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Oceanfront Problem In NC

It sounds like they are on the right track.Sealing the attic is a good thing.After all, water vapor moves or diffusues from regions higher concentration to regions of lower concentration.

Infriltation is what hurting you be it from strong winds off the ocean,leaky ductwork, or even oversize ac system in a leaky envelope with leaky ducts.

Has anyone taken any reading on the airside to help polt the numbers on a psychrometric chart to help gather more info to tackle the problem?

Like drybulb,wetbulb,relative humidity.What about on the system side.Any numbers as far as static pressure,wetbulb in to the airhandler and wetbulb out of the airhandler?


  • Christine M. Briggs
    Christine M. Briggs Member Posts: 2
    Oceanfront Problem In NC

    I have a beach house in NC that was built in 2003.

    We have continuing problems with the HVAC not handling moisture in the house and drywall damage under the air handlers. We have paid >$20,000 to have ducts sealed, ceilings replaced, a dehumidifier installed, etc. and the problems still exist.

    We need to replace both our HVAC units because the coils corrode in the salty, humid air.

    The HVAC contractors I have spoken with want us to install variable speed units of 13 to 16 SEER, we now have 10 SEER, not variable speed. They also want us to replace all of the duct work! One wants us to seal the attic too. The estimates for these proposals are coming in at well over $50,000.

    They say if we install variable speed units with the existing ductwork the moisture problem will be worse.

    I do not know what to do and would appreciate some advice from people who have dealt with this type of issue.
  • Empire_2
    Empire_2 Member Posts: 2,343
    Hey Don?, Been a while how's things?

    Actually the only problem I have w/ VFD air handlers is the cost of a blower replacement after warranty is up. On The plus side these type of systems can be set up for de-humidification which basically slows the blower to 300 cfm/ton. Getting back to your problem,....Infiltration must be addressed as stated above, but also look at the Heat gain both sensible and latent in your area. If your system is over sized this is a classic result of this scenario.

    Mike T.
  • Tom Blackwell_2
    Tom Blackwell_2 Member Posts: 126

    The use of a variable speed system will help, and the high end systems that have two stages of cooling will help even more. The problem comes whene there is very little heat load; no dehumidification occurs when the system is not called to run. A commercial ducted dehumidifier would probably be a better solution, particularly if there are periods of no occupancy. Back in the day, we used to add electric heat brought on by high humidity, but that solution is now politically incorrect!
  • tim smith
    tim smith Member Posts: 2,389
    Re: moisture problems

    I would contact a good envelope/indoor air quality specialist designer. Talk to a reputable architect about who to call in your area. Regarding the sea air problem, some mfrs make units specifically for close proximity to ocean. Do some more reasearch before going ahead. Good luck.
    I talked to an engineer at Oneal engineers in Raleigh. He comes down to Atlantic beach quite often and said if you were near there he may be able to help some. They do mostly commercial/industrial but thats no problem. His name is Craig Crowther ph# 919-840-9500
  • don_205
    don_205 Member Posts: 66
    Old saying

    We have a old saying in my area.The builder we know is tight but that does not mean he built a tight envelope.

    A tight envelope to me is less then 0.25 ach then its getting close to being tight.

    Nc has the same summer gains of moisture as we do here in virginia.Site unseen the easy way out for her sounds like bringing in some fresh air that is treated by the ac unit to help reduce the infiltration load.

    I would like to hear what type of dehumidifider she has in there now and how its controlled.
  • Christine M. Briggs
    Christine M. Briggs Member Posts: 2
    Oceanfront Problem In NC

    Here are the details of the work we had done and information on the dehumidifier. Let me know what other information I can provide. I have pictures if that would be of help. Thanks to all the respondents, I appreciate it.

    The current HVAC units are 10SEER. The duct work is flexible 6". Where the main moisture problem occurs is under the first floor air handler. Below that air handler is some rigid ductwork and then flex ducts branch off of it. Since the house is on pilings, the garage ceiling is under this air handler. This is the ceiling that rotted and fell down twice. We contracted the work below from a Moisture Abatement company. We lowered the ceiling in the garage to provide more space for greater insulation of all the duct work. This did not solve the problem.

    The bathrooms are better. I might also mention that we had to have all of the tray ceilings in the house replaced because the metal track they used rusted through. The house is always conditioned with either heat or air. That was another expensive aspect of the moisture issue. In addition, after the work below was done, mold began to grow inside all of the cabinets in the island in the kitchen and the counter top sections separated which resulted in more repairs. I did not add these details because I did not want to complicate the issue but you can understand why I am so concerned about making a good decision. I want to end this financial drain!

    The dehumidifier is Aprilaire model 1700 with air flow of [email protected]"w.c. When it is on it sounds like an airplane is landing soon! It brings in outside air as well as dehumidifying. It is installed in the attic. The house is four bedrooms, about 3,000 sq. ft. of conditioned space, the unit is sized for up to 3,500 sq. ft.

