This video shows the process I use to build my authentic Alaskan Igloos. This particular snow shelter took me about 10 hours to build at minus 15 degrees Fahrenheit. Cold temperatures are important to the strength of the blocks, so I typically don't build until the average daily temperatures are below zero.
The catenary shape of the igloo is naturally very strong. But to make it even stronger, I build a fire inside the igloo during construction to soften the blocks sightly. I then allow it to refreeze when I am finished building. The result is a very strong dome that will easily support several times my weight.
I heat the interior of the shelter to only about 40 degrees Fahrenheit to prevent it from getting damp. This may seem cold, but when the temperature outside is -20F that represents a 60 degree differential, which is quite comfortable by comparison.
I always put the fire out at night and cover the entrance, and depend on my cold-weather sleep system to keep me warm. Snow is a good insulator and I am completely protected from any wind. So maintaining a fire throughout the night is not necessary.
I build my Igloos in early November and use them as temporary winter camps until spring thaw begins, which typically occurs around the end of March in this region. I use them many times throughout the winter, stocking them with a firewood and other necessary supplies.
My camp stove is made by Kni-Co Manufacturing. It is the Trekker model. It is typically used in an insulated arctic tent, but I have found many practical uses for this lightweight stove. It does a wonderful job of heating the interior of this igloo. It is, in fact, a little too much heat. I find I have to throttle it down quite a ways to prevent overheating the interior.