BUILDING SCIENCES COLUMN Joseph W. Lstiburek More on Continuous Exterior Insulation: Hanging Cladding Z-Bar Hang On Cladding, Cladding Hang On* BY JOSEPH W. LSTIBUREK, PH.D., P.ENG., FELLOW ASHRAE Continuous exterior insulation is such an obvious thing to do-and we are finally getting serious about it-but we still seem to go out of our way to defeat its intent. One of the arguments for the use of continuous exterior insulation is to address the thermal bridging at the structural components of building assemblies-especially steel stud/frame assemblies. Done correctly it is a big deal energy-wise. It is pretty dumb to add continuous exterior insulation with the same type of thermal bridging that the continuous exterior insulation is intended to address. It boggles the mind to use a Z-bar-cold formed metal-for cladding attachment over continuous exterior insulation. Not sure if they still teach this in public school, but metal is conductive not just for electricity but also for heat.† Figure 1 and Figure 2 are common details-apparently the exterior gypsum sheathing is supposed to be the " thermal break. " What is the point of using continuous exterior insulation when you reduce its effectiveness by 30% or more?‡ Continuous Exterior Insulation Steel Stud Exterior Gypsum Sheathing Steel Studs Sheathing Peel and Stick with Lapped Joints Joint in Sheathing Cold Formed Hat Section Cold Formed Clip Angle Metal Panel Cold Formed Angle FIGURE 1 (Top) Cold Formed Metal Cladding Attachment. Apparently the exterior gypsum sheathing is supposed to be the " thermal break. " What is the point of using continuous exterior insulation when you reduce its effectiveness? FIGURE 2 (Bottom) Cold Formed Metal Is Conductive. Metal is conductive not just for electricity but also for heat. Attaching cladding through continuous exterior insulation should be done in a manner that reduces thermal *Pretty sure this was a song from the McCoys-sometime in 1965-or I might be confusing cladding with sloopy. †This often seems to be left out of the structural engineering curriculum. ‡Lots and lots of work done over the years. I use 30%, but it can be much higher. Start with the ASHRAE Handbook-Fundamentals. 42 ASHRAE JOURNAL ashrae.o rg J A N U A RY 2022http://ashrae.org