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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
Betsy Pettit

As materials and equipment have improved, energy reduction as a goal has increasingly been replaced with the goal of net-zero energy use. But the general approach to building energy efficient homes that has been recommended has always been the same. This approach to achieving net-zero energy homes is reflected in the ten general principles for the design of net-zero energy capable houses that are presented and discussed in the first part of this paper. In the second part of the paper, specific strategies and details are described that were used for the design of the Net Zero Energy Residential Test Facility (NZERTF), a NIST laboratory in the form of a typical residence for a family of four that has been constructed on the NIST campus in Gaithersburg, MD.

Research Reports
Jonathan Smegal

This report analyzes the performance of walls clad with HardiePlank fiber cement siding and compares them to traditional stucco assemblies. The data presented is a subset of experimental data from a multi-phase, multi-year research project at the Vancouver Field Exposure Test Facility led by Building Science Corporation (BSC) and Gauvin 2000 Construction Limited. The analysis includes results from normal operating conditions in a high stress exterior moisture environment (typical of the Pacific Northwest climate) and under intentional controlled wettings to the interior and exterior of the sheathing.

Research Reports
Jonathan Smegal, Aaron Grin

This report describes the construction and instrumentation of Phase IV of a multi-phase, multi-year research project at the Vancouver Field Exposure Test Facility in Coquitlam, British Columbia. The main objective of Phase IV is to determine how various configurations of exterior low vapor permeance insulation affect the moisture durability risk of structural wood-based sheathing. To assist with this analysis, the walls will be subjected to elevated interior relative humidities, and intentional controlled surface wetting of the interior and/or exterior of the OSB sheathing.

Research Reports
Aaron Grin, Jonathan Smegal

This report describes the construction and instrumentation of Phase III of a multi-phase, multi-year research project at the Vancouver Field Exposure Test Facility in Coquitlam, British Columbia. Phase III focusses on the performance of various sheathings and claddings in a high stress moisture environment that is typical of the Pacific Northwest climate. The main research goal is to examine the performance of the various walls under the influence of intentional exterior wetting events in the drainage space.

Research Reports
Jonathan Smegal, Joseph Lstiburek, John Straube, Aaron Grin

This report compares the moisture related performance of an exterior insulated wall to the performance of two other common construction methods, side-by-side. The data presented is a subset of experimental data from a multi-phase, multi-year research project at the Vancouver Field Exposure Test Facility led by Building Science Corporation (BSC) and Gauvin 2000 Construction Limited. The analysis includes results from normal operating conditions in a high stress exterior moisture environment (typical of the Pacific Northwest climate) and under intentional controlled wettings to the interior and exterior of the sheathing. There were no measured or observed moisture related durability concerns of the wood structural sheathing when 1.5” of exterior insulation was installed.

Marine
Research Reports
Joseph Lstiburek, Christopher Schumacher

This report summarizes hygrothermal analysis of specific attics constructed in California. The analysis was done using historical experience, published work in journals and trade publications, current building code requirements and WUFI hygrothermal simulations to assess benefits and risks associated with insulating the roof decks in both vented and unvented configurations. The focus of this report is on modifying conventional, ventilated attics, constructed with impermeable roof shingles (with fiberglass batt insulation on the ceiling plane) by adding fiberglass batt (or netted fiberglass or netted cellulose or spray applied fiberglass) insulation to the underside of the roof deck (i.e. on the slope) while leaving the attic air space ventilated to outdoors.

Hot-Dry/Mixed-Dry
Research Reports
Jonathan Smegal, John Straube

This report is an extension of a previous analysis study titled “RR-1014: High R Walls for the Pacific Northwest – A Hygrothermal Analysis of Various Exterior Wall Systems”, conducted by BSC for Walsh Construction, dated June 1, 2010 that examined the predicted thermal and hygrothermal performance of 17 different wall assemblies in Portland, Oregon.

Marine
Research Reports
Jonathan Smegal, John Straube

This report considers a number of promising wall systems that can meet the requirement for better thermal control. Unlike previous studies, this one considers performance in a more realistic matter, including some two- and three-dimensional heat flow and analysis of the relative risk of moisture damage.

