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  1. #14
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,326
    LOL! I'd gladly allow that!
    I think those remrate guys need to stop 'upgrading' the software
    3-4 times a year. by the time some of the houses are finished
    with upgrades (6 months average) remrate has upgraded at least once.
    this changes preliminary and final hers scores. it can be a real pita.
    when I first started back in sept of 1999 it was version 8.43
    now its version 12.93 and another upgrade has been released..I just haven't
    upgraded yet. (got houses in 12.93 I need to finish first)

    Lynn, I think that houses are tested at 50 pascals and ducts at 25pa.
    not 100% certain but I know my texas based provider has to be reminded
    that we test house and ducts at 50pa. every so often he calls me to tell
    me I've entered the info incorrectly. as I recall RESNET and SMACCA (smaca??)
    industry standard is 25 pascals for ductwork.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  2. #15
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    If you look on page 44 of the Adobe document (labelled page 39) there is a paragraph which addresses their statement of duct leakage. I interpret it as consultant bafflegab and wonder if you might agree. Use of a phrase such as "the lower end of expected results", followed by emphasis on GIGO, could that possibly be translated as "outlier which does not make sense"? Here is their paragraph, plus one about radiant barriers:
    ************************************************** *******************
    '...Duct leakage as measured by a duct blaster test appears to be related to
    summer/cooling loads, but more weakly than envelope leakage (not unexpected). The
    estimated impact is about 2 kWh of summer/cooling load per CFM25 of duct leakage.
    This result is on the lower end of duct modeling results, which vary greatly depending on a wide range of assumptions. The 2 kWh/CFM25 impact implies that duct leakage losses only total about 172 kWh for ENERGY STAR homes (86 CFM25 average), which is about 3 percent of summer/cooling loads.

    ... Radiant Barrier roof sheathing appears to reduce summer/cooling loads by about 0.09
    kWh/ft² of sheathing, which equals about 180 kWh/yr per home or 3 percent of
    summer/cooling loads.

    ************************************************** *****************

    Separately I wonder if there is grounds to suspect the 3% claim on radiant barrier, as that too is very different from what other sources tell me.

    Thank you -- Pstu

  3. #16
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Quote Originally Posted by pstu View Post
    ...consultant bafflegab...
    I think you are on to something. Obuscation and Mendacity work too.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  4. #17
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    "Bafflegab"...I'll need to remember that one...
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  5. #18
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    Note that they spend several dense sentences acknowledging the oddity of their result, and then going further to claim duct leakage of 86 CFM25.

    There had to have been some actual testing via duct blaster, and I wonder how many of those houses were down to 86 CFM25. Does it seem plausible that Houston area craftsmanship is far better than we expected?

    -- Pstu

  6. #19
    Join Date
    Jun 2009
    Location
    Jesup GA.
    Posts
    84

    25 or 50

    Quote Originally Posted by energy_rater_La View Post
    LOL! I'd gladly allow that!
    I think those remrate guys need to stop 'upgrading' the software
    3-4 times a year. by the time some of the houses are finished
    with upgrades (6 months average) remrate has upgraded at least once.
    this changes preliminary and final hers scores. it can be a real pita.
    when I first started back in sept of 1999 it was version 8.43
    now its version 12.93 and another upgrade has been released..I just haven't
    upgraded yet. (got houses in 12.93 I need to finish first)

    Lynn, I think that houses are tested at 50 pascals and ducts at 25pa.
    not 100% certain but I know my texas based provider has to be reminded
    that we test house and ducts at 50pa. every so often he calls me to tell
    me I've entered the info incorrectly. as I recall RESNET and SMACCA (smaca??)
    industry standard is 25 pascals for ductwork.
    Ita 25 pascal for the duct blaster and 50 pascals for the blower door test.

  7. #20
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Quote Originally Posted by Cool_Air View Post
    Ita 25 pascal for the duct blaster and 50 pascals for the blower door test.
    That is my understanding, also.

