First part of a four-part article on best practices for designing HVAC systems.
Glass curtain wall can offer daylight and views of the outdoors, but it can also leak water, air, and heat, and expose interiors to solar energy.
Exterior materials can have a profound impact on building performance parameters often associated with the HVAC system, like energy efficiency and humidity control.Consider glass curtain wall. This is likely the most common system used in commercial construction, but that doesn’t make it the best solution. Glass curtain walls have the advantage of providing occupants with a connection to the outdoors, but they often leak water, air, and heat, and expose interiors to solar energy.Historically, building envelopes were made of heavier mass assemblies using brick, stone, concrete, block, steel, and wood. While these systems were heavy and field-labor-intensive, they had the distinct advantage of being able to repel, absorb and drain, and manage water more effectively.With the introduction of air conditioning and energy-efficient buildings came a variety of envelope and HVAC systems that don’t work together to manage water properly. The result: water causes either physical or environmental damage.For example, air tightness is generally a good thing. Air tightness can save energy and help keep the building healthy. But exterior air tightness requires good interior ventilation systems. The ventilation systems are needed to manage the indoor humidity, which can be elevated in a relatively air tight building. For instance, in a cold climate, buildings with newly required air barriers will retain moisture that would have been “mitigated” by dry cold air entering through a leaky envelope. Condensation can now form on the cold surfaces exposed to humid indoor air. Proper ventilation, dehumidification, and air distribution are needed to mitigate these newer occurrences.To avoid problems, contemplate the intended use of the building when selecting exterior materials. Look for potential roof and envelope assemblies that are ideal for the local climate. Some wall system configurations don’t work well in cold, mixed, or humid climates. It’s a complex matter — two systems made of the same materials, but with different configurations, can fail in the same climate — so it’s difficult to give rules of thumb. Where a glass curtain wall is desired, use it judiciously and make sure installation is tight. The designer should also specify other envelope materials to work hand-in-hand with the glass that provide other necessary insulating properties. Comments Find us on Google+
