Rules Matter When it Comes to R-Value

Ken Forsythe

We all know there are ‘rules’ that everyone might not follow to the letter: “Speed Limit 55”…”Do Not Remove Mattress Tag Under Penalty of Law”…”Lather, rinse, repeat.”  When it comes to heating and air conditioning ductwork, there’s another rule many insulation contractors rarely follow:  “When installing bubble wrap insulation on ductwork, secure spacers every 24” to 36” around duct before applying wrap.”

While there’s no harm if you skip the “repeat” step when washing your hair, there can be serious utility bill consequences if installers leave out the placement of spacers between a duct and bubble wrap insulation. Bubble wrap insulation needs the thermal break provided by the air space that is created by spacers to achieve advertised R-values.  The actual R-value of improperly wrapped (i.e. no air space) duct with bubble wrap can be as low as R-0.90 to R-1.1.  Building Inspectors and owners need to be aware of what to look for to insure that the product performs properly.

In checking with HVAC insulation distributors to determine if insulation contractors routinely purchase air spacers with their bubble wrap, the answer is often “We’re still on our first shipment of spacers” or an outright, “We never sell any of those.”

Often bubble wrap insulation manufacturers do include spacer instructions with options for installers to create their own spacers by cutting and placing 2” wide strips of bubble wrap around the duct in intervals before applying the wrap around the duct or applying corner spacers specifically made for the purpose at each corner of rectangular duct.  But with so much pressure on insulation contractors to keep labor to a minimum, it’s hard to imagine that the vast majority are taking the time to create or use spacers on every project. Let’s face it: installers care about installing as quickly as possible for the lowest cost.

It’s true that quality bubble duct wrap may have good reflectivity and provides some protection against conductive heat gain or loss – as does fiber glass duct wrap with FSK (Foil-Scrim-Kraft) facing – however, the bubble wrap industry needs to do a better job educating installers and/or HVAC contractors. Educating the industry about the science behind adding air spacers and their integral role in delivering promised R-value is an important first step and is in everyone’s best interests.

 Ken Forsythe is a Senior Product Manager for CertainTeed Mechanical/Industrial Insulation