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  1. #1

    Fresh Air Intake

    Just read this article about balancing an exhaust only ventilation system with a "passive" fresh air intake.
    http://www.chandlerdesignbuild.com/f...dsComplete.pdf

    I was thinking about using his setup with one change. I would use a Fantech FB6 inline filter box to filter the Outside air.

    Use a Panasonic 13KVM

    Ducting the fresh air supply register into the middle of the living room kitchen area (open floor plan) to get better distribution of the fresh air being introduced.

    Anyone seeing a problem with this setup? It would cost a little less than $2 to operate this fresh air intake 24/7 per month with the cost of electricity at $0.12/KW. Not saying I would operate it 24/7 it can be tuned as needed for more or less fresh air.

    It beats running the fresh air intake of a dehumidifer with a fan that uses 150W cost of operating per month 24/7 $13.93. Every dollar saved adds up :-)
    Last edited by Stamas; 11-29-2011 at 08:01 AM. Reason: Removed sales links.

  2. #2
    Join Date
    Aug 2003
    Posts
    906
    I've used Fantech FB6 inline filter boxes. Regardless of wishes, with that setup very little of the fresh air will go through the passive fresh air intake, especially with a small MERV 13 filter inline, unless the rest of your house is impossibly tight (submarine kind of tight). Virtually all of the air will come from leaks everywhere else in the house. The pressure necessary to get enough air for a clothes dryer or that 130 cfm ceiling fan through a Fantech FB6 would need to be extreme in terms of normal house pressures. IMHO that Chandler design is unrealistic to start with. With a FB6 MERV 13 filter, you'll definitely need a fan dedicated to bringing air in.
    -If you won't turn it on then nothing else matters.

  3. #3
    Its pretty tight dont know about submarine tight. Hehe..... I guess I will try it and if it doesnt work out at all I can get an inline fan to suck that air inside 67W still beats 150W. :-)

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,361
    Quote Originally Posted by momoformula70 View Post
    Just read this article about balancing an exhaust only ventilation system with a "passive" fresh air intake.
    http://www.chandlerdesignbuild.com/f...dsComplete.pdf

    I was thinking about using his setup with one change. I would use a Fantech FB6 inline filter box to filter the Outside air.

    Use a Panasonic 13KVM

    Ducting the fresh air supply register into the middle of the living room kitchen area (open floor plan) to get better distribution of the fresh air being introduced.

    Anyone seeing a problem with this setup? It would cost a little less than $2 to operate this fresh air intake 24/7 per month with the cost of electricity at $0.12/KW. Not saying I would operate it 24/7 it can be tuned as needed for more or less fresh air.

    It beats running the fresh air intake of a dehumidifer with a fan that uses 150W cost of operating per month 24/7 $13.93. Every dollar saved adds up :-)
    Fresh air intakes on whole house ventilating dehumidifiers are sucking in fresh air, blending the fresh air with the house air, filtering the blended air, and circulating the filtered blended air through the home. The blend has 1/4 fresh air with 3/4 house air, which reduces the temperature differential helping blend the fresh air into the home without creating a cold/hot spot. In addition when dehumidification is needed, the moisture is removed before blending the wet air into the home.
    Also the whole dehu provides controls to operate the fresh air only when needed.
    To some, these features are have real value.
    Regards TB
    Last edited by Stamas; 11-29-2011 at 08:02 AM. Reason: Same
    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. #5
    The blending of the fresh air with inside air can be accomplished by drilling a hole in the Fantech FB6 filter and install another duct that would pull inside air through it via a inline fan.
    I do agree that it's nice to have the added dehumidifier when needed.
    But for someone trying to make the house as energy efficient as possible the use of a 150w fan that brings in 65-75cfm of fresh air is just not the best option it seems. And a house like mine (1800sq.ft) should have about 48cfm according to ASHRAE 62.2, so if we get 65-75cfm of fresh air from the dehumidifer fan then it needs to operate 64-74% of the time to deliver the minimum required fresh air.
    They also say not to ventilate more than 7.5cfm/100sq.ft in a hot humid climate.

    I am at least going to test the Chandler Design to see how much air I would actually get in through that big old Fantech FB6 filter. I will post my results when I get the cfm measured.. I am very hard headed sometimes. I have to try and see for myself I guess

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,361
    Quote Originally Posted by momoformula70 View Post
    The blending of the fresh air with inside air can be accomplished by drilling a hole in the Fantech FB6 filter and install another duct that would pull inside air through it via a inline fan.
    I do agree that it's nice to have the added dehumidifier when needed.
    But for someone trying to make the house as energy efficient as possible the use of a 150w fan that brings in 65-75cfm of fresh air is just not the best option it seems. And a house like mine (1800sq.ft) should have about 48cfm according to ASHRAE 62.2, so if we get 65-75cfm of fresh air from the dehumidifer fan then it needs to operate 64-74% of the time to deliver the minimum required fresh air.
    They also say not to ventilate more than 7.5cfm/100sq.ft in a hot humid climate.

