These include:
- Efficient use of energy, water, and other resources
- Use of renewable energy, such as solar energy
- Pollution and waste reduction measures, and the enabling of re-use and recycling
- Good indoor environmental air quality
- Use of materials that are non-toxic, ethical and sustainable
- Consideration of the environment in design, construction, and operation
- Consideration of the quality of life of occupants in design, construction, and operation
- A design that enables adaptation to a changing environment
Over the past two decades, green and sustainable construction has evolved from a fringe movement to achieving mainstream status. In a study conducted by Booz Allen Hamilton for the U.S. Green Building Council (USGBC), they predicted that green construction spending would increase from $150.6 billion in 2015 to $224.4 billion in 2018. The study also predicted that between 2015 and 2018, green construction will generate $303.4 billion in Gross Domestic Product (GDP), support 3.9 million jobs and provide $268.4 billion in labor earnings.
While the business and financial aspect is clearly relevant, what’s interesting to us is long-term building sustainability. The USGBC agrees:
Energy has emerged as a critical economic issue and top priority for policymakers. Unsustainable energy supply and demand have serious implications for everything from household budgets to international relations. Buildings are on the front line of this issue because of their high consumption of energy. Studies have repeatedly shown that efficient buildings and appropriate land use offer opportunities to save money while reducing greenhouse gas emissions.
So where do you start? By addressing the building envelope.
Air sealing and air tightness are no laughing matter. The more control a home has over the air circulating within it, the better the indoor air quality and the higher the energy savings. The U.S. Department of Energy (DOE) estimates the average American home has enough air leakage to add up to a two-foot-square hole. In practical terms, that’s like leaving a window open 24 hours a day. So how do you really know if your building is airtight? The blower door is the great litmus test of airtightness in a structure: it can either place the stamp of approval on a building’s sealing measures or expose gaps – and sometimes gaping holes! – in the system.
What Is Blower Door Testing and Why Does It Matter?
A blower door test is simply a diagnostic tool used to measure how much air filters out of your house (your home’s “airtightness”). The blower door allows testers to apply a consistent and measurable pressure to the house so that houses can be compared accurately.
Increasingly, blower door testing crops up as a required measure for new construction, under programs like ENERGY STAR® and the Department of Energy’s Zero Energy Ready Home. The 2012 International Energy Conservation Code® (IECC) also calls for a blower door assessment.
The mechanics of a blower door test are actually fairly simple. Prior to the test, it is best to walk through the property and do a visual inspection, ensuring no visible gaps appear on the exterior of the building – no windows or doors are open, dampers and inlets are closed – and to verify that any atmospheric fossil fueled appliances are turned down so they will not fire during the test.
For the test itself a powerful, variable speed fan is mounted into the frame of an exterior door. The remainder of the doorframe is sealed with a temporary panel. A pressure gauge, air manometer, and hoses for measuring airflow are attached. The fan is then turned on, sucking air out and depressurizing, or lowering the pressure, inside the home (the force exerted by the fan is the same as a 20 mile per hour wind!). The test typically takes an hour.
The reasoning behind the test is grounded in simple physics. Air moves from areas of high pressure into areas of low pressure. As the pressure drops within the building (as the fan removes air), the higher air pressure outside the structure seeks an easy entrance. Its path of preference inside is through any unsealed gaps or openings. By changing the pressures, a blower door test easily and accurately pinpoints the weak spots in a home’s envelope.
An uncalibrated blower door test is useful for simply locating leaks. If the test is a calibrated blower door test, you can learn not only where leaks are occurring in the home, but also determine the air infiltration rate, or air tightness, of the home.
Blower door tests can take place during various stages of construction, exposing pesky details like leaks around ducts or windows, so they can be fixed before the home is finished, and before fixing becomes expensive!
What Do Blower Door Testing Numbers Mean?
Your test is done and now the auditor wishes to inform you of his findings. The first couple numbers you will hear are:
- ACH at 50: This term refers to “Air Changes per Hour” at 50 pascals. In layman’s terms, it means, at a test pressure of 50 pascals, the total volume of air in your home will be replaced 5 times in one hour. Relatively speaking, ACH5 @ 50 is a semi-tight home, ACH5 – ACH9 is a moderately leaky home, and anything over that is a very loose and leaky home. Remember, the lower the number the better!
