Over the past weekend I worked tirelessly to install ductwork for the HRV and the two mini split heads.
The house will be heated and cooled solely with electricity using mini-split heat pumps. The mini-split has an indoor fan-unit called an evaporator which mounts to a wall and is connected by refrigerant lines to an outdoor condenser unit that is mounted on the side of the house.
During the winter it works as an air conditioner in reverse, extracting heat energy from the air and moving it into the house. The units are very efficient and can offer almost a 4:1 ratio of energy output related to input. It is rated to operate at full-capacity down to 0 degrees and will continue operating well below that.
The house has two units, one for the main floor and one for the basement level. The energy modeling indicated that only one unit was needed, however the cost of installing an additional unit was minimal and offered insurance should one of the units stop working.
The outdoor condensers were hung on brackets off the foundation wall. They are five feet off the ground to reduce the possibility that snow will build-up and cover them as well as provide ample space for water to drain off the coils.
As you have probably already guessed, one of the reasons the house can be heated (and cooled) with the high-efficiency mini-splits is because it is so tightly built. However, one of the issues with tightly-built homes is they need to be mechanically ventilated. To do this, I am installing a Heat Recovery Ventilator (HRV).
The HRV extracts “dirty” indoor air and exhausts it to the outdoors while simultaneous bringing fresh air into the house. The magic of an HRV is that it transfers the heat energy from the expelled air and transfers it to the incoming air.
The HRV has an intake and exhaust trunk with smaller 4 inch feeds to the registers, which are located on or near the ceiling. Tape or mastic was used to seal every duct connection to ensure the air actually makes it to/from rooms.
The HRV has been ordered and will be installed after drywalling. In the meantime, a dehumidifier is being used to reduce the indoor air humidity.