Masonry walls are generally highly durable. However, when masonry walls in cold climates stay too wet for too long, freeze-thaw damage can occur. This issue has particular relevance for energy efficiency retrofits, because the addition of interior insulation causes the masonry to stay colder and have a lower drying potential.
The following documents present details of BSC’s research and experience regarding the prevention of freeze-thaw damage in retrofit projects. Technical topics such as the critical degree of saturation (Scrit) are discussed, and case studies and recommendations are provided.
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.
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.
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.
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.
There is a large existing stock of uninsulated mass masonry buildings: their uninsulated walls result in poor energy performance, which is commonly addressed with the retrofit of interior insulation. Some durability issues associated with interior insulation have been or are being addressed, such as interstitial condensation and freeze-thaw damage issues. However, another durability risk is the hygrothermal behavior of moisture-sensitive wood beams embedded in the load-bearing masonry. Interior insulation reduces the beam end temperatures, reduces available drying potential, and results in higher relative humidity conditions in the beam pocket: all of these factors pose a greater risk to durability.
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.
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.
Condensation within walls during cold weather is a common performance problem. Most such condensation is due to air leakage, not diffusion. Although air barrier and vapor control layers can reduce the quantity and occurrence of condensation due to both mechanisms, the use of exterior insulation (even if that insulation is a vapor barrier and/or air barrier) can warm sensitive surfaces within a wall and thereby eliminate or reduce condensation risks. This digest provides the background for designers to select the insulation levels need to reach specific levels of condensation control.
Low-permeance vapor barriers are widely used on the interior of wall and roof systems in large parts of North America. Many codes and standards imply or even state that low-permeance vapor barriers should be used in all cold regions as well as many moderate climate zones. The influence of vapor barriers on the hygrothermal performance of wall and roof systems is a function of exterior climate, interior climate, solar absorptance, rainwater absorption, and the vapor and thermal resistance of all of the layers in the system. In many practical situations, a low-permeance vapor barrier will not improve hygrothermal performance and may in fact increase the likelihood of damaging condensation or trap moisture in the system. This paper will examine the role of vapor barriers on hygrothermal performance with the aid of simple and transparent diffusion calculations supported by measurements from full-scale natural exposure monitoring. The phenomenon of summertime condensation, the drying of roofs and walls, and multiple vapor barrier layers will be explored. The importance of properly assessing both the interior and exterior climate will be discussed. Vapor diffusion control strategies will be presented.
This paper is from the proceedings of the Thermal Performance of the Exterior Envelopes of Whole Buildings XI International Conference, December 5-9, 2010 in Clearwater, Florida. This paper summarizes some of the limitations of the various approaches to assessing the freeze-thaw resistance of brick masonry units and presents a detailed methodology for using frost dilatometry to determine the critical degree of saturation of brick material. Test results are presented for bricks from several historical load-bearing masonry. Recommendations are made for applying this approach together with hygrothermal model in the design of retrofit insulation projects.
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.
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.
This paper describes a fully instrumented large-scale mock-up completed in a southern Ontario private school to allow direct comparisons between insulated and non-insulated walls with a focus on the evaluation of freeze-thaw and corrosion risks. Climate conditions and wall temperature, relative humidity and moisture content are compared and discussed. Climate conditions (wetting and temperature) over the monitoring period were less severe than average. As a result, measured values were used to refine computer models to simulate wall performance under more severe climate conditions.
Exterior insulation and finishing systems (EIFS) are inherently defective and unfit of use as an exterior cladding system where moisture sensitive components are used without a provision for drainage or in locations and assemblies without adequate drying.
The American Foursquare, a Sears, Roebuck & Co. kit home, was a staple of small American towns between 1908 and 1940. More than 100,000 of them were built in America. Homes built prior to 1980 make up 80% of the housing stock in the United States, and are responsible for a majority of the residential energy use in the country. All of the renovations used systems engineering principles to ensure good indoor air quality and longterm durability while providing deep energy reductions. This posting is permission of ASHRAE. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAE's prior written permission.
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.
This digest will begin with a brief description of the system and materials, review moisture problems in buildings, and summarize how moisture control should be dealt with in strawbale buildings.
The primary function of a housewrap or building paper is rain penetration control. It is not air infiltration despite what the manufacturers say.
Stucco and EIFS are common cladding systems that appear similar from the exterior. These systems have very different attributes however. This Digest explains the reasons why face-sealed EIFS are fundamentally flawed as cladding systems for most applications, and describes how drained EIFS can be used successfully in almost all climate zones and exposures. Cracks, lamina deterioration, and movement joints are also discussed.
This digest reviews the moisture control principles that must be followed for a successful insulated retrofit of a solid load-bearing masonry wall. Two possible approaches to retrofitting such walls are presented and compared.
