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  1. #1
    Join Date
    Nov 2011
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    32

    Suggestions for New Construction in High Humidithy Area?

    Hi, I'm building a new home in the Carolinas (ie, high humidity roughly half the year) and am looking for suggestions for a "whole house product" to improve air quality. This website has been a great find, but I still need a bit of guidance (I'm a layperson in this field). Here is what I was considering, but thanks to some information on this website, I've realized that solutions may not be as easy as they appear on the surface:

    First, considered the IQ Air Perfect 16, but it doesn't pull in fresh air from outside. Then, considered a Venmar HEPA Air exchanger. I like this option (pulls in fresh air and cleans it with HEPA filters), but am concerned about running this in a high humidity area. In other words, I don't want to pull in more humid air in the spring and summer months and risk mold issues. Does anyone have any thoughts or suggestions? Is there a product that pulls in fresh air AND cleans it with Hepa AND either heats the new air (in the winter) or dehumidifies the new air (in the summer)? I'm probably asking too much, but thought that there must be others in the south (U.S.) with this issue. By my estimation, air exchangers seem to be great options in cold weather climates but not so good with humidity. thanks!

  2. #2
    Join Date
    Jan 2011
    Posts
    92
    a 2 stage a/c with a variable speed blower is a popular set-up used by us here in nc. I suggest trane's xl20i because it has two compressors which lets you run 50% airflow in the first stage of cooling. this is great for dehumidification. Combo that with a vs airhandler and a t-stat with a dehumidifying cooling-droop program like the honeywell 8000 = dry comfortable living. An ERV is a great addition to swap out air with clean outside air, but there are less expensive options as well. Of course all of this is based on having a competent installation contractor. What part of NC?

  3. #3
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,063
    Quote Originally Posted by unc99 View Post
    Hi, I'm building a new home in the Carolinas (ie, high humidity roughly half therisk mold issues. Does anyone have any thoughts or suggestions? Is there a product that pulls in fresh air AND cleans it with Hepa AND either heats the new air (in the winter) or dehumidifies the new air (in the summer)? I'm probably asking too much, but thought that there must be others in the south (U.S.) with this issue. By my estimation, air exchangers seem to be great options in cold weather climates but not so good with humidity. thanks!
    Did you ever hear of a whole house ventilating dehumidifier? Some provide fresh air ventilation when needed and maintain <50%RH whenever tha a/c is not running enough to keep the home dry.
    They start by blending fresh air with house air, filter the blended air with upto Merv 14 air filters. The blended filtered air circulated throughout the home via the a//c ducts. The dehumidifier part will remove moisture from the air whenever the %RH in the home is above your set point. The Ultra-Aire is unit I am most familar with and is granddaddy of this type of unit. The UA is also the most efficient dehu made.
    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"

  4. #4
    Join Date
    Nov 2011
    Posts
    32
    Thanks for the replies. I'm in western NC (near Charlotte).

    Would it be best to tie in the dehumidifier/ventaliator to the HVAC systems or have it stand alone? If I was building a 3800 sq foot home with two stories (downstairs is bigger and there is a two story ceiling in foyer), would I need one for each floor (there will be HVAC on each floor) or just one on the main floor. Would, of course, prefer to just get one, but there are bedroom upstairs that I would want to benefit. Thanks!
    Last edited by unc99; 11-13-2011 at 10:48 PM.

  5. #5
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,063
    Quote Originally Posted by unc99 View Post
    Thanks for the replies. I'm in western NC (near Charlotte).

    Would it be best to tie in the dehumidifier/ventaliator to the HVAC systems or have it stand alone? If I was building a 3800 sq foot home with two stories (downstairs is bigger and there is a two story ceiling in foyer), would I need one for each floor (there will be HVAC on each floor) or just one on the main floor. Would, of course, prefer to just get one, but there are bedroom upstairs that I would want to benefit. Thanks!
    If you want total control of all space, use a vent dehu on both a/cs. A dehu on the upper unit and a medium unit on the lower a/c. If on a budget, use an UA xt150H on lower unit with a supply connected to the upstairs a/c unit.

    Stand alone units are less expensive but most intrusive.
    Appreciate your consideration.
    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
    Oct 2009
    Location
    Murfreesboro, TN
    Posts
    108
    TB: Where do you connect the discharge duct from the ventilating dehumidifier: before or after the evaporator coil? Doesn't Honeywell say before and Thermastor say after? Second question: Where should the return to the dehumidifier come from: a separate return opening or simply attach to the existing return duct to the A/C unit?

  7. #7
    http://www.buildingscience.com/docum...ventilate/view

    PDF file from Building Science web site about ventilation in all types of climates.