    Recorded Measurements

    Duct Leakage1 Downstairs System:
    Before: 410 cfm(.20 T)
    179 cfm (.09 T/O)
    After 277 cfm(.13T)
    80 cfm (.03 T/O)
    Upstairs System:
    Before:116 cfm (.11 T)
    61 cfm (.06 T/O)
    After:116 cfm (.11 T)
    60 cfm (.06 T/O)

    Envelope Leakage2 Leakage: Before 3038 cfm After 2700 cfm

    House Pressure3 Static pressure -5 Pa (Pascals) N/A
    Dryer, range hood, HVAC, one
    bath fan on (worst case)
    -8 Pa N/A

    Room Pressure4 Bedroom 1 +4 Pa N/A
    Bedroom 2 +22 Pa N/A
    Bedroom 3 +7 Pa N/A
    Bedroom 4 +3 Pa N/A
    Bedroom 5 (Master BDR) +14 Pa N/A

    Bath Fans Flow
    before-Bedroom 2 Bath 36 cfm (Cubic Ft
    per minute)
    after-36 cfm (Cubic Ft
    per minute)
    Bedroom 1 (shared with office) 46 cfm 46 cfm
    Hall Bath (Main) 36 cfm 44 cfm
    Hall Bath (bath & shower area) 85 cfm 44 cfm
    Bedroom 5 (Master Bath) 21 cfm 30 cfm

    HVAC Sizing6 Under/Over-sized: N/A N/A
    (verbally they told me it was oversized.)

    • HVAC

    o Advanced duct sealing was performed on both systems where accessible.

    o There was a flex duct in the garage ceiling cavity that had been cut and the insulation
    around this duct closed duct tape. The 6” duct inside the insulation was still open,
    which pressurized the insulation around the entire duct system with cold air (in the
    cooling season). In addition to blowing cold air through the duct insulation, this air
    eventually leaked out through gaps in the insulation seal, cooling the entire cavity
    (along with the other duct leaks) between the garage and room above. Though other
    problems were found, we feel that this cooling of the duct insulation was the major
    contributor to the sweating ducts in this area. We have included a picture of this duct
    below. This flex line has now been removed and sealed at the trunk line.

    o We cut the insulation open on the main supply in the garage to allow drying over the
    winter months. We will seal this insulation back up when you return in the spring,
    before the humid months.

    o A fresh air dehumidification system was installed to provide 36 cfm of fresh air and
    continuous positive pressure to the house. This system should be left off for the
    winter months unless you are spending time in the house.

    • Envelope Sealing

    o All penetrations to exterior walls or unconditioned space were sealed.

    o The paneling around the steps leading from the garage to the house was sealed with

    o Wall plate seals were installed on all exterior wall plates.

    o The drywaller told us he would seal drywall in ceiling in garage.

    o There were some ceiling penetrations that we neglected to seal in the room above the
    garage and the East end of the house. We will seal these on our return in the spring.
    It was not recognized during work that these rooms have separate attic spaces above
    them. Unless you want us to cut an access to the attic space above the room over the
    garage, we will not be installing a back-draft damper on that bath fan.

    o Though it may not be necessary to prevent future moisture problems, we recommend
    that the underpinnings be sealed.

    o The knee wall in the attic that we feel has been responsible for pressurizing the attic
    has been blocked off.

    • Bath Fans

    o Butterfly backdraft dampers were installed on the bath fans that were accessible
    without removing drywall and soffit vent caps were installed to allow proper flow.

    o Bath fan vent caps on the first floor were not accessible without an extension ladder.
    The only one of these baths with a flow issue is the room over the garage (36 cfm).
    We can change this cap in the spring if you have access to an extension ladder, or you
    may want to get someone with a long ladder on the island to replace it for you.

    o The master bath fan was installed with a 3” vent duct that was taped onto the side of
    the fan box instead of the proper 4” adapter and duct. We were able to install one of
    our dampers on this fan and seal it (preventing the moisture issue you’ve been
    having), but were not able to replace the 3” duct and cap without removing drywall.
    So this fan is still only flowing at 30 cfm.

    o Most of the bath fans in this house are located in toilet rooms that can be closed off
    from the showers. Wile this can work if the doors to the toilet are open and fan
    turned on during showers, additional fans should actually be in the shower areas for
    proper removal of humidity.

  • don_205
    don_205 Member Posts: 66

    People please take note.When you build that dream house by the beach most times it become a nightmare with these type issue Christine is having. the name by the have many issue that one would need to address.Lets talk about the dehumidifider.How often do you hear the dehumidifider come on when the ac is running?

    Also how is this dehumidifider control? Does it bring on the hvac fan when there is a call for the dehumidifider?
    Also how is it pipe in? Does it have its on sperate vent to the outside and then ties into the return of the hvac airhandler?Or does it bypass the airhandler in tie right into the supply duct?

    Or does the return of the dehumidifider tie into the return at the airhandler and the supply off the dehumidifider tie in right at the supply duct?

    I think it would be best to gets some recorder in there that can measure air sample over time to help point you in the right direction.

