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Addition needs cooling but conflicting quotes?

RandomGRK | Posted in General Questions on

I’m in the process of closing on a house, and only during inspection did we realize the master, which as an addition was never hooked up to the HVAC. No ducts were ever connected to vents in the room. 

I’m quite partial to having central air which I lhave grown to love since I’ve been in the US. I grew up abroad with split mini wall mounted units and I never liked them as they made me feel ill every morning. Dry and soar throat, inflamed sinuses etc. I assume this is from dry air? They were also constantly blowing directly on me which did at times make me sick. 

I have had two HVAC contractors out. The first guy immediately suggested a split mini and stated that he wouldn’t want to bring duct work into the master as it would be quite a messy job and wouldn’t appropriately cool the room. Furnace and cooling are right below the master in a utilities room adjacent to the kitchen. He said, my only other option would be to put new units in the attic which would then create two zones and take care of the entire second floor. Cost would be 13k for attic vs 4.5k for mini. Attic is not conditioned. 

2nd contractor said he refuses to put anything in the attic and my only option is a split mini in the master. Cost 7.5k.

House was built in 62, current cooling unit is newer and cleared for a 3200sft home, this house is 2000sqft. Gable roof so lots of attic space. Located in South Jersey. 

I understand those are my options but I have read to never put hvac into the attic. What if I conditioned it? I realize the price would jump but this house is supposed to be a long term place for me and I want to be comfortable.   

Any thoughts?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Random,
    There is no reason to believe that a ductless minisplit will provide less comfort than the other options (extending ducts from your existing system, or installing a new ducted unit). Most homeowners with ductless minisplits note that they have better comfort, not worse comfort, than experienced with ducted systems.

    If you choose to install HVAC equipment or ducts in your attic, you should convert the attic into an unvented conditioned attic. That's expensive -- a ductless minisplit makes more sense. But if you don't agree with my advice on the ductless minisplit, here's a link to an article that explains what you need to know: "Creating a Conditioned Attic."

  2. RandomGRK | | #2

    I guess my other hope was to ensure that the house was comfortable throughout. My current residence has all the equipment in the basement. On warmer days, the ground floor is pretty cold whereas upstairs rooms are warmer. I like it cool when I sleep so when waking up and I head downstairs to start the day, its freezing on the ground floor. This is the situation I was hoping to avoid.

    I saw the cost to condition an attic is at least $2k so my total expense would be hovering at $15k which is quite scary.

  3. Jon_R | | #3

    Running ducts from a furnace immediately below a room sounds fairly easy. In most cases, systems are sufficiently over-sized to handle an additional master bedroom.

    1. RandomGRK | | #4

      Hey Jon, the HVAC guy said to me that it was going to be a complete mess of a job and that if that was the route I wanted, he wanted no part of it.

      1. Yupster | | #5

        I'm with Jon on this, you should be able to extend your existing ductwork. Selling you new equipment has a MUCH bigger profit margin than adding some ductwork. Having never seen your situation, I don't know for sure, but unless the addition is slab on grade or on piers or something, I don't see why you couldn't. Get an hvac guy in there who knows what Total System Pressure means. For something like that, an hvac tech should: check system capacity, measure system performance, determine how much air the master bedroom will need, repair existing ductwork if necessary (usually needs more returns or something), measure system performance again, use new system performance info to size ductwork for master bedroom, install new ducts to master bedroom, balance system. Oh, and collect a tidy cheque.

        Look for an HVAC company with NATE certified technicians, they should be trained in basic airflow measurements like that. You can look them up here: https://www.natex.org/site/456/Homeowners/Find-a-Contractor-with-NATE-Certified-Technicians

        1. Reid Baldwin | | #8

          If I understand correctly, the master bedroom is on the second floor and the HVAC equipment is in the basement. What is on the first floor in between? Are there other rooms on the second floor? If so, how are they cooled, if at all? How is the master bedroom heated?

  4. Expert Member
    Dana Dorsett | | #6

    Don't do any thing without calculating the loads first, and sizing the solution appropriately. Even if the existing equipment is oversized by a large margin it doesn't necessarily mean extending it is going to provide the best comfort.

    1. RandomGRK | | #7

      We're most likely going to install a wall mounted system, the Mitsubishi FH series.

      What concerned me is that my HVAC guy said he would install an 18kBTU. This sounded like overkill to me and when I challenged him on it he said if I sign off on it and ignore is professional expertise, he will install anything I want. I guess he didnt like being challenged.

      The bedroom is about 300sqft, walk in closet about 50sqft and the bathroom about 75sqft.
      1 Large window and 1 smaller one. Bathroom has a small window.
      Attic above has some insulation but could be beefed up. Newer windows which are double glazed.
      Climate zone 4.

      I know its hard to estimate without seeing the place but at a minimum, is the HVAC guy incorrect. The other HVAC company said they would put in a 12k unit which sounds just about right, but still a little high.

  5. RandomGRK | | #9

    Ok, I see the confusion :) I'm from abroad so we say ground floor and then 2nd floor. In the US they say 1st floor (ground) and then 2nd floor?

    The master in on the 1st floor. HVAC equipment is more or less below it on the ground floor, just off the kitchen in a utilities room. There is no basement, it has a concrete crawl space. The rest of the home is cooled by a central air.

    Master is heated with electric baseboard.

  6. Expert Member
    Dana Dorsett | | #10

    >"We're most likely going to install a wall mounted system, the Mitsubishi FH series.

    What concerned me is that my HVAC guy said he would install an 18kBTU"

    An FH18 for 425 square feet is plain ridiculous. (USD$7.5K for an FH18 installation is also pretty ridiculous, but $4.5K would be reasonable, if you actually needed an FH18, which you don't.)

    Your actual cooling load is more likely to be somewhat less than the 9000 BTU/hr max output of an FH06, or the "rated" output of an FH09 which can deliver 12,000 BTU/hr of cooling at AHRI conditions of 95F outdoors, 80F indoors. The 1% outside design temps in southern NEW Jersey are in the high 80s/low 90s F, not 95F, so if you're concerned about cooling to 75F instead of 80F the numbers should be close.

    Take a shot at calculating the room/zone load using the loadcalc.net free online tool, which is nominally a Manual-J-ish. It defaults to an indoor design cooling temperature of 75F, so bear that in mind when looking at Mitsubishi specs that default to 80F inside, 95F outdoors. Use the tightest possible air infiltration assumptions or it tends to oversize (sometime by quite a bit.) The R-values only need to be close- the SHGC of the big window isn't selectable in that tool, but the load numbers should be good enough to tell the HVAC guy where to get off. :-)

    If you hate the wall-blob look the MLZ-KP09NA / SUZ-KA09 ceiling cassette approacy would also probably cover your load, and fits between ceiling joists. (You'd have to address air sealing and insulating above the cassette.) They make a KP12 and KP18 too. The KPxx don't have the same modulation range as an FHxx, but they're not terrible.

    http://meus1.mylinkdrive.com/files/M_MLZ-KP09NA_SUZ-KA09NA2_SUBMITTAL-en.pdf

    Yup- in 'merican dialect the front door is on the first floor, the floor above that is the second floor.

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