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.
An edited version of this Insight first appeared in the ASHRAE Journal. To claim that something that has holes in it can act as a water control layer is a pretty interesting argument. It is both true and untrue.
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.
An edited version of this Insight first appeared in the ASHRAE Journal. Seventeen years ago we bought an old house—a fixer upper—over a hundred years old—in Westford, MA. I was going to make sure it would end up energy efficient.
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.
An edited version of this Insight first appeared in the ASHRAE Journal. The Parthenon was constructed around 450 B.C. as a temple to the Goddess Athena. More recently a temple overlooking Vancouver was constructed by the contractor Gauvin the Younger to honor the God of Building Science Hutcheon. For the past five years the Devout have been sprinkling water on the temple Icons carefully watching the results.
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.
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.
An edited version of this Insight first appeared in the ASHRAE Journal. It was the ants that finally did it. It wasn’t the shingles that needed to be replaced. It wasn’t the three-dimensional airflow network in the roof assembly. It wasn’t the lack of racking resistance. It wasn’t the lack of thermal resistance. It was the ants. Carpenter ants. There were just too many ants in my renovated barn.
An edited version of this Insight first appeared in the ASHRAE Journal. Imagine a three-dimensional molecular billiard game with billiard balls that are sometimes sticky, and where the rules depend on where you are on the table. Then assume that there are many different types of tables and pockets of different sizes.
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.
An edited version of this Insight first appeared in the ASHRAE Journal. One of the more difficult questions regarding enclosures is can we insulate the interior of a mass wall in a cold climate without causing damage from freeze/thaw cycles? The answer is usually yes, we can insulate. But, and there is almost always a “but,” it depends.
An edited version of this Insight first appeared in the ASHRAE Journal. Ice dams happen when the outside temperature is below freezing, the roof deck temperature is above freezing, and there is snow on the roof. The warm roof deck causes the snow on top of the roof deck to melt, and the melt water runs down to the edge of the roof where the water freezes leading to a buildup of ice and a backup of water, hence the term “dam."
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.
A concise history of the improvements to traditional buildings through design and materials.
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.
An edited version of this Insight first appeared in the ASHRAE Journal. It’s pretty easy to deal with new basements. If you want a challenge try dealing with century old houses sitting on top of rubble foundations. These houses are not going away and sooner or later we are going to have to fix them and insulate them.