    However, when the duct leakage test is performed with a blower door using the subtraction method, isn't that done at cfm50?

    When duct ESP in the field is often .6"wc to .8"wc, I believe that testing at cfm50 would give a more realistic estimate of duct leakage. I don't recall that duct leakage is ever tied to duct ESP of the site tested. I think it should be.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  8. #21
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,423
    Quote Originally Posted by lynn comstock View Post

    However, when the duct leakage test is performed with a blower door using the subtraction method, isn't that done at cfm50?

    be.
    Yes it is, cfm50 when doing the subtraction method with the blower door.
    Make your expertise uniquely valuable.

    Make your influence uniquely far-reaching.

  9. #22
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,326
    cool air,
    my point was that here in Louisiana
    our program tests both house and ducts @50Pa.
    with ductblaster.
    this is one of the rules for our program.

    if subtraction method was
    allowed, it would be..for us..still 50pa.

    I haven't had time to read the post pstu..
    maybe over the weekend.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  10. #23
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,423
    Will the duct blaster measure duct leakage properly at 50pa? Not saying it won't just never done it.
    Make your expertise uniquely valuable.

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  11. #24
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,893
    performed duct leak test with flow hood on many duct systems mostly duct board and flex and found plenty of them leaking 25 percent and more but most were in the 15 to 20 percent range after repairs less than3 percent, also found sheet metal duct systems that leaked in the 15 percent range . think about it paying to cool the air than through away 1/5 of it or 1/4 of it also when your duct system does not leak your filters stay clean longer duct sealing can and will save money

  12. #25
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,326
    jim..beats me. I think that the state just wanted to make processing the ratings
    standardized. like setting rate statewide for utility costs @ 9 cents per kwh when it actually fluctuates. some small towns have their own utilities and cost is .18 per kwh,
    lowest is my co-op @ .08 and the two largest utility providers are .14 cents per kwh.
    our software (remrate) allows us to change these rates to provide actual savings,
    but to submit to the state we have to use their numbers.

    for me..it isn't a big deal if the duct leakage is off a little.
    I think folks get too distracted by that minimal percentage.
    the fact is if the system provides 2000 cfm and only 1500
    is actually delivered then what does it matter if its 1550
    or 1450? you still have unacceptable duct leakage.

    in my world its more important to find the leakage and fix it.
    our program mandates 5% Energy Star 10%.
    it is difficult to seal to 5% in existing homes.
    I've taken duct systems and returns apart and put them
    back together sealing everything..including equipment leakage
    and never gotten less than 5%.

    an average is 25-30% for flex. sheetmetal ducts higher due to more
    seams & joints. harder to seal. but with a lot of time and effort
    it can be done. just delays wrapping ducts until mastic dries.

    keep in mind that probably 80% of our duct systems are in the attic.
    15% in crawlspaces and 5% in conditioned space.
    the % of ducts in conditioned space is changing with the advent of
    foam insulating the rooflines.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  13. #26
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,423
    for me..it isn't a big deal if the duct leakage is off a little.
    I think folks get too distracted by that minimal percentage.
    the fact is if the system provides 2000 cfm and only 1500
    is actually delivered then what does it matter if its 1550
    or 1450? you still have unacceptable duct leakage.
    Yup you got it!

    keep in mind that probably 80% of our duct systems are in the attic.
    15% in crawlspaces and 5% in conditioned space.
    the % of ducts in conditioned space is changing with the advent of
    foam insulating the rooflines.
    People are truly becoming educated and concerned about energy costs ( at least some are) and are asking questions. Unfortunately most in the HVAC industry have no clue!

    We started up two Energy Star Home systems ( 3.0) today, both foam homes. I know the homeowners will not believe how quiet and comfortable there new homes will be.
    Make your expertise uniquely valuable.

    Make your influence uniquely far-reaching.

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