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Med Static Pressure Minisplit + Window Questions

dcjohn | Posted in General Questions on

My wife and I are working through layout and other design decisions on an upcoming build.

We have explored other wall options, but in the area we are looking, East Ontario, the most doable “green” approach appears to be ICF (R30 – R35).  We are okay with the carbon tradeoffs for the project with ICF walls – the realities of trying to get alternatives built in a timely fashion mean that, for example, a double wall is not in the cards.
We are considering a “U” shaped floorplan.  
I am pretty set on ducted minisplit for heating and cooling.  The U means that the end-to-end distance is longer than a rectangular equivalent, say 150’ and 2 90 deg bends to start.  
Could a single, carefully-positioned and ducted medium static pressure Fujitsu unit work or does this layout suggest a two unit solution?
Will a single ERV/HRV work?
On the window front, I spoke with the Inline rep who suggested spacers that would bring the windows closer to the interior wall (~13” , to promote better airflow.  We would prefer the interior sills to be as deep as possible.
What are the tradeoffs for a window, 24” x 74”, for example?

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  1. Expert Member
    Akos | | #1

    If the ducts are within the conditioned envelope, there are very little losses with longer runs. Worst case scenario is you have to up size them a bit.

    Before deciding on the HVAC setup, do a load calc on the house. With a complicated shape like you are proposing, different sides of the house might have significantly different cooling/heating loads it might make sense to split them into two zones for comfort.

    Generally you want a single ERV/HRV. Less maintenance and cheaper install. Just size it according to the flow rate required for the house. Long duct runs are really not an issue with these (provided they are inside the house). If you have a strange layout with a room that is really out of the way, it might make sense to use a spot ERV for that room and run everything else in the house off a single main unit.

  2. dcjohn | | #2

    Thank you. Yes, all of the ducting and the units themselves will be inside the envelope.

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