The solar dog house

One of my favorite projects,  is the dog house.  My dogs usually stay outside during the day and inside during the night.  One winter before a really cold couple of days, I put  two sliding glass doors together to make a wall and roof.   2 inch hard foam for the base and inside wall,  was used to make a solar dog house for my 3 girls.  Burndee, Mavis and Skye go inside their solar house when its very cold out.  I added a couple things to help with keeping the heat in the space.  The flap door is just a piece of rug that they have to push by with their noses  So, not only does the glass from the doors act as a greenhouse, I put a pipe heater under their beds.  The pipe heater is an electrical wire meant to be taped to any pipe to prevent  freeze in cold temperatures.  It turns on below 38 degrees  and off above 50 degrees Fahrenheit. The last thing I put inside was a 40 watt bulb. Nothing exciting there.  This really just tells me the pipe wire is on and plugged in and looks cool at night.  A big animal terrarium,   There are several times where I found the outside temp to be 25 while 50 inside the solar dog house.  As soon as the sun hits the glass the temperature will easily hit 65.Finally, I put the pipe heater and light bulb on a timer so I am not heating the dog house all night while they are inside the house.   I take the house  apart each spring and reattach it just before cold begins.  It hurts me deep inside when I see a dog tied up in very cold conditions and nowhere to hide from the elements.