Portable classroom

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A portable classroom at Rockcliffe Park Public School in Ottawa, Canada

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.