This just in and hot off the press – the House in the Hollow Case Study! TC Legend built this net-zero house through the winter of 2020/ 2021.
The house-in-a-hollow isn’t really in a hollow, it’s on a knoll, above protected wetlands, northeast of Bellingham. The hollow is formed by the trees, which were preserved to shield the house from overheating, and to conserve the flora of the native wetlands.
Measuring 1950 square feet, this Department-of-Energy certified Net Zero clerestory design has a central kitchen and a 1st floor aging-in-place floorplan. Designed for an Alaskan couple whose love of the outdoors demanded a house that fully engaged with the landscape, plenty of daylight is admitted & access to outdoor living is easy.
“Builder TC Legend Homes of Bellingham, Washington, aims for quality and sustainability in every home it constructs and company founder Ted Clifton Jr. has found the U.S. Department of Energy’s Zero Energy Ready Home program is an ideal way to achieve that goal.”
“The DOE Zero Energy Ready Home program is a great benchmark not only for ourselves, but for all those looking to build or purchase a home that is eco-friendly. Since the program incorporates ENERGY STAR and Indoor airPLUS, holds high standards for energy efficiency, and is nationwide, it is an easy way to compare homes across the board and that reduces confusion for purchasers,” said Clifton.
“It’s also great that the DOE program has a very low cost barrier. There are many other certification programs that charge large fees, making it difficult for small builders to participate. Or, the cost of the fees gets passed along in higher home prices, increasing the barrier to purchase for many people,” Clifton added.
Since 2015, TC Legend Homes has built all of its homes to the DOE program criteria. The builder typically constructs one spec home and five or six custom homes for buyers each year and currently has nine homes under construction. In 2022, the builder was recognized by DOE for its efforts with a Housing Innovation Grand Award in the category “Custom for Buyer under 2,500 ft2.”
Modeled Performance Data of House in the Hollow:
• HERS INDEX: without PV: 33 with PV: -23
• Annual Energy Costs: without PV: $600; with PV: $-280
• Annual Energy Cost Savings: without PV: $1,200; with PV: $2,150
• Annual Energy Savings: without PV: 8,400 kWh; with PV: 20,350 kWh
• Savings in the First 30 Years: without PV: $48,930; with PV: $86,550
Thanks to all who came out to the Zero-Energy Home tours!
And a BIG thank you to Sustainable Connections for co-hosting! We had a great turn out both nights educating the community about what a Zero-Energy home is all about, and how it differentiates from conventional home building.
Learn more about the embodied carbon and the utilities (calculated by Talia & Nicole) saved by this Zero-Energy House in this case study!
At TC Legend Homes, we have dedicated ourselves to pursing the vision of zero-energy homes for all. We strive to be pioneers in energy efficiency, seeking to create a healthy and clean carbon neutral future that allows the next generation to thrive. Our history of excellence in reducing or eliminating the operational emissions of our homes speaks for itself. Through extensive energy efficiency measures, quality craftsmanship, and a combination of passive solar design and rooftop photovoltaic, we have created a building model that allows us to make our affordable, zero-energy home vision a reality. Over the past 7 years, we have built more than 20 homes and ADU’s that are zero energy ready at a minimum with more than 12 of the 20 being net positive homes. Now it is time for TC Legend to expand our focus to address the other element of emissions in buildings, the embodied carbon.
The carbon footprint of any building is comprised of two elements: the commonly focused upon operational carbon and the less commonly addressed embodied carbon. Since our building model has successfully addressed the operational aspect of this footprint, we are now expanding our focus to addressing the embodied component while still maintaining excellence within the operational emissions.
What is Embodied Carbon and Why does it Matter?
You might ask, “What exactly is embodied carbon and why do we care about it?” Simply put, embodied carbon is the upfront “carbon footprint” of a product. For buildings, you can think of it as the emissions that are produced to create the parts of the building, encompassing all emissions that occur before it is functioning as a home. This includes all emissions from material production and those produced during construction. In contrast the operational carbon of a home is the emissions released to heat, cool, and electrify the home over its lifetime.
Figure 1: Carbon Foot Print Formula
Since embodied carbon emissions are “stored” in the home before it is operating, the embodied carbon sets the baseline for the total footprint of the home. Even if a house is exceptionally efficient, producing little to no operational emissions, the total carbon footprint of the house is not zero because of the upfront emissions. This is why embodied carbon matters. If we solely focus on operational carbon and the future emissions of the home, we do not consider the significant portion of emissions being released NOW. And, according to the 2022 Intergovernmental Panel on Climate Change (IPCC) report, drastically reducing emissions now is what will have the greatest impact on avoiding the most severe elements of climate disaster. For years, scientists have warned of the catastrophic results to the climate and environment if the world reaches an average temperature of 1.5-2° C above prehistoric levels. The 2022 IPCC report notes that we are on a trajectory to reach the 1.5° C in the next two decades, highlighting the only way to stop this impending disaster is to focus on emission on the today-10 year timeline. Since the majority of building emissions occurring in the first 10-15 years of a highly efficient or zero-energy home are embodied emissions, these need to be our focus moving forward. While we do not want to give up operational efficiency, we need to focus on reducing the embodied carbon emissions that are produced now, and work to reduce the overall emissions of our buildings.
