For the first few weeks, you may have to provide supplemental heat in the form of a heating pad set on low. (thesprucepets.com)
He might need supplemental heat for the winter in his outdoor kennel, but, ideally, he should be brought to live his remaining life indoors, especially if he used to be an indoor pet. (washingtonpost.com)
Even in a Passive House, one always needs supplemental heat sources for when the weather turns abnormally cold. (nypassivehouse.org)