Building America Reports
This project examines implementation of advanced retrofit measures in the context of a large-scale weatherization program and the archetypal Chicago, Illinois, brick bungalow. In response to the apparent weatherization program limitations with respect to homes with masonry bearing wall construction, this research project examines two distinct strategies for insulating and air sealing the top of houses. One strategy applies best practice air sealing methods and a standard insulation method to the attic floor. The other strategy creates an unvented roof assembly using materials and methods typically available to weatherization contractors.
BA-0006: Discussion of the Use of Transfer Grilles to Facilitate Return Air Flow in Central Return Systems
Transfer grilles represent a cost-effective alternative to individual return ducts if they are properly configured for air flow, privacy, and aesthetics.
Everything you ever wanted to know about HVAC for homes-thermal comfort, air distribution, nature of and dealing with contaminants, HVAC strategies, and climate-appropriate graphics to boot.
This is a report describing the test methodology and results for experiments run on two test houses at the Bonita Springs development in Fort Myers, FL. The goal was to determine the effect of attic ventilation in a hot-humid climate; previous work had shown that little to no benefit is derived from ventilation in terms of energy use, and that it is detrimental for moisture control. Two houses with identical orientations and plans were compared; one was ventilated at the typical 1:300 ratio, and the other had sealed vents. This work was conducted in order to move houses in hot-humid climates forward in technology in their building envelope and HVAC systems.
Heat loss from basements accounts for a significant portion of the energy loss from a home. In many jurisdictions, basement insulation is a building code requirement. Cost usually determines the type of insulation system used.
PV systems have come a long way in the last two decades. While they may not work for all homes, residential installations are becoming a practical reality under more and more conditions
Combo systems use a gas water heater to provide domestic water and space heating. Find out when its appropriate to use such a system and guidelines for doing it right.
An examination of five different systems that show how to cool and dehumidify inside air while maintaining sufficient introduction of outside air for ventilation efficiently and cost-effectively.
Twenty homes were tested and monitored in the hot-humid climate of Houston, Texas, U.S.A., to evaluate the humidity control performance and operating cost of six different integrated dehumidification and ventilation systems that could be applied by production homebuilders. Fourteen houses, that also met measured energy efficiency criteria, had one of the six directly- or indirectly-integrated dehumidification and ventilation systems. Three reference houses had the same energy efficiency measures and controlled mechanical ventilation, while three other reference houses met code minimums for energy efficiency and did not have mechanical ventilation. Temperature and relative humidity were monitored at four living-space locations and in the conditioned attic where the space-conditioning equipment and air-distribution ducts were located. Equipment operational time was monitored for heating, cooling, dehumidification, and ventilation. Results showed that energy efficiency measures, combined with controlled mechanical ventilation, change the sensible and latent cooling load fractions such that supplemental dehumidification, in addition to that provided by the central cooling system, is required to maintain indoor relative humidity below 60% throughout the year. The system providing the best overall value, including humidity control, first cost, and operating cost, involved a standard dehumidifier located in a hall closet with a louvered door and central-fan-integrated supply ventilation with fan cycling.
Perhaps the single most challenging BSC performance for Building America production homebuilders is that all ducts and HVAC equipment must be within the conditioned space (this means no ducts in outside walls and no ducts or air handlers in garages, vented attics or vented crawlspaces).
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.
ASHRAE Standard 62.2-2010 may be considered to contain the “standard of care” for ventilation system design and operation in residential buildings, yet there are considerable technology gaps with that Standard. ASHRAE Standard 62.2 uses a catch-all approach that assumes that the entire house is a single, well-mixed zone and that there is no difference between different whole-building ventilation systems in providing effective ventilation.
BA-1308: Moisture Control for Dense-Packed Roof Assemblies in Cold Climates: Final Measure Guideline
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.
BA-1307: Interior Insulation of Mass Masonry Walls: Joist Monitoring, Material Test Optimization, Salt Effects
There are many existing buildings with load-bearing mass masonry walls, whose energy performance could be improved with the retrofit of insulation. However, adding insulation to the interior side of walls of such masonry buildings in cold climates may cause performance and durability problems. Some concerns have known solutions, but there are known knowledge gaps. Four topics were studied in more detail to address these gaps: the topics included moisture risks to embedded wood members, an examination of frost dilatometry test results for data patterns, the effect of dissolved salts on masonry durability, and optimization of the methodology of frost dilatometry testing.
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. There are three communities that are being constructed through this partnership: Devens Sustainable Housing (“Devens”), The Homes at Easthampton Meadow (“Easthampton”) and Phase II of the Coppersmith Way Development (“Townsend”). 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.