The below graphs illustrate how a reduction in the embodied carbon has a significant impact on the total emissions of a home on the ten year time horizon, given that the majority of emissions on this time scale are from embodied carbon. House #1 and House #2 demonstrate two houses with the same design, producing similar operational emissions. However, if we are careful in selecting materials with lower embodied carbon, we can see a significant difference in the total emissions of a house, as demonstrated by the house #2 graph. These two graphs illustrate a high efficiency home designed without a focus on embodied carbon (house #1) vs one where there is attention given to reducing embodied carbon (house #2).
Figure 2: Total Emissions of a Home on the Ten Year Time Horizon
As a company that strives to create a healthy future for all, it is our responsibility to do our part in the next 10 years. By expanding our focus to better address our homes “now” emissions through modeling and decreasing our embodied carbon, we are working to be part of the necessary change. Tackling the biggest issues and working to refine our model to achieve excellence in both areas of home emissions is our newest goal, and one we hope that through education of the public and adjustment without our own building model, we can help lead the building industry in the right direction.
We will share additional posts on the topic of embodied carbon with more details on what embodied carbon is, how its calculated, and how we are making changes in the coming weeks so stay tuned!
In our last blog about indoor air quality (IAQ), we discussed what influences IAQ, what effects it has on humans and nature, and how to create healthier IAQ in your home.
As a recap, IAQ is measured by the quantity and type of pollutants in the air within a building. The pollutants that decrease the IAQ (make the quality worse) can be anything from biological pollutants such as mold and mildew, bacteria, dust or pollen, to carbon monoxide or volatile organic compounds (VOC’s)4. These pollutants can cause a wide variety of health problems for humans and animals, from mild skin irritations all the way to damaging internal organs and causing cancer.2,5
While ventilation is just one of the many factors that affect IAQ mentioned in our previous blog, it is a multifaceted topic and requires a deeper dive than we were able to give.
We’ve already established that healthy IAQ is important, but how does ventilation impact it and what are the current shortcomings of code-standard ventilation systems?
Firstly, IAQ can be 2-5 times more polluted than outdoor air quality6; therefore, it is vital to expel a greater quantity of indoor air and intake more outdoor air to increase a building’s overall IAQ.
However, not all ventilation systems are made equally. Often, with forced air-heating and traditional air-conditioning systems, the main method of ventilation is infiltration or purely natural ventilation (opening windows)3.
This is problematic, because there will not be a great enough flow of air to expel the polluted indoor air and the outdoor air comes into the building’s envelope untreated. While outdoor air is generally less polluted than indoor air, it would be counterproductive to bring in smoky, smoggy or pollen filled air, for example, and should still be filtered before entering the building.
When mechanical ventilation is installed in a simply code-standard building, the typical system must be manually turned on and off and doesn’t have the capacity for higher airflows or continual airflows. For this reason, conscious builders like TC Legend Homes go above and beyond the less-than-optimal code-standard systems and always uses a Heat Recovery Ventilator (HRV).
HRV units allow for continual filtered airflow. They are also capable of utilizing smart technology with sensors to detect CO2 and humidity within the house, allowing the system to automatically adjust air flow.
The humidity tracking and management is a huge advantage because it creates a more comfortable environment to people, pets and indoor plants alike and helps keep mold and mildew growth in check. On top of increasing airflow and managing humidity, the HRV also contains HEPA air filters to ensure the incoming air is stripped of as many pollutants as possible.
Of course, the extra benefit to these systems beyond increased IAQ is that they “recover up to 90% of the heat and contribute to an energy savings of up to 50%.”1
This means HRV systems save money by lowering the overall energy bill, as well as decrease the building’s carbon footprint by using energy more consciously resulting in less consumption of energy, fossil fuels and other precious materials.
In all, choosing the best ventilation system can mean creating a healthier home, as well as reducing your wasted energy consumption and having a lesser impact on the environment.
2“Biological Pollutants’ Impact on Indoor Air Quality.” United States Environmental Protection Agency (EPA), EPA.gov, https://www.epa.gov/indoor-air-quality-iaq/biological-pollutants-impact-indoor-air-quality. 2/10/2022.
5“Volatile Organic Compounds’ Impact on Indoor Air Quality.” United States Environmental Protection Agency (EPA), EPA.gov, https://www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality. 2/10/2022.