Frequently we are asked how we house our kids when it is so cold in February and March. We don't bring kids into the house unless they are premature or have been very chilled. We have used these shelters for about 25 years. They are simple to build, they prevent kids from piling on top of one another and suffocating one another. We use a 100 watt incandescent light bulb in a ceramic socket and with an aluminum reflector. In short it is a heat lamp fixture but with a regular light bulb. This set up keeps newborns quite comfortable down to 10 below zero as long as they are fully dry before being put in there with a nice thick bed of clean straw. The newborn TiPi will hold up to about 7 newborns, 8 in a pinch and we have put a door that can be fastened closed on the bottom. The house that the kids step up into has no bottom door and no heat source. The kids are pretty comfortable with up to 6 in there at a time. The older kids love jumping up on the outside and sliding down. We hope you find these useful.