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  1. #1
    Join Date
    Jan 2013
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    Renovation gut job and 2 different hvac opinions-confused

    My wife and I bought a 1940 tudor style home that is just under 4000sf. We are in the middle of a complete renovation and have come to a point where we need to make some decisions on our hvac. Currently we have a newer carrier heat pump that takes care of the first floor master and the laundry room. The second unit is a 1985 vintage carrier 58ss nat. gas furnace for the remainder of the house and second floor. Since this is a gut job all of the ductwork has been scrapped because it was a cobbled mess.
    Now we have to decide what to do with the second floor which consists of a 14x16, 12x16 and 11x14 bedrooms and a 6x10 bath. Call the second floor with landing 700sf. I contacted 2 different hvac contractors locally and got two different approaches.
    Contractor 1: Replace 58ss with more efficient unit, dedicate it to first floor only, replace ductwork. Install heat pump with 5kv heater on second floor, box out ceiling to keep ducts in living space. Quote pending.
    Contractor 2: Run new ductwork from existing 58ss unit to first floor registers like originally, run trunk up to second floor through wall chase as before with return, install flex duct in ceiling to each second floor room (everything is open). Ball park verbal estimate a few thousand.

    I am hoping to get a couple more years out of my old furnace because the budget has taken a major hit with repairs we did not anticipate (inspector missed). So dollar wise, #2 is doable now but #1 told me that it would never be comfortable upstairs even with sizing the main correctly. My opinion is that since the second floor will not be occupied full time, we could zone it and use dampers. We don’t have the $$ right now to put in two new units and ductwork at $+? Are we really going to be that unhappy trying to use our main unit to heat and cool the second floor even if we replace and size the unit correctly? Both approaches make sense when talking to the contractors but one is way more $$ and really isn’t an easy thing to change after we have insulation in and drywall up. Very confused. Any help or advice is much appreciated.

    Phil
    Last edited by beenthere; 01-05-2013 at 05:22 PM. Reason: Price

  2. #2
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
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    I'm not 100% sure I understand. Are both units in the basement now? 700 s.f. upstairs and 3,300 downstairs? The one contractor feels the existing 58ss is large enough for the entire home? With more information, I'll give you my opinion.

  3. #3
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    Jan 2013
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    6
    Both units are in basement. The smaller (newer unit) is dedicated to only the master bedroom and laundry room on the first floor (750sf). It will stay as is so nothing will change there. The older larger unit supplied the second floor, living room, family room, sun porch, half bath, dining room and kitchen (about 1250sf). The second guy felt like the size unit we have now is sufficient for the second and main floors it is already serving. When we replace the furnace in the future we will have to make sure it is capable of working with the new ductwork. So I guess the answer is yes, he feels like the 58ss can handle the first and second floors.

  4. #4
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    Jan 2013
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    If it helps it is a 58ssb095-cc 114,000 nat gas unit

  5. #5
    Join Date
    May 2009
    Location
    Savannah, Ga/H.H. Island, S.C.
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    1,492
    Did either contractor perform a manual j load calculation? That is the ONLY way to determine correct equipment size.

    If they didn't do one, find a different contractor.

  6. #6
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    Jan 2013
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    The guy that is suggesting replacing the main and adding the one upstairs is, I assume, doing this because we walked the house and took a bunch of measurements and asked a lot of questions regarding type of inuslation we are putting in, etc..

  7. #7
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    Dec 2010
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    The Quad-Cities area (midwest).
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    Basically your saying the ductwork is gone for the larger system? The smaller system, which handles the master bedroom and laundry, is all intact and will remain?
    If that is the case, then the second guy is on the right track. The second floor will have it own designated duct line which can be zoned in the future, if needed. I like that idea verse a second system for only 700s.f. That makes no sense. Actually, having a separate system for the master and laundry doesn't make sense either. You mentioned 4,000 s.f. but if I add the 750s.f. and 1250s.f. I come up short. Or did you not add in the 700s.f. for the second floor. Still, that's 2,700 s.f.? Where is the other 1,300 s.f.?

  8. #8
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    Jan 2013
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    Didn't include second floor in that or basement that was 3/4 finished. Yes, all ductwork in the house is gone with the exception of the bedroom unit that is in a corner of the basement and it's trunk heads out through a crawl space under the master.

    So in your opinion, run a feed from the basement to adequately supply the second floor with a return and zone it later when we replace the 58ss?
    Last edited by flip4179; 01-04-2013 at 02:45 PM. Reason: more info.

  9. #9
    Join Date
    Jan 2009
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    Keokuk, IA
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    I vote for zoning, but the ductwork is critical as is proper sizing.

    One thing ot keep in mind, is that if it's a traditional Tudor then it's stucco on the exterior which can fool load calculations. Stucco makes a hoem fairly air tight and has a lot of thermal mass.... meaning you can usually undersize a little without any risk... you jsut get longer run times which = more effciency.

    Factor in all insulation improvements your're planning... and a original single pane with a storm window performs nearly as well as a modern double pane... so if you're on a tighter budget. Repalcement windows have a 100-200+ year ROI.

    If possible, keep as much interior plaster you can during the rennovations (probably too late). It has great thermal mass and good accoustical properties compared to drywall. You plaster walls might be on beadboard instead of lathe, making the insulation value actually pretty descent.

  10. #10
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    Dec 2010
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    The Quad-Cities area (midwest).
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    Quote Originally Posted by flip4179 View Post
    Didn't include second floor in that or basement that was 3/4 finished. Yes, all ductwork in the house is gone with the exception of the bedroom unit that is in a corner of the basement and it's trunk heads out through a crawl space under the master.

    So in your opinion, run a feed from the basement to adequately supply the second floor with a return and zone it later when we replace the 58ss?
    Yes, that's what I would do. In fact, I have one system and three thermostats in my 1946 colonial home. As Motoguy said, the ductwork needs to be done correctly. It is better to error on the side of more (ductwork) than just getting by. Dampers can always reduce the airflow if you have too much going to an area.

  11. #11
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    Jan 2013
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    So technically speaking it would be possible to use 1 furnace for the whole house as long as it was sized correctly, zoned and the ductwork is done correctly? Could do away with the smaller carrier unit that is taking up space in the corner of the basement.

  12. #12
    Join Date
    Oct 2010
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    Anderson, South Carolina, United States
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    Quote Originally Posted by flip4179 View Post
    So technically speaking it would be possible to use 1 furnace for the whole house as long as it was sized correctly, zoned and the ductwork is done correctly? Could do away with the smaller carrier unit that is taking up space in the corner of the basement.
    Correct furnace and ductwork sizing, sealing, and insulating is key to having it perform properly.

  13. #13
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    Keokuk, IA
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    Further, when you zone, you can undertake the equipment slightly size all zones are t rarely if ever calling for maximum capacity at the same time. Plus, load calculations have some built in error. Add in diversity from solar gain and internal heat loads. Some zones for example should have extra capacity such as kitchens, dining room and living room.

    The challenge can be small zones illnesses you have modulating dampers like carrier infinity zoning.

    Sent from my DROID RAZR using Tapatalk 2

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