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Community and Q&A

Utility room location – wall or central?

johngfc | Posted in Mechanicals on

I just read a post by Akos recommending the utility room be located on an outside wall. Our design has the utility room near the middle of our conditioned basement to minimize plumbing and ducting runs. The utility room will likely have: 
– main electrical panel,
– HWH,
– air handler,
– maybe treatment for hard water (we’ll install connections and see if needed).

I expect the ‘main’ ERV would most efficiently be elsewhere in the minimally finished basement (to minimize outside cold air ducting and facilitate integrating a high-efficiency smoke and dust filter). Basement walls and ceiling are required to be fire resistant (no fully exposed ceiling trusses).

Are there significant issues with the central utility room location? The electrical will need to handle r00f-mounted PV (~ 9 kW), EV chargers, a garage with 220 V tools (woodworking; not commercial) and an all-electric house. The main electrical meter (post) will be on the street, about 100 feet from the house.  We’re hoping the house will be net-zero or net-zero ready (unobstructed, outstanding S exposure and plenty of roof engineered for PV). The house is ~2,000 sq ft. ranch style (main living on one floor; 2 BR + bath on W side of central open kitchen/dining/family room; master BR + bath, pantry, laundry on E side of main level), with a full, initially unfinished basement but with plans for later finishing the equivalent of an accessory dwelling ~ 650 sq ft. downstairs (kitchen, bath, etc).

Are there significant issues with a central utility room, and/or reasons to e.g. put the electrical on a wall and other mechanicals in a separate location? We haven’t broken ground – what is ideal and/or what are trade-offs between minimizing (especially) hot water runs and mechanical room location? I’ve read posts about heat-pump HWH noise and don’t need to revisit that.

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Replies

  1. walta100 | | #1

    Just to be 100% clear if you have a basement the utility room should be in the basement.

    I think a central location makes the most sense.

    Note Yes the main floor laundry is a great convenience but my front load washer shakes the walls and is very loud my old front loader in the basement was almost unnoticeable setting on concrete.

    Walta

  2. Expert Member
    BILL WICHERS | | #2

    I would try to put the utility room near the center. Centrally located utility (mechanical) rooms allow all the branch runs to be relatively short, with the tradeoff being the main supply runs from outside have to be a little longer, which is usually a good tradeoff. If you look at any commercial building, you'll find the mechanicals tend to be in centrally located vertical chases and then branch out from there on each floor for the same reasons.

    Bill

  3. Expert Member
    MALCOLM TAYLOR | | #3

    johngfc,

    Randy Williams also prefers to locate them on an exterior wall to facilitate the entry of services. Whether that's sufficient reason to move it from a central location probably depends on what is in the room and how it would best get there. https://www.greenbuildingadvisor.com/article/designing-a-mechanical-room

  4. johngfc | | #4

    Thanks! Very timely and informative article by Randy. The only real tradeoff I see is running the main electrical line, and I think fire code requires us to have a shutoff/breaker on the outside front wall so perhaps that's not.

    Walta - a downstairs laundry (which I'd prefer due to risk of water damage) is a non-starter with my wife. I'll interpret your comment as a recommendation to install extra joist bracing in that part off the house.

    1. Expert Member
      BILL WICHERS | | #5

      An outside main breaker is required if the cable run from the meter base to the main panel will exceed about ten feet or so. It’s not a particularly big expense to put in that separate main breaker. I wouldn’t worry too much about the long-ish run of cable in this case.

      Bill

  5. DennisWood | | #6

    Central mechanical is fine…until you need to run a new service etc into it. It should 100% be on an outside wall. What makes sense today, likely will not be as clear 20 years from now. The only exception to this might be an ERV/HRV in a cold location where your best location would be closest to the preferred location for fresh air intake.

  6. Expert Member
    Akos | | #7

    I can pretty much guarantee you won't find anything with a finished basement having the utility room or dropped supply trunk in the middle of the basement. First step when finishing an old basement is taking the existing utilities and moving them out of the way. My suggestion was to avoid this step by putting them out of the way in the first place. This doesn't necessarily mean your hot water runs will be extra long, with good room layout and mechanical location it might have a couple of extra feet of pipe.

    If you look at duct losses, there is barely any difference where the trunk is located. Center trunk is slightly easier to balance.

