This cover can be fixed and removed very quickly to the ultimaker 2. It requires no hardware modifications.
Can even be closed and opened when the utlimaker 2 is running.
Cost: a few cents.
To create an heated chamber you will need a front door (not part of this project, many solutions available on the forums).
To use an heated chamber  monitor the temperature inside the Ultimaker.
The electrical components are inside so you do not want to overheat and
bake your jewel. See the forums for use and discussion on the heated chamber concept.

See a video of the cover in action

Cover and uncover the ultimaker2 (one handed...)


Effectiveness:
The cover is not air tight, but being a double sheet with air gaps it makes for a nice thermal insulation.


How to make and install the cover. (see pictures)
1. Print the parts. Use support to print the coverHolder with the tubes up.
2. join two A4 sheets along the long edge using adhesive tape. Repeat 4 times to have 4   sheets 2x1 A4.
3. fold the 2x1 A4 sheets along the long edge each 20mm to create an accordion fold. Repeat 4 times to have 4 accordion sheets.
4. fix the 4 accordion sheets on top of the Ultimaker2 with adhesive tape. (See pictures)
5. place the coverHolders (2x) on the Ultimaker2 print head
6. insert the first 2 accordion sheets below the cover holder
7. use clip2 and clip1 to fix the edges of the accordion sheets
8. insert the upper two accordion sheets over the cover holder
9. fix the upper accordion sheets with 2x clip 1.

The cover holder /print head is not fixed to the sheets. It has to be able to slide freely in X and Y direction. Study the picture and the video. The sheets are fixed to the other sheets only on the edges with the clips. the clips do not have to hinder the printhead movement. Clip2 is to fix on the lower sheets to avoid collision when the print head goes close to the border. Clip 1 are to fix the two upper accordion sheets.

Feel free to try and modify, but if you plan to use this Idea for commercial purposes please ask the author for a license.
Please give credit to the author if you use this design.
Thanks!