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  1. #27
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,171
    lots of attics and even new construction space is a premium.
    one 10" duct with 6" of insulation won't fit in a lot of spaces.

    having an attic with lots of space is an exception..most are
    tight cramped spaces.

    I think everyone agrees that having more insulation on ducts in attics
    and crawlspaces is a good idea. that we put ducts & equipment in those
    spaces is just crazy.
    unfortunately the hvac industry has not found a way to increase R-value that works
    in multiple applications.

    it takes a lot to bring about industry changes.
    good examples are the 2005 move from 10 seer a/c to 13 seer a/c as minimum
    efficiency. another is pending May 2013 elimination of 80% gas furnaces
    in northern climates.
    efficiency is improved in both examples, but it took a long time
    for the industry to mandate these changes.
    ductwork efficiency has gone from R-2 to R-4 to R-6 & now R-8 in most areas.

    in my area installers complain about the difficulty of attaching R-8
    ducts to plenum & supply boxes. to be able to attach 6" of insulation to
    start collars & supply boxes would require modification of these pieces.

    is this for your house..or your sister's house in florida?

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  2. #28
    Join Date
    Aug 2012
    Posts
    83
    I'm not sure why an energy audit is being suggested, when this is an obvious problem that energy audits don't even address because putting the duct work in attics is the construction standard.

    Here is another good thread about this issue.

    http://hvac-talk.com/vbb/showthread....ic-Ducts/page3

    it suggests buying the next biggest size flex duct and putting it over exsisting duct work. Basically a tube inside a tube.

    And this is the BEST information I have found so far
    Study done in Jacksonville, FL
    Using spray foam AND burying the ducts! Guess it is possible after all in this humid weather.

    http://apps1.eere.energy.gov/buildin...t_retrofit.pdf

  3. #29
    Join Date
    Aug 2012
    Posts
    2,650
    Just put a ductless split system in your attic and call it a day.

  4. #30
    Join Date
    Aug 2012
    Posts
    83
    sorry dont' have an extra $10,000 lying around. and you know as well as me that putting a condensor unit in the attic is insane.

  5. #31
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,724
    I used to see things exactly as you see them, and it was really hard to make the shift. It's like learning a new language, then all but forgetting your old one. Communicating that perspective shift is incredibly difficult.

    Imagine you have a leaky boat. The boat is sinking. What do you do, plug the leaks? Replace the bilge pump?

    What if you replace the pump and the boat still sinks, Failure right?
    What if you plug the holes and the boat still sinks, Failure right?

    How about gaining understanding of the leakage rate and the pump performance? Incremental improvements tend to have diminishing returns. In our world plugging all the holes is not economically viable, and getting a new pump might be poor investment. If we really want to optimize our efforts we will come up with a plan that optimizes the resources we plan to allocate.

    If it takes $1 to plug half the holes, $10 to plug 3/4 of the holes, and $1000 to plug 95%, what investment do you make in plugging holes? You really can't know without understanding the pump, and opportunities for improving the pump. These things are intimately connected.

    If it takes $1000 pump improvement to make no hole plugging work, $100 to make $1 hole plugging work, $10 to make 3/4 hole job work, and $1 to make the 95% hole plugging job work.

    In this case you can achieve success for $1000, $101, or $20. But the first step is diagnostics, the second is design, and the third is cost/benefit analysis because without them, you don't get these numbers upon which to make an educated decision.

    That's what a comprehensive home assessment should provide. It should help you understand and quantify current deficiencies understand where incremental investment should be reallocated.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  6. #32
    Join Date
    Aug 2012
    Posts
    83
    OK hypothetically I hire you to do a home energy effciency audit, pay a few hundred and.........

    would you ever recommend spray foaming attic flex duct as a solution?

    I'm asking because after days of research I've yet to talk to any energy effcincy pro, or read a report that addresses the obvious problem of having duct work in attic in humid climents. (except for the one previously linked to)

    Everyone knows it is an issue, it has been brought up multiple times on this forum.

