I have a builder building me a home right now and we had agreed to set up two separate heating and cooling systems for the first floor and second floor of the house. I raised the issue the other day that I hadn't seen the second furnace unit being installed in the attic as agreed. At first the builder said they were going to do that this week. Now he has said the HVAC company thinks its a better idea to set up a 1 unit system with 3 zones. Are they trying cover up their mistake at a discount?

2 Answers 2


You should have a meeting with your contractor and the HVAC contractor, and have them explain exactly what's going on. Ask them to show you whatever calculations they're using to determine the equipment size, and have them explain how a single unit can replace two units.

It's possible that they're installing a larger single unit, to eliminate the need for two units. This might explain why the price has not changed, though that's complete speculation.

If you're not satisfied with their explanation, it might be time to contact a lawyer.

  • i'm meeting with the HVAC contractor tomorrow. Do you have any targeted questions I should ask?
    – Martin
    Feb 12, 2015 at 4:40
  • It's also the case that if they're up-sizing a package unit it will be overdone and the reason no cost has changed is because it's cheaper. Two equal units is more costly than an equal single. More breakers, wire, plenums, coils, etc. I'd bet this isn't in OP's favor. A split unit also runs more efficiently because it has the ability to subtract adjacent areas from the other's load. This is key with the roof which looses a lot. You have a smaller unit running more often on a small area which eliminates the need for it elsewhere + back pressure issues of simulation. Feb 12, 2015 at 8:04
  • I spoke to the new HVAC company this afternoon and they summed it up as the follows. They were hired to replace the builders previous company and they say they never would have sized the project for 2 separate systems. They are going to install it with an arzel 3 zone panel and damper system with a Lenox high efficiency furnace. He said that he came in and sized the house and it only needed one unit to properly do the job. I spoke to my HVAC guy and he thought the 3 zone system was better suited and the new HVAC company does good work.
    – Martin
    Feb 12, 2015 at 20:20

You and your contractor agreed on duel split systems. However, he contacted an HVAC company who said otherwise and is interestingly, offering a down-sell on this install. (They make their real money up-charging for equipment. So as long as the zoning isn't going to cost big bucks, what's the problem?) My guess is that someone finally got around to doing the manual J and actually figured out the house's requirements and what you guys thought you needed, the HVAC guy says you don't.

If this is a trust issue, you need to do some homework about who you hired; check the BBB, ect.

  • Good chance you don't actually need two systems; just decent zoning.
    – iLikeDirt
    Feb 12, 2015 at 1:55
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    Additional issue that I'm having is that the builder is still charging the same price. The house has progressed beyond where they can do much adjustments to the ducts as it is fully sheet rocked and they never would have been brought this deviation to the plan to my attention. This is for a 3100 sq ft house + an additional 1500 sq ft in the basement in upstate NY.
    – Martin
    Feb 12, 2015 at 2:55
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    @Mazura, Fiberglass insulation rated R-19 in the exterior walls. Fiberglass insulation rated R-30 in the ceiling. All exterior facing basement walls are insulated from top to bottom of wall with R-10 foil covered insulation. When I'm playing with the load calculator, its calling for a total of a little more that 6000 BTU's. I'm planning on meeting with the HVAC contractor tomorrow. Any suggested questions to ask?
    – Martin
    Feb 12, 2015 at 4:39
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    @Martin, ask him to prove by means of a standard calculation that the system is surely adequately sized but also not over-sized. Ask them what benefits are there in doing it this way and if it will provide the same functionality expected. There should be some damper system installed to simulate. Ultimately, your agreement is with the builder who is liable for delivering what's promised. If you want to be a @#*&^ then tell them you want a "real" independent judgement (i.e.; an engineer or designer) before you'll approve any changes. An agreement is an agreement. Feb 12, 2015 at 7:51

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