http://www.buildingscience.com Digests are papers on specific building science topics written for a broad range of users. Expert advice is given with a focus on establishing an understanding of the theory and translating this theory to practical information. daily 1 2010-01-26T02:05:02Z http://www.buildingscience.com/documents/digests/bsd-005-green-building-and-sustainability The construction and operation of buildings consumes over a third of the world’s energy consumption, and 40% of all the mined resources. Striving to make buildings more sustainable, while saving construction and operating costs and improving health and occupant well being is not only possible and practical, it should be the goal of the building industry. Achieving this goal requires an awareness of the problem and the skills to design, specify, construct, and operate buildings in a manner that is often quite different from current standard approaches. This digest will review the challenge of sustainability, discuss methods of assessing green buildings, and recommend a process by which more sustainable buildings can be delivered. No publisher John Straube Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest. durability rain screen radiation ASHRAE doc-Digest photovoltaics resources-mold 2011-12-30T23:41:39Z BSC Article http://www.buildingscience.com/documents/digests/bsd-007-historical-development-of-the-building-enclosure Historical works, notably the Roman Vetruvius’ Ten Books of Architecture, that describe buildings begin with an historical overview. Archaeological and anthropological studies have furthered this understanding. The history of the built form and the building enclosure is more than just a curiosity: understanding the history helps explain many of the buildings types, construction techniques and building materials that we use today. This digest provides a brief overview of the development of the building enclosure and can serve as an entry point into a deeper historically-informed study of buildings and building science. No publisher John Straube Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest. guidance-Enclosure design principles guidance-Windows durability type-high-rise doc-Digest insulation 2011-12-29T01:55:12Z BSC Article http://www.buildingscience.com/documents/digests/bsd-010-looking-at-tomorrow Predicting the future is very difficult, but examining trends and potential tipping points is useful as an aid to understanding the direction the building industry is headed, and where it might end up. Although some future changes can only be speculated upon, other trends are already occurring and causing changes. Below is a series of changes and possible changes that may influence the building industry and society. No publisher John Straube guidance-Enclosure design principles subsystems-HVAC vapor permeance guidance-Building systems/HVAC rain screen radiation moisture-Vapor Permeance dehumidification doc-Digest residential ventilation relative humidity insulation 2011-03-19T21:16:04Z BSC Article http://www.buildingscience.com/documents/digests/bsd-011-thermal-control-in-buildings Providing thermal comfort without excess space conditioning costs is one of the primary requirements of buildings. Therefore, thermal control is an important aspect in almost all buildings. Understanding heat transfer and the temperature distribution through building materials and assemblies is also important for assessing energy use, thermal comfort, thermal movements, durability, and the potential for moisture problems. Heat flow occurs through the building enclosure via opaque enclosure elements, is directly transferred into the building by solar radiation through windows, is carried along with air across the enclosure by unintentional leakage and ventilation, and can be generated within the building by occupants and their activities. The control of heat flow in buildings requires insulation layers compromised with few thermal bridges, an effective air barrier system, good control of solar radiation, and management of interior heat generation. No publisher John Straube Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest. guidance-Enclosure design principles condensation airflow-Indoor Air Quality durability air barrier doc-Digest resources-low-energy residential ventilation ASHRAE airflow-Airtightness/Air barrier airflow-Wind washing 2011-12-30T21:26:36Z BSC Article http://www.buildingscience.com/documents/digests/bsd-012-moisture-control-for-new-residential-buildings Moisture accumulates when the rate of moisture entry into an assembly exceeds the rate of moisture removal. When moisture accumulation exceeds the ability of the assembly materials to store the moisture without significantly degrading performance or long-term service life, moisture problems result. No publisher Joseph Lstiburek moisture-Diffusion/Vapor Pressure vapor permeance moisture-Drainage plane EIFS radiation moisture-Vapor Permeance air barrier doc-Digest residential ventilation moisture-Physics of Moisture Control airflow-Airtightness/Air barrier airflow-Wind washing resources-mold 2011-07-15T21:18:54Z BSC Article http://www.buildingscience.com/documents/digests/bsd-013-rain-control-in-buildings Moisture is one of the most important agents leading to building enclosure deterioration. Understanding and predicting moisture movement within and through the enclosure is therefore of fundamental importance to predicting and improving building enclosure performance, particularly durability. Since driving rain deposition on walls and roofs is quantitatively the largest single source of moisture for most walls and roofs, it is no surprise that controlling rain penetration is one of the most important parts of a successful moisture control strategy. In fact, failure to control rain