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  1. #1
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    ASHRAE 62.2 or not?

    I think it would be best to make a new thread for pro and con arguments about ASHRAE 62.2 ventilation standards. I am very interested in factual arguments contrary to my thinking. Kmills from Florida has expressed this skepticism about whether a house needs mechanical ventilation at all:
    http://www.energystar.gov/ia/new_hom...20Builders.pdf

    His comments included:
    >>ASHRAE 62.2 was developed without doing a cost study of any detail.
    >>no wonder states aren't in a rush to make it part of their mechanical code.


    My own opinion is that I want *some* additional mechanical ventilation for my own house, but won't try to say everybody should. Yes it is certainly true that outside air carries a latent load which needs to be dealt with somehow. However you deal with it, it will carry an energy cost. Over a long time I have been convinced that Teddy Bear has a powerful point -- that a ventilating dehumidifier is the only technology capable of delivering fresh air without raising indoor humidity.

    Here is one article which I find relevant:
    ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++
    http://www.ehponline.org/members/200...novations.html

    '...Until the mid-1970s, building ventilation standards called for approximately 15 cubic feet per minute (cfm) outside air for each building occupant. Following the 1973 Arab oil embargo, however, national energy conservation measures called for a reduction of outside air to 5 cfm per occupant. Experts thought this would be sufficient to ensure adequate health and comfort, but they were quickly proven wrong.'

    'Complaints from building occupants increased, becoming commonplace in the 1980s and 1990s and bringing "sick building syndrome" into the public lexicon. In response, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has since revised its ventilation standard 62-2001 to provide a minimum of 15 cfm outside air per person, or 20 cfm per person in office spaces. This standard has been adopted by all the major building codes, which in turn have been incorporated into enforceable local building codes.'
    ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++

    If anything I post is misleading or not good info, I strongly request people to post and offer a correction. Better I learn what's right on an online board, than to experience any unnecessary problems with my own house<g>!

    I ask Kmills to contribute more to this thread if he feels comfortable doing so. While I was a little hostile on the "Ventilating Dehumidifier" thread, it was personal reasons only. Please accept my apologies for not maintaining a nicer attitude.

    Best wishes -- Pstu

    [Edited by pstu on 03-10-2006 at 09:38 AM]

  2. #2
    let me take this chance to clarify my position on 62.2...

    in a hot humid climate, moisture is a much bigger problem than our northern friends experience- practically year round... bringing fresh air in the home should be the LAST step taken to assure IAQ.(unless necessary for gas/makeup air and maintaining design pressures, or handling high occupancy or CO, CO2 issues)

    #1) moisture removal... so many GREAT products available in variable speed A/H's, advanced control systems and two stage cooling that do a much better job than typical on or off cooling in removing humidity.
    #2)filtration... get the best you can afford electronic air cleaners do a fantastic job but not in everyones budget...
    #3)tightly sealed and well insulated homes and duct... again the best that fits your budget..dont forget the big picture...
    #4)UV lights... they kill airborne viruses, fungus, bacteria and can control growth on the cooling coil...

    at this point you have a GREAT system! ....indoor pollutants should be at acceptable levels by now!

    #5)fresh air...at a cost... increased system load and loss of efficiency... possibly additional equipment to remove humidity...but absolutely necessary for gas fired equipment or excessive exhaust equipment, controlling unwanted infiltration and maintaining positive pressure...

    just makin myself clear there ARE benefits to fresh air but they should be looked at on a case by case basis because there are draw backs in a southern climate especially if humidity is a concern... if you still have money left over from buying the best products you can find for #1-4 then adding fresh air to the home can always be done later to address a specific issue or just to have every angle of IAQ covered.

  3. #3
    >I ask Kmills to contribute more to this thread if he feels comfortable doing so. While I was a little hostile on the "Ventilating Dehumidifier" thread, it was personal reasons only. Please accept my apologies for not maintaining a nicer attitude.

