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Very Cold - A very cold climate is defined as a region with approximately 9,000 heating degree days or greater (65°F basis) or greater and less than 12,600 heating degree days (65°F basis).

Cold - A cold climate is defined as a region with approximately 5,400 heating degree days (65°F basis) or greater and less than approximately 9,000 heating degree days (65°F basis).

Mixed-Humid - A mixed-humid and warm-humid climate is defined as a region that receives more than 20 inches of annual precipitation with approximately 4,500 cooling degree days (50°F basis) or greater and less than approximately 6,300 cooling degree days (50°F basis) and less than approximately 5,400 heating degree days (65°F basis) and where the average monthly outdoor temperature drops below 45°F during the winter months.

Hot-Humid - A hot-humid climate is defined as a region that receives more than 20 inches of annual precipitation with approximately 6,300 cooling degree days (50°F basis) or greater and where the monthly average outdoor temperature remains above 45°F throughout the year. This definition characterizes a region that is similar to the ASHRAE definition of hot-humid climates where one or both of the following occur:

  • a 67°F r higher wet bulb temperature for 3,000 or more hours during the warmest six consecutive months of the year; or
  • a 73°F or higher wet bulb temperature for 1,500 or more hours during the warmest six consecutive months of the year.

Hot-Dry/Mixed-Dry - A hot-dry climate is defined as region that receives less than 20 inches of annual precipitation with approximately 6,300 cooling degree days (50°F basis)or greater and where the monthly average outdoor temperature remains above 45°F throughout the year.

A warm-dry and mixed-dry climate is defined as a region that receives less than 20 inches of annual precipitation with approximately 4,500 cooling degree days (50°F basis) or greater and less than approximately 6,300 cooling degree days (50°F basis) and less than approximately 5,400 heating degree days (65°F basis) and where the average monthly outdoor temperature drops below 45°F during the winter months.

Marine - A marine climate meets is defined as a region where all of the following occur:

  • a mean temperature of the coldest month between 27°F and 65°F;
  • a mean temperature of the warmest month below 72°F;
  • at least four months with mean temperatures over 50°F; and
  • a dry season in the summer, the month with the heaviest precipitation in the cold season has at least three times as much precipitation as the month with the least precipitation.


Building Science Insights are short discussions on a particular topic of general interest. They are intended to highlight one or more building science principles. The discussion is informal and sometimes irreverent but never irrelevant.

Building Science Digests provide building professionals from different disciplinary backgrounds with concise overview of important building science topics. Digests explain the theory behind each topic and then translate this theory into practical information.

Published Articles aare a selected set of articles written by BSC personnel and published in professional and trade magazines that address building science topics. For example, our work has appeared in Fine Homebuilding, Home Energy, ASHRAE's High Performance Buildings, The Journal of Building Enclosure Design and The Journal of Building Physics. We thank these publications for their gracious permission to republish.

Conference Papers are peer-reviewed papers published in conference proceedings.

Research Reports are technical reports written for researchers but accessible to design professionals and builders. These reports typically provide an in-depth study of a particular topic or describe the results of a research project. They are often peer reviewed and also provide support for advice given in our Building Science Digests.

Building America Reports are technical reports funded by the U.S. Department of Energy (DOE) Building America research program.

Designs That Work are residential Case Studies and House Plans developed by BSC to be appropriate for residential construction in specific climate zones. Case Studies provide a summary of results for homes built in partnership with BSC’s Building America team. The case study typically includes enclosure and mechanical details, testing performed, builder profile, and unique project highlights. House Plans are fully integrated construction drawing sets that include floor plans, framing plans and wall framing elevations, exterior elevations, building and wall sections, and mechanical and electrical plans.

Enclosures That Work are Building Profiles and High R-Value Assemblies developed by BSC to be appropriate for residential construction in specific climate zones. Building Profiles are residential building cross sections that include enclosure and mechanical design recommendations. Most profiles also include field expertise notes, material compatibility analysis, and climate challenges. High R-Value Assemblies are summaries of the results of BSC's ongoing High R-Value Enclosure research — a study that BSC has undertaken for the U.S. Department of Energy (DOE) Building America research program to identify and evaluate residential assemblies that cost-effectively provide 50 percent improvement in thermal resistance.

