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.
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.
An edited version of this Insight first appeared in the ASHRAE Journal. Engineers are pretty funny people. Engineers say that 1 inch of water exerts a force of – wait for it – 1 inch. Yup, 1 inch of water weighs 1 inch of water. It’s a gift we engineers have. Let me help you all out a little bit here, go suck on a straw and draw 1 inch of water up into the straw.
