Portable classroom
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A portable classroom (in Australian English a demountable and often referred to as a Terrapin or a "Portakabin" in the UK and Ireland) is a temporary building installed on the grounds of a school to provide additional classroom space where there is a shortage of capacity. Such a classroom would be installed much like a mobile home, with utilities often being attached to the main building to provide light and heat for the room. It would be removed once the capacity situation abates, whether by a permanent addition to the school, another school being opened in the area, or a change in student population.
Sometimes, the portable classrooms are meant to be long lasting and are built as "portapacks". A portapack combines a series of portables and connects them with a hallway. Portapacks are usually separated from the main building but can connect to the school. In most cases, portapacks are accompanied with a few separate portables.
Portable classrooms are also colloquially known as t-shacks, trailers, terrapins, or portables.
Remarkably, when portable classrooms are properly set up and operated, experience has shown that they can present a very long useful life, low maintenance, and healthy, comfortable environments for all occupants.
Portable classroom operational defects are as follows:
- Excessive or inadequate ventilation, especially in hot, humid environments. Demand control ventilation (DCV) or carbon dioxide based ventilation can deliver precisely correct ventilation despite changing occupancy, minute by minute. A usual desired ventilation rate is 15 cubic feet of outdoor air per minute per occupant.
- Poor roof maintenance and leak prevention
- Depressurization of the breathing zone, and especially of exterior wall cavities. Depressurization sucks hot, humid air into wall cavities where the moisture can support bugs, mold and rot.
- Poor maintenance of energy recovery ventilator sections
- Poor exterior pressure envelope maintenance which makes pressurization difficult.
- Failure to provide a pressurization system to pressurize the entire building in a hot, humid climate to about +1 to 6 pascals most of the time.
- Inadequate delta t cooling across the AC cooling coil. For good dehumidification, delta t should be around 20 degrees F.