Guides and Manuals are "how-to" documents, giving advice and instructions on specific building techniques and methods. Longer guides and manuals include background information to help facilitate a strong understanding of the building science behind the hands-on advice. This section also contains two quick, easy-to-read series. The IRC FAQ series answers common questions about the building science approach to specific building tasks (for example, insulating a basement). The READ THIS: Before... series offers guidelines and recommendations for everyday situations such as moving into a new home or deciding to renovate.

Information Sheets are short, descriptive overviews of basic building science topics and are useful both as an introduction to building science and as a handy reference that can be easily printed for use in the field, in a design meeting, or at the building permit counter. Through illustrations, photographs, and straightforward explanations, each Information Sheet covers the essential aspects of a single topic. Common, avoidable mistakes are also examined in the What's Wrong with this Project? and What's Wrong with this Practice? mini-series.


Building America Reports
Joseph Lstiburek, Peter Baker

This measure guideline provides information regarding the design and construction of wall assemblies that are using thick layers of rigid exterior insulation (in excess of 1.5 inches) that require a secondary cladding attachment location exterior of the insulation to be provided. The document is separated into several distinct sections that cover: 1) fundamental building science principles relating to the use of exterior insulation on wall assemblies, 2) design principles for tailoring the use to the specific project goals and requirements, and 3) construction detailing to help with the understanding of how the various elements of the design are implemented.

Building America Reports
Betsy Pettit

Of the various measures that can drive building performance towards net zero, passive measures are the most preferable. They result in durable construction, increased comfort, health, and resiliency, and are the most cost-effective, up to a point. In the larger picture, conservation plays a critical role in scenarios trying to shift the current energy economy towards a sustainable energy economy. Stringent conservation guidelines are necessary in addition to the aggressive build out of renewable energies so that the targets can be met. In late 2011, a volunteer Technical Committee (TC) was formed at PHIUS, and was tasked to work on standard adaptation, among other things. The involvement of the committee set the frame for the work reported here.

Building America Reports
Peter Baker

Changes in the International Energy Conservation Code (IECC) from 2009 to 2012 have resulted in an increase in minimum insulation levels required for residential building. Not only are the levels increased, but the use of exterior rigid insulation has become part of the prescriptive code requirements. With more jurisdictions adopting the 2012 IECC builders are going to find themselves required to incorporate exterior insulation in the construction of their exterior wall assemblies. This research is an extension on the previous research that has provided significant insight into the mechanics as well as long term performance of exposed assemblies that use wood furring strips attached through the insulation back to the structure to provide a cladding attachment location.

Building America Reports
Kohta Ueno, Joseph Lstiburek

Hygrothermal simulations such as WUFI are coming into increasingly common use among building science researchers and practitioners, architects and designers, and energy analysts. Such simulations have been shown to be powerful and validated tools. However, with increasing dissemination of these types of modeling tools–most notable WUFI–less-experienced or less-informed practitioners have run models that provide unrealistic results. Therefore, Building Science Corporation led a Building America Expert Meeting where presenters from national laboratories, consulting firms, and building material manufacturers presented on their research, followed by a group discussion on various topics.

Building America Reports
Phil Kerrigan

BSC worked directly with the David Weekley Homes (DWH) – Houston division to redesign three current floor plans in order to locate the heating, ventilation, and air conditioning (HVAC) system in conditioned space. The purpose of this project is to develop a cost-effective design for moving the HVAC system into conditioned space. In addition, BSC conducted energy analysis to calculate the most economical strategy for increasing the energy performance of future production houses. This is in preparation for the upcoming code changes in 2015. The builder wishes to develop an upgrade package that will allow for a seamless transition to the new code mandate.

Building America Reports
Cathy Gates, Ken Neuhauser

Between December of 2009 and December of 2012, participants in a deep energy retrofit (DER) pilot program sponsored by National Grid and conducted in Massachusetts and Rhode Island completed 42 DER projects. Building Science Corporation (BSC) provided technical support to program participants and verification of measures for the program sponsor, National Grid. The pilot program required aggressive upgrades to building enclosure systems, implementation of ventilation and combustion safety measures and also provided incentives to upgrade mechanical systems. Thirty-seven of the projects completed through the pilot were comprehensive retrofits while five were partial DERs. The collection of 42 DER projects represents 60 units of housing.