    Best wishes -- Pstu


    no hard feelings -- sorry I hijacked your thread
    Kmills

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Originally posted by kmills
    let me take this chance to clarify my position on 62.2...

    in a hot humid climate, moisture is a much bigger problem than our northern friends experience- practically year round... bringing fresh air in the home should be the LAST step taken to assure IAQ.(unless necessary for gas/makeup air and maintaining design pressures, or handling high occupancy or CO, CO2 issues)

    Kmills, thanks for making your points and allowing the discussion. One point at a time. True, more total latent load closer to the Gulf. But, the highest averge monthly on record is St. Louis MO. The midwest states with the fresh water lakes have a high dew point but fewer months. All green grass climates have enough moisture that high latent load is present with low sensible loads. Maintaining <50%RH is always difficult with rainy cool weather. Renewing oxygen and purging indoor pollutants(VOCs from indoor materials) are the main need for ventilation. Clothes drier, bathfans, kitchen hood, and other appliance all require make-up air to function. On a windy day, the homes breathes much better than on quiet day by a factor of 5. 50 cfm of make-up air has little impact on a windy day. On a quiet days, 50 cfm make-up air is all fresh air the home gets. The overall increased impact of 50 cfm of is less than a couple hundred dollars a year.
    Two adults in a bedroom with a closed door without air circulation will exceed 2,500 ppm CO2. Not ideal but not life threatening. Many of the long term effects of other internal pollutants are unknown. It makes sense to avoid living in a plastic bag and strive for some balance with a minimal fresh air source. More to follow.. I must say, ptsu, you make me proud. TB

  5. #5
    Here is one article which I find relevant:
    ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++
    http://www.ehponline.org/members/200...novations.html

    '...Until the mid-1970s, building ventilation standards called for approximately 15 cubic feet per minute (cfm) outside air for each building occupant. Following the 1973 Arab oil embargo, however, national energy conservation measures called for a reduction of outside air to 5 cfm per occupant. Experts thought this would be sufficient to ensure adequate health and comfort, but they were quickly proven wrong.'

    'Complaints from building occupants increased, becoming commonplace in the 1980s and 1990s and bringing "sick building syndrome" into the public lexicon. In response, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has since revised its ventilation standard 62-2001 to provide a minimum of 15 cfm outside air per person, or 20 cfm per person in office spaces. This standard has been adopted by all the major building codes, which in turn have been incorporated into enforceable local building codes.'

    this is standard commercial application not residential... commercial buildings by their very nature have different needs than the average home....

  6. #6
    Join Date
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    Madison, WI/Cape Coral, FL
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    Originally posted by kmills
    let me take this chance to clarify my position on 62.2...

    #1) moisture removal... so many GREAT products available in variable speed A/H's, advanced control systems and two stage cooling that do a much better job than typical on or off cooling in removing humidity.
    Next point, yes the new systems remove more humidity and do a better job. They are more complicated and cost alot more money. With all the complexity, they still require a significant cooling load to remove the 70-100,000 btus of latent load everyday to maintain <50%RH. They are unable to provide any kind of humidity without cooling the home during unoccupied times. This makes it impossible to take advantage of t-stat setup during routine vacancy. Is it acceptable to let the indoor %RH float when its 65-70^F, raining, and providing 75 cfm of fresh air in the home? It's ok for a day but not several days. Uncomfortable and unhealthy. For the increased cost of the of the most complicated a/c systems, a whole house ventilating dehumidifier canbe added to a high SEER a/c. Heat pumps are another problem because of having to sizing for heating load. This is not for everyone. Set 50%RH ac on or off regardless rain or not. I get to the next point tommorrow. TB

  7. #7
    Originally posted by teddy bear
    Originally posted by kmills
    let me take this chance to clarify my position on 62.2...