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.
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.
In multifamily buildings, central (typically rooftop) ventilation systems often have poor overall performance, overventilating some portions of the building (resulting in excess energy use), while simultaneously underventilating other portions of the building (resulting in diminished indoor air quality). These issues are often tied to multistory stack effects (warm air rising at cold outdoor conditions), and a lack of compartmentalization (airtightness) between floors and between units. These issues are exacerbated by the presence of multistory shafts (e.g., elevator shafts, stairwells, and ventilation shafts). Central corridor supply and makeup air systems combined with rooftop central exhaust systems are particularly problematic. The recommended solution is to isolate the units from one another and from corridors, shafts, elevators, and stairwells by means of greater airtightness.
Project Home Again is a development in New Orleans, Louisiana, created to provide new homes to victims of Hurricane Katrina. Building Science Corporation (BSC) acted as a consultant for the project, advocating design strategies for durability, flood resistance, occupant comfort, and low energy use while maintaining cost effectiveness. These techniques include the use of high density spray foam insulation, LowE3 glazing, and supplemental dehumidification to maintain comfortable humidity levels without unnecessary cooling. Stringent airtightness goals were achieved by the project, helping to meet the Builder’s Challenge targets set by Project Home Again. Floor plans, enclosures, and heating, ventilation, and air conditioning attributes are quite similar among different homes in the project.
BA-1206: Measure Guideline–Combination Forced-Air Space and Tankless Domestic Hot Water Heating Systems
This guideline pertains to design and application guidance for combination space and tankless domestic hot water (DHW) heating systems (combination systems) used in residential buildings, based on field evaluation, testing, and industry meetings. As residential building enclosure improvements continue to drive heating loads down, using the same water heating equipment for both space heating and domestic water heating becomes attractive from an initial cost and space-saving perspective. This topic is applicable to single- and multifamily residential buildings, both new and retrofitted. Before committing to wide-scale implementation of such combination space and domestic water heating systems for high performance buildings, whether new or retrofit, design decisions and site conditions affecting performance, maintenance, and occupant acceptability should be well understood. Current performance rating procedures for this type of hot water heating system and its many variants are inadequate to provide convincing prediction of estimated savings. In order to be assured of meeting the Building America savings goals, and the persistence of those savings after installation, continued sharing of lab and field testing results is needed.
This research project developed baseline engineering analysis to support the installation of thick layers of exterior insulation (2” to 8”) on existing masonry walls and wood framed walls through the use of wood furring strips (fastened through the insulation back to the structure) as a cladding attachment location. Furthermore, water management details necessary to connect the exterior insulated wall assemblies to roofs, balconies, decks, and windows were created to provide guidance on the integration of exterior insulation strategies with other enclosure elements.
This measure guideline provides information and guidance about rehabilitating, retrofitting, and replacing wood window assemblies in residential construction. It is intended primarily to help contractors and homeowners understand the options for safely improving the performance of their wood windows.
BA-1202: Byggmeister Test Home—Cold Climate Multifamily Masonry Building Condition Assessment and Retrofit Analysis
Building Science Corporation (BSC) has been working with Byggmeister, a partner on the Building America (BA) team, on retrofit projects under the BA program. Byggmeister is a local design-build firm that specializes in energy efficient retrofits and new construction. The Duclos, Eldrenkamp and Panish Energy Group (DEEP Energy Group), which is associated with Byggmeister, conducts design-phase energy analysis and monitors completed projects. The Byggmeister multifamily test home located in Jamaica Plain, Massachusetts (Jamaica Plain or J.P. Three-Family) is a three-story brick row house . The test home is examined with the goal of producing a case study that could be applied to similar New England homes. Basic areas of research that this report is expected to contribute include finding the combination of measures that are feasible, affordable, and suitable for this type of construction and acceptable to homeowners.
Through discussion of five case studies (test homes), this project evaluates strategies to elevate the performance of existing homes to a level commensurate with best-in-class implementation of high performance new construction homes. The test homes featured in this research activity participated in Deep Energy Retrofit (DER) Pilot Program sponsored by the electric and gas utility National Grid in Massachusetts and Rhode Island. Retrofit strategies are evaluated for impact on durability and indoor air quality in addition to energy performance.
BA-1109: High Impact Project: Support of Standards Development–Dense-pack Airflow Resistance Final Research Report
Historically, weatherization programs have required that cellulose insulation materials be dense-packed to a minimum installed density of 3.5 pcf. This density limit was, in part, required to realize beneficial reductions in air leakage. The Building Performance Institute (BPI) currently has under development two standards that will set requirements for the airflow resistance of insulations used in retrofit cavity (i.e. dense-pack) installations (BPI-102) and define acceptable test methods to measure the airflow resistance of insulation materials used in dense-pack applications (BPI-103).
