Ambient House

Buildings account for nearly half of US carbon emissions, with a large fraction being from heating and cooling. The situation is similar in other developed countries. To limit climate change, we must eliminate essentially all of these emissions. In recent history, buildings have typically worked against their surrounding environment, burning fossil fuels to isolate occupants from the prevailing weather conditions outdoors. Ambient House represents an innovative method for designing a building to cooperate with their surroundings so that all the thermal energy necessary to maintain indoor comfort is derived from ambient sources of thermal energy, such as the sun, sky, ambient air and the ground. These sources can be variable and unreliable, thus storage of thermal energy is important for bridging times when the appropriate heating or cooling source is unavailable. 

This concept was inspired by pioneering MIT researcher Maria Telkes, of whom it is said that after studying 65 years of historic weather patterns for Dover, MA, and finding nine days as the longest duration of continuous clouds, designed the 1948 Dover Sun House with ten days of storage (https://www.technologyreview.com/2010/06/22/202508/the-house-of-the-day-after-tomorrow/). Telkes also recognized that a different climate would dictate different building characteristics, but did not describe how to quantify them. The Ambient House method consolidates and formalizes this simple, but revolutionary, idea into a mathematical model that can be applied to any climate. Indeed, the model has been tested in locations from Phoenix to Fairbanks, and in every case has shown the potential to maintain indoor temperature within a comfortable range with no furnace and no air conditioner. The model is validated by a few historic homes, such as the Dover Sun House, which was heated entirely by the sun for over two years of experimental data collection, and by the 1981 Norm Saunders Shrewsbury, MA, house, which has remained comfortable for decades with only occasional use of a portable electric heater, as well as by preliminary data for a new Ambient House in Pagosa Springs, CO.

Because of the large current carbon emissions of the building sector and, in particular for heating and cooling, disseminating this solution to the world has the potential to contribute to a carbon emissions reduction that is unparalleled and unparallelable by any other single solution.

    This solution comprises a math-based method for designing buildings such that they maintain indoor temperature within a comfortable range year round using only ambient sources of thermal energy. While dissemination of the solution to the building design community is key to accomplishing its potential for climate change reduction, this section will summarize how Ambient House design is different from that of conventional homes and of Passive House.

 Building performance can be reduced to a simple, first-order differential equation with two main parameters - the asymptotic indoor temperature and a time constant. The asymptotic temperature describes the temperature that the house will approach after a long period of constant weather conditions, and the time constant defines how long it takes to reach the asymptotic temperature. If the asymptotic temperature is comfortable, then the time constant is not important. But if it is uncomfortable, the the time constant must be long enough to delay temperature changes within the house until more favorable conditions exist, such as after the storm ends and the sun comes out in the winter. The normalized asymptotic temperature is determined by a ratio of thermal gains (typically solar and internal heat gains) to losses (envelope losses and, when required, cooling to ambient sources). Weather is, of course, constantly changing, so the asymptotic temperature changes with it. The time constant is a ratio of thermal capacitance to the envelope loss coefficient. It does not vary with instantaneous weather conditions.

     To maintain comfort, the characteristics of the building are adjusted so that the values of these two parameters maintain indoor temperature within a comfortable range over an entire year of local weather data. Within these limits, a wide range of building designs are possible to meet the aesthetic choices of the owners. 

     From my initial study of example buildings in each ASHRAE climate zone, some trends became apparent. For most climates, it is prudent to begin with envelope losses that are comparable to current Passive House standards. These envelope losses are significantly lower than  the typical home, but are being widely accepted by a growing market of homebuilders. Ambient House design goes beyond Passive House standards by also accounting for solar heat gains and ambient cooling. The area of south-facing windows for solar gains should be adequate to provide sufficient winter heating, but not so much as to produce overheating the rest of the year. Cloudy climates typically need larger solar apertures. In my initial study, solar apertures of about 10-30% of the floor area of the building were necessary. These areas are within the range of typical homes. Nighttime ventilation is capable of providing cooling in all climates, though sky radiation is beneficial in hotter regions. 

     Control of solar gains and ambient cooling is necessary during unseasonal weather. While manual control (e.g., shades to limit solar gains and opening windows for ambient cooling) can suffice, model-based automatic control can be more accurate and more convenient for the occupants. Automated control of otherwise passive systems is an Ambient House innovation that is a largely untapped resource for significantly improving building performance.

     Thermal mass is added to bridge periods of cloudy weather during the heating season, and periods of continuously hot weather during the cooling season. In some temperature climates, thermal mass typical of conventional construction is adequate, but in others, additional thermal mass is required. This thermal mass can be provided by architectural materials such as concrete, as well as by water and phase change materials.

     In summary, the Ambient House software incorporating the first-order model provides a user-friendly tool for testing different values of parameters and their effects on building performance when no auxiliary energy is used for heating and cooling. The results will specify insulation levels, internal heat gain, solar aperture area and ventilation loss coefficient necessary to achieve a given range of indoor comfort temperature for a particular set of local weather data.

