Dynamic buffer zone - Controlling moisture and heat flow

The building envelope is primarily an environmental separator, which allows indoor spaces to bemaintained at different conditions from the outside environment. Intentional humidification during the heating season is a common practice in cold climates. Moisture escaping from a humidified building due to air leakage through flaws in the air barrier system can negatively affect the durability of the building envelope. Hence, an effective air barrier is an essential component of any building envelope exposed to large condensation potentials.The Dynamic Buffer Zone (DBZ) performs the function of the air barrier and can act as dynamicinsulation in a building envelope. The DBZ system creates conditions in an existing or purpose built air space (DBZ cavity) located within an exterior wall that effectively separates the interior and the outdoor environments.Conditions within the DBZ cavity that need to be controlled are air pressure, moisture content, and temperature.To effectively prevent exfiltration of humid interior air through the building envelope during coldweather, the air pressure of the DBZ cavity is maintained slightly higher than the interior air pressure.Theoretically, the cavity air pressure needs only to be nominally higher than that of the interior space to prevent air leakage from the interior. During winter conditions, outdoor air will have a low moisture content which makes it an ideal air supply for the DBZ cavity. The requirements for pressurization of the DBZ cavity will ensure that interior humid air will not leak outwards into the building envelope. If any leakage of air from the DBZ cavity to the outside occurs, the low moisture content of the DBZ air will eliminate the threat of condensation within the building envelope.When utilizing the DBZ cavity as an air barrier or as a dynamic insulation system, it is desirable tominimize the amount of heat that is initially added to the incoming outdoor air. Dynamic insulation can reduce the cost associated with initial heating by allowing the DBZ air to capture some of the heat that would otherwise have been lost to the exterior environment.This paper will discuss the DBZ and its uses in cold climates. The fundamental principles governing the DBZ will be presented. The different modes of operation will be discussed, addressing constructability, both in new and retrofit applications. Finally, case studies will be presented, addressing the installation of the DBZ in both a restoration and new construction application.