replacing ductless mini-split system with envi?
Dear GBA friends,
I got three HVAC bids and found someone I really like who seems to be actually thinking about the specifics rather than throwing oversized units into the bid. He came up with a plan to use the HRV to ventilate the bathrooms, move air in & out of the crawlspace as well as provide fresh air to the dwelling.
I will have a woodstove which I believe is sized correctly, and then the other component was a 2 head ductless minisplit.
Because I got three bids, I was able to get a sense of people’s estimates for the heating loads, and feel comfortable with this as a solution. However, I have just come across the envi heaters, and they seem like a much more affordable way to provide heat. Basically no installation costs.
The bid for the ductless set up would be about $6300.
– Mitsubishi MXZ 20,000/BTU multi-zone inverter heat pump
– Mitsubishi GL 12,000/BTU wall-mounted indoor unit in soft white for main living area
– Mitsubishi GL 12,000/BTU wall-mounted indoor unit in soft white for bedroom wing
I estimate I might need 6 or 8 envi units to provide the heat I’d need for my 868 square feet, with high ceilings in half the home. It would be a little silly looking having these units scattered all over, but considerably cheapter – $159 each for a unit that supposedly heats 150 square feet comes to $900-1200.
Is this worth pursuing?
Other facts that may be relevant: R23 in the walls, R 49 in the ceiling, doing my best to air seal and will do blower door test. 16 foot ceilings at the highest point in my shed roof living room, sloping down to 12 feet in kitchen (I know I’m crazy). Which is why I’m diligently air sealing.
The other part of the house is 12 feet sloping down to 8 feet (bed/bath area).
Conditioned crawlspace.
I look forward to hearing from you all. Here is a picture of my project recently:
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Replies
I would also look at Cove Heaters, which are radiant heat. You can buy plug-in versions or hard wired.
Since you are a new build, I would spend the money and hard wire whatever you decide.
The bottom line is electrical resistance (including Envi I believe) and radiant heaters are effectively 1:1 electricity usage vs. heat generated. While air source heat pumps average 1:2 to 1:3 depending on your location and season. So the heat pump will cost you only 1/2 or 1/3 in monthly electrical charges to generate the same amount of heat.
On the other hand, the advantages of electrical resistance/radiant heating units are that you can control the temperature room by room much easier, and there is a comfort factor with the radiant heat units.
The other advantage of heat pumps is they will provide air conditioning as well.