The purpose of a building mechanical system is to create a comfortable and/or functional indoor environment which might be at a very different temperature and relative humidity than the outdoor ambient conditions. The building envelope is the only separation between these two environments, and it has to be able to adequately control temperature, air and moisture flow, while remaining durable.  The successful design of the building envelope must take into account the environmental loads across it, which inherently ties it to be the function of the building HVAC system. Some HVAC and envelope relationships are relatively simple to address, however, the times that they are not can result in considerable building damage and loss of durability.

This presentation discusses some of the relationships between the HVAC “weather markers” and building envelope systems, such as reducing indoor condensation and minimizing energy losses. Some specific practical solutions to HVAC and envelope interaction problems are discussed.