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  1. #1

    New house/foam insulation/fresh air question

    I am in a new home that is approx. 3400 sq. ft. and have 2 a/c units along with foam insulation. Had major issues/differences with HVAC installer regarding fresh air which resulted in him quitting after roughing everything in. He did not believe fresh air was needed but reluctanly ran vents from the outside into the air handlers. (foam installer refused to put the insulation in the house without fresh air) My issue is that my son has asthma and we all have allergies which makes me worry about the IAQ. Wish I had seen this site while I was building. Interested in all opinions/suggestions regarding this issue. We live in the deep south where it is hot and humid. Thank you very much.

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    What climate, number of occupants, basemen/crawlspace,and fuel sources?
    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"

  3. #3
    Join Date
    Aug 2003
    Posts
    906
    You need a lot of fresh air in a new home. When new, many things outgas solvents or chemicals like formaldehyde. Foam makes a very tight house, so mechanical ventilation is needed. For allergies, it depends what you're allergic to. In general, filtering as much as possible of the incoming air is much more effective than trying to recapture allergens after they've been introduced into the home. For example, a small HEPA filter inline with the fresh air intake (perhaps wired with a relay to run when the HVAC system fan runs) would be a much more effective solution than a much larger HEPA running separately or a number of portable HEPAs running throughout the house. My favorite solution, after years of trying many different things, is to condition (filter, dehumidify & cool) a steady stream of fresh air. Unfortunately, DOAS (Dedicated Outdoor Air Systems) are mostly a commercial solution. I don't know of any residential systems. I believe it's because the capacity needed ranges from about 1/2 to 1.5 tons so they would be small things in a small market so nobody bothers.
    -If you won't turn it on then nothing else matters.

  4. #4
    Join Date
    Aug 2003
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    906
    If I had a house big enough for 2 HVAC systems, I'd think about dedicating one to bringing in fresh air. I'd make it the smallest size available (1.5 tons), perhaps a heat pump, and distribute that evenly throughout. I'd fit it with large filters so the air would flow slowly through them: a MERV 11 prefilter, a carbon-filled element (honeycomb type with several pounds of activated carbon) and finally a MERV 16 (20x25x4 size filters would be about right and provide a low pressure drop). It would need to have a variable blower speed that would run more slowly when outside air was hot and humid. Ideally it would regulate the dew point of the air exiting the system at no more than 50 degrees F. There would also be a dehumidifier with it, or it would be a humiditrol-type system.
    -If you won't turn it on then nothing else matters.

  5. #5
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    6,260
    Quote Originally Posted by Nugeman View Post
    I am in a new home that is approx. 3400 sq. ft. and have 2 a/c units along with foam insulation. Had major issues/differences with HVAC installer regarding fresh air which resulted in him quitting after roughing everything in. He did not believe fresh air was needed but reluctanly ran vents from the outside into the air handlers. (foam installer refused to put the insulation in the house without fresh air) My issue is that my son has asthma and we all have allergies which makes me worry about the IAQ. Wish I had seen this site while I was building. Interested in all opinions/suggestions regarding this issue. We live in the deep south where it is hot and humid. Thank you very much.
    Hello?? Are still out there?

    It would help to know where you located.
    Congrats on recognizing the need for fresh air ventilation to purge indoor pollutants and renew oxygen. Next point is the amount of fresh air and when to provide the fresh air. Most experts feel, you need enough fresh air to change the air in the home in 5-6 hours.
    In cold climates during moderate wind, expect that your home may get air change in 5-6 hours. The natural pressures from the stack effect and wind cause stale air to exfiltrate and fresh air to infiltrate. On the other extreme, during warm, calm weather, you get no natural infiltration because of the lack of pressure.
    Clearly, the fresh air ventilation is critical whenever you have the lack of natural infiltration. Also your clothes drier, kitchen/bath exhaust need make-up air to function.
    During calm, warm weather, usually 100 cfm of mechanical make-up fresh air when the home is occupied is suggested for a 2,000-3,000 sqft home.
    During cold, windy weather, much less mechanical fresh air required to supplement the natural ventilation. Also keep in mind, if the home is unoccupied for many hours per day, fresh air may be avoided. Also many hours during the year, outdoor conditions are neutral temp/humidity. The remaining occupied hours during the high moisture spring/summer/fall seasons have potiential for high moisture in the outdoor air. For comfort and to avoid mold/dust mites in the home, maintain <50%RH. This requires supplemental dehumidification for the times that the a/c does not operate enough to provide <50%RH in the home.
    An ideal method to provide fresh air and maintain <50%RH in the home is a whole house, ventilating dehumidifier. They blend the desire amount of fresh air with the house air, filter the blend, circulate the air throughout the home via a/c ducts. You set the amount of fresh air needed, when you want the air, and the %RH you want the home to be. When the a/c is cooling enough to provide <50%RH, the WHVdehu will dehumidify the home. A/c contractors/builder are not familar with this technology yet.
    Brands are older premium unit are Ultra-Aire/Honeywell/etc.
    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"

