We are reconstructing an old house. Step1 is getting a fairly airtight envelope and a lot of insulation installed.
We have the designs and a heat load analysis, saying at peak delta (minimum -17C external temp, 20C internal) there will be a total heat loss of 6kW including ventilation.
The MHRV unit has an integrated air heater and recirculating air route but our design does not allow for large warm air heating duct work, so we don't think that we could get more than 1kW or 2kW from that.
To supplement it we were offered underfloor radiant, but the price is astronomical here and we don't like it much. We much prefer the minisplit ductless feel of heating and cooling.
We are looking at supplementing the heating with Mitsubishi hyperheat, and we would really like to know if we can get away with heads in the main rooms and upstairs hallway, or would every small room need its own head? My thinking is I could get away with an 8kW heat pump and 4 heads. One in each main area, while MHRV recirculating routes would cover bedroom thermal losses. Each bedroom has a heat load of only 400 watts. Bathrooms have radiator ladders.
Is this viable or am I looking at an indoor multisplit unit per room?,