Wednesday, December 19, 2012

The Rainforest

Recently, I was asked to assist in the design for an enclosed rainforest exhibit. The project has a lot of glass and is in a very southern climate zone (near the Gulf of Mexico). I have looked at a couple of other similar projects in the past and, of course, volunteered to assist. As a preliminary, we managed to get a tour of the Dallas Aquarium, which includes a large enclosed rainforest. 

We were met by the head of maintenance, who seemed to have worked there for 20 years and knew all the history of the HVAC system. Much of the air distribution system was custom built by the facilities folks themselves, in an effort to make the air outlets nearly invisible. I made several general observations concerning projects of this size.

Vents at the top of the structure are essential. At the Dallas facility, we were told that while the vents at the top of the tall glass wall were able to be opened and closed, they just leave them open year round. This seems to be a pretty general recommendation, as all tall structures exhibit stack effect, and releasing the hot air always seems to assist in controlling the space temperatures.

Clear glass seems unwise, especially on the roof. Having the east wall transparent seems to provide sufficient UV for the plants to thrive. It is unclear how much UV passes through the translucent panels used throughout most structures of this type. In general, it seems that displacement ventilation is a natural candidate for these types of spaces, especially as the use of relatively warm water (62°F) to the fan coils results in 65-68°F air at the outlets.

It was very interesting to see how the facilities folks managed the systems and how they often created their own air distribution devices.

Authored by: Dan Int-Hout, Chief Engineer Krueger