Basements can account for up to one quarter of the typical energy consumption in a house. Therefore, insulating foundations is a critical measure for achieving high performance buildings. This is important in both new construction and retrofits of existing buildings. The fundamental problems and “best practice solutions” for moisture-safe basement insulation have been well established. However, many foundations are damp (either due to bulk water or capillary “wicking” of moisture) or of a type of construction that is not easy or straightforward to insulate (such as rubble foundations). Damp foundation repair methods can be “leveraged” to provide energy efficiency benefits. An example of this “hybrid” approach is spray foam insulation, which can be an effective means of liquid phase water control (leaking basement), vapor phase water control (diffusion and air leakage transported condensation) as well as an effective insulation.
Building Science Corporation seeks to further the energy efficiency market for cold climate, New England area retrofits by supporting projects based on solid building science fundamentals and verified implementation. The utility company National Grid engaged BSC as a partner to develop guidelines for its Deep Energy Retrofit Pilot Program. In addition to guideline development, BSC has acted as a consultant for these projects and others following similar retrofit strategies.
BA-1106: Leveraging Limited Scope for Maximum Benefit in Occupied Renovation of Uninsulated Cold Climate Multifamily Housing
This project examines a large scale renovation project within a 500 unit, 1960’s era subsidized urban housing community. The development comprises low-rise and mid-rise structures both of which exhibit exposed concrete frames with uninsulated masonry infill walls. The renovation project has a particular focus on indoor environmental quality and energy performance. The nature of occupied rehabilitation necessarily limited the scope of work implemented within apartment units. This research focuses on the airflow control and window replacement measures implemented as part of the renovations to the low-rise apartment buildings.
Load-bearing masonry buildings are a significant portion of the existing building stock. Given the Building America goals of reducing home energy use by 30%-50% (compared to 2009 energy codes for new homes and pre-retrofit energy use for existing homes), insulation and air sealing of mass masonry walls will need to be a component of this work if mass masonry residential buildings are to be addressed.
BA-9802: Performance of Building America Initiative Houses with Unvented Attics and Tile Roofs Constructed by Pulte Homes, Las Vegas Division
A residential attic model, contained in the finite element computer program FSEC 3.0, was empirically aligned with measured attic data from three roof research facilities in Florida and Illinois.
BA-9908: Design Methodology and Economic Evaluation of Central-Fan-Integrated Supply Ventilation Systems
Residential ventilation systems can be categorized as supply, exhaust, or balanced systems. This effort focused on establishing a design methodology for central-fan-integrated supply ventilation systems.
Successfully executing strategies to control bulk water for foundations is critical for building durability, indoor air quality, and creating acceptable conditions and/or living spaces within the foundation space. Although the energy impacts of properly done bulk water control are small to insignificant, it should be considered a base requirement for any high performance house. In addition, measures such as basement insulation are predicated on properly managed foundation bulk water.
BA-1009: Building America Special Research Project—Space Conditioning Systems for High Performance Homes
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. The main focus for this research project is the integration of a combination space and domestic hot water heating system (“combi system”) with a high-efficiency air source heat pump to optimize efficiency and comfort.
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. The main focus for this research project is on the AAON heat pump system with digital scroll compressor and modulating hot-gas condenser reheat installed in the GreenCraft Builders prototype house in Lewisville, TX.
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. The goal of this research is to find optimally designed, cost effective roof insulation systems that can be included with other enclosure details to help reduce whole house energy use by 70%. This report will compare a variety of roof insulating strategies and present their advantages and disadvantages according to several comparison criteria.
BA-1005: Building America Special Research Project: High R-Value Enclosures for High Performance Residential Buildings in All Climate Zones
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. Many concerns, including the rising cost of energy, climate change concerns, and demands for increased comfort, have lead to the desire for increased insulation levels in many new and existing buildings. Building codes and green building codes are being changed to require higher levels of thermal insulation both for residential and commercial construction. This report will review, and summarize the current state of understanding and research into enclosures with higher thermal resistance, so-called “High-R Enclosures”. Recommendations are provided for further research.
