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  1. #222
    Join Date
    Apr 2002
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    11,808
    Quote Originally Posted by pstu View Post
    Again: what is wrong with using attic fans in pairs, one supplying "cooler" air to the attic from a favored location, the other in the expected place to suck hotter air out from the top of the attic? Why wouldn't this eliminate the objection of negative pressure in the attic?

    Hope this helps -- Pstu
    Why be Rube Goldberg and develop a ducted supply and EXHAUST system to ventilate an attic when the concept is bad in the first place.

    It is so low tech to seal an attic and have a white roof, it is KISS. That must be the problem, it makes too much sense to do it, we have to Rube it up

    You grew up in a house with a white roof.

    It is entrenched in a building code to avoid icycles. Codes need to vary with the climate they are not universal. We have wording for roof snow loading in the code down here.
    Last edited by Carnak; 08-30-2009 at 03:22 PM. Reason: changed "return" to "EXHAUST"
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  2. #223
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    Not ducted, just pick a good eave location where you normally have a passive vent, and locate the forced intake there. So far I see 2 fans, not enough to qualify for Rube Goldberg. I know you and Lstiburek hate the very idea of a ventilated attic. For whatever reasons Pulte Homes tried building Lstiburek's way in the Cinco Ranch Building America experiment, and Pulte did not want to continue after the experiment. Pulte does not want to talk about it but there must be two sides to this issue.


    Regards -- Pstu

  3. #224
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    Apr 2002
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    11,808
    Attic space can be big, pressurize one end with a fan depressurize the other with another fan. If you want the balanced approach you are going to have to duct it. Its getting more convoluted on how to make a dumb idea work better.

    the Cinco study also had conclusions like "we should try an inline fresh air fan to boost up the fresh air intermittently"

    I have been doing this for quite a while. Started out with a hypochondriac's house, then one where it was a mile of flex to try and retrofit a fresh air intake, then it was me practising what I was preaching in my own office.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  4. #225
    Join Date
    Apr 2002
    Posts
    11,808
    Try this one out

    http://www.baileyeng.com/paston_effect.htm

    I get these conditions in spades down here.

    One point they make is how old time Florida Houses were unvented and worked just fine
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  5. #226
    Join Date
    Apr 2002
    Posts
    11,808
    75 years later it says..............

    Mr. Bailey is a reputable guy, a big player

    Addison Mizner, a noted architect of many Palm Beach estates and city buildings, designed and built many homes with no attic ventilation. Seventy-five years later, inspection of these attics reveal pristine conditions of all the materials in the attic.
    Many commercial buildings with a flat roof, built up deck, white membrane. We call the air space above the ceilings, in such buildings, where the bar joists are a return plenum, when in reality it is a sealed attic
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  6. #227
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,338
    Quote Originally Posted by Carnak View Post
    75 years later it says..............

    Mr. Bailey is a reputable guy, a big player



    Many commercial buildings with a flat roof, built up deck, white membrane. We call the air space above the ceilings, in such buildings, where the bar joists are a return plenum, when in reality it is a sealed attic
    So why when it comes to residential construction, the almighty dieties of northern building science still hold sway, when down here in cooling climates more and more of us are realizing that the gods are crazy?

    • 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.

  7. #228
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,187
    I know I know...
    because they can!!!
    seriously I went to code classes put on by IBTS earlier this summer,
    since La. has been so very slow in adopting the IRC code they
    are training code inspectors en masse.

    seems that codes came to be after great tragedy with many lives
    lost to force the cities to build safer.
    fire in Chicago..you know that lady's cow kicked over the lantern..
    the next year fire codes..
    northern states were more progressive at the times when codes were
    written.
    it has been the path of least resistance to follow the footsteps instead
    of forging new ones.
    I agree that we do a lot of stuff to here prevent ice dams..(as if...), but
    ventlation codes are northern based, we can but follow.

