Heat mat question

[Mentat]

...and then place a heat mat to the side of the cage where night-glo was. Experience tells me side-mounted mats aren't the most efficient means of heating. But if I put plastic wrap over that side, would it trap enough of the heat the mat emanates to keep that side warm enough (I'd like a minimum temp of 75 on said side of inside of the cage)?

...What I meant about placing plastic wrap was to place over the screen, on the lid. Not on the mat itself lol. That WOULD be a bad idea. I was just wondering if the heat emanating from the mat would be stuck in the air by the plastic on top of the screen. I do have this thing to control it with.
Amazon.com: Zoo Med ReptiTemp 500R Remote Sensor Thermostat: Pet Supplies

THIS is what I'm thinking about, if it helps:

...

As stated by Louis, heat mats are inefficient when placed on an enclosure side. IRT your description and drawing; would place mat above substrate level and away from any water source to prevent splashing on hot glass and shattering it. The plastic wrap on screen top will help retain heat on enclosure. It will also increase humidity and decrease ventilation.

There is no way to predict if mat is going to be warm enough for your enclosure heating needs. You can experiment by covering around 50% of top and then increase as required. Since you got a thermostat, would use the largest mat that can fit the on the intended side, without exceeding the thermostat wattage. Good luck !