GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Zehnder ERV + One minisplit head

nexp | Posted in Mechanicals on

I’m in the middle of an extensive renovation of a 150 year old house in zone 4a with design-day temp of 17 (Long Island, NY). It is tall and narrow, with the kitchen and dining room in the double-wyth brick basement. The basement is mostly below-grade on the south side, sloped on the east, and above grade on the north and west sides. The north/south are about 15′ wide, and the east/west 30′ long, plus a 7′ framed addition on the north side (with a subbasement below it). The basement has been completely gutted, and a new slab poured over 2″ (low-gwp) XPS, with slab-edge insulation. The 2×4 walls are stood 1″ away from the brick, and will be insulated with CCSF. The windows are being replaced with Marvin Ultimate dual-pane casements. Not the most energy-efficient, I know, but there were other considerations.

My issue regards HVAC. We currently have (grossly oversized) multi-splits – the house had 3 heads on a 32k and and 4 on a 48k Carrier outdoor unit. We’ve removed the 80kbtu atmospheric boiler that was supplying a poorly-designed hydronic system, and intend to solely rely on the mini-splits. We’re installing a Zehnder ERV. I’m particularly concerned about oversizing (and resulting summer humidity problems) and the poor-modulation of multi-spits, and am wondering if precise locations of the ERV supply/return ducting would allow a single head on a 1:1 system to maintain even temps throughout the whole space. I imagine this approach would function best with the head located in the top (north) area, as it has far more window/wall ration than the dining room, but that is also where a conventional ERV design would specify the exhaust be.


GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. StephenSheehy | | #1

    I think the problem with expecting the ERV to circulate conditioned air is that the ERV doesn't move nearly enough air. And doesn't the ERV have separate tubes from each supply/exhaust back to the unit? So the exhausted air is being constantly expelled from the house and gets replaced by outside air.
    Maybe one if the pros here can correct me if I'm wrong.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |