Field Monitoring and Simulation of a Historic Mass Masonry Building Retrofitted with Interior Insulation
By: Kohta Ueno, John Straube, and Randy Van Straaten.
Load-bearing masonry buildings are a significant portion of the existing building stock, and there is a great deal of interest in adding thermal insulation to the walls of these structures. Exterior insulation provides the ideal conditions for building durability; however, many buildings cannot be retrofitted with insulation on the exterior for reasons such as historic preservation, aesthetics, zoning, or space restrictions. Adding insulation to the interior side of walls of such masonry buildings in cold, and particularly cold and wet, climates may increase risks of performance and durability problems.
A circa 1917 construction mass masonry building located on a Boston-area university campus was retrofitted with interior polyurethane spray foam insulation.Sensors were installed in the retrofitted walls to measure temperature and moisture conditions within the assembly; interior and exterior boundary conditions were also monitored. Experimental variables included orientation, spatial location of monitoring, and assembly type (insulated experimental versus uninsulated control). Hygrothermal simulations were run on the original and retrofitted assemblies using measured site environmental data, both to assess durability risks, and for comparison with the measured data.
Measured data indicated that the insulated masonry walls were colder and had higher moisture contents than uninsulated assemblies, as would be expected. Hygrothermal simulations had good correlation to temperature measurements, but moisture measurements were less consistent. These differences may be due to sensor response, driving rain exposure, or anomalies within the mass masonry wall assembly. The simulations indicated a low risk of freeze-thaw damage.
The effect of thermal bridging through structural elements (uninsulated floor slabs) was examined with cold weather infrared thermography.
Note: This article was published in Proceedings of Buildings XII, 2013 and subsequently on buildingscience.com. The link below goes to the full article on buildingscience.com. Copyright 2013 ASHRAE.