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Texas Builder’s Passion for Passive House Comes to Life

Most people would assume it makes zero sense to build a passive house in a hot, humid climate. The indoor/outdoor temperate differences aren’t as extreme as they tend to be in other climate zones.

But a passive house still offers a huge performance increase from traditional building methods, and a great improvement in the indoor air quality – a major attraction to homeowners. Not to mention the reduction in energy bills. In a cold climate, a passive house is projected to reduce energy expenses by 90%. In a hot climate, more like 70%*.  Still a signifiant savings, and worth the investment in additional time and materials up front.

 

Choosing Investment vs. Expense

From the financial side, the theory is that you’re spending more money on performance, then that money gets divided over the life of your mortgage. If you can spend $30 more a month on a mortgage, while achieving $100 savings a month in utilities – you’re at a major advantage.

Not only does it make a lot of sense, it’s something energy efficient builder Mark Larson, CPHC, Built Green Texas, can readily convey to his clients as a professional builder and consultant. 

“When you allocate your money this way, you’re choosing to invest in the value of your home, not the expense of living in it.

-Mark Larson, CPHC, builder, Built Green Custom Homes, Austin, Texas, and homeowner

 

Performance Metrics Make the Difference

Mark Larson started his career in corporate real estate. He decided to make the leap into building because he loved that side of the business. If he was going to completely change careers and build houses, he wanted them to be the best ones on the market.

That’s how he discovered passive house design. It’s the most stringent building metric in the world, but also the only one that is performance based. It’s not prescriptive like LEED, meaning certified to operate a certain way in theory. Passive houses MUST perform as they are designed, or they don’t achieve passive house certification. They have to hit certain metrics for air tightness, measured with a “blower door test”.  The fact that the performance is completely measurable was much of the appeal.

“I’m a huge fan of performance based metrics – which is exactly what passive house offers. I knew my family would live and breathe in the highest indoor air quality. It really matters.”

-Mark Larson, CPHC, builder, Built Green Custom Homes, Austin, Texas, and homeowner

 

Blower Door Testing

IAQ Texas conducted the initial blower door testing. But Mark didn’t get the results he was hoping

for, so he employed his own blower door contraption to help find leaks. Mark used a 2500 cfm construction ventilation fan and taped roof underlayment around the door opening.

He found some opportunities for better air sealing between the top plates, and at plate boards butted together. The attic hatch was also a source of leaks. Zip tape was sealed into a 90 degree corner, but air leaked out the ends of the length of tape. Some random nail holes and a few casements windows needed slight adjustments to better seal when closed.

Once those changes were made, Mark’s passive house rater from ATS Engineering did another blower door test before adding interior insulation. These results surpassed Mark’s expectations, and made it below the Passive House metric of .6ACH, and hit .57ACH. (via instagram, Feb 1, 2019). This figure is expected to drop even lower once interior insulation and drywall are added.

The Building Envelope

Mark spent a significant amount of time researching the materials he wanted to use for his home. For the building envelope, he used 2″ x 6″ studs, 16″ on center, Zip sheathing, Rockwool ComfortBoard exterior insulation, and Alpen windows. He had discovered ThermalBuck years prior, and was excited about finally having the chance to use it on his own home.

“ThermalBuck simplifies the water, air, and thermal control layers of window and door installation. It solves a specific problem of how and were to flash windows within continuous insulation. ThermalBuck will always be a tool in my design toolbox to solve the complexities of “outies” in CI,” said Larson. 

“It solves a specific problem of how and were to flash windows within continuous insulation.”

-Mark Larson, CPHC, builder, Built Green Custom Homes, Austin, Texas, and homeowner

 

Passive House Austin

Mark is part of a dedicated group of building industry professionals working to make passive design well-known in the Texas market. Passive House Austin promotes the principles of passive design through events, podcasts, workshops, and most notably, the Humid Climate Conference. Held annually in Austin, the Humid Climate Conference recently featured Joe Lstiburek, widely recognized as the leading building science expert in the industry. It draws building professionals from all over the South, to focus on issues specifically related to their climate – offering a huge benefit over national or international events.

To learn more about Passive House Austin, and view more photos from the recent Huber sponsored happy-hour event at Mark Larson’s passive house build with IAQ Texas and Positive Energy, click here.


