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  1. #14
    Join Date
    Sep 2005
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    Atlanta GA area
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    21,079
    Quote Originally Posted by Timber View Post
    These foam houses really do not impress me so far. Especially if u need an ERV or even worse a dehumidifier. Seems u just need more equipment to deal with the tightness of the home. Then u got to maintain / repair this additional equipment.

    If I built again dont think I would use foam. JMO
    Here in the Atlanta area... I know a couple of spec builders.

    They do the roof (under the roof) with foam, then use conventional insulation in the walls. The result seems to work out as a good compromise.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  2. #15
    Join Date
    Nov 2001
    Location
    East Texas
    Posts
    898
    Quote Originally Posted by ga-hvac-tech View Post
    Here in the Atlanta area... I know a couple of spec builders.

    They do the roof (under the roof) with foam, then use conventional insulation in the walls. The result seems to work out as a good compromise.
    Do you still need the ERV's / vetalation / or dehumidifiers ? If not, then I would consider that option.

  3. #16
    Join Date
    Sep 2005
    Location
    Atlanta GA area
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    21,079
    Quote Originally Posted by Timber View Post
    Do you still need the ERV's / vetalation / or dehumidifiers ? If not, then I would consider that option.
    Mostly no. Depends on how tight one builds the house... but generally no.

    The main thing about a foamed attic (under the rafters) is not having that 'oven' just above the ceiling of the upper floor.

    Hope this helps.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  4. #17
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,373
    Quote Originally Posted by Timber View Post
    These foam houses really do not impress me so far. Especially if u need an ERV or even worse a dehumidifier. Seems u just need more equipment to deal with the tightness of the home. Then u got to maintain / repair this additional equipment.

    If I built again dont think I would use foam. JMO
    Any well built home needs fresh air ventilation to pruge indoor pollutants and renew oxygen during the calm warm weather. Even worse, supplemental dehumidication is needed in green grass climates if you want the best in comfort and avoid growing mold/dust mites.
    ASHRAE, American, Lung ASS, EPA and most modern building codes suggest mechanical fresh air ventilation for the above reasons.
    The posters on this site represent traditional opinion not the building research community. Check out the above IAQ experts or researchers like Building Science.com for the state of the art specifications.
    It hard to part with tradition when dealing a changing industry.
    I have been involved with IAQ for 25 years and find is hard to believe how difficult is has been to get the concept of controlled fresh air ventilation and real humidity control in a modern well built home.
    Good luck on getting a quality home to live in.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  5. #18
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,724
    TIPS, I've yet to see load, modeling or any cost/benefit software that can accurately reflect the energy or load impact of foam.

    As you may be seeing in these threads, guys talk about going to foam houses on 100f days and the equipment doesn't run once the whole time they are there. That indicates gross oversizing to me, how about you?

    Quote Originally Posted by teddy bear View Post
    Good luck on getting a quality home to live in.
    Regards TB
    Since you were considerate enough to respond I guess I'll drop in behind you.

    I think when people don't do or ask what the numbers are, they're defining their ability to make smart decisions.

    Some would rather pay $2 per sf/year for energy than $0.25 per sf/year for energy and $0.50 per sf/year for the increased mortgage for the better home. To me that's living in a crappy home and throwing away $1.25 per sf a year.

    The difference between ignorance and stupidity is ignorance doesn't yet know, stupidity doesn't have the capacity to know.
    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. #19
    Join Date
    Sep 2005
    Location
    Atlanta GA area
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    21,079
    Quote Originally Posted by tedkidd View Post
    TIPS, I've yet to see load, modeling or any cost/benefit software that can accurately reflect the energy or load impact of foam.

    As you may be seeing in these threads, guys talk about going to foam houses on 100f days and the equipment doesn't run once the whole time they are there. That indicates gross oversizing to me, how about you?



    Since you were considerate enough to respond I guess I'll drop in behind you.

    I think when people don't do or ask what the numbers are, they're defining their ability to make smart decisions.

    Some would rather pay $2 per sf/year for energy than $0.25 per sf/year for energy and $0.50 per sf/year for the increased mortgage for the better home. To me that's living in a crappy home and throwing away $1.25 per sf a year.

    The difference between ignorance and stupidity is ignorance doesn't yet know, stupidity doesn't have the capacity to know.
    Sometimes stupidity knows and does not care... I hate to see that... but it is out there.

    I cannot tell you the number of folks that say: Gee, it will not pay back in a year... why bother. Amazing IMO.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

  7. #20
    Join Date
    May 2009
    Posts
    274
    The homes we have done were so tight they really needed a dehumidifier to remove moisture. An 85 degree day was simply not enough to cause the units to run with the stat set at 78. Gross oversizing?

    Well even 2 stage units are "grossly oversized" on a light load day with a homeowner who doesn't have thermostat set as low as the "design conditions" were determined in the load calc.

    Not to mention that big oak tree on the west side of the house that reduces the load by 3/4 ton in some circumstances. Needless to add, the load calc is a great tool, but it does not answer all things.

  8. #21
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,373
    Quote Originally Posted by ChaseAir View Post
    The homes we have done were so tight they really needed a dehumidifier to remove moisture. An 85 degree day was simply not enough to cause the units to run with the stat set at 78. Gross oversizing?

    Well even 2 stage units are "grossly oversized" on a light load day with a homeowner who doesn't have thermostat set as low as the "design conditions" were determined in the load calc.