Building America Reports
Robert LePage, Christopher Schumacher, Alex Lukachko

This report explains the moisture-related concerns for high R-value wall assemblies and discusses past Building America research work that informs this study. Hygrothermal simulations were prepared for several common approaches to high R-value wall construction in six U.S. cities (Houston, Atlanta, Seattle, St. Louis, Chicago, and International Falls) representing a range of climate zones (2, 3, 4C, 4, 5A, and 7, respectively). The simulations are informed by experience gained from past research in this area and validated by field measurement and forensic experience.

Building America Reports
Ken Neuhauser, Cathy Gates

In this project, the post-retrofit results for 13 existing homes from the DER Pilot program were analyzed. Ten of these homes are single-family homes; two are two-family homes, and one is a three-family home. The information available for each home included pre- and post-retrofit blower door test results, a project description, reason for doing the project, and project cost information; and actual post-retrofit energy use information provided by the utility companies. The post-retrofit energy use for this project was for the 12-month period from August 2011 through July 2012 and for the 6-month period from January 2012 through July 2012. The post-retrofit performance and cost ranges provided by this research can provide concrete input for homeowners who are considering a DER.

Building America Reports
Peter Baker, Robert LePage

The addition of insulation to the exterior of buildings is an effective means of increasing the thermal resistance of both wood framed walls as well as mass masonry wall assemblies. For thick layers of exterior insulation (levels > 1.5 in.), the use of wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location. The research presented in this report is intended to help develop a better understanding of the system mechanics involved and the potential for environmental exposure induced movement between the furring strip and the framing.

Building America Reports
Robert LePage, Joseph Lstiburek

Exterior sheathing insulation is an effective strategy in increasing the overall R-value of wall assemblies; other benefits include decreasing the effects of thermal bridging and increasing the moisture durability of the built assembly. Vapor-permeable exterior insulation, such as mineral board or expanded polystyrene foam, are one such product that may be used to achieve these benefits. However, uncertainty exists on the effects of inward driven moisture and the interaction of increased sheathing temperatures on the moisture durability of the edifice. To address these concerns, Building Science Corporation (BSC) conducted a series of hygrothermal models for cities representing a range of different climate zones.

Building America Reports
Aaron Grin, Jonathan Smegal, Joseph Lstiburek

Unvented roof strategies with open-cell and closed-cell spray polyurethane foam insulation sprayed to the underside of roof sheathing have been used since the mid-1990's to provide durable and efficient building enclosures. There have been isolated moisture related incidents that raise potential concerns about the overall hygrothermal performance of these systems. This project involved hygrothermal modeling of a range of rainwater leakage and field evaluations of in-service residential roofs using spray foam insulation. The exploration involved taking a sample of spray foam from the underside of the roof sheathing, exposing the sheathing, then taking a moisture content reading. All locations had moisture contents well within the safe range for wood-based sheathing.

Building America Reports
Ken Neuhauser

This project examines the implementation of an exterior insulation and over-clad strategy for brick masonry buildings in Chicago. The strategy was implemented at a free-standing two story two-family dwelling and a larger free-standing multifamily building. The test homes selected for this research represent predominant housing types for the Chicago area. The retrofit measures are evaluated in terms of feasibility, cost and performance. Through observations of the strategies implemented, the research described in this report identifies measures critical to performance as well as conditions for wider adoption. The research also identifies common factors that must be considered in determining whether the exterior insulation and over-clad strategy is appropriate for the building.

Building America Reports
Armin Rudd

This document covers a description of the need and applied solutions for supplemental dehumidification in warm-humid climates, especially for energy efficient homes where the sensible cooling load where the sensible cooling load has been dramatically reduced. Available supplemental humidity control options are described and discussed, with application guidance. Some options are less expensive but may not control indoor humidity as well as more expensive and comprehensive options. The best performing option is one that avoids overcooling (cooling below the requested set point) and avoids adding unnecessary heat to the space by using waste heat from the cooling system to reheat the cooled and dehumidified air to room-neutral temperature.

