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  1. #1
    Join Date
    Mar 2008
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    #/placement Mini-splits for EE 1000sf ROW home


    My question is this. For a super energy efficient home, can I size the mini splits for the entire house size- ie TWO 12K BTU units and just put one in the hallway upstairs and one in the basement hallway and assume the heat/ac flow will migrate naturally into the bedrooms/bathrooms. Or do I need one unit in each bedroom/bathroom???? Or perhaps put them in one bd upstairs and one bedrm downstairs and leave the doors open???

    BACKGROUND: I am building a home in Historic Baltimore (only the front brick wall stayed--even the foundation was redug--so its new construction). I need to make decisions regarding the heating and air conditioning system but have run into difficulties determining the best system because of the unusual aspects of my home. I'm hoping someone here can shed some light on this. Basically i'm wondering how many and where i have to put minisplits if i go that route.

    Home details:
    -3 levels (including finished basement with bedroom and bath in basement)
    -10' wide ( yes you read correctly-my entire house is only TEN feet wide) by 38' deep (basement only 10' wide by 27'deep)
    -sq footage approx 1000
    -2bd 1 bath upstairs
    "open" first floor
    -party walls are "conditioned"- ie people live in the houses next door and heat/cool them so i'm assuming almost no heat loss or gain from 38' walls.-
    -front and back walls 10' by 18' are R-19. Roof is R-38
    -heat gain/loss (3) front triple pane low e argon EE windows 30”x48” in the front and two same in the back (plus French doors)

    Everything I can find for minisplits says you need one per room—but my rooms are only 100-130 square feet that putting the smallest mini splits in each bedroom and one on the open main floor ((3) 9K BTU- bd rooms, 12BTU main floor) would still be completely oversized for my house size –especially considering it will be approx 50-70% more efficient than most homes due to size, high insulation, and little heat loss/gain from majority of exterior walls (party walls).

    The alternative is a heat pump for heat/ac ducted to all the rooms but I have low (7’) ceilings in many parts of the home and its only 10’ wide so I really don’t want to waste the space to ductwork. I also read mini splits were 20-30% more efficient then a similarly efficient heat pump due to no losses in ductwork—and with Electricity rates at 14 cents/kwhr I definitely want to put the MOST efficient system in!

    Thank you so much for any insights on this.

  2. #2
    Join Date
    Jan 2004
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    It won't work like you think.

    Use a central. The second floor supplies can be wall supplies if the walls line up.
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    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Jul 2004
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    As a first step, find a company that does heat gain/loss load analysis on a room-by-room basis. That will tell you exactly what you need in each room rather than just guessing. In all likelihood, that same company sells a line of mini-splits. The Mitsubishi Mr. Slim line is excellent if a conventional system isn't to your or your structures liking. With a Mr. Slim, you'd be getting inverter (variable speed) technology, which lets the HP/AC operate at a speed that puts out only as much heat/cool as the room needs. The also can do up to 4-tons and 4-zones off one outdoor unit. But the most important thing is to find the right company. So interview them over the telephone, ask how the determine the proper size equipment for your home and invite in the company(s) that say they do it by load analysis or Manul 'J' calculations or whatever. By-pass those that say they do it by square footage, experience or the size of the existing equipment.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  4. #4
    Join Date
    Mar 2008
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    Thread Starter
    Thanks, I guess I've just been talking to the wrong people because none of them have offered to do a "j" load anslysis and just ask for squarefootage and the give me systems that I believe are far oversized. I'll just have to keep asking around. Thanks for the pointer.

  5. #5
    Join Date
    Nov 2004
    SW FL
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    Smile Sanyo contractor locator ...

    Quote Originally Posted by ecogirl22 View Post
    Thanks, I guess I've just been talking to the wrong people because
    none of them have offered to do a "j" load analysis
    and just ask for square footage
    and the give me systems that I believe are far oversized.

    I'll just have to keep asking around.
    I guess ECOgirl is looking for an ECO _ _ _ heat pump system.

    Or more realsitically try a multi split heat pump with 3 diffusers

    You can find a local contractor though the distributor.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  6. #6
    Join Date
    Mar 2008
    VA - MD
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    Where to get more info...

    I am in a similar situation; I have bought a 1940's 2-story house in Cambridge, MD with no A/C and a very old oil boiler system and am looking at what is possible and cost effective for HVAC. As a layperson I know next to nothing about HVAC. I have found searching on www dot toolbase dot org, www dot eere dot energy dot gov and www dot achrnews dot com under "ductless" and "mini duct" heat pumps to be very informative. I happened to fill out a form on the Mitsubishi Electronics website for more info, and was sent a list of local contractors, three of whom immediately got in touch with me. Mitsubishi has a "Diamond" program for the contractors/installers who meet certain education and performance criteria, which I am relying on to help ensure I get a good HVAC company. Two of the 3 are diamond. There are alot of Mitsubishi installers on the "eastern shore," so there many be alot around Baltimore, as well.

    Hope this helps.

  7. #7
    Join Date
    Sep 2006
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    What you seem to be looking for (dan has already pointed you in this direction) is one of the smaller VRV or VRF systems. These systems (avalible form Mitusbishi under the City Multi name, Daikin VRV-S, and Sanyo Eco-i Mini) have one outdoor unit that is fully modulating in its output and multiple indoor units that are also fully modulating in output.

    They have both ducted and ductless indoor units in a wide range of capacities that will probably work with any situation. Mix and match as you need. Both the indoor and outdoor units are small in physical size and very quiet.

    Each indoor unit is considered a separate zone so it will operate independently of the other zones - all with a single controller in a discreet location like a closet.

    These are some of the most sophisticated and efficient systems available and what is primarily used in other countries.

  8. #8
    Join Date
    Mar 2003
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    look up either a mitsubishi or Daikin distributor and take a look at the multiple evaporator, variable refrigerant flow systems. They go by different names by manufacurers. These systems can operate over a wide range due to inverter technology, and are very energy efficient. You would have to run piping and electrical to each unit, but that could easily be hidden in wall cavities.

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