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The mission of the Building Performance Knowledge Community (BPKC) is to increase building performance related to occupant comfort and health, and to the function, durability, sustainability, and resilience of buildings.
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Codes on Basement Vapor Drive

By Drake A. Wauters AIA posted 07-15-2015 08:44 AM

  
Habits are very hard to break and this is why we have regulations and codes.  A large part of our nation is experiencing many times the normal summer rain and attendant water problems this.  Yet we continue to build homes with no vapor impermeable waterproofing in basements and at some lowest story slabs and we still build some nonresidential buildings with subsurface waterproofing that is substantially vapor permeable (allowing humidity/vapor to travel through it even when liquid water is controlled).  In many regions and for many building types this means high to very high vapor drive all year round from the soil in to the occupied space leading to very high relative humidity and condensation.  The resulting moisture damage and health problems are immense and commonly understood.  What is not understood is why building codes did not change decisively decades ago to address the problems with moisture drive they started surfacing as occupying and finishing basements became the norm and as houses and other building were further closed up and air conditioned with far lower air changes than before.  Designing to the building code minimum is not only the norm but so engrained in the culture of our profession that it is expected by most clients as a de facto standard of care.  This is why changing the code to effectively address vapor drive from the soil should have been a done deal decades ago and certainly needs to be addressed now.  The energy we use to dehumidify dank spaces solely because vapor drive to interior spaces from the soil is so prevalent is immense and a greenhouse gas nightmare.  The tiny cost that a vapor impermeable basement would ever have added to any building is completely dwarfed by the cost of using so much energy to manage the problem decade after decade.  The debate about rock bottom first costs creating higher continuing costs should have been won by now.
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