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climates

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.

information

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.

Research Reports
John Straube, Rachel Smith, Graham Finch

This report is available from the Canadian Urethane Foam Contractors Association. It is reproduced here for convenience. A common question encountered by SPF applicators, building designers, and code officials is the need for an additional vapor barrier or retarder. Experience by many contractors and some consultants suggest that special low permeance layers such as polyethylene are rarely needed in many types of walls. Theory indicates that closed cell foam is sufficiently vapor impermeable to control diffusion condensation and that low-density open-cell foam applications may require additional vapor diffusion control in some extreme environments. However, the need for, and type of additional vapor control layers remains unanswered to many.

Research Reports
Joseph Lstiburek

Two seemingly innocuous requirements for building enclosure assemblies bedevil builders and designers almost endlessly: keep water vapor out, let the water vapor out if it gets in. It gets complicated because, sometimes, the best strategies to keep water vapor out also trap water vapor in.

Research Reports
Joseph Lstiburek

Good design and practice involve controlling the wetting of building assemblies from both the exterior and interior and different climates require different approaches. Ideally, building assemblies would always be built with dry materials under dry conditions, and would never get wet from imperfect design, poor workmanship or occupants. Unfortunately, these conditions do not exist.

Research Reports
Joseph Lstiburek

Roofs can be designed and constructed to be either vented or unvented in any hygrothermal zone. Air barrier systems are typically the most common approach, however, air pressure control approaches are becoming more common especially in cases involving remedial work on existing structures. Vapor diffusion should be considered as a secondary moisture transport mechanism when designing and building roofs. Specific vapor retarders are often unnecessary if appropriate air movement control is provided or if control of condensing surface temperatures is provided.

Research Reports
Joseph Lstiburek

Builders for many years have put mechanical equipment and ducts in non-living spaces such as crawlspaces and attics primarily to save valuable floor space. Be that as it may (there are lots of good reasons for having this equipment in conditioned spaces, GIVEN proper attention to ventilation and pressurization issues), it makes perfect sense to condition these areas, for a variety of energy, moisture and durability reasons.

Research Reports
Joseph Lstiburek

Brick is a reservoir cladding, meaning that it absorbs and stores water (rain) when it becomes wet. In some homes, with brick veneer cladding systems, mold contamination has occurred within exterior wall cavities. In some homes, wood decay at bottom plates has also occurred.

Research Reports
Joseph Lstiburek

Most of us are not aware of just how differently these two barriers work in building assemblies. This article makes the differences as clear as the polyethylene film that should (or more likely should NOT) be in your walls.

Published Articles
John Straube, Christopher Schumacher, Jonathan Smegal, M. Jablonka

Adhered veneers, in which masonry units are directly attached to a substrate via mortar and ties without a drainage or ventilation gap, have become a very popular finish in residential and light commercial construction. Reprinted with permission from Journal of Building Enclosure Design, Summer 2009, pages 31-35.

Published Articles
Joseph Lstiburek

Top ten blunders that rot your house, waste your money, and make you sick. Reprinted with permission from Fine Homebuilding Magazine, April/May 2004, pages 52-56. 

Published Articles
Joseph Lstiburek

When designing a building’s envelope and its interaction with the mechanical system, temperature, humidity, rain, and the interior climate often are ignored. The focus for the building may be more on aesthetics and cost than on performance. This article was first published in ASHRAE Journal, February 2002, pages 36-41. Reprinted with permission.

Information Sheets

Good design and practice involve controlling the wetting of building assemblies from both the exterior and interior and different climates require different approaches. Vapor Permeance...
Information Sheets

As they are typically used in buildings today, vapor barriers are a cold climate artifact that has migrated into other climates more from ignorance than need. However, they often prevent assemblies...
Information Sheets

The requirements in the code can be used for wood framed structures with temperature and humidity conditions typical of residential occupancy.Three classes of vapor control are defined depending on...
Information Sheets

Claddings made of wood, fiber cement, stucco, concrete, and masonry all absorb water to varying degrees. Once the reservoirs get wet, the stored water can migrate elsewhere and cause problems....
Conference Papers
John Straube

The influence of vapor barriers on the hygrothermal performance of wall and roof systems is a function of exterior climate, interior climate, solar absorptance, rainwater absorption, and the vapor and thermal resistance of all of the layers in the system. In many practical situations, a low-permeance vapor barrier will not improve hygrothermal performance and may in fact increase the likelihood of damaging condensation or trap moisture in the system. This paper examines the role of vapor barriers on hygrothermal performance with the aid of simple and transparent diffusion calculations supported by measurements from full-scale natural exposure monitoring.

Conference Papers
Theresa Weston, Liza Minnich, Jonathan Smegal, Jennifer Van Mullekom, Christopher Schumacher, Jessica Conlon

This paper evaluates the performance of typical residential wall systems that incorporate water-resistive barriers with a range of vapor permeability. These systems included both absorbent and nonabsorbent claddings in hot-humid climates for direct comparison. This paper describes the test design, the test facility construction and installation, and the resulting data. The approach chosen was to use a real-time natural exposure test hut located in Tampa, FL where the interior conditions were controlled by point-terminated HVAC. Wall specimens were instrumented with a variety of temperature, humidity, and wood moisture content sensors for remote monitoring. In addition to natural weather exposure, the wall specimens were periodically wetted to simulate rain leakage by a water injection system.

Hot-Humid
Conference Papers
M. Jablonka, Achilles Karagiozis, John Straube

Improved energy efficiency building enclosures generally means an increase in R-value and reduced air leakage, which commonly reduces the drying potential of wall assemblies. Essentially, less energy is available from inside the structure to assist the transport of moisture away from the building enclosure. As energy efficiency requirements are pushing towards zero-energy structures, passive means the sun or wind become more critical approaches for achieving enhanced drying. This paper investigates the hygrothermal performance of wall assemblies with brick veneer cladding as well as manufactured adhered stone veneer with two different types of water resistive barriers.

Conference Papers
John Straube

Adhered veneers, in which masonry units are directly attached to a substrate via mortar and ties without a drainage or ventilation gap, have become a very popular finish in residential and light commercial construction. Typical applications apply masonry over a bed of lath-reinforced mortar over a drainage plane (often of building paper or felt). When used over wood- or steel-framed walls, numerous reports of moisture problems and failures have been received.

Very Cold
Conference Papers
Peter Baker

Providing rigid insulating sheathing to the exterior of a wall assembly is a technique that has been used in cold climates for more than 40 years. Recently it has begun to be integrated into enclosure designs in all climates. As with any newly adopted technology, there can be concerns for its proper application. This paper examines methods of incorporating insulating sheathing into the thermal and moisture management systems of the building enclosure in a variety of climate zones across North America. This is done through examining the material properties of the various products and how these properties can be used to achieve an energy efficient and durable building enclosure design, while avoiding problems relating moisture accumulation and degradation of materials.

Building Science Insights
Joseph Lstiburek

Where did the term “punched openings” come from to describe window and door openings in building enclosures?

A little bit of history…back in the day the United States was known for its manufacturing prowess[1].  In high speed and high volume production “punching[2]” was and is the least expensive method of...

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