This is part of a series; see the first post here.
This shouldn’t be news to anyone: In most homes, insulation and air sealing are the most effective ways to improve comfort and reduce heating and cooling costs.
This holds true regardless of heating systems or fuels used. So why is it emphasized even more when talking about heat pumps and electrification? Four reasons.
1. Heating System Capacity and Cost.
Say your home has a design heating load of 60,000 Btu/h. If heating with fuel, you’ll need a furnace or boiler with a capacity of at least 60,000 Btu/h. These are easy to find. (In fact, you may have a hard time finding heating systems with capacities lower than this.) Air-source heat pumps, on the other hand, have smaller capacities. I don’t think you’ll find an ASHP with heating output of 60,000 Btu/h at cold winter temperatures. So to meet this load, you’ll need multiple ASHPs. And that gets pricey.
Even if you are not talking about multiple heat pumps, a 3-ton heat pump is quite a bit less costly than a 5-ton heat pump. Costs of heat pumps scale more dramatically than costs of boilers and furnaces. So lower heating loads → fewer, smaller heat pumps → lower upfront costs.