Exterior insulation prevents thermal bridging, which can threaten the efficiency of your insulation. It occurs when conductive components of a building's structure – like wall studs, for example – allow heat to transfer into the building easily. If thermal bridging is untreated, R-value does not as effectively illustrate thermal performance because the heat simply finds its way in through poorly insulating materials.
If you want to perform your retrofit on the exterior, you can also give your building a different look with insulated facade systems or structural insulated panels (SIPs).
“For buildings that need a facelift, consider some of the new high-performance insulated facade systems as an alternative to the overused and occasionally problematic synthetic stucco exterior insulation and finish system (EIFS) products,” says NREL.
However, if you prefer to provide interior insulation, preventing thermal bridges is not a lost cause. You simply need to be proactive about it.
“In some buildings, thermal bridging may be more important to address than insulation,” claims Pacific Northwest National Laboratory. “Such bridges can be corrected by adding a thermal break, though this often entails replacing entire door or window assemblies.”
Insulation installed in interior walls, floors or ceilings will provide clearer benefits to acoustics in the building in addition to providing thermal stability. Insulation with a higher Sound Transmission Class (STC) rating will improve sound dampening.
You ultimately have more options when insulating the interior of your building than the outside, so do plenty of research about insulation types and attributes that will work best for your building. Utilize resources like the DOE's Buildings Performance Database (available at www.commercialbuildings.energy.gov) to forecast energy usage based on similar projects.
Finally, and perhaps most importantly, make sure your insulation is properly installed. Retrofitting can be quite the investment, and if the building lacks a proper air barrier or if moisture can enter, it will not work properly or last long.
Justin Feit email@example.com is assistant editor of BUILDINGS.
5 Types of Insulation
Batts, Blankets and Rolls
Batts made from fiberglass, rock and slag wool are easily customizable for a retrofit, providing a variety of R-values, thicknesses and sizes, according to the North American Insulation Manufacturers Association’s Insulation Institute. Blankets can be cut to fit into the wall cavity. They are relatively inexpensive and fire-resistant but can cause gaps in coverage if you are not careful.
Loose-fill insulation is made up of small particles of fiber, foam or other materials that can conform to spaces without disrupting any structures. The DOE says, “This ability to conform makes loose-fill insulation well suited for retrofits and locations where it would be difficult to install other types of insulation.”
Structural Insulated Panels (SIPs)
SIPs are comprised of an insulating foam core located between two structural facings that are typically oriented strand board (OSB), according to the Structural Insulated Panel Association. Manufacturers usually fabricate them to fit a specific building’s design.
Liquid foam insulation expands to fill cavities in the interior of buildings, and the application varies depending on the type. “Some installations can have twice the R-value per inch of traditional batt insulation and can fill even the smallest cavities, creating an effective air barrier,” explains the DOE.
Foam Board or Rigid Foam
Foam boards, which are rigid panels of insulation, provide a versatile solution because they are lightweight and are easy to cut to form. “They provide good thermal resistance and reduce heat conduction through structural elements like wood and steel studs,” notes the DOE.