For our house the problem is/was that its old (about a 105 years) and while we've done renovations to it, it still doesn't have the R value of modern house, by a lot. The house was converted from radiators to baseboard back in the 80's but the outside walls have only had blown in insulation. A gut reno is needed to insulate it the way a newer house would be built today. The boiler does fine until we get much below zero, then the space heaters have to save the day. They did last night.