    The public has a skewed perception of code based on the builders
    and contractors they deal with..these people dis code..home owners
    follow suit. you don't hear the builder telling the home owner that
    code is the legal MINIMUM that can safely be accepted..bet home owners
    would make the jump to...better than code...what a concept!!

    pstu..joe also got himself in a mess with foam roofline installs in Atlanta.
    closed cell holds moisture, we need open call to allow moisture to
    dry...guess this is 'experience'.(LOL!)
    not dissing the man at all..I think he really knows stuff..and is willing
    to learn what does and doesn't work. we need more folks willing
    to walk the walk.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  8. #229
    Join Date
    Apr 2002
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    11,808
    he was always one for allowing moisture a way out if it got in
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  9. #230
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
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    11,338
    Quote Originally Posted by Carnak View Post
    he was always one for allowing moisture a way out if it got in
    Until I read articles written by Dr. Joe I had not the vaguest concept of moisture drives through wall assemblies. Also enlightening: the hollow building.

    Pertaining to the latter, my first full time job right out of high school was at a Marriott hotel in Dallas, TX in the maintenance department (which hotels call "engineering", a term often apt for what the "engineers" must do to keep the good ship "hotel" afloat). I was tasked with learning vinyl wallpaper repair from our resident expert, who could cut out a gouged section of vinyl in the hallway, and no matter how complex the pattern, patch it with new vinyl to where it was nearly impossible to tell. Anyway, I saw many of the pink patches Dr. Joe often writes about, and replaced my fair share of same, only to have patch job go pink again at some point. Never in my young man's' mind did it enter that a vapor/air drive combined with cold interior surfaces via the PTACs (that I was also charged to learn about) the culprit.

    I did learn during my time at the hotel how it was built, being naturally curious about such stuff. I can now see it was the perfect storm for a mold and mildew factory, just as so much of our residential construction in hot climates is the perfect storm of being exactly wrong for the climate in which it is to perform.

    We can keep on perpetuating the same tired stupidity, or we can learn from our mistakes, alter the codes, and give sustainability some actual real world meaning vs. green marketing mania.
    • 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.

  10. #231
    Join Date
    Apr 2002
    Posts
    11,808
    ptacs and all the hotel bathrooms lined up with common exhaust risers with central fans are a complete disaster here, "indoor rain makers"

    A framed building like that , with fibreglass in the stud cavities, is just a massive filtered fresh air intake

    "It works great in Arizona"
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  11. #232
    Join Date
    Apr 2002
    Posts
    11,808
    I plagerized your constant battle with pink patches this morning on an investigation.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  12. #233
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    2,110
    Going clear back to the 8th thread, you say there are plenty of soffit vents, but are they open. When I check the attic for insulation before doing a load calc I usually find the soffit vents are closed off with insulation that was added later to lower utility bills. IF the vents are blocked, it doesn't matter how many you have.

  13. #234
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,338
    Quote Originally Posted by Carnak View Post
    ptacs and all the hotel bathrooms lined up with common exhaust risers with central fans are a complete disaster here, "indoor rain makers"

    A framed building like that , with fibreglass in the stud cavities, is just a massive filtered fresh air intake

    "It works great in Arizona"
    The Marriott, eleven stories tall, had central exhaust fan stacks for paired guest room baths from top to bottom. Each guest room was separated from one another with hadite block CMU covered with drywall over furring strips. There's your hollow points right there, and the area over the entry was furred down, even though it did not contain a fan coil. The exhaust grills in the baths were in the lowered ceiling, IIRC, so any leakage in the ducting above the ceiling drywall would make the entire furdown void go negative, pulling make-up air from whereever it could.

    And...to add insult to injury, the exterior walls of each guest room were nothing but aluminum storefront framing, sliding glass door, and a hardi-board like panel directly over the PTAC. Whatever vapor drive there is through a substance like that, the vinyl wallpaper above the PTAC indicated it was an ongoing reality.
    • 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.

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