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  1. #40
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    To be fair, it is a more complex issue than either "side" of this argument has expressed.

    There are variations in construction quality and style from region to region, and within a region. Differences in what the primary reason for venting the attic is, etc..

    I think we can pretty much all agree that slapping a powered attic ventilator and some soffit vents in the average home "as built" is going to have some undesirable consequences.
    This fact has been well established by basically everybody that has ever made a study of the subject.

    We can also agree that it is possible to seal the conditioned space off from the attic well enough to prevent most of the usual list of undesirable consequences of PAV's from being an issue.
    I say "most" because, short of replacing all of the offending combustion appliances with sealed combustion 100% outside combustion air models, you cannot used forced attic ventilation in a home that has combustion appliances located in the attic, or that draw their combustion air from the attic.
    That bit excludes a good 2/3 or more of the homes in my service area from using PAV's.

    So lets say we have established agreement that the average home needs some improvement before going forward with using a PAV, and that except for specific exclusions, it is possible to make enough improvements to allow the use of a PAV without undesirable air leakage from the conditioned space.

    Now we have to look at how much those improvements will cost, vs what they will save.

    In most cases, most of the improvements will be worthwhile in and of themselves, regardless of how the attic is ventilated, so on average are not really factors in the PAV vs no PAV debate.

    So lets take an average all electric home that we have sealed adequately to prevent air movement between the conditioned space and the attic, and has a continuous soffit vent with plenty of free area.
    Now we have to decide between a PAV and effective passive ventilation.

    Unfortunately there is only very limited information available from the building science community to help with that decision.

    If you stitch together the handful of very small scale studies that have been done under relatively ideal conditions on properly sealed instrumented test houses, the data suggests that the energy savings from a PAV will be only little higher than the energy input to operate it.
    The sample size of the instrumented house testing that has been done is very small though, so the results are not conclusive.

    While I'll admit that there are situations where a PAV is a perfectly acceptable attic ventilation method, for now I'm sticking to my blanket recommendation against them in my part of the country.
    To be quite honest, the average quality of construction in my area, even on $million+ homes, is horrible. Little attention is paid to the integrity of the pressure or thermal envelope of the homes.
    In most cases it is not even remotely economically feasible to do much more than seal the big leaks enough to stop naturally occurring air movement between the conditioned and unconditioned spaces.
    In most of the 2 story homes around here, it would be an expensive effort in near futility, that may require some reconstruction of parts of the house, to try to seal well enough against a mechanically induced pressure difference.

    I've mentioned the combustion appliance issue enough already, but I understand that not all parts of the country do stupid crap like put furnaces and water heaters in attics, or duct their combustion air from the attic.

    My recommendation, for my area, will continue to be effective passive ventilation, a radiant barrier, sealing the ducts as tight as possible, sealing the big leaks between the conditioned space and the attic, and blowing in more insulation.
    If more government is the answer, then it's a really stupid question.

  2. #41
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,943
    Quote Originally Posted by tipsrfine View Post
    The percentage of HVAC contractors who would know how, and perform, air sealing in conjunction with an attic fan install is likely to start out with a .00%

    I can honestly say you & robo can be blamed for not understanding what I wrote. It has degraded into silliness, but you are adding to it.
    Nope! Still doesn't make any sense. I still have no clue as to what your point is.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  3. #42
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,965
    Quote Originally Posted by RoBoTeq View Post
    Nope! Still doesn't make any sense. I still have no clue as to what your point is.
    Turn it into a poll question or something. I'm done with it unless provoked.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  4. #43
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,943
    Quote Originally Posted by tipsrfine View Post
    Turn it into a poll question or something. I'm done with it unless provoked.
    You never made a point. There is nothing to poll. You came out of the blue with some off the wall comment that had no relevance to anything and then refused to explain what the heck you were talking about.

    Are you even in the HVAC industry?

    Geez...I just checked out your website. No wonder you are acting the way you are. You really have a disdain for HVAC contractors and HVAC techs, don't you?

    Now that I know where you are coming from and how you feel about our industry professionals, I can just avoid your negative commentaries about HVAC professionals.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  5. #44
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,943
    Quote Originally Posted by captaincompressor View Post
    My Home Has two units...One up and one down. My house cools much easier since I have two 1300 cfm attic power fans that are on thermostats. One thermostat is set on 90F and the other is on 95F. This way the fans sort of operate in a two stage arrangement. I have plenty of make up air coming in the attic from outside so the attic does not get into a negative static pressure pulling my ac or interior air from the conditioned space. Plenty of make up air vents is key.

    I have my upstairs air handler in the attic horizontally mounted just above the floor with a diversitech overflow metal pan under it that has its own backup drain line. I also use a condensate cop switch that break the red wire to stop the unit if the pan gets water in it.

    I used four layers of reflective bubble insulation on my ducts and entire air handler. I know this may sound stupid but it works. I also used foil duct tape and completely sealed my air handler access panels and insured all screws were tight. I know this will make it a pain to work on but I can deal with that.

    I have no problems with efficiency or air losses to my attic. My attic door is well sealed and all penetrations to the attic are siliconed around wires and cables.

    I filled around the register boots on the attic side with expanding foam insulation so I do not have sweating issues and thermal losses around register boots in the ceiling.

    Attic fans when properly installed a good thing and necessary in my opinion.
    IMPOSSIBLE! Don't you know that there is a .00% number of HVAC professionals that understand what you claim to have actually done?......

    Well, maybe you raised to bar to 0%, which we now know is a higher value than .00% is. So, good job.....

    Now get your post count up so you can apply for professional membership and see what's on the dark side of this site.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  6. #45
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,965
    Quote Originally Posted by RoBoTeq View Post
    You never made a point. There is nothing to poll. You came out of the blue with some off the wall comment that had no relevance to anything and then refused to explain what the heck you were talking about.

    Are you even in the HVAC industry?

    Geez...I just checked out your website. No wonder you are acting the way you are. You really have a disdain for HVAC contractors and HVAC techs, don't you?

    Now that I know where you are coming from and how you feel about our industry professionals, I can just avoid your negative commentaries about HVAC professionals.
    OK, I've been provoked; but I'm watching Master Chef, so I have to wait. We should take this to a pro only forum so I can unload on you Robo. Just kidding about the unloading part, but I would welcome debating this and other HVAC/Building Science Topics in the closed forums. You will lose. Challenge.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  7. #46
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,943
    Quote Originally Posted by tipsrfine View Post
    OK, I've been provoked; but I'm watching Master Chef, so I have to wait. We should take this to a pro only forum so I can unload on you Robo. Just kidding about the unloading part, but I would welcome debating this and other HVAC/Building Science Topics in the closed forums. You will lose. Challenge.
    I still have no idea what it is that you are even debating. You don't even know that nothing expressed two different ways is still nothing.

    I am providing you some lyrical training to help you with your deficiency in mathamatics....enjoy and learn; http://www.youtube.com/watch?feature...&v=KQ5-BTdcqjk
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  8. #47
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,326
    Quote Originally Posted by RoBoTeq View Post
    I still have no idea what it is that you are even debating. You don't even know that nothing expressed two different ways is still nothing.

    I am providing you some lyrical training to help you with your deficiency in mathamatics....enjoy and learn; http://www.youtube.com/watch?feature...&v=KQ5-BTdcqjk
    You beat me to it!

    Billy Preston = math whiz.
    • 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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