Dave, W3IGT recently built and used an igloo in his back yard. He checked into the CARS net and spent one of the coldest nights
recently (February 27th) in his igloo.
With only a candle for heat (and him), he reported inside temperature got down to 3 degrees while the outside was -11!
He was "....toasty warm but felt claustrophobic all wrapped up in a mummy bag with four layers of clothes."
Pictures are all his.
His story was recently published in the newspaper and a link is here .