    #1) moisture removal... so many GREAT products available in variable speed A/H's, advanced control systems and two stage cooling that do a much better job than typical on or off cooling in removing humidity.
    Next point, yes the new systems remove more humidity and do a better job. They are more complicated and cost alot more money. With all the complexity, they still require a significant cooling load to remove the 70-100,000 btus of latent load everyday to maintain <50%RH. They are unable to provide any kind of humidity without cooling the home during unoccupied times. This makes it impossible to take advantage of t-stat setup during routine vacancy. Is it acceptable to let the indoor %RH float when its 65-70^F, raining, and providing 75 cfm of fresh air in the home? It's ok for a day but not several days. Uncomfortable and unhealthy. For the increased cost of the of the most complicated a/c systems, a whole house ventilating dehumidifier canbe added to a high SEER a/c. Heat pumps are another problem because of having to sizing for heating load. This is not for everyone. Set 50%RH ac on or off regardless rain or not. I get to the next point tommorrow. TB
    i dont agree that controls cost alot more money compared to the installation of whole house dehumidifier ...compare the cost of VS A/H and on/off A/H... optional humidistat controls with reduced fan speed... or variable speed control installation on existing equipment... results vs. cost... 70-100,000 btu latent load dramatically decreases in a well sealed home and 65-70 F days with high humidity are few and far between in hot and humid climates. also maintaining CONSTANT 50% RH is a moot point when it comes to personal comfort when temp and humidity both play a role but a very valid point in some cases (basements, preserving objects)... heat pumps are a problem? not compared to electric heat strips and the cost of energy...heat pumps are also sized for cooling load not heating...if additional load exists then it is handled by supplemental heating methods or the heat pump can be placed in the role of supplemental heat and teddy bear what does a H/P have to do with IAQ?

  8. #8
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    read the comments at BUILDINGSCIENCE.com

    BTW, low humidity here in Huntsville AL is anything under 85%! we had 65% yesterday before the rain at 4p.

    And, you should have lived in St Louis before a/c. I lived there from 1946- 1953 -- we had oscillating fans & ate supper behind house in shade= sandwiches to keep from cooking!
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  9. #9
    Join Date
    Jun 2004
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    4H: Hot, Humid Houston H.O.
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    Second that opinion

    I am very glad to hear from the people in the discussion. Now I understand the position of Kmills much better, and that helps. However I may not adjust my conclusions all that much, we shall see.

    I tend to agree about considering every other assist, before resorting to a ventilating dehumidifier. My position is that I *have* considered the other methods and found them wanting, therefore I am forced to agree with the person who sells dehumidifiers for a living. Of course it's good for me to reconsider each option until I am sure of the conclusion. I plan to offer a couple of reports originating with Lstiburek's Building Sciences Corporation later today. BSC completely accepts the need for ASHRAE ventilation, despite the irony that BSC would like to see ASRAE numbers replaced with something better. If you search using the word "Lstiburek" there is a world of quality study to be found.

    Best wishes -- Pstu

  10. #10
    Join Date
    Apr 2002
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    For years ASHRAE would just publish a design dry bulb temperature with a coincidental wet bulb temperature. Wet bulb indicates total heat but these old design parameters had people designing systems for a target 'hotness' outside and dealt with the humidity at this hotness.

    The problem is in many places is the highest ambient dewpoints do not coincide with the hottest outdoor temperatures.

    So systems designed for the old conditions can handle the temperature but they can not handle the humidity. Having the humidity peaking at less than design dry bulb situations is a double edged sword.

    1)The system is not designed to remove enough moisture in the first place
    2) With dewpoint peaking during lower dry bulbs, the systems can easily short cycle off as they are controlling temperature. A lot of band aids on old systems like electric reheat being retrofitted, but you can still end up short on the latent capacity.

    Now you have design humidity levels to deal with, I think ASHRAE has been publishing them since about 1993.

    The cadallac system in the hot humid environment is a 100% outside air unit, something that could deliver dry air without the full reheat of a dehumidifier. Something that supplies dry air from high 60s to room temperature. You get your constant supply of fresh air and the positive pressure it creates can pretty much stop infiltration in a reasonably well bulit home.

    A waste of time pressurizing something with the envelope integrity of swiss cheese. 100% outside air units are available but extremely expensive. Tough to make for the lower CFM needed for homes but available. Actually the blower wheel itself is a challenge.