This solution serves all building owners and occupants by eliminating costs and environmental impacts of fossil fuel combustion for heating and cooling. The empowerment of eliminating dependence on utility companies for space conditioning, along with uncertain future energy rates and uncertain sustainability of energy production, should not be underestimated. New construction or remodeling to Ambient House standards is something that homeowners can do now to substantially reduce their carbon footprint. No other design method is currently available to do this.

By helping to reduce climate change, this solution benefits all life on Earth, particularly those organisms with limited capacity to adapt or migrate toward suitable habitats as their local environment changes.

My family has been builders for at least four generations. My great grandfather would go to the woods and cut trees, store them in a barn for year, and then come back a year later to square the logs and construct timber-frame barns. I grew up around carpenters. My parents tell the story of me "helping" to build one of their own houses when I was six years old. I have home-building in my blood.

My academic training includes studying solar energy at Colorado State University, which had arguably the best experimental facilities for solar buildings in the world at the time. I built my own passive solar home around 1990 and learned first-hand about the dynamics of building response. I am an ASME Fellow, past chair of the Solar Energy Division of ASME and chaired the ASME 2018 12th International Conference on Energy Sustainability. I am a life member of the American Solar Energy Society.

My academic research evolved from serving a part of the heating load with solar energy, to also addressing overheating, and finally to serving the entire heating and cooling load with ambient sources, i.e., the Ambient House concept. I developed the mathematical model that quantifies the building characteristics that accomplish this across all US climates. One journal article describing the model has recently appeared and another has been submitted. The model was used to design a new Ambient House, which has performed according to predictions.

Ambient House is a radical concept compared to the prevailing dogma that there are diminishing returns for increasing solar fractions for heating systems, i.e., that getting to 100% is impractical if not impossible. Maria Telkes knew better. I simply rediscovered her approach and reduced it to a mathematical description. Having (re-)invented the Ambient House idea, I am the most qualified to spread it to the world.

Dissemination is critical to realizing the potential carbon reduction of this solution. We will begin by developing a website and downloadable software. Builders and homeowners will provide feedback to improve our presentation. We will deliver training sessions for builders and homeowners, where feedback will be in-person. As our audience grows, an annual conference will be organized where the latest research will be shared and new technologies and construction methods for accomplishing Ambient House performance will be introduced. The vision of this solution is to serve and support the community of builders, homeowners and product providers who share our goal of supplying 100% of space conditioning needs with ambient energy.

We need skilled professionals to develop the website, to answer building design and construction questions and to organize and execute training sessions. We need experienced building thermal engineers to review building designs and evaluate construction documents for compliance with Ambient House standards. We need business and accounting help to review our program and keep us solvent, even though the plan is to be nonprofit.

Energy conservation can only go so far in reducing energy consumption for space conditioning of buildings. Incorporating ambient energy sources opens up fundamentally new possibilities beyond conserving energy. The sun is a vast resource that has the capacity to heat every building on the planet many times over, while nighttime air or sky radiation can provide sufficient cooling . Thermal mass is inherent in any building, and is easily enhanced if necessary. 

Each of these subsystems has decades of research and demonstration. However, consolidating all of them into an integrated system that serves the entire heating and cooling needs of a building is uncommon. Only a few examples exist, such as the Telkes Dover Sun House and the Saunders Shrewsbury House. Telkes recognized that her Dover house might not have the same performance in a different climate, and that building characteristics elsewhere would likely need to be changed. However, she did not provide a formal method for designing such buildings across different climates. What is innovative about Ambient House is the mathematical model  that uses local weather data and outputs the necessary building parameters to ensure the Ambient House standard of performance in any climate.

Passive House serves as a template for Ambient House. The first Passive Houses were constructed in Germany 30 years ago. The Passive House Institute was formed five years later. After a slow start, the number of certified Passive Houses has grown exponentially (https://passivehouse.com) to 330,000 units with over 3 million square meters of floor area. 

In the first year, we expect to establish the website and downloadable software, and document the construction and performance of the first Ambient House (in the USA). Over the next five years, we will work to recruit, review and certify 20 new Ambient Houses, along with establishing the supporting programs and resources for training, and construction document and product review. Because the website will be available to the world, these houses may be anywhere in the world. At the end of five years, we will host the first Ambient House conference.

Preliminary data for the first Ambient House shows that it has been comfortable indoors for over a year without the need for auxiliary energy of any kind for heating or cooling. Installation of one additional ambient energy subsystem (a ground heat exchanger for the energy recovery ventilator) will occur this summer, then more extensive data acquisition will begin in collaboration with a National Science Foundation funded researcher. (Note that the NSF funding is for a related topic, but not for Ambient House, and can only be used for data acquisition.)

Building performance prediction software has been written and used to analyze the first Ambient House, as well as example buildings in each US climate zone. One journal article has appeared and another submitted with results from the software. Further work is needed to make the software accessible to a broader audience of users. 