is likely the oldest and most common serious building enclosure performance problem. Commentators as long as Vitruvius (70 BC) bemoaned the challenges of controlling rain penetration. This document will consider rain control from a general to a specific level. The following sections will cover: basic moisture control principles that should be employed in the design of above-grade building enclosures; driving rain as a moisture load on walls; a classification system of the various rain control strategies available for walls; and finally, good design practises for walls. The rain control of roofs will be covered in more detail in another BSD. No publisher John Straube Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest. vapor permeance moisture-Drainage plane type-high-rise deflection type-institutional moisture-Flashing/Deflection driving rain drying radiation enclosure-Foundation assembly residential ventilation guidance-Roof design enclosure-Roof assembly flashing comp-roofs moisture-Driving rain enclosure-Wall assembly rain screen guidance-Below-grade enclosure moisture-Vapor Permeance rain guidance-Wall design moisture-Drying guidance-Enclosure design principles airflow-Indoor Air Quality comp-walls rain control type-low-rise doc-Digest drainage 2011-08-23T22:57:18Z BSC Article http://www.buildingscience.com/documents/digests/bsd-014-air-flow-control-in-buildings The control of air flow is important for several reasons: to control moisture damage, reduce energy losses, and to ensure occupant comfort and health. Airflow across the building enclosure is driven by wind pressures, stack effect, and mechanical air handling equipment like fans and furnaces. A continuous, strong, stiff, durable and air impermeable air barrier system is required between the exterior and conditions space to control airflow driven by these forces. Air barrier systems should be clearly shown and labelled on all drawings, with continuity demonstrated at all penetrations, transitions, and intersections. In addition, enclosure assemblies and buildings should be vertically and horizontally compartmentalized, may require secondary planes of airtightness (such as those provided by housewraps and sealed rigid sheathing) and may need appropriately air impermeable insulations or insulated sheathing. No publisher John Straube Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. diffusion guidance-Enclosure design principles condensation durability exfiltration moisture-Vapor Permeance air barrier doc-Digest residential ventilation ASHRAE infiltration airflow-Airtightness/Air barrier airflow-Driving forces/stack effect vapor barrier airflow-Wind washing 2011-12-29T01:06:28Z BSC Article http://www.buildingscience.com/documents/digests/bsd-018-the-building-enclosure_revised That part of any building that physically separates the exterior environment from the interior environment(s) is called the building enclosure or building envelope. Environmental separator is another term used to describe the enclosure, but note that this generic term also applies to separators of two different interior environments. The term building enclosure is preferred to the term building envelope largely because it is considered both more general and more precise. Also note that the building enclosure may contain, but is not the same as, the so-called thermal envelope, a term that is used to refer to the thermal insulation within the enclosure. The enclosure, the loadings it must resist, and its functions are addressed in this digest. No publisher John Straube guidance-Enclosure design principles durability guidance-Below-grade enclosure radiation ASHRAE doc-Digest residential ventilation relative humidity 2011-07-18T19:12:27Z BSC Article http://www.buildingscience.com/documents/digests/bsd030-rain-control-theory The design of building enclosures to control rain penetration and control rain shedding is typically based on experience and rules of thumb that make use of traditional details. Unlike heat flow, vapor diffusion, air leakage, etc. there is no theory of rain control to aid the designer or analyst of building enclosures. An edited version of this document was published in Journal of Thermal Insulation and Building Envelopes, July 1999, pp. 41-56. No publisher John Straube rain screen rain control resources-technical rain doc-Digest moisture-Physics of Moisture Control driving rain moisture-Driving rain 2011-07-15T22:14:13Z BSC Article http://www.buildingscience.com/documents/digests/bsd-102-understanding-attic-ventilation Attics or roofs can be designed and constructed to be either vented or unvented in any hygro-thermal zone (Map 1). The choice of venting or not venting is a design and construction choice not a requirement determined by the physics or by the building code. The model building codes allow both vented and unvented roof assemblies. The applicable physics impacts the design of attic or roof systems as does the applicable building code but neither limit the choice. No publisher Joseph Lstiburek Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest. diffusion moisture-Diffusion/Vapor Pressure moisture-Interstitial Condensation thermal-Insulation vapor permeance moisture-Vapor Permeance air barrier doc-Digest guidance-Roof design enclosure-Roof assembly airflow-Airtightness/Air barrier airflow-Driving forces/stack effect comp-roofs 2011-12-29T01:03:37Z BSC Article http://www.buildingscience.com/documents/digests/bsd-103-understanding-basements Buildings used to be constructed over cellars. Cellars were dank, dark places where coal was stored. People never intended to live in cellars. Now we have things called basements that have pool tables, media centers and play rooms. Cellars were easy to construct – rubble, stone, bricks and sometimes block. If they got wet or