Portable classroom

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A portable classroom (in Australian English a demountable and often referred to as a demountable, a Terrapin or a "Portakabin"(after the company) in the UK and called a prefab in Ireland (not to be confused with a prefabricated building)) 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.

[edit] Occupant Health and Building Durability Issues

Portable classrooms are frequently criticized for presenting mold, moisture, comfort and unhealthy environment issues. 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:

1. 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.
2. Poor roof maintenance and leak prevention
3. 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.
4. Poor maintenance of energy recovery ventilator sections
5. Poor exterior pressure envelope maintenance which makes pressurization difficult.
6. 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.
7. Inadequate delta t cooling across the AC cooling coil. For good dehumidification, delta t should be around 20 degrees F.

[edit] Smart Practices

In hot, humid climates (in order of importance):

1. Utilize demand control ventilation to reduce moisture loads on dehumidification equipment while providing precisely correct ventilation rates for the occupants at all times. DCV will immediately increase and decrease the ventilation rates as occupants come and go and will do it within seconds. Correct and economical ventilation of portables almost NEVER occurs, even in the newest designs. A good DCV design can also maintain essential positive building pressurization. Sophisticated DCV retrofits for existing air conditioning units are available.
2. NEVER use wall finishes that can slow the release of moisture from the walls and into the breathing zone where the water vapor can be removed by dehumidification. (vinyl wall covering, gloss or semi gloss paint, foil, mirrors)
3. Prevent any depressurization/pressurization of the exterior wall cavities by air conditioner operation. This is very simple and easy to accomplish however it is almost NEVER done.
4. Ensure that the exterior shell or pressure envelope is air and moisture tight to prevent entry of water vapor as well as water.
5. Correct roof leaks immediately. Poor workmanship and improper material use is more than common.
6. NEVER close off the ventilation air intakes in an attempt to control moisture or humidity problems. To do so almost always causes the building to become negatively pressurized with terrible mold and moisture problem consequences.
7. Ensure that the air conditioner can maintain a temperature drop of about twenty degrees as the air passes through the cooling coils.
8. Use occupancy sensors to operate exhaust fans when bathrooms become occupied and for a few minutes after they become vacant. Use significantly reduced exhaust airflow rates when vacant.
9. In hot, humid climates, expect that mold and moisture issues will be worst in the late fall and early spring when air conditioners are not often operating and dehumidifying indoor air. Use dehumidifiers during such periods.

Modular buildings shorten construction time for deadline driven school facility projects. Whether growing enrollment, modernization or budgets are driving your temporary building needs, portable classrooms allow speed and flexibility to adjust to the demands of a school's student population. [1]

[edit] See also

• Mobile home
• Modular home
• Classroom
• Portakabin
• Caravanim
• Semi-permanent mobile unit