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Old 01-01-20, 11:28 AM   #10
MN Renovator
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Originally Posted by dfhuynh View Post
I think I'll put my money into triple-glazed windows (R9), or even quad-glazed (R17) in one or two places. I will have a lot of big windows but fortunately they face the North-East direction and only get about 1 hour of sun in the early morning. For the windows facing South-West, I'll install external solar shades and pull them down in the summer.

Overall, it sounds like I can just go completely electric for heating/cooling and even have fewer heat pumps (3 x 9000 BTU) given excellent insulation. I'll run two air handlers on one condenser for any pair of rooms that don't usually get used simultaneously, like the "big room" downstairs and the master bedroom upstairs.
I think you'll find the price difference between energy star 2 pane windows and 3 pane windows R5 to be high but could be worth it, but aiming for glazing that is R9 or higher might be very cost prohibitive. Not sure I'd go with any sort of quad glazing or suspended film stuff. You don't have a large temperature spread like what can happen in Minnesota(our design heat load is based on -13f) which is 83 degrees difference between 70 and -13. I'd personally aim for R5 or better triple pane (0.2 U-value or less) and if I find better for a similar price I'd take that.

I agree that you could go completely electric for heating and cooling, if you use ductless mini-splits you've just removed ductwork and/or hydronic lines entirely and inverter mini-splits will have no trouble heating efficiently in your climate and you probably won't see them defrosting on anything but the worst days which is a major bonus.

I like the idea of two separate outdoor mini-split units, if one fails you've got a backup. I'd put one mini-split on it's own for the largest area and if I wanted more than 2 total indoor heads I'd use a multi-split off of that unit. I think these units are generally reliable, especially big names like Mitsubishi, but the cost of two single head units and a single mutli unit isn't too much more money and the smaller single head units seem to be slightly more efficient. This would be my personal preference, but I recognize it might not be the most popular idea.
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