Helpful Links & More Info:

Mark Larson Instagram
Built Green Custom Homes, Austin Texas
Passive House Alliance – US

* homebuilder estimates from personal research

Building a Better Mousetrap: The Development of ThermalBuck

People often look at ThermalBuck and ask, “How did you come up with this idea?”

Like any good idea, it starts with figuring out you’ve got a problem in the first place. And that’s exactly how this whole process began. John Brooks, developer of ThermalBuck, built his family an extremely energy-efficient, well-insulated house. And he was surprised with how frustrating and difficult it was to install the windows.


So you’ve added exterior insulation to a building, and the depth of the insulation extends past the rough opening, where the windows are installed. The question of “What do we do about the windows?” becomes an important consideration – and a real challenge to overcome.

Rough openings have always presented concerns for air & water sealing on any building, and changing the mounting point for the windows makes them even more vulnerable to moisture damage.

High-performance architects and builders have used exterior insulation for years, recognizing the importance of eliminating thermal bridges in the building envelope. Traditionally, most U.S. builders have insulated between the studs, if they decided to use insulation at all.

But the building practices of the past are giving way to innovation.

“If you see a failure on a building, you can pretty much bet that it started with water.”

John Brooks, president, BRINC Building Products, developer of ThermalBuck

More states are adopting IECC energy codes that require continuous insulation, and builders are striving to understand how building science impacts the energy efficiency and quality of their work. Use of exterior insulation in both new construction and renovations is growing significantly, so solving this challenge has become a priority.

Mounting Windows Directly Over Foam

Often builders choose to mount windows and doors right over the exterior insulation, particularly for depths in the .5″ and 1.0″ range. But the nail flange compresses the insulation, creating gaps for air and water to enter. There is also a lack of good support for wide, heavy windows, which can affect the long-term operation of the window. Martin Holliday of Green Building Advisor spoke with Cordell Burton, an installation engineer at Pella Windows, about the issue in 2011.

“You can’t screw through foam sheathing – the foam will compress. You have to have something solid to attach the window to.”

Cordell Burton, Pella, as quoted in Musings of an Energy Nerd, Green Building Advisor, May 2011 

For insulation depths over 1.5″, builders generally built “wood bucks”, made of plywood or dimensional lumber, to extend the mounting point of the window.

The Traditional Wood Buck

While wood solves the problem of extending the mounting point, it creates some new problems of its own in that it often will warp, rot, and shrink.

Wood is a poor insulator, so wood bucks allow air to transfer around each window and door through the rough opening. Cold air is denser than warm air, so in the winter the heated indoor air heads outside, and in the summer, the hot, humid air outdoors moves into the cool air-conditioned interior. This transfer of energy is called thermal bridging, which is what continuous insulation is designed to eliminate in the first place.

 

The Problem with Thermal Bridging

Thermal bridging isn’t just about wasted energy – although a home that’s more expensive to heat and cool and isn’t comfortable is a legitimate problem. But it’s really about water. Builders know if bulk water isn’t managed properly, it can cause extensive damage to a building. But the moisture that forms from condensation also causes issues over time.

Another hidden concern is condensation, which can be a consequence of thermal bridging. When warm air comes into contact with a cold spot on the floor or wall, water vapor in the air cools and collects as droplets on the colder surface. This can result in durability problems, as well as poor indoor air quality,” said Joanna Grab, Senior Sustainability Consultant, Steven Winter Associates.

The more we insulate our buildings, the more important it becomes to reduce the potential for condensation to form – good building sense in any climate.

“Another hidden concern is condensation, which can be a consequence of thermal bridging. This can result in durability problems, as well as poor indoor air quality.

-Joanna Grab, Senior Sustainability Consultant, Steven Winter Associates, as written by Kate Danielsen, High Performance Walls on swinter.com, January 2017

Building a Better Mousetrap: The Process

John Brooks was very familiar with the problems associated with wood bucks. After losing his home in a fire, John built a new home for his family with his own hands. They settled in to make a new start, only to watch as condensation and mold formed around the new windows. Not only did the wood bucks he built cause condensation issues, the flashing process was so difficult that the whole installation process amounted to an exercise in frustration. He began to think there had to be a better way to install windows.

