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  1. #1
    Join Date
    Apr 2008
    Posts
    10

    2nd Floor Climate Control Problem-Need help evaluating options

    I'm seeking advice evaluating options that different HVAC contractors and consultants have presented for fixing a 2nd floor climate control problem. We live in the mixed-humid zone (near Washington, DC).

    The problem:
    The building contractor who renovated our 65-year-old house and added an addition screwed up the HVAC very badly (long story, photos available). Many of the problems have been fixed, but the 2nd floor is still screwed up. Prior to our renovation, climate control on the 2nd floor was fine. The HVAC sub replaced the original two upstairs bathroom air supplies, which had been separately ducted from the furnace with strong air flow from wall registers at floor level. These 2 bathrooms are now supplied by one smaller duct that travels a tortuous route from the basement up through 2 stories and into the attic where it then splits into two flex ducts that make further twists and turns across the attic floor to the ceilings of each bathroom. As a result, the bathrooms receive virtually no air. We now have a 40% reduction to the air supply to the 2nd floor, leading to problems not only in the bathrooms but the entire 2nd floor -- too hot in summer, too cold in winter. Our contractor has agreed to resolve this problem, but exactly what to do has not been determined yet.

    The options:
    We have been presented with the following possible options. Some of these are not mutually exclusive.
    1. Put a booster fan in the duct to the bathrooms.
    2. Raise the wall returns in the 3 bedrooms from floor level to near the ceilings.
    3. Create a separate zone for the 2nd floor by adding a 2nd plant (Trane heat pump, etc.) in the attic with a 2nd Trane condenser for A/C. (Our main plant is a Carrier Infinity system.)
    4. Install damper-controlled zoning for the entire house using the existing plant (2, maybe 3 zones).
    5. Increase the size of the duct running to the bathroom supplies.
    6. Reduce the size of the registers in the 2 bathrooms. (I frankly don't understand this option, which was proposed by an HVAC subcontractor from an established, registered company. When I asked how it would increase air flow, he told me that "The air is getting lost in the register box.")

    Conditions/Constraints:
    Our 2-story house is now about 3000 square feet, with a finished basement and a 1st-floor, single-story addition over a conditioned crawlspace. All ceilings are 8-ft, except for a cathedral ceiling in the 800-sq. ft. addition that is 13-ft. at the highest point.
    The original plant was replaced during the renovation, and we now have a 5-ton Carrier Infinity, one zone, in the basement. The contractors and consultants have all agreed that the current plant has sufficient capacity to do the whole house.
    The 2nd floor is about 700 total sq. ft. with three bedrooms and 2 baths. Each bedroom has a supply and return at the base of the walls, the bathrooms have no returns. Attic is unconditioned, but it has a well-insulated floor, a ridge vent, and a powered attic fan at one of the two gable vents. It has no soffits due to the roof's design and is in effect a crawlspace.

    Questions:
    Basically, I need to know the pros and cons of the different options. I also have some specific questions:
    1. Assuming for the moment that all options are feasible, is there any one that would be the best way to go to achieve the best combination of good climate control, energy efficiency, and operating and maintenance costs? I've heard that two plants are cheaper and more efficient to run than one, but also more expensive to run if you include maintenance costs.
    2. Will a 2nd plant work in an unconditioned attic? I've read that it's a bad idea, especially given our attic's very high temperatures (120+) in the summer, but I can't find any solid analysis on this. Also, since a heat pump's efficacy is significantly reduced by extreme summer/winter exterior temperatures, I'm having trouble seeing how a heat pump will provide us with good, efficient climate comfort for the 2nd floor.
    3. Does adding a 2nd plant require shutting off the current supplies and returns to that floor, or is it possible to add something to supplement the existing climate control? If the 2nd floor needs to be self-contained, how can we control humidity for the 2nd floor in winter? Do we need a 2nd humidifier?
    4. Assuming a proper (e.g., fantech) booster fan is installed in the duct, how noisy are they and what are the operating costs?
    5. If available space in the walls and joist bays prevents simply running another bathroom supply duct up to the attic, are there other ways to get more air up there? For example, figuring out a way to straighten the existing duct, replacing the current oval duct in the walls with a rectangular duct that fills the stud bay?
    6. Are there other options the contractor should be considering? For example, would it make sense to close in and condition the attic?