- CFM at 50: This term refers to “Cubic Feet per Minute” of air at 50 pascals. Basically, it’s telling you in its most basic form, how much air is moving from your home, through the fan, and to the outside. This number is used to calculate the above-mentioned ACH at 50. Typically, tight homes will be under 1250 CFM at 50, moderately leaky homes will be between 1300-3000 CFM at 50, and any number over that would indicate a very leaky home, as seen in most older built structures.
- ACHnat or ENIR (Estimated Natural Infiltration Rate): You may hear this term, but it isn’t considered by many to be very accurate. It is simply a measure of the “Natural Air Change Rate.” But, don’t get overly bothered by this number.
For reference, one square inch of air leakage is equal to about 10 CFM. So, if your home had, let’s say, 2200 CFM at 50, you would have roughly 220 square inches of leakage. For reference, the IECC lists a mandatory air leakage of ≤5 ACH @ 50 pascals in Climate Zone 1 and 2, and ≤3 ACH @ 50 pascals in zones 3-8. These specific test requirements are calculated on the flow rate of air produced by a blower door at a specified pressure (50 pascals or 0.2 inches of water).
The bottom line here is: Do not get lost in the numbers. Think of them as a reference point to use as you begin to seal and tighten your house. Choose a professional who specializes in blower door testing and check their credentials. Use the results of the blower door test to get an understanding of where your home is leaking and why. For example, leaking from around your front door might not be as bad as leaks from under your home in the crawl space. It all depends on where and how much air is entering (or leaving) your home.
What is the HERS Index?
HERS, or the Home Energy Rating System® Index, is another tool in the energy efficiency toolbox. It’s one of the most dominant and well-known industry standards for determining and visualizing a home’s energy efficiency. Developed by the Residential Energy Services Network (RESNET), and launched in 2006, you’ll run across the HERS Index Score offering official verification of energy performance for a number of agencies and their programs, including the Department of Energy (DOE), Department of Housing and Urban Development (HUD), and the Environmental Protection Agency (EPA) and ENERGY STAR®.
More specifically, a HERS home energy rating can only be conducted by a certified RESNET Home Energy Rater. Showing up at your home with blower door equipment, a duct leakage tester, combustion analyzer, and infrared cameras in tow, the rater is determining:
- The amount and location of air leaks in the building envelope.
- The amount of leakage from HVAC distribution ducts.
- The effectiveness of insulation inside walls and ceilings.
- Any existing or potential combustion safety issues.
Unleashing all the weapons in their arsenal, a HERS rater will test your home’s building envelope, duct systems, and air quality, searching out leakage and intrusion issues. They will determine the amount and location of air leaks in the building envelope, the amount of leakage from HVAC distribution ducts, and the effectiveness of insulation inside walls and ceilings. A key weapon in the fight against air leaks is tape. High-quality tapes, selected specifically for the unique application and material, are essential in stopping gaps and sealing at joints, penetrations, and ducts. A thoughtfully and well-taped home will score better in HERS due to reduced leakage.
Once the data is gathered, the rater feeds this information into an approved simulation analysis tool (typically REM/Rate) to generate a score. A home’s score typically falls between 150 to 0 on the HERS Index.
The lower the score, the more efficient the home. The average score for an existing home tends to be 130, according to the U.S. Department of Energy; new-built homes usually score at 100. A score of 0 means a house is “net-zero” and produces or conserves as much or more energy than it uses. Each one-point change up or down on the scale indicates a 1% change up or down in energy efficiency.
That said, the HERS Index Score is not an energy audit, but rather results from a home energy rating. The chief difference here is that a rating is both a measurement and a comparison of a home’s efficiency, whether against a similar home or a national scale, or via another method of appraisal. An audit, on the other hand, is an individual assessment of a home that generates valuable information about efficiency issues and how to fix them. In the end, a rating, first and foremost, offers an assessment of where a home’s performance falls within a defined efficiency standard; an audit highlights real issues in an individual home that detract from its efficiency.
