A: I have a lot of concerns about Passive House designs including: the cost, mold, the use of big south facing windows for passive gain, the lack of a standard for renovations and the lack of adjusting the standards for either where the house is located or how big it is. Please see this for more details:
A: The economics of batteries is highly dependent on the local subsidies. In MA with Eversource as your electricity supply company the subsidies are very generous. I have just ordered a Sonnen battery to go with an existing array of SunPower panels. I have also just ordered a Generac battery to go with a new array of Solaria panels. Generac is not good as a retrofit to an existing array because you need to use a Generac inverter with a Generac battery. I have not bought a Tesla battery, despite it being the cheapest per kWh of storage, because Tesla is not currently able to deliver batteries.
A: Correct. Academic studies have found that ducted heat pumps are about 20% more efficient that ductless installations. Personally, I prefer the air circulation from a ducted system and I prefer the look of traditional floor registers to having units on the walls or floors.
A: The sill (the area above the concrete foundation and the floor joists) is a major source of drafts and heat loss in a house so sealing gaps and insulating it makes a lot of sense. However, don’t stop there. The ceiling of the basement losses a lot of heat from the house to the outside and insulating that will greatly reduce your heating bills and carbon emissions.
A: Adding a single pane of glass or plastic (these are called window inserts) adds a similar amount of insulation benefit (R value) to going from a double-glazed window to a triple-glazed window. You will not save enough money on the heating bill to payback the full cost of taking out existing windows and replacing them with triple-glazed windows in under several decades. This is why I recommend installing triple-glazed windows only when you need to replace your windows for other reasons like they are rotting or falling apart as ours were. In this case the additional cost of triple-glazed over the cost of double-glazed is a good investment. If your windows are in good shape I suggest adding windows inserts.