When I saw the MakerBot Replicator 2X with the "six sided enclosure for stabilized abs cooling," I knew I needed that for my machine.
I've closed off the sides with paper and duct tape before, but never the top.
Using cardboard and duct tape, I've created a "lid" that lets me test "extruding" with an enclosure (before I go to the effort of building something pretty out of acrylic).
Preliminary tests indicate at least 20 degrees F higher temperature with the lid.
I started with a 17 inch by 3 inch piece of cardboard for the upper rear.
As you can see, my thoughts and my measurements didn't produce the correct result.
That's the nice thing about cardboard--next step.
I just cut out a little more and things look better.
I found a box that was 17 inches long and I cut it down to 6 inches in height.
I cut the two front sides to open up the box.
With duct tape, I added my first piece to the box and secured a couple of "wobbly" spots.
Next, I cut a 6 inch strip, bent it and added it to the box with duct tape.
I had to add another little piece to complete the enclosure.
I'll have to see if this improves the pulling and cracking on big builds, but it does look hopeful!