    I hope this is ok with Mr Holohan that I post another web site.If not,then please delete. Give them a try.They understand moisture better then most other dehumidifer company I've come across.
  • Jack
    Jack Member Posts: 1,045
    At some point

    you have to look and ask if it is worth trying to resurrect a poor system, specifically the ductwork. The two speed and variable speed suggestions are correct, but you are still trying to correct a distribution sytem and can do so only where accessible, which means an incomplete repair. Do you want to continue down that track? What guarantee can be given that the dollars are going to be well spent and the system actually work and be an asset to the house.

    I would suggest that you look at mini-split heat pumps. I represent Fujitsu, ( so my bias is acknowledged, but they are the most efficient units out there, up to 26 SEER and 12 HSPF. You can use an assortment of interior evaporators, all of which are variable speed, very, very quiet and excellent dehumidifiers as well. You will also have "net to the space" efficiency as you have only .5-1% loss in the line set, as opposed to your current duct system.

    I am sorry to hear of your problems and shudder at what this must have cost you, in both $ and heartache, but at some point you have to say enough money spent on a failed system and look at better alternatives.

    As you have started this thread, please let us know how things work out for you as you go forward. Good luck!
  • Techman
    Techman Member Posts: 2,144

    An Aprilaire dehumidifier should not bring in outdoor,in a hi humidity area. Let it simply dehumidify the air in the house .If the dehumidifier is tied into the same duct's as the A.C.{supply and return} then it {dehumidifier} MUST be wired to bring on the indoor fan of the AC when ever dehumidification is called for. The dehumidifier should also be controlled by a dehumidistat preferably located in the house near the AC thermostat.The moisture damage sure seem's excessive.Is the air handler sitting on the floor?Is the bottom of the A.H.wet when the AC is running?Is the indoor blower set on too hi of a speed,forcing water into the supply duct?Does air flow into the last room of the duct system"feel" O.K. / Not stuffy?For some air exchange check into E.R.V.'s air exchangers.
    GREG LAUER Member Posts: 103

  • Jack
    Jack Member Posts: 1,045
    Greg is correct

    You will find that all the primary mini-split manuf (Fujitsu, Mitsubishi, Sanyo and Daikin) offer true variable speed equipment, which includes, variable speed compressors, condenser fans and indoor evaporator fans
  • Dave Yates (GrandPAH)_2
    Dave Yates (GrandPAH)_2 Member Posts: 377

    No question in my mind. We've installed hundreds of these very efficient and quiet systems. Given the cost you mentioned and the issues with the existing duct system and, perhaps most importantly, the humidity issues - mini-splits using inverter (variable-speed) technology offer the best solution to the issues you've mentioned. Many come with a dehumidification setting that will extract the moisture while maintaining set temperature within a degree or two. Properly installed, they will be quieter than your existing ducted system. You'll also have zoning by default, which will allow you to save even more money. 13-SEER? Left in the dust with nothing but mini-split tail-lights waaaaayyyyy off in the distance!

    Inverter + ultra-high efficiencies - the best of both worlds.
  • don_205
    don_205 Member Posts: 66

    What your thought on using your equipment on a wine cellar?
    May have to add a water fountain to keep up the humidity.
    Your thought?

    Also I know I've asked this question before however,other then the liquid line being a part of the metering device why is it we have no access to a highside port?

    No doubt they are a great piece of equipment.It just in the retro fit market, they have some limitation with all the linset cover running all over on the outside of the house.

    Also why do they always have to run the indoor motor on low speed without a call for cool? Are you guy saying the water left on the coil is not a big issue with the fan running during the off cycle?

    We did several muti-zone heatpump system last year when oil prices were thru the roof.Easy sell.Great results.

  • Jack
    Jack Member Posts: 1,045
    Wine cellar

    Don, I lived in the Napa Valley for several years, so when you say "wine cellar", are you talking Joe Phelps wine cellar or a little room. Exactly what conditions are you looking to maintain and for how much space?

    You don't get a high side port because the metering device is in the condensing unit so while they call them liquid and suction you are really looking at two gas lines.

    When you look at these things they are a true variable speed unit and they will continue to monitor temperatures about 500 times a second. As the actual t-stat is the thermistor mounted on the evaporator it is, shall we say, ever vigilant. As well, they do their best dehu in those low fan speed cool coil conditions.
  • don_205
    don_205 Member Posts: 66
    Napa valley

    Then I'm sure you have push one of your products on someone with a wine room.LOL.

    The wine cellar in question is in size ..15x20x14.I'll have to run a load on it being two of the outside walls are under ground.As for how much product we do not know yet.
    I'll have to check on the cabinets temps.The last wine cellar we did if i recall correctly was any where from 45 to 50 degree drybulb and humidity not under 45% or over 50%.

    How are you guys handling oil return at low capacity? I assume like most will ramp up the compressor after 30 mintues of run time.

    Please explain to me if you will about how the fan is reduce to control humidity.
    Is it done like most that it runs the unit below setpoint and if controller see the humdity is still high that it will reduce the fan speed then and only at below set point?

    TIA for your replys.
This discussion has been closed.