Here in the Atlanta area... I know a couple of spec builders.Quote:
Originally Posted by Timber
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.
Here in the Atlanta area... I know a couple of spec builders.Quote:
Originally Posted by Timber
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.Quote:
Originally Posted by ga-hvac-tech
Mostly no. Depends on how tight one builds the house... but generally no.Quote:
Originally Posted by Timber
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.
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.Quote:
Originally Posted by Timber
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
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.Quote:
Originally Posted by teddy bear
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.Quote:
Originally Posted by tedkidd
I cannot tell you the number of folks that say: Gee, it will not pay back in a year... why bother. Amazing IMO.
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.Quote:
Originally Posted by ChaseAir
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?Quote:
Originally Posted by teddy bear
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?
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.Quote:
Originally Posted by tipsrfine
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
2668 sq ft homeQuote:
Originally Posted by tipsrfine
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.Quote:
Originally Posted by rickboggs