The Green “Blowback” Effect

A recent study initiated by the EPA and conducted by the Institute of Medicine indicated that unintended and potentially serious health risks could be the result of too much “weatherization.”  The report stated, “Even with the best intentions, indoor environmental quality issues may emerge with interventions that have not been sufficiently well screened for their effects on occupant safety and health.”

MTI has made this point many times in presentations that we have done, and our AIA/CES courses, “Breaking the Mold…” (MTI409) and “Don’t Waster Your Energy…” (MTI509), detail the sustainability and health risks that careless weatherization can cause.  Don’t get me wrong, we are not against saving energy through tightening buildings, but like the report from the IOM, we feel that planning and coordination of efforts need to take place first.

For too long, building has been done in a compartmentalized fashion.  All the parties involved tended to “do their own thing” rather than working as a team.  With a plethora of new materials and methods in the construction world, holistic building is a must!  Architects, specifiers, engineers, contractors, and manufacturers of building materials need to be on the same page.

For example, entrapped moisture in the building envelope has skyrocketed over the last 25-30 years (a time period following the first energy crisis of the 1970s).  Why, because better windows, more and better insulation materials, more sealants, more unintended vapor barriers, etc. were being used without much thought to unplanned consequences.  When you seal the building envelope too tight, you get moisture issues.  You also get a building that has less fresh air injected into the living environment.  The IOM report states, “By making buildings more airtight, building owners could increase indoor-air contaminant concentrations and indoor-air humidity.”  This could lead to mold and rot issues and poor indoor air quality.

When you tighten the building envelope, you must know how all the materials and techniques are going to work or not work together, and then include materials and methods to counteract any negative outcomes such as entrapped moisture.  In most cases you need to include effective building envelope moisture management systems.  You also need to work with the manufacturer of these systems to make sure you have the right products and design for your specific details.  That’s why the architects, specifiers, contractors, and building owners need to be on the same page.

Those our my thoughts, I welcome yours!

*I have added some pictures from a house built in the 1960s that show how buildings used to be able to breathe.  Notice how clean and dry the wood looks after the old siding was torn off.  There is no rot or water-staining, not even next to the window, and the window is a bathroom window.  Air was able to get behind the siding and into the building envelope to keep it dried out.


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