I am building an outdoor enclosure for my Hermanns and I need input on how to best heat her hide box.

i live in Denver so it gets cold in the winter and I'd like to keep her outside year round. I was planning on building a 4x2x2 house and separating a 1.5x2 area and placing a pig blanket there and filling that with hay or straw. The other area would have one or 2 CHE's and it would be kept around 50 degrees. In theory, the pig blanket would heat the straw so that she could find a spot she like as far as temp goes. I would mount a temp probe about 6" above the mat and keep a temp of 42 degrees there.
So does anyone use a pig blanket and place begging ontop and will this work? We can get temps to -10 on rare ocassion, but I would think that the CHE's along with the insulation provided by the straw would allow me to be able to maintain the 40-45 degree temps I need in the straw area.

Any input would be greatly appreciated.