No work has yet been done on the website.

Long term impact will be estimated in terms of number of Ambient House units, floor area, and energy consumption and carbon emissions avoided for space conditioning. These measures will be straightforward to calculate with the results of the software compared to the performance of conventional buildings.

"Never doubt that a small group of thoughtful, committed individuals can change the world. In fact, it's the only thing that ever has." Margaret Mead (attrib)

While Farrington Daniels, Hoyt Hottel, Maria Telkes, George Lof, David Wright, Norm Saunders, William Shurcliff, Douglas Balcomb, Edward Mazria and many others contributed to the foundations of knowledge of solar and super-insulated buildings, Wolfgang Feist deserves tremendous credit for pushing the Passive House Institute to its current level of development and popularity. Even though this solution advocates improvements upon the Passive House concept, Feist's original idea of establishing standards for deeply energy-conserving buildings and offering certification plaques that the owners can proudly display was ingenious. Further, even though much more progress till needs to be made to reduce energy use and carbon emissions from buildings, the success so far of his idea is remarkable.

Ambient House follows in the footsteps of Feist and his students and staff. We are in search of that "small group of thoughtful, committed individuals" to carry Ambient House forward.

The logical connection between our desire to reduce energy use and carbon emissions in the building sector and actually accomplishing this in the Ambient Houses that we certify is exceeding direct. However, going significantly beyond the 330,000 units that Passive House has enrolled still does not solve the larger problem of the entire building stock. Long-term plans include wider-ranging outreach to improve building codes, demonstrate Ambient House performance in public buildings, establish a collegiate Ambient House competition (like the Solar Decathlon), and to push for transdisciplinary education that incorporates Ambient House engineering principles into architecture programs.

There is no novel technology required to make Ambient House successful, other than the paradigm shift that discards the prevailing dogma that ambient sources have diminishing returns that stop short of supplying 100% of a buildings heating and cooling loads. The concept that thermal storage can be sized to bridge periods of unavailability of solar energy dates back at least to the 1940's (Maria Telkes' Dover Sun House). The mathematical model that comprises Ambient House requires minimal computing capacity.

That Ambient House performance can be achieved with current technology does not mean that innovations would not be beneficial. Indeed, model-based control, a relatively new technology, of exchanges between the house and ambient sources of energy is incorporated into the model, but is not necessarily essential to achieving the goals of Ambient House. Countless other developments could make Ambient House performance easier to accomplish, for instance, transparent insulation (windows with lower thermal losses), active insulation, heat pipe systems (for one-way heat transfer in both heating and cooling subsystems), durable and high performance covers for sky radiators, automatically-controlled shading and moveable insulation, and economical and effective thermal storage subsystems, including sensible and/or phase-change materials.

Being one person, there is currently no diversity in the leadership team!

Nonetheless, as the team grows, every effort will be made to recruit from diverse and disadvantaged populations. Since the headquarters is currently in Colorado, a particular effort will be made to identify Native Americans who can contribute. The team will also reach out to reservations in the area to learn how Ambient House principles might improve housing there.

The international Passive House Institute (PHI, https://passivehouse.com) and Passive House Institute US (PHIUS, https://www.phius.org) serve as templates for the Ambient House business model. Each comprises a website, design software, training,engineering consultants, certified builders, workshops and an annual conference all focussed on constructing buildings that meet strict energy conservation standards. Prospective homeowners use the website to locate designers and builders in their area. Designers take advantage of downloadable software that assists in predicting home energy use and water vapor transport (to avoid mold and moisture damage, which is a concern for this type of building). Builders become certified by taking training courses that cover the specialized construction methods that meet Passive House standards. Products and building components from manufacturers may also be submitted for evaluation and certification.

This broad range of customers is tied together by a common concern for passing on to future generations a planet that is less impacted by fossil fuels, and by the empowerment of personally doing something about it for their own homes and those that they provide for their clients.

While PHI and PHIUS focus on energy conservation, which can reduce home energy use by an impressive 70-90%, Ambient House further incorporates controlled exchanges of heat between the house and ambient sources so that the entire heating and cooling loads are served.

Startup funds and/or volunteer effort are needed to develop the website and software. In the longer term, certification fees will cover the costs of staff reviews of submitted construction documents and performance analyses. Building products will be certified annually as suitable for Ambient House construction, and fees will exceed the cost of review to help cover operating expenses. Annual builder and designer certification fees will also help cover general expenses. Training sessions will be sustainably priced. Conferences and other special events will be priced to be self-sustaining. Donations and grants would allow greater outreach and expansion of efforts to impact the building sector more broadly, and to pursue key innovations that could make achieving Ambient House performance easier.

This plan follows that of Passive House, which is still thriving after 30 years.

All progress to date has been personally funded, including developing the mathematical model, submitting journal articles and analyzing and building the first Ambient House.