In the heart of Colorado’s Rocky Mountains, Cillian Liam Barrett and Habitat for Humanity in Gunnison Valley are creating a new paradigm in home construction.

The owner of Hearth Design Build, Barrett is on a mission to influence his profession to construct houses that are not only more affordable, energy efficient, and environmentally sound, but also safer for homeowners and building crews. His methods may seem unconventional compared to traditional building practices. However, he is passionate about innovating the way dwellings are constructed and influencing the future of design-build—a method of project delivery in which a single entity designs and builds a structure, creating a unified flow of work from initial concept through completion. By combining the inherently low-impact, durable building strategies of the past with a modern understanding of building science and current technology, Barrett and his team are able to create a design and process that strengthens the local economy, reduces environmental impacts, and binds the community.

Last year, Barrett oversaw the design-build of a 1,000-square-foot, two-bedroom home for Habitat for Humanity in Gunnison, Colorado, a community nestled in the valleys of the Rocky Mountains at an elevation of 7,703 feet. Gunnison has some of the coldest winters in the country, with an average January low of −8 degrees F (−22 degrees C), but it also has warm summers that average 82 degrees F (28 degrees C) during the month of July. The challenge was to build a high-performance, energy-efficient, and temperature- and humidity-controlled house for this radically-varying climate—all while creating a friendlier ecological footprint and reducing financial burden on the homeowner.

For many decades, a standard industry practice has been to install a “vapor barrier” on the interior walls of buildings in cold climates. In recent years, builders in the United States have been using toxic, high-GWP (Global Warming Potential) foams to create this barrier. Barrett has chosen not to use a typical interior vapor barrier or foams for his projects, opting instead for less toxic/dangerous materials and “vapor-open” wall assemblies. Therefore, his approach for the Gunnison home was to create a double-stud, super-airtight, but vapor-open, thermal envelope containing a continuous “smart membrane” air-control layer on the exterior, which allows any seasonal condensation buildup to dry out easily in either direction. The 20-inch wall cavity is filled with materials that have an inherent ability to absorb, distribute, and release moisture, such as untreated framing lumber, strawbales, and cellulose insulation. This “breathable” wall system is primarily made up of cellulose composed of 75-85% recycled paper fiber, the highest recycled content of any insulation available, and with the least environmental impact.

Another design consideration was to make the home as airtight as can be, to achieve the greatest possible efficiency in terms of temperature and humidity control inside the house, with the structure achieving a blower door test result of 0.33 ACH50, a very important metric for determining a home’s energy efficiency. Heating and cooling of the Gunnison house is achieved by an innovative heat recovery ventilation (HRV) system, which uses a heat pump to recover energy and control internal humidity, while providing continuous fresh, filtered air.

Barrett knew that data collection would be essential to monitoring the home’s performance and ensuring the efficacy of the exterior air-control layer, the overall construction design, and the ventilation system. At the suggestion of Rich Stromberg of Western Colorado University, which partnered with Barrett on the project, Barrett chose affordable Bluetooth-enabled HOBO MX2302A temperature/relative humidity data loggers from Onset for this important task. Approximately 20 loggers were deployed in and on the home’s walls to monitor interior and exterior temperature and humidity.

“The HOBO data loggers are extremely important to monitoring the temperature and humidity in the house. And because of the Bluetooth technology, the loggers can be configured, and data can be downloaded with just a smartphone or tablet, up to 100 feet from the logger,” Barrett said. “The ability to conveniently collect accurate data enables us to prove that there are viable alternatives to longstanding industry practices, and these alternatives ultimately benefit the consumer, as well as homebuilders.”

Besides the environmental benefits, the family now living in the home is seeing an economic benefit as well: a $50 electric bill in a completely electric-powered home – in the month of January, usually the coldest month of the year in Gunnison. And with the homeowner planning to install a net-metered solar array this summer, the house will be fossil-fuel-free very soon.

Now, another house is in the works for Habitat for Humanity in Gunnison Valley and Barrett plans to use HOBO MX2302A data loggers for that project as well.

“Industry wisdom says that houses with no vapor barrier on the interior walls will fail and that we need foams to achieve high-performance goals,” Barrett observed. “We’re proving that’s not true, particularly in this arid climate, and having tools like HOBO loggers will help builders and designers create a new paradigm in home construction that has a much lower health impact on our people and our ecosystems.”


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