Don’t Skimp on Insulation


Spray foam insulationOn February 5, Martin Holladay from Green Building posted a Blog entitled “It’s OK to Skimp On Insulation, Icynene Says.” This was in response to open-cell spray foam manufacturer, Icyene’s position advising builders to install less insulation than the code requires and for building officials to approve insulation that doesn’t meet minimum R-value requirements.

Martin makes some very good points regarding the flaws in this thinking.  Icynene’s position is that air-tightening a home will have a significant impact on the energy consumption of the home–which is absolutely true, but they are also saying that by doing this you can accept lower R-values.  There is no reason to accept lower R-values.  Builders should be able to do both:  air-tighten a home and have the R-values that the code requires.

Heat moves to and from a home in three ways simultaneously; conduction, convection and radiation.

R-value just deals with conduction and not with air loss.  So to say that building code officials can reduce our requirements on conduction because we are helping to deal with air leakage is a weak argument.  Why should we settle for less? The building code requires that homes be air sealed and have a minimum R-value. There is a reason for that. We have to deal with all three modes of heat transfer simultaneously.

Martin points out that there is language in the 2006 International Residential Code (IRC) that gives air sealing requirements.  Here are a few examples Martin publishes about where buildings are to be air-tightened:

  • Sealing all joints, seams and penetrations;
  • Sealing around windows, doors and skylights
  • Sealing openings between window and door assemblies…

These are not places we put thermal insulation. Putting insulation between two studs doesn’t even address what the code language is saying as to where buildings need to be air-tight.  Different measures need to be taken.  If you look at Icynene’s argument you might infer that because they are air-tightening between two studs they can reduce the R-value required between those studs or in the attic.  There is no reason to accept that.

We consumers can and should have both air-tightness and high R-values because energy is too important to have less than what the code requires. 

Lucas Hamilton

Lucas Hamilton

Lucas Hamilton is Manager, Building Science Applications at CertainTeed Corporation. 


  1. There are a number of strategies by which we can insulate our loft space depending upon the materials chosen to be used. Since heat strikes upwards and escapes via loft space, adding layer of insulation in the standard thickness will probably be effective to block heat transfer. Although the beneficial thickness for Wall insulation boards is 270mm, older homes with shallow house between joists restrict such loft insulation depth.

  2. You appropriately point out that people who only have one dog in a fight always swear it’s the only dog needed but that often isn’t the case. The world simply isn’t that simple. Is “tin foil” a reference to the often inflated “Equivalent R Value” claims of radiant barrier foil insulations?

  3. B-b-b-but Lucas, you’re forgetting that foam is like, magic. The merest mention of foam (let alone a skim coat) cures cancer, solves world hunger, and protects us from mind control rays.

    Oh, wait, thats tinfoil:)

Leave A Reply