    Not to mention that big oak tree on the west side of the house that reduces the load by 3/4 ton in some circumstances. Needless to add, the load calc is a great tool, but it does not answer all things.
    Good post but there is some confusion. During high dew point summer weather, extremely air tight homes have less moisture moisture infiltration than the excessively leaky homes. The sources of moisture in all homes is the infiltration/ventilation of outside fresh air and the occupants.
    Well insulated air tight homes need mechanical fresh air ventilation when occupied. Yes the a/c will not run enough to remove the mositure from the minimal fresh air ventilation and the occupants. This is usually 2-4 lbs. of dehumidification moisture per hour. Let the a/c run as much as needed to maintain the desire temperature and use a high efficiency dehumidifier to remove the enough of the remaining moisture to maintain <50%RH. When the home is unoccupied, the t-stat can be raised to avoid any cooling. The dehu will maintain <50%RH at a fraction of the cost of trying to cool to <50%RH.
    Sorry about picking on a small point, but there is a lot of confusion about these issues. Thanks for the support.
    REgards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  9. #22
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,966
    Quote Originally Posted by teddy bear View Post
    Good post but there is some confusion. During high dew point summer weather, extremely air tight homes have less moisture moisture infiltration than the excessively leaky homes. The sources of moisture in all homes is the infiltration/ventilation of outside fresh air and the occupants.
    Well insulated air tight homes need mechanical fresh air ventilation when occupied. Yes the a/c will not run enough to remove the mositure from the minimal fresh air ventilation and the occupants. This is usually 2-4 lbs. of dehumidification moisture per hour. Let the a/c run as much as needed to maintain the desire temperature and use a high efficiency dehumidifier to remove the enough of the remaining moisture to maintain <50%RH. When the home is unoccupied, the t-stat can be raised to avoid any cooling. The dehu will maintain <50%RH at a fraction of the cost of trying to cool to <50%RH.
    Sorry about picking on a small point, but there is a lot of confusion about these issues. Thanks for the support.
    REgards TB
    How does having one of your de-humidifier included in the design of one of these "tight" homes affect the manual j load, and for that matter the manual S calc?
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  10. #23
    Join Date
    May 2009
    Posts
    274
    We used the dh90 from Honeywell. Yes ALWAYS have fresh air. The offgassing of that foam has to be toxic as you can smell it years later. On one home we pulled the air out of the attic. I would think the systems would last longer as they hardly run and do not cycle back on rapidly. Great for warranty service. Dh90 is Probly not big enough for these areas but man that 180 is expensive. Is there a better one?

  11. #24
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,373
    Quote Originally Posted by tipsrfine View Post
    How does having one of your de-humidifier included in the design of one of these "tight" homes affect the manual j load, and for that matter the manual S calc?
    Good question. The dehumidifier will not have any effect on your manual J calc. The dehumidifier will not run during high cooling loads because the a/c removes more than enough mositure to maintain <50%RH. If the a/c is not maintaining <50%RH during peak cooling load, slow the air flow to get a colder a/c cooling coil. The a/c coil should be 25^F cooler than the desired temp in the home to remove enough moisture.
    As the cooling load declines during the evening hours or on a rainy day, the indoor RH will exceed 50%RH. The dehumidifier will be activated by the dehumidistat removing the excess moisture keeping the home at <50%RH.
    The Honeywell dehumidifier is a good dehumidifier. A 90 dehu will handle large air home with 70-90 cfm of fresh air ventilation and 4 occupants.
    The best dehumidifier is the Ultra-Aire with DEH 3000 controller for scheduled fresh air ventilation. Certianly the Honeywell is ok. There are others that work I am sure.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  12. #25
    Join Date
    Jul 2006
    Posts
    1,091
    Quote Originally Posted by tipsrfine View Post
    Could one of the pro's do a quick comparison test with their manual j calcs to answer a question I have? Take any house that you have a manual j done on and leave everything the same except for the attic (with no ducts or air handler in attic) and see what happens to the load when you change from a vented attic with traditional insulation levels of fiberglass or cellulose on the attic floor(whatever the R-level is for your area) to an attic spray foamed at the roof with 3 inches of foam (closed cell and/or open cell). Which method results in a higher cooling load? Remember, no ducts in attic. Thanks to anyone willing to do this.
    2668 sq ft home
    R38 Ceiling
    R13 Walls
    Total 22506
    Sensible 18025
    Latent 4479

    R25 Foam Encapsulated
    R13 Walls
    Total 20720
    Sensible 17494
    Latent 3226

    Add duct in the attic

    R38 Ceiling
    Total 33307
    Sensible 26707
    Latent 6600

    R25 Foam Encapsulated
    Total 26620
    Sensible 21476
    Latent 5144

  13. #26
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    21,079
    Quote Originally Posted by rickboggs View Post
    2668 sq ft home
    R38 Ceiling
    R13 Walls
    Total 22506
    Sensible 18025
    Latent 4479

    R25 Foam Encapsulated
    R13 Walls
    Total 20720
    Sensible 17494
    Latent 3226

    Add duct in the attic

    R38 Ceiling
    Total 33307
    Sensible 26707
    Latent 6600

    R25 Foam Encapsulated
    Total 26620
    Sensible 21476
    Latent 5144
    It would appear the BIG advantage is if the system (equipment and ducts) is in the attic. Logical for the style of construction down here... probably not that big a deal in areas where equipment and ducts are in conditioned space.
    GA-HVAC-Tech

    Quality work at a fair price with excellent customer service!

    Romans Ch's 5-6-7-8

    2 Chronicles 7:14

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