Building America Reports
Armin Rudd, Daniel Bergey

Airtight homes require rational and predictable ventilation. A key gap and area of ongoing research is to allow credit for better performing ventilation systems, such as supply and balanced ventilation compared to exhaust, and systems with predictable filtration of outside air and recirculation filtration. This would yield energy savings and reduced moisture control risk in humid climates, without compromising indoor air quality relative to the least performing system allowed by ASHRAE Standard 62.2. Building on previous research dealing with ventilation air distribution, this study added new elements of ventilation effectiveness research, accounting for source of outside air, particle contaminants, and VOC contaminants.

Building America Reports
Christopher Schumacher, Robert LePage

There is little consensus on the incidence of and physics behind moisture problems in dense-packed roof assemblies. Only a handful of field research projects have considered the moisture performance of dense-packed roof assemblies and the majority of these were proprietary studies that were not made public. This document focuses on dense-packed insulation retrofits to roof assemblies in cold climates and identifies, describes and compares four strategies that designers, builders and manufacturers have implemented to avoid moisture problems in dense-packed roof assemblies.

Building America Reports
Kohta Ueno, Randy Van Straaten, Christopher Schumacher

Adding insulation to the interior side of masonry walls in cold climates may cause performance and durability problems. Four such concerns were studied in more detail in this work. Embedded wood joist ends were monitored for moisture content and relative humidity, in a solid brick building that is being retrofitted with interior insulation. The effect of dissolved salts on masonry durability was examined, including their effect on freeze-thaw behavior, subfluorescence effects, and the effect on material property testing. The methodology of the frost dilatometry testing was optimized. Changes included sample size reduction, length measurement protocols, and optimization of the freeze-thaw cycle time. These changes improve throughput without loss of test accuracy.

Building America Reports
Kohta Ueno, Honorata Loomis, Daniel Bergey

Transformations, Inc. is a residential development and building company that has partnered with Building Science Corporation to build new construction net-zero energy houses in Massachusetts under the Building America program. This report covers all of the single-family new construction homes that have been completed to date. The houses built in these developments are net zero energy capable homes built in a cold climate. The set of measures offered by the developer exceeds the 30% energy saving goals set by the Building America program for New Homes in the cold climate for 2013. The houses will contribute to developing solutions and addressing gaps in enclosures and space conditioning research.

Building America Reports
Kohta Ueno, Phil Kerrigan, Honorata Loomis, Randy Van Straaten

Merrimack Valley Habitat for Humanity (MVHfH) has partnered with Building Science Corporation to provide high performance affordable housing for 10 families in the retrofit of an existing brick building (a former convent) into condominiums. The condominium conversion project will contribute to several areas of space conditioning, water heating, and enclosures research. Enclosure items include insulation of mass masonry building on the interior, airtightness of these types of retrofits, multi-unit building compartmentalization, window selection and roof insulation strategies. Mechanical system items include combined hydronic and space heating systems with hydronic distribution in small (low load) units, and ventilation system retrofits for multifamily buildings.

Building America Reports
Aaron Grin, Joseph Lstiburek

This research provides simple, long term, and durable solutions when using tapes and flashing membranes in conjunction with the exterior face of rigid polymeric foam sheathing to create the drainage plane of a wall system. The knowledge gained from this research will be used in future Building America construction prototypes and well as other residential construction projects to increase the long-term moisture related durability of the enclosure, and reduce the risk of liquid water intrusion. The following are best practice and product recommendations from the interviewed contractors and homebuilders who collectively have a vast amount of experience.

Building America Reports
Aaron Grin, Joseph Lstiburek

Based on past experience in the Building America program, BSC has found that combinations of materials and approaches—in other words, systems—usually provide optimum performance. No single manufacturer typically provides all of the components for an assembly, or has the specific understanding of all the individual components necessary for optimum performance. Integration is necessary and is the reason for the teaming approach that has been taken with this research project. The hybrid walls analyzed utilize a combination of exterior insulation, diagonal metal strapping, and spray polyurethane foam and leave room for cavity-fill insulation. These systems can provide effective thermal, air, moisture, and water barrier systems in one assembly and provide structure.