Montana Superinsulation Project


New low-cost housing can affordably include large improvements in energy efficiency, with dramatic results in measured performance. In addition, high-quality ventilation systems are affordable and deliver substantial performance in this type of housing, if the system is designed into the house from the beginning.

These are some of the findings of the Montana Superinsulation Project, a unique in-field learning laboratory that measured results in high-performance housing, including heat recovery ventilation. The housing was low cost and met Habitat for Humanity design guidelines for affordability.

Montana Superinsulation Project Background

In the late 1970s, researchers concluded that the best deal for consumers was to build with high levels of energy conservation at time of construction, rather than looking for a more efficient heating or cooling system while the house stayed inefficient. Several research and demonstration houses in Canada and the Northwest led to the development in 1982-4 by Corbett/Hansen and Associates of detailed house plans that transferred the technology known as “superinsulation” in new residential construction for cold climates.

The Montana Superinsulation Project was designed to document the performance of this highly affordable cold-climate prototype. Funded by the state of Montana, a group of research organizations banded together to develop a highly useful study of the potential of these particular energy measures.

The project was based on more than six years of research, including optimization studies and computer simulations of performance. These studies led to these unique stock house plans that showed the methods in great detail. (endnote 1)

The goal of the house plans was to make it easy for builders, no matter what the experience level, to correctly use the new methods. Changes in construction approach were aimed at making energy-saving techniques easy to employ, and through overall engineering of the house, costs were kept at or below overall costs for a house of this type.

The Montana project featured the construction of five thermally identical houses from a detailed stock house plan, a 1,288 square foot ranch-style home with a full basement, for 2,400 square feet of living space.

A variety of research projects were undertaken at the five houses, and they were the focus of the project’s public information and builder education campaigns.

The House Plans and the Builders

Builders in the Montana project included an inexperienced owner-builder couple, a young contractor who used the house as his first professional project, and three professional contractors with various degrees of familiarity with these methods. Three of the builders took part in a two-day training program, while two others did not. One goal of the project was to test the use of detailed house plans as a means to ensure energy performance.

Measurements and Tests

To verify the expected thermal performance of the sites and better understand the occupants’ influence on energy consumption, each site was instrumented with a 17-channel data acquisition system that collected hourly thermal measurements, including indoor temperature, outdoor temperatures, solar radiation, temperatures in the ventilation system, and electrical consumption for space heat, hot water, clothes dryer, and overall consumption. Gallons of hot water used were also a part of the project. Continuous hourly data were collected for more than two years. In addition, fan pressurization tests, using a blower door, were conducted three times during the project. (endnote 2)

Heat Recovery Ventilation Field Study

In 1986, the Montana Superinsulation Project received support from the Northwest Power Planning Council, the Bonneville Power Administration, and Montana to perform an in-depth study of the heat-recovery ventilation (HRV) systems in two of the sites. One goal of the study was to characterize the energy and ventilation delivery performance of these systems, which represented a state–of-the art (1984) installation. The project house plans were the first in the nation to show the HRV integrated into the architecture of the house. An additional 36 channels were added to the measurement system, with hourly data collected from the two sites through mid-1987. This testing focused primarily on the ventilation system. In addition, the project conducted a pioneering study of the use of perfluorocarbon tracer (PFT) to measure ventilation effectiveness.

Thermal Results

Space Heat Savings – The houses used an average of 66% less space heating than control houses built to current practice (HUD Minimum property standards) by BPA in Montana. Total annual average electrical savings were projected at 10,900 kilowatt hours (kWh). At national average electricity prices, these savings would have a value of about $817 annually. Total space heating costs annually were only $311 in climates with more than 8,000 heating degree days.

The houses also compared favorably with those built to the regional Model Conservation Standards proposed by the Northwest Power Planning Council, saving more than 2,000 kWh ($150 at national electricity prices) over these energy-efficient homes built in Montana. Moreover, the houses performed very similarly in regard to measured thermal performance. The project illustrated the impact of occupant preference on performance. Space heat consumption varied from two to one across the houses, based on differences in thermostat settings and preferences for temperature differences between rooms.

Hot Water Savings – On average, the houses used about 36% less electricity for hot water than did the control houses built by BPA. A total savings of about 1,900 kWh (about $140 at national electricity prices) annually on average were reported across the sites.

Ventilation results – The study showed that the HRV provided an average of about 22 percent of the total space heating savings achieved at these houses, while providing a continuous and controllable level of ventilation throughout the heating season. While the houses generally stayed comfortably cool in summer, the HRV’s were also used as part of a cooling strategy in summer during particularly hot weather. (endnote 3)

Consumption Summary – The houses used less than 5,000 average kWh per year for space heat, compared to more than 15,000 kWh per year for houses built to current HUD standard. Total annual savings combining hot water and space heating was $950. Occupants rated the homes as very comfortable and were able to set thermostats at a comfortable range at an affordable cost.

Conservation Costs

As built from the Montana project house plans, the houses were sold for a complete cost of $25-35 per square foot, depending on land and finish costs. According to the project builders, these houses with conservation features properly engineered into the house, cost no more to build than conventionally constructed homes without these conservation features. This means that the payback for adding the conservation features in this case was immediate.

Without this attention to reducing other costs throughout the construction process, the marginal cost for the conservation measures in similarly sized houses has been reported to be about $3,000, depending on builder expertise and other factors. (endnote 4) If the Montana Superinsulation Project houses had these marginal costs, the payback on the measures would still be under four years.