Marine
Research Reports
Joseph Lstiburek

Every exterior cladding system needs an air space and drainage plane for performance and durability. This article presents the right materials and spaces for most exterior claddings—brick, stucco, and wood, metal and vinyl lap siding.

Research Reports
Armin Rudd

An hourly simulation study using DOE2.1E was conducted to determine the annual difference in energy consumption between various ventilation options in different climates.

Research Reports
Joseph Lstiburek

The general principle of building durability has two components: buildings should be suited to their environment and the laws of physics must be followed. We tend to ignore the first and find the second inconvenient.

Research Reports
Armin Rudd, Kohta Ueno

Duct leakage is a concern in the HVAC field, due to energy consumption, pressure balance problems, bypassing of the filter by leakage air, and contaminant draw from unconditioned spaces. Therefore, certain energy efficiency programs set duct leakage performance requirements that must be met to enter the program. However, the overall duct system tightness is limited by leakage at the air handler.

Research Reports
Joseph Lstiburek

Understanding the significance of the complex flow and pressure distribution problems created by the interaction of the building envelope with the mechanical system and climate can lead to changes in building design, commissioning, operations, maintenance, diagnostics and rehabilitation.

Research Reports
Armin Rudd, Kohta Ueno, Joseph Lstiburek

Unvented-cathedralized attics are known to be advantageous in hot-humid and hot-dry climates, whereby, exterior moisture would be excluded for hot-humid climates, and attic mounted air distribution systems would be inside conditioned space for both climates. Current work focuses on the performance and durability of unvented-cathedralized attics in hot-humid climates with both tile and asphalt shingle roofing. The advantages for the hot-humid climate are expected to be even greater than for the hot-dry climate.

Hot-HumidHot-Dry/Mixed-Dry
Research Reports
Armin Rudd

Energy efficient homes are inherently airtight and require ventilation for acceptable indoor air quality. Of all the options currently available, the low cost and low maintenance central fan-integrated ventilation approach is the most acceptable to large production builders and manufactured home producers. This is a resource and energy efficiency strategy that utilizes the existing air ducts and the normal cycling of the fan, in response to demand from the thermostat, to distribute ventilation air and conditioned air at the same time. The patented AirCycler™ control can be used to automatically operate the fan if the fan has been inactive for a period of time, and to control a motorized outside air damper to limit the intake of ventilation air independent of fan operation.

Research Reports
Armin Rudd, Joseph Lstiburek

Sealed attic construction, by excluding vents to the exterior, can be a good way to exclude moisture-laden outside air from attic and may offer a more easily constructed alternative for air leakage control at the top of residential buildings.

Hot-Dry/Mixed-Dry
Research Reports
Armin Rudd, Joseph Lstiburek

In cold climates, the primary purpose of attic ventilation is to maintain a cold roof temperature to avoid ice dams created by melting snow, and to vent moisture that moves from the conditioned space to the attic. In cooling dominated climates, the primary purpose of attic ventilation is to vent hot air, heated by solar gain on the roof, thus reducing the cooling load contribution from the roof. The magnitude of the roof cooling load contribution is often in the area of ten percent of the total cooling load for an occupied house.

Hot-Dry/Mixed-Dry
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
John Straube

The balance between wetting, drying, and safe storage is critical to the long term performance of building enclosures. Where wetting cannot be controlled to acceptable levels, safe storage and drying become critical. The use of one-dimensional hygrothermal simulation software has been well established for a wide range of wall and roof assemblies. However the use of such software has previously had a limited ability to accurately model the physics of enclosures with ventilated claddings. The most recent version of WUFI 4.1 has added the ability to model enclosure systems that incorporate embedded sources and sinks of moisture and heat. This capability can be used to model source effects such as air and rain leakage within a wall assembly or sinks such as drainage and ventilation.

Research Reports
John Straube

The research reported in this paper is aimed at increasing the understanding of the hygrothermal performance of interior basement insulation systems by a combination of field monitoring of four assemblies and one-dimensional computer modeling. The work described here is part of a Canada Mortgage and Housing Corporation (CMHC) sponsored research program to determine the significance or insignificance of potential moisture problems due to an impermeable polyethylene layer in above- and below-grade walls (Wilkinson et al. 2007).

Cold

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