  7. #33
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,724
    Spray foam is difficult enough to apply to flat clean surfaces. But you can ask your consultant what improvements they can, cannot, and prefer to model.

    If you paid to mobilize a spray foam rig I don't think you'd want them attempting to coat flex duct. It's a bit like gold plating a turd. Really tough, and in the end what have you done?

    I've sprayed rigid, but that is a double benefit of insulating and air sealing, and the guys were there for the rim anyway. I don't see it paying for mobilization.

    If you insulate your attic you will want to know leakage before and have some type of leakage after target. Air sealing tends to be the big, often missed opportunity most people miss. Having measurements is you only ability to have a true Quality Control measure.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  8. #34
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    6,848
    I would recommend spray foaming the roof and sealing the duct if found after testing it would benefit you to do so, this option would be included in the most expensive solution to the houses' problem and it take a special customer to pull the trigger on such an expensive investment but you don't know if they are the one if you don't ask.

  9. #35
    Join Date
    Aug 2012
    Posts
    83
    "I don't think you'd want them attempting to coat flex duct. ....... Really tough, and in the end what have you done?"

    Is that a rhetorical question? You've increased the R value with a closed cell foam that will not sweat because the dew point temperature will not be reached even in humid areas. Just like the study conducted in Jacksonville, FL pointed out that I linked to.

    I've seem some pretty small spray foam rigs, not sure why mobilization is an issue. they can easily fit in the back of a pick up truck and a couple of guys could put them in an attic.

    any ways I appreciate your emphasis on air sealing. Deffinetely need to check on that too.

  10. #36
    Join Date
    Aug 2012
    Posts
    83
    duplicate post
    Last edited by newstudent; 10-01-2012 at 06:32 PM. Reason: duplicate post

  11. #37
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,724
    Not well explained.

    Spray foam is tough to apply. To a round irregular plastic coated surface, getting a uniform cocoon of foam would be nearly impossible, and I wonder if anyone would attempt it. Flex duct is not considered a very durable material. So improving it on this level might be like replacing the engine in a Yugo. Maybe someone more knowledgable about flex will comment.

    It is very likely redefining the attic wouldn't be much more expensive, and that would be much more effective. Might be interesting to see insulating flex modeled. if you get an audit, put that on your questions list.

    And if you get a spray foam guy to consider spraying flex please share what they say.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  12. #38
    Join Date
    Dec 2005
    Location
    Cincinnati, Oh
    Posts
    5,015
    Quote Originally Posted by tedkidd View Post
    Not well explained.

    Spray foam is tough to apply. To a round irregular plastic coated surface, getting a uniform cocoon of foam would be nearly impossible, and I wonder if anyone would attempt it. Flex duct is not considered a very durable material. So improving it on this level might be like replacing the engine in a Yugo. Maybe someone more knowledgable about flex will comment.

    It is very likely redefining the attic wouldn't be much more expensive, and that would be much more effective. Might be interesting to see insulating flex modeled. if you get an audit, put that on your questions list.

    And if you get a spray foam guy to consider spraying flex please share what they say.
    Spray foam on flex is like putting a diamond ring on an old bar whore.

    If your going to spray foam anyways, spray the attic.

    If you want to get better r-value out of the flex, install foil-faced r-8 flex.

    If your want to be green, call a professional.
    "Better tell the sandman to stay away, because we're gonna be workin on this one all night."

    "Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."

    "Just get it done son."

    Dad adjusted

  13. #39
    Join Date
    Aug 2012
    Posts
    83
    " Might be interesting to see insulating flex modeled."


    What does that mean exactly?

    "Spray foam on flex is like putting a diamond ring on an old bar whore.:"


    Why do you say this? Scientific study didn't have anything negative to say about the process. Yes you are a putting a relative expensive type of insulation on a relatively cheaper one, but added together they increase the R value? Right?

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