Cheap, simple and effective 3d printer enclosure made from two plastic boxes by rjacobsson.
He used Ikea boxes, but I think it will work with any plastic container and keep temperature of your print volume constant and elevated from surrounding.
It also reduces the noise and contains the fumes.
Like any enclosure without thermostat it overheat the motors but you should experiment until you discover what works best for you.
Build guide on Instructables:
http://www.instructables.com/id/Enclosure-for-3d-printer-using-Ikea-box/
Here is another low cost solution for enclosure, made from PIR foam but with 3d printed hinges:
http://diy3dprinting.blogspot.com/2014/03/diy-3d-printer-enclosure-made-from-pir.html
Wooden enclosure heated by hair dryer to prevent warping:
http://diy3dprinting.blogspot.com/2014/03/diy-3d-printer-enclosure-made-from-wood.html
