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Old 01-10-20, 10:21 AM   #16
Apprentice EcoRenovator
Join Date: Oct 2014
Location: SE MI
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Originally Posted by BillG View Post
Your idea of a little heat pump in each room is a good one. What you might look into is what is called a "VRF" (variable refrigerant flow) mini-split system, ...
I am not familiar with VRF systems, but they sounds like a good solution. The cost for the electronics (actually a variable frequency single to 3 phase drive) has come down a lot in the past 5-10 years !
My research, however, show that systems with multiple air handlers are a lot less efficient than those that only have one air handler. I don't know why, unless it is just from the long refrigerant lines.

Originally Posted by BillG View Post
I'm currently thinking through my next home in northern Wisconsin and coming to the same conclusions. I will be insulating well (R55 walls, R45 under the floor slab, and haven't settled on the roof insulation method yet), heating the floor using a condensing domestic water heater (my design day is a LOT colder than yours), and little mini-split heat pumps in the rooms.
Friend of a friend built a super insulated house in MI. He actually built double 2x4 walls with ZIP sheathing. The double 2x4 allowed easy placement of standard fiberglass rolled insulation. Kind of tricky to install and trim out the windows and doors.
Another "non typical" wall insulation method is spray foam all the joints from the inside, apply skrim and then blow in cellulose or fiberglass. Much faster so reduced labor cost.
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