Concealed Condensation

Concealed condensation in wall and ceiling-roof cavities is primarily

associated with airflow from the indoors into the cavities, which is

called exfiltration. The air flow paths include electrical outlets and

switches; holes drilled for wiring and plumbing; cracks between interior

trim and drywall; and poorly-fitted exhaust fan ducts. During the

winter, moist indoor air that penetrates into cavities condenses on wall

and roof sheathing, as well as on the backside of siding. Siding

condensation may be more pronounced in high locations in walls with

fiberboard sheathing and, in other walls, concentrated a joints of

plywood and rigid insulated sheathing.

It appears that most wall and ceiling cavity condensation dries rapidly

at the end of the heating season and there is little risk of decay.

However, if sheathing paper or other components severely retard the

drying of concealed condensation, rapid decay can occur. Furthermore,

other superficial indicators of concealed condensation are generally

unacceptable: buckling of siding; moisture blisters in exterior paint;

moisture staining of exterior paint; and ceiling damage due to melting

of frozen condensation in roof-ceiling cavity (may be mistakenly blamed

on roof ice-damming).

The risk of concealed condensation should be reduced by sealing air

leakage bypasses into wall and roof-ceiling cavities. For further

information, contact:

- the Minnesota Energy Information center at 296-9747 (ask for

"Energy") elsewhere in Minnesota; or the National Center for

Appropriate Technology (NCAT) at 1-800-428-2525; or

- your local utility.

The 6th Symposium on Building Physics in the Nordic Countries, in Trondheim, Norway, June 17-19, 2002

http://www.bygg.ntnu.no/batek/buildphys/

This Symposium is the sixth one focusing on recent Building Physics research and development in the Nordic Countries (Denmark, Finland, Iceland, Norway and Sweden). The Symposium is arranged every third year in one of the Nordic countries. The previous symposia have been held in Lund (1987), Trondheim (1990), Copenhagen (1993), Espoo (1996) and Gothenburg (1999). In Gothenburg 95 papers were included in the symposium proceedings. The objective of the Symposium is to provide a forum for building physicists to meet for an exchange of experience of recent research and development work, with a special focus on problems and subjects that occur in our northern cold climate.