  6. #6
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,137
    chances are pretty small that hvac systems are sized correctly.
    probably not two 2 ton (or 1.5 ton) units.
    more than likely two 3 ton units 6tons X500 sq ft per ton = 3500sq ft.
    sizing used. possibly more.
    hopefully vs units so that oversizing can be regulated somewhat by fan speed.
    not suprised that hvac contractor quit..didn't understand anything
    other than what he/she has been doing for 20+ years.

    what type of make up air vents?
    does house require make up air?
    tested at less than .35 ach?
    where in the south?

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  7. #7
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    6,260
    Quote Originally Posted by energy_rater_La View Post
    chances are pretty small that hvac systems are sized correctly.
    probably not two 2 ton (or 1.5 ton) units.
    more than likely two 3 ton units 6tons X500
    what type of make up air vents?
    does house require make up air?
    tested at less than .35 ach?
    where in the south?

    best of luck.
    Explain how testing the home for less than .35 ach determines the need for make-up air.
    Regardless what the blower door test shows, the BD test is not proof that you do not need fresh make-up air during warm, calm weather. The BD test only proves that the home as leakage area somewhere in the structure. It does not tell you how much a home will leak when at the average winter temperature and average winter wind.
    During warm weather and calm, you get near nothing for pressure on the home. No pressure means no fresh air. Be safe and provide minimal fresh air when occupied during spring/summer/fall seasons.
    All this fuss about minimal sized a/c is all hard to understand. During moderate cooling loads, all a/cs are grossly oversized. Two speed a/cs using the super large cooling coils and low speed of the compressor and a low speed fan are unable to get enough moisture out of the home to maintain <50%RH. Add the moisture from minimal fresh air and the moisture from the occupants, you end up with a damp home.
    Add a good whole house ventilating dehumidifier for adequate fresh make-up air and <50%RH even with no cooling load. You can have an oversized a/c and still keep the home dry.
    Looks like our original poster make a clean getaway!
    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"

  8. #8
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,137
    TB
    the program I work with was until recently administered by state goverment
    I guess it still is, although in part federal goverment has come in also.
    the .35 ach was the 'safe' number they gave us..back in 2000
    lower than .35 the answer was to add fresh air.
    & you should have seen the people run from that!
    .35 was target for the powers that admin'd program.

    granted blower door testing is just a snapshot of at this particular
    time, under these forced depressurization levels..this is how the
    house if performing.

    I agree that a whole house dehumidifier is a good solution.
    unfortunately the hvac companies that understand why
    & how to sell these systems are far and few between.
    bear rules needs to come south. I'll make you a gumbo..
    well maybe I'll get someone who cooks better than I to make
    you a gumbo!
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  9. #9
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by energy_rater_La View Post
    TB
    the program I work with was until recently administered by state goverment
    I guess it still is, although in part federal goverment has come in also.
    the .35 ach was the 'safe' number they gave us..back in 2000
    lower than .35 the answer was to add fresh air.
    & you should have seen the people run from that!
    .35 was target for the powers that admin'd program.

    granted blower door testing is just a snapshot of at this particular
    time, under these forced depressurization levels..this is how the
    house if performing.

