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Thread: Cost to duct small house for HVAC ??

  1. #1
    General Engineering Contractor ballvalve's Avatar
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    Default Cost to duct small house for HVAC ??

    This is an easy question to hate, but can anyone give a range of cost for coming in and flexible ducting a very simple structure?

    Hung on the outside wall is a package heat cool unit. 60m btu. standard York rig.

    All work on one level attic surface, flat floor, ducts laying in the corner where rafters meet the floor.

    One return air run to the filter grille about 30 feet long

    5 or six air outlets totalling about 80 feet of smaller duct off the main plenum.

    Would have to supply the square to round transition off the installed hvac unit.

    Its a rental, one floor, 24 x 46 feet footprint. simple box. You can stand up in the attic easily and it has a standard staircase acess.

  2. #2
    Engineer Furd's Avatar
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    You may think it is an easy question but I assure you that it is not.

    Are you going to take full responsibility that the HVAC unit is correctly sized? Are there multiple rooms in this construction? Has a room-by-room heatloss/heatgain calculation been made and the ducts sized accordingly? What kind of terminal units (air registers) are you specifying? What R factor do you want on the flexible duct? What is the cost of various diameters of flexible duct ?

    Are you going to use a union sheet-metal shop to fabricate the transitions from the HVAC unit to the round duct? Are you planning on a "star" distribution or do you want a plenum duct with branches? Is the duct installer going to be a skilled worker with experience or a handyman that you found in an envelope of Val Pak coupons?

  3. #3
    Homeowner Thatguy's Avatar
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    Last edited by Thatguy; 11-07-2010 at 05:31 PM.

  4. #4
    General Engineering Contractor ballvalve's Avatar
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    Send me the val pac coupons, ........no unions, no responsibility for btus, size of ducts to follow standard trade practice. This is a mild climate and the energy calcs determined the furnace.

  5. #5
    In the trades Dana's Avatar
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    In California, CATitle 24 2008 requires that the duct design be compliant with ACCA Manual-D, and meet a specified and VERIFIED max leakage numbers, which is WAY better than the national average installation, if that's what you mean by "...size of ducts to follow standard trade practice...".

    It also requires that heating/cooling equipment be no more than 15% (?) oversized for the load as determined by a Manual-J calc, if that's what you mean by "...the energy calcs determined the furnace." (Also way better than the national average.)

    But it also means that the Val Pak coupons on stuff like this has a different value in CA than they do in most places, eh? Truly bad or even somewhat mediocre duct guys can't make a living (at any wage rate) the way they can in less-regulated states.

  6. #6
    General Engineering Contractor ballvalve's Avatar
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    California can regulate duct leakage all they like, but no inspector in the tri county area even glances at ducts unless its about too big of a hole in some wood member.

    Our delightful # 24 will not allow electric heat or water heater even though on propane the cost is much higher, especially after installation costs.

    Plan check missed my electric water heater on the plans, so I am going to go ahead and install it.

    my renters with propane switched to electric on my suggestion, and save about 200$ a month. Granted I have an old reduced electric winter rate in place, but its still about 9 to 15 cents per KW.

    Since no one seems interested to venture a cost for ducting I will get a bid and report back.

  7. #7
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by ballvalve View Post
    I will get a bid and report back.
    Depending on the cost of this job and how much your time is worth, get enough bids to form a cluster when you plot them on a line. It's a dot plot. The center of the cluster is the true cost of your job, today, in your ZIPcode.

    Eyeballing this dot plot example
    http://www.google.com/imgres?imgurl=...ed=0CDEQ9QEwAw
    I'd say 0.3 is the most likely value.
    Last edited by Thatguy; 11-12-2010 at 01:48 PM.

  8. #8
    In the Trades brownizs's Avatar
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    A bid I got to just do 12' of 12" duct changed to 6" was $700. Tell me that that is not a huge mark up in labor costs.

  9. #9
    General Engineering Contractor ballvalve's Avatar
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    I was guessing the project of mine was worth about $700... thats way out of line - even if you use thatguys "line"

  10. #10
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by brownizs View Post
    A bid I got to just do 12' of 12" duct changed to 6" was $700. Tell me that that is not a huge mark up in labor costs.
    How much do the materials cost? I think I could do this job in 2 hours without cutting myself.

  11. #11
    Nuclear Engineer nukeman's Avatar
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    I do everything myself, but considered bringing someone in to reroute some trunk line. Since it is rectangular and some fittings would need to made custom made, I figured it would be easier just to get it done. Everything open/exposed and I even had most of the old stuff removed. Got three companies to come out to give quotes:

    Quote 1: Showed up, took measurements, told me that they need to go back to the shop and run the numbers...never got back to me.

    Quote 2: Guy showed up over an hour late, then basically a repeat of quote 1.

    Quote 3: This guy figured things out while he was here. He had an app on his phone to add/calculate and a printer in his truck to print out the quote. He wanted over $1600 for the job. I couldn't believe that it could be that high. Nearly all of the materials could have been reused. Only needed 3-4 fittings made and move some takeoffs. Even if I wanted to take this quote, I would have had to wait 3-4 weeks since it was summer and they were focusing on new installs only. In fact, another company I called wouldn't even look at the job since they only wanted to do new installs.

    In the end, I did it myself. I figured out what I needed and had the fittings custom made by a company in NC. They made them up in just 2 days and got them shipped to me. Doing the job myself, it was a bit over $200. This is the comapny that I used to make the fittings:

    http://www.monroemetal.com/

    Thatguy: 6" duct is really cheap. There has to be more to this job then going 12" to 6". That is 4x loss in area, so I'm not sure what the plan might be there. Anyway, the materials might be $30 or less for a straight shot of 6". Each elbow might be $6-7. Could also go with flex duct. I don't like the stuff too much, but it is easy to run and you don't need elbows and such.

  12. #12
    In the Trades brownizs's Avatar
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    Materials $40. Time to do the job, 15 min's.

  13. #13
    General Engineering Contractor ballvalve's Avatar
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    Unfortunately, you charge $2,250 per hour and include travel time at half cost.

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