Using his background in construction and his experience in the insulation industry, John began to make prototypes for a product that would be better than a wood buck. It needed to solve multiple problems and still be cost-effective. Here’s the wishlist John had for his new product:

An early attempt at ThermalBuck, EPS without the waterproof coating.
An early attempt at ThermalBuck, EPS without the waterproof coating.
    • Extend the mounting point
    • Prevent the compression of exterior insulation
    • Insulate the rough opening
    • Protect the rough opening from moisture damage
    • Support the window
    • Handle shear & wind loads
    • Provide durability, strength & flexibility
    • Install easily
    • Simplify flashing & integrate with the WRB
    • Maintain the long-term operation of the window.

Anyone who has ever come up with a great idea for a new product will agree that the “eureka” moment doesn’t happen without a long period of not-so-great ideas, that take you back to the drawing board time and time again, testing both your patience – and your determination.

This was no different for John, who spent all of his spare time and most of his money on this project, often struggling not to give up. A chance meeting with some strangers at a restaurant, the desire to build a strong business to help sustain their community, and shared Christian beliefs poured new life into his research. After 4 years of prototypes, trial & error, third-party testing, and an unwavering personal faith, John realized his vision for ThermalBuck as it exists today.

The Innovation: ThermalBuck

ThermalBuck is an L-shaped window buck that goes inside the rough opening, and extends outward to create a flush plane with exterior insulation and/or rainscreens.

ThermalBuck is made of a type XIV high-density EPS, and coated in a waterproof resin. Not only does it have the compressive and shear strength to handle the weight of large, high-performance windows, but it also insulates the rough opening with an R-value of 4.4 per inch to limit thermal bridging around the rough opening.

The High-Performance Future of Building

In 2016, Scott Gibson of Green Building Advisor presented ThermalBuck as “An Alternative to Wood Bucks”, and the building industry took notice.ThermalBuck began to receive widespread media recognition, and garnered a lot of attention at conferences and trade shows, because there was nothing like it – it’s simple to use, and solves a common problem.

“This is an impressive product. Once you see it, you really understand the problem this solves for builders like me.”

-Matt Risinger, Risinger Construction, The Build Show

John met Matt Risinger at the EEBA conference in Dallas, Texas, in 2016. Based in Austin but originally a Pittsburgh native, Matt had a western Pennsylvania connection with John.

Matt is a highly respected builder, educator, and self-proclaimed “building science geek” with over 300,000 followers on his popular YouTube channel, Build with Matt Risinger.

He’s well known for sharing solutions and new products to his thousands of followers – and appreciated for his candor. Risinger took home our tabletop displays to share with his building community and gave ThermalBuck great feedback. John was fortunate to film some videos with Risinger & Co. in Austin, and the building community took notice.

The rest, as they say, is building history.

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Follow ThermalBuck’s path in the media here.


Want to learn more? We recommend these excellent building science resources: Heat Rises… and Falls – Stack Effect, Air Movement and Heat Flow, Allison Bales, Energy Vanguard. How it Works: Vapor Drive, Rob Yagid, Fine Homebuilding. Plan Ahead to Save Energy – Martin Holladay, Fine Homebuilding. 

 

 

PHIUS Verified Installation with Alpen

Alpen 925 Zenith Nail Fin Window + 2.5″ ThermalBuck

Energy efficient windows are an essential component of any high-performance building. But the installation was always a challenge for nail flange windows, which have to be mounted on the same plane as the exterior insulation.

ThermalBuck teamed up with North-American passive house window manufacturer Alpen High Performance Products to introduce their PHIUS Verified Window Installation Detail featuring the Alpen 925 Series Fiberglass window with 2.5″ ThermalBuck.

PHIUS Verified Window Installation Data:

Alpen 925 Zenith Nail Fin Window + 2.5″ ThermalBuck 

ThermalBuck effectively limits thermal bridging at the rough opening, provides a superior air & water barrier than a wood buck, and also a strong support for the weight of the window.

Passive house designers and builders now have the data they need to confidently include ThermalBuck into their specifications.


The Alpen HPP Zenith Series ZR-9/ 925 window features up to R-9.1 insulation, 99.5% UV protection, insulated frames, and Alpen Glass, Alpen’s renowned Suspended Film Technology. Every Alpen window has 9 key design features that make these highly engineered windows some of the best in the industry. Read more about the technology and craftsmanship of Alpen windows here.

Alpen High Performance Products is a national distributor for ThermalBuck. thinkalpen.com