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Old 01-10-20, 10:57 AM   #17
Lurking Renovator
Join Date: Jul 2016
Location: Minneapolis
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Originally Posted by theoldwizard1 View Post
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.

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.
Thanks for the thoughts.

I wouldn't call the indoor units "air handlers." They are maybe 35" wide, 8" deep and 11" high, with a small fan and coil inside. The fan motor is a permanent magnet, electronically commutated, DC motor (ECM), continuously variable speed, and incredibly efficient. You might be able to find something about these systems by searching for Mitsubishi VRF, Daikin VRV, or LG Multi V. Many brands out now. The compressor is also variable speed driven by a similar motor - similar to the AC compressor on a Prius. It is really hard to get more efficient.

Not intending to hijack the original poster's thread... but so far, my walls will be ICF with 6" of additional foam, so 6" reinforced concrete plus 11" of continuous foam (no thermal bridging or joints for air leakage). Wife wants it tornado safe.
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