I'm honestly wondering if the tin-foiled covered sides are of any benefit at all. This is a very, very common problem encountered with reptiles kept in glass tanks with meshed roofs; heat rises. It doesn't matter if the sides are solid - if the roof is meshed, your heat will escape.
The lid of your cage appears to be uncovered, yet all the sides are sealed... your heat is going to rise and escape. all sides covered or not; the roof is exposed. If you wish to continue to use the unregulated CHE, you need to cover at least half of the roof if you want the heat to remain somewhat-trapped. Covering at least some of the roof should be far more effective that sealing all four sides.
To be perfectly honest; I would much rather give Igor a hot water bottle (wrapped up, and not made with boiling water) at night vs risking using no heat source or an unregulated CHE; it's just far too dangerous, in my opinion at least.
Last edited by Emc; 04-21-2019 at 04:39 PM.