In the Montana project, the extra cost for the hot water conservation improvements was less than $50. The hot water system is a conventionally priced electric tank hot water heater that is more efficient and better insulated. In which standby losses from the tank are cut to a minimum through easy-to-install conservation improvements. The payback on these measures is about four months.

Clearly, these conservation improvements, as demonstrated in the Montana project, were very cost effective. The project also proves that these improvements are possible in housing that is very low cost, by any standard.

Public and Practitioner Outreach

Due to the fact that the house plans were well-researched, and that the results were fairly certain, the Montana project team confidently included builder training and public information activities as a major part of the Montana project. Public open houses were conducted in the winter of 1985, with more than 1,000 Montanans touring the homes. The computer data logger system was developed with the idea of these open houses, and was a real focal point for explaining the performance of the houses. (In sub-zero weather, people could see for themselves that no space heat was required.)

In addition, builder training programs were conducted for about 100 builders in Eastern Montana. A special manual was developed for this outreach. The State of Montana distributed 1,000 copies of this five-publication manual to builders throughout the state.

Another part of the project was an international and regional conference on energy conservation in buildings, held in Butte in May 1985. Conservation in Buildings: Northwest Perspective was a conference dedicated to putting the Northwest conservation programs and results into a context with those in Canada and elsewhere. Another aim of the conference was to assist the Northwest in building relationships among the professionals in research, building construction and program administration. The conference featured the pre-publication of a 450-page proceedings containing more than 50 papers from the region and Canada.

In the last several years, Montana project staff have worked to transfer lessons learned in this project, and the Pacific Northwest in general, through the development of a technical network of research and assistance organizations called the National Affordable Housing Network. The goal of the Network is to rally resources to bridge the gap between the energy community and low-cost housing producers, including design, research, technical assistance and training.

Research, Verification and Technology Transfer are Critically needed in Low-Cost Housing

Combined with data from other field projects, the Montana results illustrate the vast “lost opportunity” of energy and water savings in low-cost housing. Based on available knowledge and technology, excess energy and water charges of $350 to $1,000 a year per household are currently being borne by those who can least afford it. The federal budget for low-income energy costs is more than $2.3 billion a year, but only a quarter of those in need are being served, with an estimated 20 million household going without help with energy bills. Resulting in the loss of heat for part of each winter for many low-income households.

Since more than 5,000 organizations provide low-cost or affordable housing across the country, there are many challenges to address. The Network’s goal is to provide technical guidance to five climate regions to develop thermal recommendations for efficiency in low-cost housing, including new construction, rehabilitation and manufactured housing. The Montana Superinsulation Project suggests certain principles of technology transfer that may help ease the transition toward greater resource efficiency:

The technology or method change must be built on firm research.

Technology transfer of methods that are not well understood or researched can lead to poor results or even disaster. Over the years, Network staff routinely receive reports from the field related to difficulties or building failures due to misapplication of new methods or technologies. These failures lead to unfair judgments as to the effectiveness of a properly applied technology as well as slow down overall transfer of good approaches.

The results of research and analysis may best be transferred through graphic forms, such as detailed house plans.

The house plans used allow an inexperienced builder to learn about energy-conserving methods and the technical application of them, as well as learn good standard practice in non- energy-related construction techniques. This makes this type of plan highly useful to owner-builders, students, and those entering the construction trades. The plans represent a synthesis of cost, energy and construction practice that allows energy efficiency at an overall cost that is the same or even less than that of a conventionally built house.

Direct information and education of occupants and builders is highly desirable to effect orderly technology innovation.

All successful technology transfer programs feature a combination of direct technical assistance, information and education to all groups affected by the changes. Along with well-documented specifications for change in rehabilitation and manufactured housing, technical assistance is critical to the success of the change.

For more information on this project or to request information about the Network’s other work, contact the National Affordable Housing Network, Barbara Miller, Executive Director, P.O. Box 632, Butte, MT 59703; (406) 782-8145; (406) 782-5168 (fax); or send e-mail to


1. “A Low-Cost, Three Bedroom, Two-Bath Superinsulated House for Cold Climates: (House Plans), Version 2.1, copyright 1984, Superinsulation Designs/Corbett-Hansen and Associates. This version of the house plan was used for three of the Montana houses. Version 2 was used for the other two. Other plans in the series include a small, two-bedroom house (Plan1), and a modular version of the same house (Plan 1M). Call or write the Network for information about these plans.

2. Superinsulation Close-Up: Results from the Montana Superinsulation Project Thermal; Measurement Effort, pre-publication draft, October 1986, This report includes most of the technical papers produced during the course of the project, as well as the project references. For information about this report, call or write the Network.

3. Heat Recovery Ventilation for Cold Climates: Field Experience in Montana, Aug. 31, 1987. This final report describes the history of the HRV technology and summarizes results from the Montana experience. For information about this, write or call the Network.

4. A Review of Costs and Benefits, Five years of Experience under the Northwest Power Act, draft report of the Northwest Power Planning Council, Portland, Oregon, July 14, 1987. This draft report includes estimates of unit costs for conservation improvements in new construction programs supported by BPA in the Pacific Northwest, as well as an evaluation of the last five years’ effort in conservation research and implementation in the Northwest.