were damp so what? Basements are different. They are not easy to construct if we intend to live in them. They need to be dry, comfortable and keep contaminants out. Over the last 50 years there has been a notable expansion of living space. The useful conditioned space of building enclosures is expanding to the outer edge of the building skin (Figure 1). Attics, crawlspaces, garages and basements are valuable real estate that are being used to live in or used for storage or places to locate mechanical systems. Basements are viewed by many as cheap space that can easily be incorporated into a home. Keeping basements dry, comfortable and contaminant free is proving to be anything but simple. No publisher Joseph Lstiburek Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest. moisture-Diffusion/Vapor Pressure airflow-Indoor Air Quality thermal-Insulation guidance-Below-grade enclosure moisture-Vapor Permeance resources-technical comp-below-grade doc-Digest enclosure-Foundation assembly moisture-Interstitial Condensation vapor barrier resources-homeowner resources-mold 2011-07-18T19:17:00Z BSC Article http://www.buildingscience.com/documents/digests/bsd-104-understanding-air-barriers Controlling heat flow, airflow, moisture flow and solar and other radiation will control the interactions among the physical elements of the building, its occupants and the environment. Of these four, airflow “merits major consideration mainly because of its influence on heat and moisture flow” (Hutcheon, 1953). Airflow carries moisture that impacts a materials long-term performance (serviceability) and structural integrity (durability). Airflow also affects building behavior in a fire (spread of smoke and other toxic gases, supply of oxygen), indoor air quality (distribution of pollutants and location of microbial reservoirs) and thermal energy use. One of the key strategies in the control of airflow is the use of air barriers. No publisher Joseph Lstiburek Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest. enclosure-Wall assembly moisture-Diffusion/Vapor Pressure airflow-Indoor Air Quality comp-walls analysis-Modelling Tools doc-Digest moisture-Convection/Air barriers airflow-Airtightness/Air barrier airflow-Wind washing 2011-12-29T01:53:33Z BSC Article http://www.buildingscience.com/documents/digests/bsd-105-understanding-drainage-planes Controlling rain is the single most important factor in the design and construction of durable buildings and in the control of mold. Drainage planes are used in the design and construction of building enclosures to control rain. All exterior claddings pass some rainwater. Siding leaks, brick leaks, stucco leaks, stone leaks, etc. As such, some control of this penetrating rainwater is required. In most walls, this penetrating rainwater is controlled by the drainage plane that directs the penetrating water downwards and outwards. No publisher Joseph Lstiburek Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest. enclosure-Wall assembly guidance-Enclosure design principles moisture-Roofs comp-walls moisture-Drainage plane resources-technical radiation comp-below-grade moisture-Flashing/Deflection doc-Digest guidance-Roof design enclosure-Roof assembly guidance-Wall design enclosure-Wall assembly-insulation comp-roofs 2011-07-18T19:19:59Z BSC Article http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers The function of a vapor barrier is to retard the migration of water vapor. Where it is located in an assembly and its permeability is a function of climate, the characteristics of the materials that comprise the assembly and the interior conditions. Vapor barriers are not typically intended to retard the migration of air. That is the function of air barriers. No publisher Joseph Lstiburek Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest enclosure-Wall assembly guidance-Enclosure design principles comp-walls moisture-Drainage plane moisture-Vapor Permeance resources-vapor-barrier-code-changes doc-Digest moisture-Drying residential ventilation guidance-Roof design enclosure-Roof assembly guidance-Wall design moisture-Diffusion/Vapor Pressure comp-roofs 2011-07-18T19:23:43Z BSC Article http://www.buildingscience.com/documents/digests/bsd-107-understanding-ventilation-in-hot-humid-climates Adding outdoor air in hot humid climates causes moisture problems right? Sometimes. It depends on the condition of the house before you start to add outdoor air. Contrary to popular belief, most houses in hot, humid climates are over ventilated due to duct leakage and induced air change from internal air pressure effects due to unbalanced air flow and door closure. No publisher Joseph Lstiburek Building Science Digests are information articles intended for professionals. The author and the publisher of this article have used their best efforts to provide accurate and authoritative information in regard to the subject matter covered. The author and publisher make no warranty of any kind, expressed or implied, with regard to the information contained in this article. The information presented in this article must be used with care by professionals who understand the implications of what they are doing. If professional advice or other expert assistance is required, the services of a competent professional shall be sought. The author and publisher shall not be liable in the event of incidental or consequential damages in connection with, or arising from, the use of the information contained within this Building Science Digest. guidance-Enclosure design principles subsystems-HVAC-controls subsystems-HVAC airflow-Indoor Air Quality subsystems-HVAC-ducts guidance-Building systems/HVAC ASHRAE airflow-HVAC interactions doc-Digest subsystems-HVAC-air handlers comp-mechanical resources-mold 2011-07-18T19:25:50Z BSC Article