Insulation II - Points from articles

• Adding insulation to the interior side of walls of such masonry buildings in cold, and particularly cold and wet, climates may cause performance and durability problems.  There are specific moisture control principles that must be followed for a successful insulated retrofit of a solid load-bearing masonry wall. 

• Uninsulated masonry (even “thick” multi-wythe construction) would have an average R value of roughly R-5, which is far below current energy code requirements; application of insulation has substantial benefits.

• Increasing the building airtightness (which would result from this interior retrofit) can cause indoor air quality problems: mechanical ventilation, pollution source control, and combustion safety measures must be implemented to manage this risk. 

• When examining the moisture problem, the fundamental premise is that mass masonry walls manage moisture in a different way than modern, drained assemblies.  Therefore, the balance of moisture (into and out of the wall) is strongly affected by the application of interior insulation.  For one, the masonry wall becomes colder: the inside face of the masonry wall changes from seeing moderate temperatures to regularly experiencing freezing temperatures.  In addition, the wall has reduced drying to the interior (by cooling the masonry, and by adding vapor impermeable layers on the interior), and the amount of energy flow through the wall (and thus drying potential) has been minimized.  In addition, moisture flow due to air leakage into the interface between the masonry and insulation can result in condensation problems; excellent airtightness is desirable to prevent this.  Another issue is rot/corrosion of embedded elements: embedded wood timbers are a common embedded element with durability concerns.  

• A more successful approach involves spraying an airtight insulating foam directly to the interior side of the existing masonry: all air leakage condensation is strictly controlled, and it is the most practical approach to achieving high levels of airtightness in existing buildings.  The spray foam also acts as a moisture barrier, and any small amount of incidental rain penetration will be localized and controlled.  High-density closed cell polyurethane foam is generally a good solution for thinner applications (e.g., 2” of ccPCF), and open-celled semi-permeable foams (e.g., 5” ocSPF) can be a good choice for greater thickness if the interior is kept at a low humidity during winter and the outdoor temperature is not too cold.