BA-1004: Building America Special Research Project—Deployment of Advanced Framing at the Community Scale
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. This report investigates the implementation of advanced framing in both production and prototype built homes built in a variety of climate regions across the USA. This work is part of a large research project on High R-value enclosures. The current industry standard wall is being replaced by a 2×6 frame at 24-inch centers with single top plates, two-stud corners, no jack studs, no cripples and single headers (and in many cases no headers at all). The advanced framing system is cheaper because it uses 5% to 10% less board feet of lumber, and it is faster because it uses 30% fewer pieces. It saves energy because it provides a 60% deeper cavity (which allows 60% more cavity insulation) and because it reduces the framing factor. Advanced framing can save energy, greenhouse gas emissions, and money if properly implemented. Through BSC’s experience we have found that builders can save $1000 per house on advanced framing. To maximize cost savings and energy savings for the homeowner, the builder financial savings are best shifted to implementing more energy saving measures.
The following report is an excerpt from the 2010 Building Science Corporation Industry Team Building America Annual Report. Many concerns, including the rising cost of energy, climate change concerns, and demands for increased comfort, have lead to the desire for increased insulation levels in many new and existing buildings. Building codes are improving to require higher levels of thermal control than ever before for new construction. This report considers a number of promising foundation and basement insulation strategies that can meet the requirement for better thermal control in colder climates while enhancing moisture control, health, and comfort.
This paper describes a hygrothermal modeling study, including all of the US climate zones, a range of interior humidity levels and numerous arrangements and types of insulation. The results showed that so long as airtightness is provided, and wintertime humidity is controlled, numerous unvented solutions using either or both spray foam (open and closed cell) and fibrous insulation (cellulose and mineral fiber) can be successful. Climate, the solar properties and exposure of the roofing, the air and vapor permeance of the insulation(s) and interior humidity are the most important factors to be considered in the design of moisture-safe unvented roof systems.
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 true three-dimensional heat flow and the relative risk of moisture damage.
The following report is an excerpt from the 2008 Building Science Corporation Industry Team Building America Annual Report. The purpose of this research project is to design and install a solar hot water system that features a tankless water heater integrated with a solar hot water panel such that consistent temperature control can be achieved at the domestic taps.
This report is an excerpt from the 2008 Building America Annual Report. Following the almost complete destruction of Greensburg, Kansas by a tornado in May, 2007, Building Science Corporation (BSC) was contracted to provide example house plans, support for the reconstruction of energy efficient houses and training for builders and trades. This report describes the planning, execution, and results of BSC’s builder training program in Greensburg.
BA-0801: Towards Sustainability—Green Building, Sustainability Objectives, and Building America Whole House Systems Research
This paper discusses Building America whole house systems research within the broad effort to reduce or eliminate the environmental impact of building and provides specific recommendations for future Building America research based on Building Science Corporation’s experience with several recent projects involving green home building programs.
Given what happened in New Orleans during hurricane Katrina, changes in the way we build are needed. Looking to key sustainability concepts of durability and energy efficiency, new flood resistant design concepts were developed.
Primarily as a resort location, Hilton Head Island has a somewhat different residential housing market than other more traditional areas.
In order for dilution ventilation systems to provide predictable results independent of the geometry of individual homes, outside air must be uniformly distributed throughout the house
This report summarizes indoor temperature and humidity data that have been collected from houses by the Building Science Consortium of the US Department of Energy Building America Program.
The overall goal of the DOE residential research program is to reduce average whole house energy use in new residential buildings by 30-90 percent by 2020, including homes that achieve zero net energy use on an annual basis. High performance space conditioning and control systems that match the high performance of Building America enclosures are necessary to meet performance targets. Conditioning systems with integrated mechanical ventilation and year-around temperature and humidity control are necessary. The most significant climate-specific need is for system-integrated dehumidification for humidity control without overcooling the space. Cost-effective dehumidification without overcooling will enable continued and further reduction of sensible loads (including high-performance glazing) that would otherwise exacerbate humidity control problems in humid climates.
This is one of eleven projects from the full report of Building Science Consortium’s research efforts for 2004. The research program is aimed towards advanced building systems that have the potential to reduce residential building energy use by 50-60%. It is based on evaluation of market trends, industry partner needs, and initial results from our team’s system engineering research program. A total of eleven individual research projects were detailed in this report. This project report explores the development of more cost-effective, integrated supplemental dehumidification systems.
This is a test form used in the Building America program to ascertain house performance and specifications.
SNAPSHOT stands for Short, Non-destructive Approach to Provide Significant House Operation Thresholds.
Using four Building Science Consortium Building America community-scale projects, this paper investigates the nature, strength, and durability of connections between high performance dwellings and developments.
High performance compact fluorescent lighting (CFLs) is not just about energy savings; it’s also about the other aspects of performance such as color rendering.
