Warming up a small dogloo for ferals?

Any suggestions on how to make a small dogloo as warm as possible for feral who's really starting to hang around? Currently has added layer of insulation taped all over inside, inside is stuffed with straw up sides as high as possible, straw on floor, covered by electric outdoor sanctioned cat bed mat heater. More straw mounded toward entrance, entire thing is up on bricks so not on ground, and added an angle piece of plexiglass so it a-frames down from top to front of dogloo entrance to ground (cat can see through but blocks a lot of wind, rain,etc. Thinking about snuggling a I& H heated house inside it for extra warmth -has anyone tried that?i worry the pad isn't enough -particularly given relative large opening for entrance of dog gloo.....thoughts? My hubby swears it's as good as it can get -and better than most ferals get it, but he's rapidly becoming a part of the family (almost) and I want him as comfy as possible (maybe at some point inside but he's not there yet).

A heating pad if you have electric or they have microwavable discs that keep warm for up to 12 hours.

But he may be warm enough. If there's plenty of straw in the Igloo and the wind is blocked, his own body heat may be enough to keep him cozy.

I had two ferals who refused to use their houses with the microwave discs. I think it got too warm for them.

It's already got an electric outdoor cat/dog heating pad at the bottom, and we've put up a plexiglass windbreak so he can see out. Just worried it's not trapping enough of his heat. Think it's worth buying another outdoor cat heating bad and running it out & putting it on the side! My husband will kill me, but I want him to be as warm as possible.

Oh, I missed that. Maybe you should put a thermometer in there first to gauge the temps. Two heaters may make it too warm. I guess it depends on how low the outside temps go.

They're those pads that only heat up to cat body temp once they lie on them - otherwise they don't seem to put off much radiant heat. But I'll check it out with a thermometer just in case!