    I agree that a whole house dehumidifier is a good solution.
    unfortunately the hvac companies that understand why
    & how to sell these systems are far and few between.
    bear rules needs to come south. I'll make you a gumbo..
    well maybe I'll get someone who cooks better than I to make
    you a gumbo!
    Thanks for following the logic of this. I agree that the blower door test tells the leakage area of the home. It does not predict the air leakage from the stack effect and wind unless the leaks are spread randomly accross the all of the exterior surfaces of the home. An example my point is take an perfectly air tight structure. Make one large opening at any spot in the structure and subject structure to stack and wind. For air to exfiltrate/infiltrate stack effect, we need leaks at the top and bottom. For air exfiltration/infiltrate from the wind, we must have air leakage up wind and down wind.
    That is why the CO2 monitoring is much better way of determining the real fresh air venitlation rate of the home. I am attaching CO2 data from last week on a WI .2 ach home with a scheduled ventilation of 80 cfm with to occupants in/out. The vent schedule does not match the occupancy which illistrates the lack of fresh occasionally.
    Also the ventilation for this week is with a fresh air fan into the cold air return, VS fan "on" "low". There is whole house dehu in the basement.

    Also have the outdoor dew point and the inside %RH. No cooling this week.
    Your thoughts.
    Regards TB
    Attached Images Attached Images
    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"

  10. #10
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,137
    Good info TB.
    Unfortunately CO monitering is something that just now is becomming addressed
    by the program I work with.
    Back in weatherization days..we tested gas appliances for CO levels.
    but the way they 'taught' me was not the correct testing method.
    I had to sit down with the literature & floppy disc to learn the correct
    way to measure these appliances. (floppy disc is a clue to how long ago this was!)

    about a month ago I got notice that there was a class 250 miles away
    put on by the guy who is training new energy raters. unfortunately
    the agenda was posted on a tuesday..class was the next evening.
    too short of notice for me to attend.
    hopefully..once it cools off some and business slows a bit..they will
    hold this class again.

    I'd like to get some data like yours, but for a hot humid climate
    to take to the class. If I can't, I'd like to know if it is ok with
    you if I take the attached pdf?
    I've asked them to reschedule and give us more notice
    in hopes of attending.

    dnr gives us 'target' baselines, erring on the side of caution.
    while it isn't the best way to do it, I can understand that it is just
    very general info. It is up to us to learn more through ceu's
    and become better at what we do.

    your posts have been a great educational experience for me.
    it is always a pleasure reading your info & that you are so willing
    to share your experiences with us. too bad I can't get ceu's from hvac-talk!!

    take care.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  11. #11
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    6,260
    Quote Originally Posted by energy_rater_La View Post
    Good info TB.
    Unfortunately CO monitering is something that just now is becomming addressed
    by the program I work with.
    Back in weatherization days..we tested gas appliances for CO levels.
    but the way they 'taught' me was not the correct testing method.
    I had to sit down with the literature & floppy disc to learn the correct
    way to measure these appliances. (floppy disc is a clue to how long ago this was!)

    about a month ago I got notice that there was a class 250 miles away
    put on by the guy who is training new energy raters. unfortunately
    the agenda was posted on a tuesday..class was the next evening.
    too short of notice for me to attend.
    hopefully..once it cools off some and business slows a bit..they will
    hold this class again.

    I'd like to get some data like yours, but for a hot humid climate
    to take to the class. If I can't, I'd like to know if it is ok with
    you if I take the attached pdf?
    I've asked them to reschedule and give us more notice
    in hopes of attending.

    dnr gives us 'target' baselines, erring on the side of caution.
    while it isn't the best way to do it, I can understand that it is just
    very general info. It is up to us to learn more through ceu's
    and become better at what we do.

    your posts have been a great educational experience for me.
    it is always a pleasure reading your info & that you are so willing
    to share your experiences with us. too bad I can't get ceu's from hvac-talk!!

    take care.
    A fine point, I was limiting my post to the CO2 produced by people breathing as opposed to CO from combustion. We know how much CO2 people produce from breathing. By measuring the CO2 levels, we can calculate the amount of infiltrating fresh air. The lower the CO2 levels, the more fresh air is being mixed the CO2 from the occupants.
    Thanks for your kind comments.
    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. #12
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,137
    welcome, and thanks for the education you have provided to me.
    so it is ok if I use your info for our rater meeting??

    take care.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  13. #13
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,260
    Quote Originally Posted by energy_rater_La View Post
    welcome, and thanks for the education you have provided to me.
    so it is ok if I use your info for our rater meeting??

    take care.
    Certianly
    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"

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