What does HERS mean for builders?
According to Building Scientist and Residential Construction Expert Colby Swanson, “HERS matters because it has become the benchmark ‘energy rating’ system for the majority of new construction builders in the U.S. When the auto industry added the Miles Per Gallon index in 1975, it drove the auto industry to build more energy efficient vehicles. The HERS rating is effectively an MPG sticker for homes. Today there are more than 150,000 homes a year getting a HERS rating (both new and existing) and it is continuing to increase. Cities like Austin (TX), Santa Fe (NM), and Newton (MA) are moving towards mandating a HERS rating be given to all existing homes when they are sold.”
Nationwide, seven states have incorporated the HERS option into their residential building energy codes thus far: Arkansas, Colorado, Idaho, Kansas, Massachusetts, New York, and New Mexico. Additionally, as of April 2016, there are now a total of 10 states that have adopted the Energy Rating Index as a compliance option to their state energy code: Alabama, Florida, Illinois, Maryland, Michigan, New Jersey, New York, Texas, Utah, and Vermont.
While State mandates might be forcing the adoption of HERS in the long term, profitability may spur action faster. Studies have shown that energy efficient homes can sell between 8 and 30 percent more than non-efficient homes. And there’s no clearer indication of the bottom-line value of HERS than seeing six major U.S. builders embrace it in their marketing and advertising. KB Home was the first builder to make arrangements with RESNET to use the HERS Index to educate its buyers about their home’s energy efficiency. Other major builders such as David Weekley Homes, Heritage Homes, M/I Homes, and the PulteGroup quickly followed suit as have smaller home builders, like Arbor Homes in Indianapolis, IN who uses HERS certification throughout its marketing endeavors.
Without a doubt, as energy efficiency becomes more important to home buyers, i.e. comparing HERS Index scores between new home options, more builders will pay attention and work harder to improve their efficiency game. So yes, builders are going to take HERS seriously, sooner or later.
Adhesive Tape and Energy Efficiency
So what does all this have to do with tape strategy, and how you build? As a matter of reference, right now, a large coalition of major homebuilders are working to have IECC 2015 adopted, instead of the next code in sequence (IECC 2012), to better promote a performance, rather than just a prescriptive, approach to energy efficiency. So, like it or not, the blower door test is here to stay. To limit air leakage, builders use tape to seal the seams of a variety of membranes and buildings products, including housewrap, polyethylene, OSB, and plywood. Seaming Tape is also being used to seal leaks around penetrations through air barriers — for example, to seal around plumbing vents — and to seal sheet goods to a variety of materials, including concrete. Furthermore, tape can create a continuous barrier when applied correctly, which is what you need an air seal to be for it to be effective. This is hard to get with other kinds of fastening systems.
Indeed, trend reports indicate that overall, tapes used on job-sites will outpace the overall construction industry growth (3%-5%) with an estimated 6%-7% annual growth rate. New residential tape use will increase the fastest in double digits due to code compliance. In the past, tapes were used sparingly on joists and viewed as a temporary fix or cheap solution. Today, tapes have transitioned into high value and highly functional products that both enhance building airtightness (seaming tape) and prevent water intrusion (flashing tapes).
The benefit of using high-performance tapes for air sealing the building envelope and bonding in all kinds of manufacturing applications is inarguable. Building codes are adapting to include, or even require, tape in high-performance commercial and residential structures. And even more powerful tape options are being explored for speedy manufacturing processes. As such, tapes will continue to increase market penetration as it finds new application uses on job sites and continued efforts towards more durable and energy efficient buildings.
At ECHOtape, we believe green building is the future of building and construction. We also believe that over the next 10-20 years, blower door tests and HERS ratings will likely be mandated on all existing home sales and new homes. Perhaps the tests and tools will be further refined, but buildings are only going to get healthier and more efficient. Which is why we are investing in learning, developing, and improving on these technologies, to better meet the growing need of our customers. How can we help you meet your green building needs?