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Message
Moisture control
Posted on 9/3/24 at 10:07 am
Posted on 9/3/24 at 10:07 am
I live in an old house in SELA. House is pier and beam with knotty pine ceilings throughout and it’s smaller than 1500 sqft. We’ve foamed the subfloor and roof rafters and this has helped tremendously with the moisture. I am considering a whole house dehumidifier and my question is, has anyone tried a crawl space dehumidifier in lieu of a whole home (one that connects to air return/plenum). The price difference is considerable.
I mention the ceilings because there are plenty of holes and seams to allow air movement.
TIA
I mention the ceilings because there are plenty of holes and seams to allow air movement.
TIA
3
Posted on 9/3/24 at 11:44 am to TaderSalad
Not sure of the cost of what you're looking at but have you considered a variable speed AC?
Posted on 9/3/24 at 12:44 pm to LEASTBAY
I discovered variable speed A/Cs the year after I replaced mine.
Whole how would be about $1500 plus install. Crawl space would be about half of that.
Whole how would be about $1500 plus install. Crawl space would be about half of that.
Posted on 9/3/24 at 5:28 pm to TaderSalad
Fans with humidistats on the leeward side is the best solution
Posted on 9/3/24 at 6:16 pm to TaderSalad
You’ve encapsulated the subfloor & ceiling. Open or closed spray foam? Are you not getting sufficient humidity-moisture control with your AC in this summer heat with long run times? Or are there other moistures issues you are dealing with? I guess the question is what is the nature of your moisture issue you are trying to fix?
If you have an open crawlspace I don’t think a crawlspace dehumidifer would be effective - if it is closed and you placed a vapor barrier covering the soil then it might. Read these articles LINK LINK LINK
If you have an open crawlspace I don’t think a crawlspace dehumidifer would be effective - if it is closed and you placed a vapor barrier covering the soil then it might. Read these articles LINK LINK LINK
Posted on 9/3/24 at 8:07 pm to CrawDude
Adding the foam cut down on HVAC run time. Our avg month,y electric bill in the summer is about $90. House doesn’t heat up but it gets humid, so trying to make it less sticky without cranking the house down to 71 degrees all day.
Not sure the proper terms of the units, but I see ones advertised as “crawlspace” with a square footage rating. Due to my house size and air flow between the attic and rest of the house, my question is would one advertised for crawl spaces be effective if I tuck it in the attic? Trying to go from 65% to say 45-50%.
Not sure the proper terms of the units, but I see ones advertised as “crawlspace” with a square footage rating. Due to my house size and air flow between the attic and rest of the house, my question is would one advertised for crawl spaces be effective if I tuck it in the attic? Trying to go from 65% to say 45-50%.
Posted on 9/3/24 at 9:12 pm to TaderSalad
quote:
TaderSalad
OK - I understand now. Now that you’ve spray foamed your attic & subfloor your existing HVAC is now over-sized for the heat load of your house, you have short run times of the HVAC and as a result not getting humidity removal associated with longer run times. This not an uncommon problem.
Before investing in a dehumidifier, I would first try lowering the blower speed of the furnace-air handler in cooling mode. Often blowers are set at the factory to the highest speed of 400 CFM per ton, but in humid climates reducing the blower speed to 350 CFM per ton, possibly around 320 CFM will aid in reducing humidity. Reduced air flow keeps the humid air in contact with the cold evaporator coil longer increasing moisture removal from the air reducing humidity. But you can’t lower air flow too much otherwise the evap coil will freeze up. For example if the blower fan speed is set on high in cooling mode, it can be lowered to medium-high or medium. This done either with a switch on the furnace-air handler control board or possibly moving blower motor wires on the control board. That info is in the furnace or air handler owners manual.
Now if that doesn’t work to sufficiently to lower the humidity to 45-50% at a temperature of 75 F then yes, you’ll likely need a dehumidifier. I wasn’t aware there were different dehumidifiers that are cheaper used in crawlspaces compared to comparable whole-house dehumidifiers placed in attics. So I can’t answer that question, I’ll have to look into it, but given your attic is now semi-conditioned and not exceedingly hot, compared to crawl space temperatures, perhaps you can.
TLDR: try reducing the fan speed on the furnace-air handler to reduce humidity in the house before spending $ on a large house dehumidifier.
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