This paper discusses the differences between vented, unvented and conditioned crawlspaces. Best practice construction techniques and assemblies for conditioned crawlspaces are discussed, the results of a field monitoring program are presented, and the code language addressing crawlspaces is explained.
Heat loss through uninsulated basement walls can account for up to one-third of the heat loss from an average home. Installing insulation on basement walls is often inexpensive, easy to accomplish and frequently combined with “finishing the basement.”
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 has been dramatically reduced.
BA-1311: Evaluation of Two CEDA Weatherization Pilot Implementations of an Exterior Insulation and Over-Clad Retrofit Strategy for Residential Masonry Buildings in Chicago
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. High heating energy use typical in these buildings threaten housing affordability. Uninsulated mass masonry wall assemblies also have a strongly detrimental impact on comfort. Significant changes to the performance of masonry wall assemblies is generally beyond the reach of typical weatherization (Wx) program resources. The Community and Economic Development Association of Cook County, Inc. (CEDA) has secured a Sustainable Energy Resources for Consumers (SERC) innovation grant sponsored by the United States Department of Energy (DOE). This grant provides CEDA the opportunity to pursue a pilot implementation of innovative approaches to retrofit in masonry wall enclosures. The exterior insulation and over-clad strategy implemented through this project was designed to allow implementation by contractors active in CEDA weatherization programs and using materials and methods familiar to these contractors. 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.
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. Explorations of eleven in-service roof systems were completed. 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. One full-roof failure was reviewed, as an industry partner was involved with replacing structurally failed roof sheathing. In this case the manufacturer's investigation report concluded that the spray foam was installed on wet OSB based on the observation that the spray foam did not adhere well to the substrate and the pore structure of the closed-cell spray foam at the ccSPF/OSB interface was indicative of a wet substrate.
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.
Twenty homes were tested and monitored in the hot-humid climate of Houston, Texas, to evaluate the humidity control performance and operating cost of six different integrated dehumidification and ventilation systems that could be applied by production homebuilders.
Building America is a program of the U.S. Department of Energy, in which teams of architects, engineers, builders, equipment manufacturers, and others collaborate in a systems engineering approach to produce homes that use up to 50 percent less energy to operate.
This report is an excerpt from the 2008 Building America Annual Report. Following the almost complete destruction of Greensburg, Kansas by a tornado in May, 2007, Building Science Corporation (BSC) was contracted to provide example house plans, support for the reconstruction of energy efficient houses and training for builders and trades. This report describes the results of BSC’s work to construct more than 20 energy efficient, affordable, durable houses in Greensburg, Kansas.
The following report is an excerpt from the 2008 Building Science Corporation Industry Team Building America Annual Report. This summary includes whole-house performance and systems engineering, construction support, source energy savings and quality control requirements and integration.
Based on Building America experience, this report is about selecting furnaces, water heaters, both or sometimes just one to accomplish both space heating and domestic hot water.
Americans have been building homes with wood—shaping logs, joining timbers, nailing studs—for almost 400 years. Our current approach, stick framing, grew poplular in the mid-1800's because it too less skill, required simpler tools, and took fewer people than timber framing. We apparently really like waste haulers, too.
The following reports are excerpts from the 2009 Building Science Corporation Industry Team Building America Annual Report.
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.
BA-1315: Evaluation of Early Performance Results for Massachusetts Homes in the National Grid Pilot Deep Energy Retrofit Program
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 that was used in this analysis 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 project can provide concrete input for homeowners who are considering a DER.
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.
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, meaning that high performance retrofit was implemented for a single major enclosure component or a limited number of major enclosure components. The collection of 42 DER projects represents 60 units of housing.
Building America Case Study: Whole House Solutions for Existing Homes—National Grid Deep Energy Retrofit Pilot: Massachusetts and Rhode Island
Building America Case Study
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.
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.
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 (typically overly conservative). In some cases, these results clearly contradict extensive field experience and known history of assemblies, showing failure when they do not occur in reality. In other more worrisome cases, models run on assemblies that clearly have not performed historically show successful performance. This has resulted in confusion in the building industry—specifically, problems with advancing knowledge of moisture-safe building enclosure/shell assemblies. Therefore, Building Science Corporation led a Building America Expert Meeting on “Guidance on Modeling Enclosure Design for Above-Grade Walls.” Presenters from national laboratories, consulting firms, and building material manufacturers presented on their research, which matched field measurements of wall hygrothermal behavior to simulations. This was followed by a group discussion on various topics, including required expertise for running WUFI, education requirements, and the need for material property testing.
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.
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.
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