As a student of this work, rather than a teacher, I am going to take information directly from two articles that can better explain the need for both dehumidification and air conditioning in areas of high humidity.
Dehumidifier and AC Unit
From Fine Homebuilding Magazine, “Excess humidity can encourage the growth of mold and even damage a house’s structure and furnishings over time. Many homes control indoor humidity with a dehumidifier. A liquid refrigerant passes through evaporator coils, which contact incoming air. Moisture from the air condenses on the cool coils and drains into a tray. While passing through the coils, the low-pressure liquid absorbs heat from the air and evaporates into a gas. The compressor squeezes it into a high-pressure, high-temperature gas before it flows into the condenser coils. There the refrigerant gives up its heat to the outgoing air and condenses back to a liquid.” The liquid is expelled from the structure.
From the Journal of Light Construction, “In the commercial market, vendors have started to provide equipment that can cool air down enough to dry it out, then reheat the delivered air stream to return it to design temperatures for people in the space. But on the residential side, no single company today makes both the cooling equipment and the dehumidification gear to solve the shoulder-season humidity problem in houses.
That means designers and contractors need to custom-craft solutions that mix and match equipment from different companies, and devise control systems that can effectively manage the whole system. A fairly widespread approach is to choose an air conditioner for cooling—either a central system or one or more mini-split heat pumps—and team up that cooling equipment with a dehumidifier for air drying and an energy recovery ventilator (ERV) for fresh air.
On some days during the hottest part of the year, the air conditioner alone may adequately control humidity as well as temperature. The ERV will also help, in any season, by passing moisture from the incoming air stream to the exhaust stream. But for many hours out of the year (especially in spring and fall), the dehumidifier will shoulder a load that the home’s other equipment can’t handle.
One house was cooled with a ducted mini-split, but the owner knew that hot, humid air would tend to accumulate at the open-plan building’s peak in the upstairs living room. So when he built the house, his HVAC contractor lined one stud bay in the home’s elevator shaft with metal duct material and installed a fan to pull air from the home’s peak down to the entry stairwell at ground level.
Dehumidifier Unit
Later, the owner tied a dehumidifier into the air-mixing system, with a dehumidistat at the upper story’s peak. A simple meter on his desk tells him the relative humidity in the living space. ‘We’ve had some really foggy cool mornings this spring,’ Dugan told JLC in April. ‘It’s sitting right at 100% dew point and it’s 60°F outside, and right now my indoor humidity is 45%. I say, OK. I like that.'”
The next step is to investigate companies that make whole-house dehumidifiers that will work with a (proposed) Mitsubishi Mini-split system. One company, Ultra-Aire, has dehumidifiers have been used with a Mitsubishi Mini-split system. Another issue is “are there local contractors who are familiar with whole-house dehumidifiers and how they work with air conditioning systems?”
3 comments
I was traveling through the internet and found your blog. I am also considering purchasing a lot somewhere along the Keys destination unknown as of right now. I did read the notes you have regarding dehumidification and the cooling system for the home. I have 14 years in residential HVAC sales and design in Florida so I have seen pretty much every installation design possible in Florida homes both existing and new Construction. First off let me say that when it comes to central heat and air the most important part is proper design, rather it be mini splits or a heat pump system. If you have the space for a ducted system that’s probably the way I would go that way you can install variable speed airhandlers. With proper duct design include HoneyWell zoning and high SEER up to 19 depending on Manufacture (seasonal energy efficiency ratio) split system, tie in high energy efficient windows, roof and such you will be set. Mini splits are also a great alternative these days with Manufactures like Mitsubishi offering Multi Zone systems they also are very energy efficient plus offer individual zones through out the home allowing you to cool only the areas your using. Separate Dehumidifiers aren’t very common in residential settings so I would focus on cooling equipment and you can also and I recommend UV Lights if you go with HVAC Airhandlers but there are stand alone UV type filtration systems available in the market. Good luck and if you can’t find a local HVAC company that sounds like they know what their doing reach out to a Carrier/Mitsubishi factory authorized dealer in Miami there’s a couple excellent dealers in that area. I am not being reimburse for any of the recommendations made. I have only shared the information I have had most experience with personally.
For ICF, use mini-split AC units in the different rooms. They don’t require ducting, they are easily serviceable and the whole unit can be changed in a day. They are efficient and you only need to turn on the units in the rooms as you use them so they are cheaper on electricity. Best thing is, if one goes out, you just use a different room until it gets fixed unlike central air where if the unit goes down the entire house loses AC.
Thank you for the informative replies! A lot has happened since I last posted.
The ICF plans we had came in at +$900,000 and that was way more than our dry lot was worth carrying.
My original designer did not tell me he had heart disease and he died during the process. His boss was a thief, and stole more money and did not deliver the work. The next design/build guy came in at $650k and after his engineer got done the cost was $1 million!!!! Not going to happen…..
So I’ve lost 3 years in Marathon’s BPAS process due to this stuff. I am waiting for the City Council’s March 2021 decision. So we went with block, metal roof with the carport at +8.01 feet. It’s the best we can do, considering…..