    I realize this is a lot of info and questions, but your advice, insights, and suggestions on any part of this would be greatly appreciated.

    Thanks!

  2. #2
    Join Date
    Feb 2005
    Location
    Massachusetts
    Posts
    305
    That's a tough one. It's hard to offer specific comments. So, what was your old system (fuel, age, etc), and why did the duct system have to get re-routed to the second floor? I'm trying to understand the big picture. The rest of the second floor is ok?

    I'm not sure how a zoning system will help the two bathrooms. If the ducting system leading to the bathrooms is as long as you're describing, you've got issues.

    If you set up a system in the attic, wow, what a job just to overcome two bathrooms. Now your 5 ton system is oversized, and you need a new system in the attic...

    "lost in the box"? Think of air like water. If you were pumping water up the ducts, would the water get lost in the box or come on out? If there's nothing coming out, there's nothing there to begin with.

    Perhaps the in-line fan may be the best option to start with.

    Gary

  3. #3
    Join Date
    Apr 2008
    Posts
    10

    Further explanation

    The furnace is gas-fired. The old one was a single-stage Sears (both furnace and A/C). The new ones are both two stage.

    The two ducts for the bathroom supplies had previously come up through a wall that was removed to create a center hall. They had each taken a single right angle turn and traveled to the bathrooms via 2nd-floor joist bays. With the wall gone, the supplies had to be rerouted, so the first HVAC contractor (who designed by rule-of-thumb, as far as I can tell), decided to route the ducts for the baths up through the attic and put the supplies in the ceiling rather than find another way to route them under the 2nd floor.

    At the time, we were told that the change was made to improve the airflow by mixing low and high registers on the 2nd floor, but later we were told there was no other way to get the air up to the bathrooms given the disappearance of the wall and how other bays are used. I'm not completely convinced that's true but it is true that the options are certainly limited at best.

    The ducts for the 3 2nd floor bedrooms are all original and they do have good airflow.

    The change has created problems for the whole 2nd floor, not just the bathrooms. First, the bathrooms get virtually no heat or cooling. They're both small but there is a noticeable effect, unpleasantly so in very hot or cold weather. Second, the bedrooms are noticeably affected--hotter in summer and colder in winter than before the renovation. Attempts at balancing via damper adjustment have not solved the problem. So unfortunately the rest of the 2nd floor is not ok.

    As for "lost in the box" I was sure the guy was slinging it and told him so, as politely as I could muster. This chestnut came from the 2nd HVAC contractor, who was brought in to fix the problems created throughout the house by the first one, and who diagnosed the basic problem with the whole installation as "a five-ton plant with two-ton ducts." (An independent HVAC consultant had said this to us as well.) He greatly increased the ducting at the furnace and into the addition, greatly improving the climate control on the first floor, but did nothing about the 2nd floor problem, for reasons we can only speculate about.

    I was definitely worried about the possibility of a 2nd system making the main plant oversized. Thanks for confirming that this could be an issue.

    I hope this clarifies things a bit.

  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    The options:
    We have been presented with the following possible options. Some of these are not mutually exclusive.
    1. Put a booster fan in the duct to the bathrooms.
    2. Raise the wall returns in the 3 bedrooms from floor level to near the ceilings.
    3. Create a separate zone for the 2nd floor by adding a 2nd plant (Trane heat pump, etc.) in the attic with a 2nd Trane condenser for A/C. (Our main plant is a Carrier Infinity system.)
    4. Install damper-controlled zoning for the entire house using the existing plant (2, maybe 3 zones).
    5. Increase the size of the duct running to the bathroom supplies.
    6. Reduce the size of the registers in the 2 bathrooms. (I frankly don't understand this option, which was proposed by an HVAC subcontractor from an established, registered company. When I asked how it would increase air flow, he told me that "The air is getting lost in the register box.")

