GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter 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

Multifamily HVAC Solutions

cmfischer | Posted in Green Products and Materials on

I’m developer of small (6-20 unit), low embodied carbon, low operating carbon, 100% electric multifamily housing in Minnesota and would love the community’s thoughts on the most efficient, scalable and readily available solution for energy efficient heating and cooling an air tight (<1 ACH50) building in climate zone 6. 

The default for most multifamily builders here is either a PTAC in each unit, sometimes VTAC. In comparison to mini splits, these appear to use WAAAAY more energy and create WAAAY more opportunity for air sealing issues. 

In the 6-unit building I am currently building (all 1-bed, 620 sf units), I opted to equip each unit with a its own 1-ton Fujitsu mini split.

https://www.fujitsugeneral.com/us/products/split/wall/12lzas.html

This works for 6-units…but isn’t really scalable. 

So my questions:
(1) Anyone have experience with or thoughts Ephoca’s products?
Their HPAC and VHP products look like they address a lot of my needs. For example, the HPAC (specs attached) truly minimizes wall penetrations / risk for air leaking, look better than most PTACs, claims to be quiet, and is somewhat efficient (e.g. SEER of 16). 

BUT…they don’t distribute in Minnesota yet, and I’m not Dana Dorsett so I can’t decipher how they would perform compared to my Fujitsu units in cold temps. Specific questions here are:
        A) How do you get a distributor to pick up a product line?
        B) How much importance should I place on having a local distributor carry it vs. buying direct from a distant manufacturer (service, maintenance)?
        C) Would these be able to provide primary heat at -13F like the Fujitsu?
        D) DirectionallyHow would the energy usage for one of these in a 620 sf unit compare to the Fujitsu I’m putting in?  Not specific numbers…but order of magnitude. 

2) What is the most energy efficient (and air tight) solution for a building comprised of 12-16, 625sf units…assuming a single zone heat pump for each unit is out of the question. VRF? HPAC + electric resistance backup?

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.

Replies

  1. DCContrarian | | #1

    While I wait for someone like Bill Zephyr with more expertise to chime in, I'll offer that you might want to look at hydronic systems. Specifically, something with hydronic fan units that handle both heating and cooling. This is the traditional way that large buildings are heated and cooled. They are conceptually similar to minisplit heads but they scale much better.

    Traditionally these are done with an air-source chiller and a fossil-fuel burning boiler. The question I would ask is whether there are emerging alternatives, including air-source heat pumps of sufficient size to replace the boiler, or even ground-source for the whole system.

    It's also pretty easy to configure a hydronic system to use air-source heat pumps in mild weather and switch over to fossil fuels at a certain temperature.

  2. Walter Ahlgrim | | #2

    Do you really want a central system with the heat and AC included in the rent pricing? This seems to bucking a 70 year old marketing trend. The other drawback to a central system is a single fault could easily take down the system leaving everyone without heat.

    A Generally it is about volume how many unit a month will they sell.

    B Generally the distributor do not provide service or maintenance with the exception of stocking some parts and sometime making them available 24-7 for an extra charge. Most manufactures will only sell to distributors.

    C Not as a heat pump looking at their chart at 5°the unit is down 90% on heat output. They do list models with electric resistant backup heat.

    D it seems unlikely you can do better than a mini split.

    The reason PTAC are popular is that the system are so redundant no single failure can affect more than one room. When there is a failure almost no skills are required to swap out the unit for a spare unit. Also very low cost to install.

    Walta

  3. Expert Member
    Akos | | #3

    This is a good read about this topic:
    https://www.greenbuildingadvisor.com/article/designing-multifamily-building-approaches-passive-house-performance

    My takeaway is that building an energy efficient structure and heating it with resistance heaters is less costly than any heat pump solution. It doesn't take much extra effort to get near passive house performance at which point heating costs are small enough that there is no ROI for a heat pumps.

    I remember reading about a multi family project that used a shared oversized HRV feeding a ducted air handler for a number of units. This way the shared unit was not only providing fresh air to every unit (which is needed if you make the place sealed) but also sufficient airflow to handle cooling loads. You don't need all that much cooling for a 600sqft apartment with well designed glazing and shading. Something like a 1500CFM HRV+5 ton air handler is probably in the ballpark for 16 units.

    This would mean the owner still takes needs to cover some operating cost but in colder climates with an efficient AC unit, this cost is minimal. Tenets would still carry the larger cost of heating the place rest of the year.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |