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This case study by the U.S. Department of Energy’s Building America research team Building Science Corporation is a test implementation of an unvented tile roof assembly in a hot-humid climate (Orlando, Florida; zone 2A), insulated with air-permeable insulation (netted and blown fiberglass).
Exterior sheathing insulation is an effective strategy in increasing the overall R-value of wall assemblies; other benefits include decreasing the effects of thermal bridging and increasing the moisture durability of the built assembly. Vapor-permeable exterior insulation, such as mineral board or expanded polystyrene foam, are one such product that may be used to achieve these benefits. However, uncertainty exists on the effects of inward driven moisture and the interaction of increased sheathing temperatures on the moisture durability of the edifice. To address these concerns, Building Science Corporation (BSC) conducted a series of hygrothermal models for cities representing a range of different climate zones. This report describes the research project, key research questions, and the procedures utilized to analyse the problems.
This measure guideline, written by the U.S. Department of Energy’s Building America team Building Science Corporation, provides information about the design and construction of wall assemblies that use layers of rigid exterior insulation thicker than 1-½ in. and that require a secondary cladding attachment location exterior to the insulation. The guideline 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 this use to the specific project goals and requirements; and (3) construction detailing to increase understanding about implementing the various design elements.
Even builders who are relatively new to energy-efficient construction can consistently reach a target whole house airtightness of 1.5 air changes per hour at 50 Pascals (ACH50) with high R-value enclosures that use a hybrid insulation approach. The City of Wyandotte, Michigan, started a construction program in 2010 to build affordable, energy-efficient homes on lots in existing neighborhoods. A goal of the program was to engage local builders in energy-efficient construction and be able to deliver the new houses for less than $100/ft2. By the end of 2012, approximately 25 new houses were built by five local builders under this program. To help builders consistently achieve the airtightness target, a local architect worked with researchers from Building Science Corporation, a U.S. Department of Energy Building America team, to develop a technology specification with several key pieces. A high R-value wall and roof assembly made use of 2 ?6 advanced framing and a hybrid insulation approach that included insulating sheathing to control thermal bridging and closed cell spray polyurethane foam insulation (ccSPF) for its airtightness and vapor control benefits. This approach allows the air barrier to be completed and tested before any finishing work occurs, ensuring that problems are spotted and corrected early in the construction process.
In this project, the Building Science Corporation team studied a historic brick building in Lawrence, Massachusetts, which is being renovated into 10 condominium units and adding insulation to the interior side of walls of such masonry buildings.
Fire-resistance rated (or area separation) wall assemblies present a great difficulty in air sealing/compartmentalization, particularly in townhouse construction. To address this challenge, Building Science Corporation partnered with builder K. Hovnanian Homes to determine whether taping exterior sheathing details improves air sealing in townhouse and multifamily construction, and to better understand air leakage pathways.
The 2012 IECC has an airtightness requirement of 3 air changes per hour at 50 Pascals test pressure for both single-family and multifamily construction in Climate Zones 3-8. Other programs (LEED, ASHRAE 189, ASHRAE 62.2) have similar or tighter compartmentalization requirements, driving the need for easier and more effective methods of compartmentalization in multifamily buildings. Builders and practitioners have found that fire-resistance rated wall assemblies are a major source of difficulty in air sealing/compartmentalization, particularly in townhouse construction. This problem is exacerbated when garages are “tucked in” to the units and living space is located over the garages. In this project, Building Science Corporation examined the taping of exterior sheathing details to improve air sealing results in townhouse and multifamily construction, when coupled with a better understanding of air leakage pathways. Current approaches are cumbersome, expensive, time consuming, and ineffective; these details were proposed as a more effective and efficient method. The effectiveness of these air sealing methods was tested with blower door testing, including “nulled” or “guarded” testing (adjacent units run at equal test pressure to null out inter-unit air leakage, or “pressure neutralization”). Pressure diagnostics were used to evaluate unit-to-unit connections and series leakage pathways (i.e., air leakage from exterior, into the fire-resistance rated wall assembly, and to the interior).
Double stud walls have a higher risk of interior-sourced condensation moisture damage when compared with high-R approaches using exterior insulating sheathing. In this project, Building Science Corporation monitored moisture conditions in double-stud walls from 2011 through 2014 at a new production house located in Devens, Massachusetts. The builder, Transformations, Inc., has been using double-stud walls insulated with 12 in. of open cell polyurethane spray foam (ocSPF); however, the company has been considering a change to netted and blown cellulose insulation for cost reasons. Cellulose is a common choice for double-stud walls because of its lower cost (in most markets). However, cellulose is an air-permeable insulation, unlike spray foams, which increases interior moisture risks. The team compared three double-stud assemblies: 12 in. of ocSPF, 12 in. of cellulose, and 5-½ in. of ocSPF at the exterior of a double-stud wall (to approximate conventional 2 × 6 wall construction and insulation levels, acting as a control wall). These assemblies were repeated on the north and south orientations, for a total of six assemblies.
This needs assessment was conducted by the Washington State University (WSU) Energy Program and Building Science Corporation (BSC), with support from the U.S. Department of Energy's (DOE) Building Technologies Office. The primary goal of this research was to identify moisture durability, energy savings, and savings-to-investment ratio (SIR) research needs related to the retrofit of attic insulation in the DOE Weatherization Assistance Program (WAP). Specifically, manufactured homes that comply with building codes established by the U.S. Department of Housing and Urban Development (HUD) built after 1976 and sited in colder climates. This project assessed current practice of WAP insulation and/or roof venting solutions that improve attic insulation energy savings and durability. WSU and BSC conducted outreach to stakeholders via email, phone, one-on-one interviews, and group meetings designed to inquire about relevant issues that they may have observed. Needs assessment feedback was provided from stakeholders involved with attic insulation retrofits in existing HUD-code manufactured housing in the colder climates of the United States. The list of more than 50 stakeholders who provided input into this needs assessment is provided in Appendix A.