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  10. #10
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,063
    Quote Originally Posted by TalkingHead View Post
    TB: Where do you connect the discharge duct from the ventilating dehumidifier: before or after the evaporator coil? Doesn't Honeywell say before and Thermastor say after? Second question: Where should the return to the dehumidifier come from: a separate return opening or simply attach to the existing return duct to the A/C unit?
    Ideally, connect the dehumidifier to the supply duct down stream of the fan/a/c coil. This connection maximizes the amount of moisture removed by the a/c. If the supply duct has +.4" of positive pressure, avoid the supply side or interlock the avoid dehu operation when the a/c is operating. When connecting a dehu to two a/cs, split the supply of the dehu to both of the a/c supplies.
    There various methods of getting distribution of the dry air throughout the home and not require the a/c blow to operate when the dehu is operating.
    A properly setup a/c will maintain <50%RH during lengthly operation. The dehu should only need to operate during low/no cooling loads. I am open to other suggestions.
    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"

  11. #11
    Join Date
    Aug 2003
    Posts
    906
    Quote Originally Posted by teddy bear View Post
    ...
    I am open to other suggestions.
    Regards TB
    After years of trial and error, I found that what worked best for my house was to have a tight-band dehumidistat on the main floor, with the dehu's output directly in the open basement with a long stretch of straight flex duct to absorb noise, and drawing air from the return ducts. A relay cuts off the dehu when the A/C runs. The dehumidistat is a "Columbus Electric", which has internal Honeywell parts essentially identical to the Honeywell dehumidistat, but set at the factory to operate with a much narrower deadband.

    Fresh air is fed with a "T" junction to the dehumidifier's intake, after being filtered with a HEPA filter running at a low speed. An autotransformer (variac) controls the HEPA filter speed, and a pressure switch at the HEPA filter's intake turns on a light if the HEPA is unable to maintain enough suction on the fresh air intake. When this happens and the variac has no more power to give to the HEPA filter, or it's too noisy, it's time to change the HEPA filters. Outside air is surprisingly dirty...

    I think that the dehu configuration that works best is a function of the house's design and dehumidification needs. There isn't a single configuration that's the optimal one for all houses. Discharging the dehu in the basement has evened the temperatures between floors in my house, besides the desired effects on mold and insects.
    -If you won't turn it on then nothing else matters.

  12. #12
    Join Date
    Nov 2011
    Posts
    32
    Thanks to all for the responses. I'm leaning towards going with a venting dehumidifier on the first floor, and two air cleaners (such as either the Perfect 16 or the Lennox Hepa model) on each floor. Although perhaps this is too over the top.

    A couple of questions:

    1. Is there any issue with putting an air cleaner along with a venting dehumidifier? If I understand them correctly the air cleaners are just boxes with filters, so I'm guessing not but am not sure.

    2. Does the venting dehumidifier expel indoor air, or just bring in out door air? In other words, does it work like an air exchanger? If not, is it problematic to having air forced in the house and not having indoor air mechanically expelled?

    3. Is anyone aware of an EVR which also dehumifidies? If so, it seems this would erase if any issues I noted in point # 2 above.

    Thanks very much in advance....this site has been a wealth of information...much appreciated.

  13. #13
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,063
    Quote Originally Posted by unc99 View Post
    Thanks to all for the responses. I'm leaning towards going with a venting dehumidifier on the first floor, and two air cleaners (such as either the Perfect 16 or the Lennox Hepa model) on each floor. Although perhaps this is too over the top.

    A couple of questions:

    1. Is there any issue with putting an air cleaner along with a venting dehumidifier? If I understand them correctly the air cleaners are just boxes with filters, so I'm guessing not but am not sure.

    2. Does the venting dehumidifier expel indoor air, or just bring in out door air? In other words, does it work like an air exchanger? If not, is it problematic to having air forced in the house and not having indoor air mechanically expelled?

    3. Is anyone aware of an EVR which also dehumifidies? If so, it seems this would erase if any issues I noted in point # 2 above.

    Thanks very much in advance....this site has been a wealth of information...much appreciated.
    You also have some options on the filtering of the fresh air/house air blend flowing through the dehumidifier. There is a Merv 14 option option available with the Ultra-Aire. Suggest a minimum of a Merv 11 for the air handler.
    Regarding the make-up air issue, the ventilating whole house dehumidifier blends fresh air with the house air, filters, and circulates the filtered blend throughout the home. The amount of air should be enough to change the air in the home in 4-5 hours. There is no exhaust of stale air. You have several appliances that need make-up air to function. The clothes drier, kitchen hood, and bath fans exhaust air and benefit from the make-up air. Also, make-up air reduces untreated air from naturally infiltrating the home which is benefical. See no need to ventilate when the home is unoccupied for extened periods of time, but maintaining <50%RH is important to avoid mold, mildew, and dust mites. The DEH 3000 controller has a good occupancy schedule provide fresh air when you are in the home on a routine basis.
    Being able to control fresh air on a routine basis that matches occupancy schedules also reduce cost of conditioning the make-up air.
    Keep us posted.
    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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