5 Things that have changed in building design to cause today’s issues

I received a link to an excellent article by someone whose writing I follow.  His name is Dr. Joe Lstiburek and he is to me THE authority on building moisture issues.  His article is titled, “5 Things”, and the link to it is:  http://www.buildingscience.com/documents/insights/bsi-039-five-things/files/BSI-039_Five_Fundamental_Changes.pdf.

Those 5 things that Dr. Lstiburek lists as changes that have occurred to buildings to cause today’s moisture issues are:

  1. Increased thermal resistance.
  2. A change in the permeability of the linings that we put on the inside and outside of building enclosures.
  3. Water and mold sensitivity of building materials.
  4. The ability of the building enclosure to store and redistribute moisture.
  5. Complex three dimensional airflow networks that inadvertently couple the building enclosureto the breathing zone of the occupied space via the mechanical system.

Let me see if  I can translate from the engineer-ese.

  1. Thermal resistance is the ability of a material to transfer heat, similar to the way a wire conducts electricity.  A higher thermal resistance material, such as fiberglass, slows heat transfer.  Dr. Lstiburek says that with reduced thermal transfer, building materials do not dry as rapidly in newer buildings as older ones.
  2. Permeability is a measure of how easily moisture can move through a material.  Over the years, the exterior wall materials have become less permeable.  The result is that moisture that gets into walls cannot get out and moisture inside the home cannot get out of the home the way it used to.
  3. Dr. Lstiburek uses the term sensitive in his list of  Things, but then uses a better term later in his article–resistant.  Basically, the materials being used in today’s buildings are not as resistant to mold growth as those in older homes.
  4. Dr. Lstiburek states that older building materials were able to absorb and not be harmed by moisture than newer materials.  We still have buildings with lath and plaster walls that are over 100 years old because they could take moisture exposure.  The same moisture exposure would have demolished drywall in one exposure to the same moisture quantity as the older homes.
  5. In the older homes, the building exterior was usually more solid than now and it acted as an air barrier.  Nowadays, the exterior is not as resistant to airflow as back then.  The stud and joist cavities serve as runs for wiring, plumbing and supply and return airflow.  Every time a hole is made in a stud or joist, a new airflow path is created.  Then, we open holes in walls for electrical outlets, which are air paths.  So, the newer buildings are holier than the older ones–and not in a good way.

Dr. Lstiburek provides recommendations for resolving these issues in the latter part of his article, and you can read those as well as I.  So, check out the article and if I have not adequately translated the terminology in an understandable way, send in your comments and I will do better.  BTW, if you want other excellent articles on building construction, visit the Building Science website at http://www.buildingscience.com/.

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