    Even if you don't want to finish the basement, not bumping your head into ducts when working down there is a bonus.

    Having the mechanicals near an outside wall also makes outside connections much shorter which can simplify things like ERV and refrigerant lines. Make sure to put a floor drain into the utility room wherever it is located.

    Putting the panel in the utility room is generally not worth it. You already have a lot of things going on in there adding a bunch of wiring into the mix adds complication for no benefit. Electrical panels area easy to hide, put it where the power comes into the house.

    For 9kW PV make sure to get either a PV ready panel (these are the ones with a dedicated PV feed) or a big 200A panel that has 400A busbars. A standard 200A panel with 200A busbars is limited to 7.6kW of PV. It is unlikely that an all electric house even with EV charges should need more than a 200A service.

    1. jadziedzic | | #11

      As an alternative the PV inverter output could be tied directly (through an independent breaker) to the load (house) side of the meter; this was done at my last house by a licensed electrician with the blessing of the original PV installer and local AHJ when a whole-house standby generator was installed after the PV system.

      In this scenario the PV inverter output MUST be fed to the utility "before" the automatic transfer switch. The "PV breaker" was installed on the exterior of the house with a prominent label as to its purpose.

  7. Expert Member
    BILL WICHERS | | #8

    Since I was one who recommended a centralling located utility room, I wanted to add that in a finished basement with hard ceilings, modifications are going to be more difficult without access to an exterior wall. In my example using commercial buildings (which is where I usually work), we have something that is uncommon in residential structures: drop ceilings, also sometimes known as 'access ceilings', which have *removeable* tiles to make access to things in the ceiling easy. There is no reason you couldn't use such a ceiling in a residential basement, but you lose ceiling height with a drop ceiling, since it's suspended below the structural ceiling. If you plan for that at construction time, you'd be OK, otherwise it's probably not desireable in a basement where the ceiling is already probably not all that high.

    For a finished basement, I think and outside mechanical room -- ideally in a corner -- does have some advantages. With an unfinished basement, the centrally located mechanical room has some advantages.

    Bill

  8. johngfc | | #9

    Thanks for the very informative comments. To be clear, the utility room is in the basement and we can easily keep the electrical separate from the rest. We've fully planned the future finished part of the basement and will rough in plumbing and electrical. The basement ceiling is 8', with 10" I-joists and a center-of-house steel beam on the long axis of the house (perpendicular to the joists). I've pondered what to do about the required 'finished' ceiling and thought it was likely best to use sheet rock, but I'll look further for fire-approved drop ceiling, perhaps just for the non-living part since the drop ceilings I'm familiar with are rather industrial-looking. Thanks again - really helpful to get these considerations on the table.

    1. Expert Member
      Akos | | #10

      You can read through this:
      https://www.mwboa.org/uploads/4/9/8/4/49847095/apa_fire_protection_of_floors_sr-405.pdf

      The simplest is 1/2" drywall strips sitting above the I-joist flange. Once this is all in, I would spray the whole thing including the I-joist flange white, this really brightens up the place. A layer of mineral wool batts above the drywall in the utility room area is a good idea for a bit of extra sound control.

      Make sure to stay on top of the trades to run all the services inside the joist space, not just tack it under it. With I-joists this takes only a small amount of extra work but makes finishing the space much easier down the road.

      I use my unfinished basement mostly as a workshop, the one recommendation is to run power for lights and tools. What I did is mount octagonal boxes in the ceiling and run 14/3 to it. This lets you have both switched and un-switched power. Onto the boxes I mounted duplex NEMA 5-15R outlets with the bridging bar snipped, the switched power goes to one outlet and the un-switched to the other one. This lets me plug in 4' shop lights where needed and also a convenient power feed for any tools.

      Even if unfished, a slop sink and a toilet doesn't hurt. Doesn't have to be a full washroom not pretty but a Pittsburg toilet will do.

      I'm a big fan of washer and dryer close to the bedroom but can create noise issues as Walta points out. The key to minimizing this is to put the washer near the outside of the house as close to the foundation as possible, avoid the middle of a long span. If you must put it in the middle, put a post/wall under it. Doesn't have to be a fully structural post with a full footing, a mini wall or a 4x4 sitting a small pad will do the job. I've also found putting 1" of rubber under the feet makes a big difference, I use stacked strips of horse stall matt for this.

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