Recently RDH has been investigating an increasing number of buildings with problems related to interior condensation. Condensation can occur on the interior surfaces of walls and windows for a variety of reasons including exterior environmental conditions, thermal resistance of layers within the wall assembly, location of heaters within a suite, and interior sources of moisture (commonly produced from cooking, bathing, and washing).

Condensation problems are becoming more pronounced due to some recent trends.  These include: more air-tight building enclosures and large areas of fenestration.

"It's the fairly complicated interaction of architectural design, HVAC design, and occupant behaviour that will make or break the success of an exterior wall assembly with respect to condensation control," says Brian Hubbs, P.Eng., Principal at RDH.

Once the problem has been correctly diagnosed and understood, developing the solution typically involves several components. "We will typically undertake computer simulations of various re-design strategies and analyze the effects," he explains.

When the problem is multi-faceted, usually the solution is too, says Hubbs. "Solutions must be viewed in the overall building context. We have found that using an integrated design approach together with appropriate maintenance and operational procedures are necessary to control humidity and condensation."

See RDH Paper from Building Envelope Technology Symposium (2010, San Antonio)