    RESPONSE;
    1.Bandaid ,considering it was their remodel design.
    2.Only if it's to get more airflow or less resistancein the ducts.No if the the high location will make a comfort difference.
    3.Only if there is no other way,first floor to be downsized is a must.
    4.Best opition,but the duct system may not be adequate,sounds like it's not.
    It's unusal that you had no issue with one system for two stories before.
    5.Likely needs to be done regardless of what else is done.
    6.No way.





    Questions:
    Basically, I need to know the pros and cons of the different options. I also have some specific questions:
    1. Assuming for the moment that all options are feasible, is there any one that would be the best way to go to achieve the best combination of good climate control, energy efficiency, and operating and maintenance costs? I've heard that two plants are cheaper and more efficient to run than one, but also more expensive to run if you include maintenance costs.
    2. Will a 2nd plant work in an unconditioned attic? I've read that it's a bad idea, especially given our attic's very high temperatures (120+) in the summer, but I can't find any solid analysis on this. Also, since a heat pump's efficacy is significantly reduced by extreme summer/winter exterior temperatures, I'm having trouble seeing how a heat pump will provide us with good, efficient climate comfort for the 2nd floor.
    3. Does adding a 2nd plant require shutting off the current supplies and returns to that floor, or is it possible to add something to supplement the existing climate control? If the 2nd floor needs to be self-contained, how can we control humidity for the 2nd floor in winter? Do we need a 2nd humidifier?
    4. Assuming a proper (e.g., fantech) booster fan is installed in the duct, how noisy are they and what are the operating costs?
    5. If available space in the walls and joist bays prevents simply running another bathroom supply duct up to the attic, are there other ways to get more air up there? For example, figuring out a way to straighten the existing duct, replacing the current oval duct in the walls with a rectangular duct that fills the stud bay?
    6. Are there other options the contractor should be considering? For example, would it make sense to close in and condition the attic?


    RESPONSE;

    1.Infinity zoning,4 zons,and solve the duct/air flow issues.
    2.It'll work just fine.However there is additional operational costs due to the temperatures there.
    3.Depends on their location if they can be connected to attic ducts.
    4. Their not noisey,but it may not correct all the issues.Where would they loacte it?
    5.A chase thru closets that line up from the floor basement to the attic.
    6.lots of ways to remediate duct systems,but a ton of information would be needed to answer from here.Just a couple,duct static(think resistance to air flow ) can be reduced by adding turning vanes to any 90 degree elbows,better fittings can be used,additional "helper" ducts can be added.Lowering the static ,to the areas with issues,will increase air flow.

    Have you checked the static on your User Interface??

  5. #5
    Join Date
    Nov 2003
    Location
    northern mass
    Posts
    411
    common problem.

    Builder re-aranging house...additions and remodel and what not. Getting paid to do a certain scope of work, and the hvac system needs alot of work to make work again with the new layout. BUT, the builder is reluctant to rip open walls that have to be re-plastered, and other work that is out of the scope of the contract. I see this alot. Wires are either connected or not....simple to see. Pipes have water coming out or not, easy to see. But ducts can be run where they're supposed to and not be right at all, not so easy to see to some people.

    OK options...
    Booster fan--I would say last resort. never used one. I don't see that as a fix.
    Moving returns---not a fix
    another unit in attic---are you kidding me....no.
    Zoning the system---a definate maybe, i like it.
    Increasin gthe bathroom duct size---well it's either right or it aint. MANUAL D....actual vs. equivelant etc
    Reduce diffuser---??? huh ? it's a bathroom, i'm sure it's small as it is. Grills are sized according to throw needed, meaning how far they need to throw the air that is being supplied to them. So...at a certain CFM and FPM a grill will throw air XXX amount of feet. I think he thinks he can squeeze air out like a thumb over a hose.
    I only try to be the best.....though i'm not......but in my efforts to be, I hope to learn and achieve more than most !!

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