    Somewhere along the line, I remember some one saying the 5 CFM per person came from old mine ventialtion strategy, the miners would get dopy and unproductive with less air than that. Builidngs tightened up and it moves to 15 to 20 CFM a person, areas with cigarette smoke even higher.

    On a residential basis, something which provides an higher level of ventilation intermittently, will provide decent IAQ and while running keeps the humid air out. In the hot humid environment CONSTANT negative pressure is a problem as it creates CONSTANT infiltration of humid air.

    I just have a problem with 'thou shalt always maintain less than 50% RH' and forcing in constant fresh air, when a compressor cycles off. You pay to remove moisture from the home, then as soon as it cycles off, you are pumping the moisture right back into the space.

    As I was alluding to in the other thread (hi-jacked too funny by the way with two people talking), I just received the latest ASHRAE IAQ and it goes on about the problem of over ventilating by meeting 62 in a hot humid climate.

    Easy to burn some extra fuel in the north for the ventilation air, hard to deal with 80F dewpoints without custom built stuff.

    Office buildings systems can handle the 20 CFM per person. Something with a denser occupancy, and higher internal latent gains is a real challenge to ventilate to ASHREA 62.

    A free chapter from a decent book http://www.masongrant.com/pdf/design...DG_C7_Mold.pdf

    [Edited by Carnak on 03-11-2006 at 09:31 AM]
    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. #11
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    We are in the 'dry season' right now, conditions at 9 AM 82F with 79F dewpoint, lol
    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. #12
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Originally posted by kmills
    [

    i dont agree that controls cost alot more money compared to the installation of whole house dehumidifier ...compare the cost of VS A/H and on/off A/H... optional humidistat controls with reduced fan speed... or variable speed control installation on existing equipment... results vs. cost... 70-100,000 btu latent load dramatically decreases in a well sealed home and 65-70 F days with high humidity are few and far between in hot and humid climates. also maintaining CONSTANT 50% RH is a moot point when it comes to personal comfort when temp and humidity both play a role but a very valid point in some cases (basements, preserving objects)... heat pumps are a problem? not compared to electric heat strips and the cost of energy...heat pumps are also sized for cooling load not heating...if additional load exists then it is handled by supplemental heating methods or the heat pump can be placed in the role of supplemental heat and teddy bear what does a H/P have to do with IAQ? [/B]
    I assumed you were refering to two speed a/c regarding high cost. As a basic system, I agree with VS AH setup for max latent to the point of avoiding condensation on the equipment and providing adequate circulation. My Heat pump comment had to do with oversizing the a/c to provide enough heat.
    With typical weather, a couple hot days and a wet day, you are ok. A wet couple weeks are different story. Draughts and wet weather come in streaks of a week-month. The rational for <50%RH is to avoid dust mites in bedding and upholstered furniture. Mold under carpets on concrete require <50%RH. A week of high indoor humidity starts the problems. I have no problem with your comments as long as with the customer understands what is going to happen inside the home while a 10 day cool, low pressure system hangs over the home for a week or two. We fix hundreds of homes every year that have the best of systems that are unable to avoid mold and dust mites. You are right that supplemental dehumidification can be added later. Most buy the most expensive 2 speed a/c systems feeling all that the potiental problems are taken care of and the IAQ is the best. No fresh air, poor humidity control during wet cool weather, and overcooling during moderate temperatures are problem. I give up on UVs. Lite up if you must. TB

  13. #13
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    Apr 2002
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    Kirby vacuum salesman and duct cleaners like to talk about dust mites and their dung too.

    Carpets on concrete can be problematic. I am lucky there is so much beach sand here it makes carpets a pain in the a$$.

    When mold first 'germinates' its not sucking the water out of the air, it gets its water from a wet food source. The RH of the air is irrelevant. A wet surface will get moldy anywhere in the world.

    The wet surfaces tend to dry out faster with low RH.



    [Edited by Carnak on 03-11-2006 at 01:04 PM]
    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/

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