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.
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.
The current building industry focus on durability is in part a reaction to the current perceived lack of it. Warranty claims and callbacks are viewed as increasing. Litigation and insurance costs are felt to be rising as a result. Another reason for the current focus on durability is the recognition that sustainability is not possible without durability. If you double the life of a building and you use the same amount of resources to construct it, the building is twice as resource efficient. Therefore durability is a key component of sustainability.
It seems that one thing that both the development community and the environmental community can agree on is that durability is a good thing.
What do we know about durability and how do we know it? The lessons of durability have come principally out of failure. Engineering is an iterative process of design by failure. Buildings are constructed. Problems are experienced. Designs and processes are changed. Better buildings are constructed.
The building industry is in essence a reactive industry, not a proactive industry. It can be argued that the industry continues to do things until they become intolerably bad and then the industry changes. Examining failures gives us guidance on increasing the durability of building constructions.
