Results 1 to 9 of 9
  1. #1
    HVAC is not the area to skimp on obviously. I have new construction 3000 apx sq ft. with a full basement. We are zone 5 with cool summers but in my location I have very damp conditions every evening right off the lake. What is the best way to reduce the RH inside? We will have a very tight home so make up air is necessary. I hear words like venmar, HRV, ERV and I know I just don't have a grip on this. I don't want to heat just to dehumidify in the summer. What do I need? Also, is one unit less expensive than 2 units. A 120 output with 5 tons of cooling was priced out and then another wanted me to have 2 sets one for the walkout and the other unit for the rest of the 2 story house. I need the best energy approach I can get for the least monthly expense. Also, how do I know if my HVAC contractor is in the know and will do a good job prior to signing with him?

  2. #2
    Join Date
    Jan 2004
    Posts
    108
    Low monthly expense starts with lots of insulation and good air sealing. More insulation equals smaller furnace and A/C which results in lower monthly expense. A 120,000 BTUH furnace and a 5 ton A/C would indicate a poorly insulated house.

    A mechanical ventilation system will eliminate stuffiness. It is especially important in a tight house. It may include an ERV or an HRV, whichever is more appropriate for your climate.

    A dehumidifier will keep the indoor humidity under control during those damp evening conditions. Thermastor makes the most efficient dehumidifier.

    Your HVAC contractor should be able to discuss all of this, including the savings from adding more insulation. If he sizes the HVAC system from square feet, find another contractor.

  3. #3
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,260
    Originally posted by rained out
    HVAC is not the area to skimp on obviously. I have new construction 3000 apx sq ft. with a full basement. We are zone 5 with cool summers but in my location I have very damp conditions every evening right off the lake. What is the best way to reduce the RH inside? We will have a very tight home so make up air is necessary. I hear words like venmar, HRV, ERV and I know I just don't have a grip on this. I don't want to heat just to dehumidify in the summer. What do I need? Also, is one unit less expensive than 2 units. A 120 output with 5 tons of cooling was priced out and then another wanted me to have 2 sets one for the walkout and the other unit for the rest of the 2 story house. I need the best energy approach I can get for the least monthly expense. Also, how do I know if my HVAC contractor is in the know and will do a good job prior to signing with him?
    Zone 5?? From my biased point of veiw, the best package for make-up air ventilation and humidity control(<50%RH), check out adding the whole house ventilating dehumidifier. They provide the air needed for clothes drier, kitchen exhaust hood, and bath fans to function. During the damp, cool times of the year, they control indoor humidity while blending fresh air with house air, filtering both, and distributing it throughout the home. The unit is attached to you air handler. The ventilation device you mention are balanced air devices, meaning remove and add equal amounts of air. This does nothing for the cloths drier or kitchen hood. ERVs transfer a portion of the moisture in the wet stream to the dry stream. They have no ability to dry the home. As the indoor %RH rises they transfer less moisture. After a home is damp, ERVs transfer moisture form the exhaust to dry incoming air keeping the home moist. They are excellent for extreme cold climate requiring a lot of ventilation.

  4. #4
    Join Date
    Mar 2004
    Posts
    1,042
    Zone 5 is a gardening reference... means nothing to the folks on this board. How about a city and state? Then we'll know what climate we're talking about. We may be able to come up with a local contractor recommendation, too.

    Either way it does sound like a good application for a central dehumidifier.

    Go for one nice top-end system with zone control to distribute the air as needed across each level of the home. The size of the system should be determined with a Manual J load calculation; square footage is just the first of a great deal of data you need to get the calculation right.

    You can do your own calculation with the HVAC-Calc software for sale on this site, you can get an HVAC contractor or mechanical engineer to do one for you, or your architect may have done the calculations already from the plans.

    If your contractor isn't ready to do a Manual J calculation (albeit not necessarily for free), is hesitant about zone control systems, or isn't familiar with central dehumidifiers, they probably aren't up to snuff for the job. The 120k/5 ton guy probably isn't the right choice, though.

    [Edited by wyounger on 07-28-2005 at 03:37 PM]

  5. #5
    Thank you for the info. Is there a particular Central Dehumidifier that is less expensive to run or the best overall in it's class. I will admit that I am having trouble finding qualified contractors. I tried to tell a guy today about venmar air exchangers and then I just gave up since he, as well as many, insist that I don't need all that high tech junk. OH, boy - Airtight drywall approach, caulk at all the sill plates etc, foam insulation and no air. Even I can figure that's trouble. I'm in the metro detroit area of Michigan.

  6. #6
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,234
    Originally posted by rained out
    Is there a particular Central Dehumidifier that is less expensive to run or the best overall in it's class.

    OH, boy - Airtight drywall approach, caulk at all the sill plates etc, foam insulation and no air.
    Detroit, Michigan.
    http://www.thermastor.com/prod_150h.htm

    If your existing unit is more than 3.5_Tons,
    it should not add too much more load.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  7. #7

    solution

    Thermastor UV150 at the supply into a smaller furnace than 120BTU with a venmar exhausting the baths through a separate duct system for a balanced house. Or the baths could just go through the roof as I understand it. Is the venmar a good approach to exhaust baths? Thank you again.

  8. #8

    Big trouble

    OK guys,

    I'm in big trouble. The pros around here corrected me saying I meant Thermador. What are some questions I can ask to help me find qualified HVAC contractors. One guy gave me some load calcs only I can't see what on earth it was based on. I'm going to ck to see if 1.3 multiplier was automatically used to calc the total load from the sensible load. I'll ck to see what inside temp is in the estimate.

    I am saying I can't find anyone that even thinks it's a good idea to seal ductwork. I feel like I'm trying to build the star ship or something around here. Thank you for your help. I just can't risk failure on this system and at this time the project is on hold while I try to find the right contractor.

  9. #9

    Hmm Manual J

    OK, I am studying the Right-J worksheet it is one page. The square footage is listed as 1476 on first and second floor. But I actually have 1600 and 1000. The basement is undersized as well here.

    The window numbers are messed up showing more glass upstairs than down.

    Infiltration is shown as 791 whole house. Duct loss is 8% but only reflected in the heating column. The same number is just stars in the cooling column.

    The whole thing stops at number 20 and doesn't tell me anything. Gish. I could be dead wrong and just don't know what I should look for. Anyone within 500 miles of MI? I'm only half kidding. Just don't try to get me to buy that Thermador for my furnace.

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