    I am at least going to test the Chandler Design to see how much air I would actually get in through that big old Fantech FB6 filter. I will post my results when I get the cfm measured.. I am very hard headed sometimes. I have to try and see for myself I guess
    You do not have the facts. ASHRAE suggest 7.5 cfm per person for the designed space plus 1 cfm per 100 sqft. of space as a minimum. The intent is that the home will recieve additional fresh from activities and natural forces. A three bedroom house should have 4 X 7.5 plus 1 cfm per sqft.. minimal.
    Regards TB
    But go ahead an do whatever you want, keep us posted on your results.

    Few are equiped to measure results of their actions. I admit, you are far ahead of most on these blogs.

    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"

  7. #7
    (7.5x4)+(1800 x 0.01)= 30+18= 48 cfm

    48cfm/65cfm= 0.738 rounded up to .74 that is 74%
    48cfm/75cfm= 0.64 that is 64%

    So if 48 cfm is supposed to be delivered constantly to meet ASHRAE than a fan that gives 65-75cfm will have to operate 64-74% of the time to meet those requirements, right!?

    Or do I have that wrong somehow?

    Thanks!

  8. #8
    They also say not to ventilate more than 7.5cfm per 100sq.ft in a hot humid climate. According to ASHRAE 62.2 2010

    I had messed that one up..

  9. #9
    I haven't received my filterbox yet but I did do a test by unhooking the dryer duct from the 4" vent and turned on my 140cfm Broan bathroom fan (which actually pulls around 100-105cfm measured) located on the other side of the house from dryer vent. I measured 25cfm of air being brought in from the outside at the dryer vent of course that's without any form of filter hindering the air flow. I am guessing that the other 75cfm is being drawn in through the 2 other bathroom fans with crappy backdraft dampers.

    I will post more when I get the filterbox hooked up to my 6" fresh air duct and my Panasonic 130cfm bathroom fan installed instead of the Broan. (Panasonic is supposed to compensate fan speed to deliver a constant 130cfm).

  10. #10
    Join Date
    Nov 2011
    Location
    Central VA
    Posts
    29
    This may be a stupid question but it's something I've always wondered: why can't you just have a return grill on the outside of the house that pulls fresh air in, then distributes it through the existing duct system? If you always had the fan set to on then you would always have fresh air right?

  11. #11
    Ok, So I did some testing.
    Used my 6" insulated flex duct that is bringing in fresh air from my soffit connected it to the Fantech FB6 filter-box with a MERV 13 filter in it.
    Cold day and windy outside, turned on my 100 cfm bathroom fan and I could not measure any stable amount of fresh air coming in through the intake (except for when the wind outside would blow I would get air coming in. So I turned on all my bathroom fans that's one 70cfm and one 50cfm to prevent any air being drawn in through the leaky backdraft dampers of those fans and in doing so I was able to pull in at a low constant 25cfm and high was around 44cfm (wind doing it's magic I assume

    So it looks as if I need to completely seal off the other bathroom fans before I can get a good reading. At this point I believe that I will need some form of booster fan on the fresh air intake that runs when bathroom fan is running to make this work.. :-/ Maybe a Low voltage Panaflo DC fan will do the trick...We shall see...

  12. #12
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,361
    What did you expect? Your house probably has a square foot of air leaks. Why not power the make-up air through the filter and forget about the exhaust. During windy weather or cold weather, forget about ventilating. You will get enough nature air change. During calm warmer weather, powered make-up through the filter makes more sense. Sort of like a whole house ventilating dehumidifier.
    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"

  13. #13
    Teddybear,
    I did turn off the fresh air intake from the dehumidifier today. I will see what it smells like, what the Co2 measures and what it feels like when I get home.

    Why I prefer to use the bathroom fan is because I get much better distribution in the house of the fresh air when I used that with the current dehumidifier fresh air intake. The bedroom air is much better because the bathroom is on the opposite side of the fresh air intake with bedroom in the middle. The draw back is that currently my Broan (150w) bathroom fan and the 150w blower in the dehumidifer is not synchronised and they both draw more power than some other options like the Panasonic 13w 130 cfm bathroom fan and the 57w 240 cfm inline fan. I am simply trying to make the fresh air intake "system" use as little power as possible while still being effective.
    I also find it interesting to find out how these systems work in my house, climate etc.. So once I settled on one system I will post it here to let you know what the efficiency is so others might benefit from a real world example and not only from sales pitch talk.

    The dehumidifer comes in real handy as a backup to keep humidity under control but may not be the best/most efficient way of bringing in fresh air.

    Thank you for your continued input.

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