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  1. #1
    Join Date
    Jul 2004
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    How best to approach upstairs?

    I've had 3 very highly-reviewed, professional, knowledgeable contractors out to my home and I have a feeling I'd be pleased with the quality of the work from all of them. However, they all have different ideas on how to approach what I'm trying to do upstairs here, but I don't know what to think. I'd therefore be really curious to get any advice possible here!

    I just bought a two story, 5000sf center hall colonial home in northern NJ that was built in 2003. Shockingly, it only has a 3-ton downstairs and 2.5 ton upstairs. Both furnaces are in the basement and all ductwork feeds up from below. With a few exceptions, most registers are on the floor and returns are on the on the high wall (on both floors). When I bought the house I thought it'd never be able to keep up on hot summer days given the low capacity of both units compared to the size of the house. I like it quite cool (68-70 setpoint at 50% humidity no matter how hot it is outside). However, boy was I wrong -- downstairs can hold it as cold as I want no matter how hot it is outside. Upstairs does just fine too except on the really hot days during the western late afternoon -- then it's gotten as high as 74-75 (max) upstairs during the late afternoon/early evening until the sun starts going down.

    Here's what I'm trying to accomplish:

    1) Be able to hold 68-70 upstairs even on the hottest of summer days (high 90s), yet not short cycle during much more moderate weather. I therefore feel I need variable speed systems that have high capacity but that can modulate down to much lower capacity.

    2) There will be an addition put over one of the downstairs rooms that currently has no second floor room above it, which will create an additional playroom upstairs off two of the upstairs bedrooms. This room will need cooling (and heating).

    3) There's no return air at the top of the stairs (the "bridge" that overlooks the foyer and the 2-story great room), nor is there any supply air there either. A few of the floor supplies are in spots that are going to be problematic for furniture placement. In the master, the return is directly above the supply which I can't imagine works very well (and certainly looks dumb). Some of the returns are quite loud and I worry the upstairs is a little starved for return air. And finally in the two bedrooms adjacent to where the playroom addition will go, the highwall returns are right where the doors will go into the new room, and I fear getting new returns up there from the basement could be very costly (and the $ to do so would be better suited towards a new duct system). These duct issues have me really thinking about new ductwork for upstairs.

    That said, the upstairs system works quite well overall. (I'm actually shocked by how well it works.) As long as the downstairs system runs enough (which requires it to be set a tad cooler than upstairs), the upstairs bridge stays cool enough also. I just want to get it working better so it's truly "right."

    Contractors have recommended not fixing what isn't broken -- i.e., not replacing the upstairs ductwork, but the system can't be enlarged much due to existing ductwork size. They recommend adding zoning so that if not all of the upstairs is calling, the rest can get more air. (I am incredulous about this. I've never liked zoning.) They also recommended adding a small supplemental system (high velocity or ducted ductless system) in the attic that only kicks on when the late afternoon load gets high on the hotter days. (I'm open to this but it feels like a kludge and I'm not sure how I feel aesthetically about a duplicate set of supplies on the ceiling.) They went on to recommend a ductless mini-split for the new room to be added upstairs. (But that would leave that room heated with a heat pump versus a furnace, and aesthetically I don't like it; I want the room to look and feel like it was always there, and not seem like an add-on or get second-rate HVAC.)

    None of the contractors recommend putting totally new (primary) systems in the attic, but I can't help but thinking that's the only logical choice on how to truly do this the right way. However, the attic has its insulation on the floor of the attic. I've read that in order to have the attic system work properly, the thermal barrier should be moved to the roof by moving the insulation. That would be extremely costly and I don't want to have to go through that. I've had prior homes with attics the same as mine and systems in the attic and they worked beautifully. Perhaps they had to be upsized a bit to compensate (not sure -- I assume so), but they worked wonderfully. So why wouldn't it work wonderfully here? The ducts would surely be very well insulated.