This needs assessment was conducted by the Washington State University (WSU) Energy Program and Building Science Corporation (BSC), with support from the U.S. Department of Energy's (DOE) Building Technologies Office. The primary goal of this research was to identify moisture durability, energy savings, and savings-to-investment ratio (SIR) research needs related to the retrofit of attic insulation in the DOE Weatherization Assistance Program (WAP). Specifically, manufactured homes that comply with building codes established by the U.S. Department of Housing and Urban Development (HUD) built after 1976 and sited in colder climates. This project assessed current practice of WAP insulation and/or roof venting solutions that improve attic insulation energy savings and durability. WSU and BSC conducted outreach to stakeholders via email, phone, one-on-one interviews, and group meetings designed to inquire about relevant issues that they may have observed. Needs assessment feedback was provided from stakeholders involved with attic insulation retrofits in existing HUD-code manufactured housing in the colder climates of the United States. The list of more than 50 stakeholders who provided input into this needs assessment is provided in Appendix A.
Between December, 2009 and December, 2012, 42 deep energy retrofit (DER) projects were completed through a pilot program sponsored by National Grid and conducted in Massachusetts and Rhode Island. Thirty-seven of these projects 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. Building Science Corporation developed a consistent "package" of measures in terms of the performance targeted for major building components. Based on the community experience, this DER package is expected to result in yearly source energy use near 110 MMBtu/year or approximately 40% below the Northeast regional average.
Between December, 2009 and December, 2012 42 deep energy retrofit (DER) projects were completed through a pilot program sponsored by National Grid and conducted in Massachusetts and Rhode Island. Thirty-seven of these projects 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. Building Science Corporation developed a consistent "package" of measures in terms of the performance targeted for major building components. Pre- and post-retrofit air leakage measurements were performed for each of the projects. Each project also reported information about project costs including identification of energy-related costs. Post-retrofit energy-use data was obtained for 29 of the DER projects, and was analyzed based on the net energy used by the DER project regardless of whether the energy was generated on site or delivered to the site. Based on the community experience, this DER package is expected to result in yearly source energy use near 110 MMBtu/year or approximately 40% below the Northeast regional average. Larger to medium sized homes that successful implement these retrofits can be expected to achieve source EUI that is comparable to Passive House targets for new construction. The community of DER projects show post-retrofit airtightness below 1.5 ACH50 to be eminently achievable.
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 research performed for this project provides information regarding advanced retrofit packages for multi-family masonry buildings in Cold climates. In particular, this project demonstrates safe, durable, and cost-effective solutions that will potentially benefit millions of multi-family brick buildings throughout the East Coast and Midwest (Cold climates). The retrofit packages provide insight on the opportunities for and constraints on retrofitting multifamily buildings with ambitious energy performance goals but a limited budget. The condominium conversion project will contribute to several areas of research on enclosures, space conditioning, and water heating. 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.
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 research performed for this project provides information regarding advanced retrofit packages for multi-family masonry buildings in Cold climates. In particular, this project demonstrates safe, durable, and cost-effective solutions that will potentially benefit millions of multi-family brick buildings throughout the East Coast and Midwest (Cold climates). The retrofit packages provide insight on the opportunities for and constraints on retrofitting multifamily buildings with ambitious energy performance goals but a limited budget. The condominium conversion project will contribute to several areas of research on enclosures, space conditioning, and water heating. 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.
Changes in the International Energy Conservation Code (IECC) from 2009 to 2012 have resulted in the use of exterior rigid insulation becoming part of the prescriptive code requirements. With more jurisdictions adopting the 2012 IECC, builders will be required to incorporate exterior insulation in the construction of their exterior wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use of wood of 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. However, there has been resistance to its widespread implementation due to a lack of research and understanding of the mechanisms involved and potential creep effects of the assembly under the sustained dead load of a cladding. This research conducted by Building Science Corporation evaluated the system mechanics and long-term performance of this technique.
The conversion of an older Massachusetts building into condominiums illustrates a safe, durable, and cost-effective solution for heating and ventilation systems that can potentially benefit millions of multifamily buildings. Merrimack Valley Habitat for Humanity (MVHfH) partnered with U.S. Department of Energy Building America team Building Science Corporation (BSC) to provide high performance affordable housing for 10 families in the retrofit of an existing mass masonry building (a former convent). The original ventilation design for the project was provided by a local engineer and consisted of a single large heat recovery ventilator (HRV) located in a mechanical room in the basement with a centralized duct system providing supply air to the main living space and exhausting stale air from the single bathroom in each apartment. This design was deemed to be far too costly to install and operate for several reasons: the large central HRV was oversized and the specified flows to each apartment were much higher than the ASHRAE 62.2 rate; an extensive system of ductwork, smoke and fire dampers, and duct chases were specified; ductwork required a significant area of dropped ceilings; and the system lacked individual ventilation control in the apartments.
The conversion of an older Massachusetts building into condominiums illustrates a safe, durable, and cost-effective solution for heating and ventilation systems that can potentially benefit millions of multifamily buildings. In this project, Merrimack Valley Habitat for Humanity (MVHfH) partnered with U.S. Department of Energy Building America team Building Science Corporation (BSC) to provide high performance affordable housing for 10 families in the retrofit of an existing mass masonry building (a former convent).
In this Top Innovation profile, Building Science Corporation guides contractors through several options for repairing or replacing old windows to improve air sealing and thermal performance.