Haven't done it yet but thinking about it. For the last few nights I've been toting 2 buckets filled with hot soapstone rocks that were heated on our woodstove. Now that's love! Trying to stay off grid for now. It bumps the temps up about 5 degrees and I'm also working on the humidity. Not sure how long this is going to last - the rocks are pretty heavy. It was below zero last night and the coop was 22 this morning. Its insulated.