    I'd think that installing new systems in the attic to drop the air down from above for upstairs would be easier than making the ductwork larger for upstairs down the basement and ripping open walls and ceilings to get more runs upstairs from the basement ductwork. Also aesthetically having everything on the ceiling upstairs addresses some of the problematic register placement issues and the two returns I'd lose (and need to replace) upstairs when the doors to the new addition go in.

    One of the contractors I had out is actually the one who originally installed the systems in the home back when it was built in 2003. He said the design temperature was 75 inside at 90 outside, and the systems are definitely outperforming that. He said the house was really well-built, is super well-insulated, and that the existing ductwork is all in conditioned space in the basement (and all the runs come up interior walls), which is why it's working so well with such small systems. He was the most conservative and wanted to change the least. (He said ripping it all apart to change everything will spoil how efficiently it's working, and to leave the existing systems alone for the most part.) He knows the house best having installed everything originally when it was built. I'm just not sure his approach will solve my problem upstairs. I need extra capacity up there somehow and as well as it works overall, there are some duct issues I want to solve.

    Would love any / all thoughts, ideas, suggestions, etc. Can provide additional info and / or pics as requested. I just want to do this right -- both functionally and aesthetically. I want it to all feel congruous intelligently done.

    Thanks so much,


  2. #2
    Join Date
    Oct 2002
    Plano, TX
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    Energy code requires HVAC contractor to design to Manual J design calcs. The inside temperature dictated is 75 degrees at 50% RH. Much warmer then you would like. At that inside temperature, on a warm summer day, the AC will run 100% of the time. The rational is an AC unit take some time to equalize and 100% runtime achieves the highest efficiency.

    I believe if you condense your long post, you would get more responses

  3. #3
    Join Date
    Nov 2006
    Athens, Ohio
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    Be aware that installing bigger equipment to make it colder upstairs will necessitate enlarging or adding to the duct system.
    I suggest you consider having a whole house dehumidifier installed because lower humidity contributes to comfort. With that in mind, do you have a measurement of the relative humidity in the house? 50% or lower is a good target.

    Additionally, keeping the house too cold can lead to condensation forming inside the walls. That's a bad thing.
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  4. #4
    Join Date
    Sep 2008
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    I would not accept this job. There is absolutely NO reason a house should be set for 68°-70°. I heard so many people claim health conditions require them to stay cool, they are hot blooded etc... It's all BS. Houses are NOT refrigerators, and you WILL develop mold inside your home. Dehumidify, don't over cool. There's a little thing called dew point temperature. This is what temperature the air will condense on a surface. When you get your walls to 68° and the dew point is 72°, condensation occurs. If you want a cold room, have a walk-in cooler installed.

    My home is set for 77° 50% RH. I've never heard one complaint from guests. I actually get comments about how they can't understand why my house is so comfortable compared to theirs, and they set their AC at 70°. From time to time when we have a lot of company, and in the evenings I'll drop it to 76°
    Note we sleep under a down blanket even in the Summer, upstairs stat set for 76°, 50%RH.
    "The only true wisdom is in knowing you know nothing" Socrates

  5. #5
    Join Date
    Oct 2002
    Plano, TX
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    I have seen 6 month old jobs with backside of sheetrock dripping with dew from powerful 65 degree ac. No matter how dry the interior RH is, you must depend on a perfect vapor barrier and you cannot with an existing house.

  6. #6
    Join Date
    Nov 2004
    SW FL
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    < 74'F is not a Good operating temperature to maintain PROPER I.A.Q.

    IF MOLD were to form,
    one remedy COULD be to REMOVE ALL the DRYWALL.

    not more A/C.

    It is now a norm with superior BUILDING THERMAL ENVELOPES
    to see > 1,000 Sq Feet / Ton A/C designs IN THE SOUTH.
    One shoud definitely not be at all surprised in NJ to see even LOWER cooling requirements.
    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

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