Here is an example of winter houses that have worked for me and my tortoises for the past many years.
This is built in my car port under a roof and on a cement slab. First of all I lay down a 4'x8' sheet of 1/2 inch styrofoam insulation then a sheet of plywood over that. I use 1/2", but I think any thickness would do ok. I use an existing wall to build the enclosure up against so I only have to use enough cinder blocks to make three sides. Then I start stacking up the cinder blocks on the plywood floor. I use three-high so I have enough clearance for the lighting. I start building the front wall and once I have that wall standing, I cut a piece of styrofoam and a piece of plywood to fit. then I start stacking an end wall. This holds the foam and plywood in place. I make the plywood for the end walls ever so slightly wider than the space they're going to fit into so they fit snugly and there's no need for nails or screws to hold them in place, tapping them into place with a hammer. I glue another piece of styrofoam to another sheet of plywood for the lid, which just lays on top. You can prop it open with a broom handle on good days. I've cut pieces of 2x6 to fit along the top brick and bunched up plastic grocery bags and stapled them to the wood to keep cold air from blowing in the roof crack. I had trouble with the roof laying flat, so I screwed three redwood fence pickets to it.
I used 1x1's to hang the lights from. There's a pig blanket across one end, a day light (just a plain old 100w incandescent bulb) and a black light for night time, and they're both on a timer. There's a thick layer of orchid bark on the floor, and a large plant saucer for water.
This system has been in use for over 15 years with no problems at all. You can make it smaller, which I've also done there on the car port, and I have 6 of these in various sizes on my carport. I call this my hospital area because it is usually used by tortoises that can't be hibernated due to illness, accident, or rescues.
For my desert tortoises outside, I use a similar structure.
First of all I built up a pad, up against a fence and under a mulberry tree. Then I put down masonry caps (rectangular stepping stones) and stacked cinderblocks two-high, leaving a small space for a doorway. This house is not insulated. I have a piece of plywood over the top, and in the fall I usually add some plastic feed bags over the plywood for water proofing. After the trees in the desert tortoise pen have dropped their leaves, I rake them all up and pile them on top and around the house. I also fill the inside cavity with leaves. Then, when the tortoises are all inside and don't come out anymore to sun, I block the door and finish piling leaves against the walls. I have successfully hibernated my desert tortoises in this house for about 4 years now.
The leaves are a pretty good insulator and they also help keep the house cool in the summer.
This is built in my car port under a roof and on a cement slab. First of all I lay down a 4'x8' sheet of 1/2 inch styrofoam insulation then a sheet of plywood over that. I use 1/2", but I think any thickness would do ok. I use an existing wall to build the enclosure up against so I only have to use enough cinder blocks to make three sides. Then I start stacking up the cinder blocks on the plywood floor. I use three-high so I have enough clearance for the lighting. I start building the front wall and once I have that wall standing, I cut a piece of styrofoam and a piece of plywood to fit. then I start stacking an end wall. This holds the foam and plywood in place. I make the plywood for the end walls ever so slightly wider than the space they're going to fit into so they fit snugly and there's no need for nails or screws to hold them in place, tapping them into place with a hammer. I glue another piece of styrofoam to another sheet of plywood for the lid, which just lays on top. You can prop it open with a broom handle on good days. I've cut pieces of 2x6 to fit along the top brick and bunched up plastic grocery bags and stapled them to the wood to keep cold air from blowing in the roof crack. I had trouble with the roof laying flat, so I screwed three redwood fence pickets to it.
I used 1x1's to hang the lights from. There's a pig blanket across one end, a day light (just a plain old 100w incandescent bulb) and a black light for night time, and they're both on a timer. There's a thick layer of orchid bark on the floor, and a large plant saucer for water.
This system has been in use for over 15 years with no problems at all. You can make it smaller, which I've also done there on the car port, and I have 6 of these in various sizes on my carport. I call this my hospital area because it is usually used by tortoises that can't be hibernated due to illness, accident, or rescues.
For my desert tortoises outside, I use a similar structure.
First of all I built up a pad, up against a fence and under a mulberry tree. Then I put down masonry caps (rectangular stepping stones) and stacked cinderblocks two-high, leaving a small space for a doorway. This house is not insulated. I have a piece of plywood over the top, and in the fall I usually add some plastic feed bags over the plywood for water proofing. After the trees in the desert tortoise pen have dropped their leaves, I rake them all up and pile them on top and around the house. I also fill the inside cavity with leaves. Then, when the tortoises are all inside and don't come out anymore to sun, I block the door and finish piling leaves against the walls. I have successfully hibernated my desert tortoises in this house for about 4 years now.
The leaves are a pretty good insulator and they also help keep the house cool in the summer.
