This photo shows the Mitsubishi indoor “ducted mini-split” unit on the 3rd floor. These units are slim so the unit and the ductwork can all be run below the ceiling to save floor space.
Now that we have reached the point where we can keep the weather out (see previous post: “Dried-in” - at last) and move more easily from floor to floor (see previous post “Focusing on the inside: getting from floor to floor“) our priority has shifted to the mechanical, electrical, and plumbing system “rough-ins”. Rough-in is the term that refers to all of the wiring, ductwork, and piping that will get concealed behind the drywall and hidden from view, but that is critical to the function and comfort. Each of these three systems (mechanical, electrical, and plumbing) requires a separate licensed contractor who has the technical expertise and knowledge of the code requirements related to their trade. Since this project is a comprehensive renovation, all of the components of these systems will be new which allows for the entire house to be brought up to meet contemporary code requirements and will result in increasing the reliability and safety of the house.
The new electrical system for the house is fairly typical except for the fact that we will be installing a rooftop solar PV system (more on that in an upcoming post). As for the plumbing, the new system is also fairly typical except that we chose soldered copper pipes for the water lines instead of the cheaper and increasingly popular “pex” plastic plumbing lines. Copper is certainly more expensive but we think it is worth it.
The Mechanical system that we went with is less typical (and more expensive) but has several advantages that influenced our decision. Most homes are heated and cooled with a fully ducted system that is connected to a central furnace and air conditioner. While this type of system is the most common system in US homes it does have its drawbacks - the first of which is space. In a house as small as this one every square foot matters. Devoting space for a furnace and for ductwork to run from floor to floor would have meant less living space. We also wanted a system that would allow for the temperature to be controlled on each floor as a separate zone. This is possible with a single central furnace/AC but not necessarily easy.
This shows the indoor mini-split unit on the 2nd floor which was installed over the closet which allowed for the ceilings in the living area to remain at full height
The system that we chose is referred to as a “ducted mini-split” system. It uses all electric fan-coil units on the interior (one on each floor) that are all connected to a condenser/heat pump unit on the exterior. Between the outdoor units and the indoor units there is no ductwork, only small flexible refrigerant lines and electrical lines. The ducting only runs between each individual indoor unit to the adjacent spaces on the floor where the unit is located – and it can all be routed along the ceiling since there is no ducting from floor to floor.
The individual indoor units will allow for the temperature to be adjusted by zone since each unit each has its own thermostat and can be controlled independently (just one unit can be run at a time or all four can be run simultaneously). Even though we chose this system mostly due to the space that it saved, we also like the flexibility and variability offered by the controls and the configuration of this type of a system.
Also, since the system is all electric there is no need to vent flue gases from a furnace. And an all-electric system seemed much more attractive since we will be installing solar so we will be able to offset our electrical use with the energy that will be generated from the solar panels.