-Well a few things have to be taken into consideration first as far as cost, plus the added comfort of humidity control needs be taken into account also. Lower humidity levels in the summer will aid the AC operational cost and effectiveness, and the overall comfort. Plus the lower humidity in the winter will stop the "rainforest" effect of the heat.
-First as I mentioned the optional installation method of a ventilating dehumidifier, this method would most likely not be needed if the dwelling were built in the 70s. But V-DH is an option if "fresh" outdoor air is wanted/ needed for IAQ, and careful consideration would be needed on placement of the outdoor air intake to avoid areas near furnace exhaust, plumbing exhaust, parking areas, trash cans/ dumpsters, and that's just a few unwanted areas that can really cause a stink or potential health risk.
-The grow-out tanks in the basement evaporation may be able to be handled with a simple bath fan exhausted though the available opening you mentioned, another means of outside air would needed to supply fresh air into the basement as the fan exhaust will create a negative pressure if not and pull air down from the living area exhausting your heated and cooled air outside (neighborhood cats will enjoy it tho!).
-Now the air in the living space where the 210 DT will be will have evaporation that will most likely need to be dealt with or you will end up with puddles of water on window sills and door sills. Sweating windows and doors will start to grow spots and green fur which is not healthy. Also elevated moisture inside the home will cause excess water in the HVAC system and can cause elevated growth in the ducting due to the extra water molecules settling inside the duct.
- If the basement is fully finished and this is where the DT is going also the use of a straight dehumidifier would be preferred because a finished basement would be heated and cooled along with the rest of the house and an exhaust fan will blow your heat and AC right out with the moisture, plus the more humid the air the more heat it can hold.
- If the basement is unfinished/ partially finished (unheated by the central HVAC) and the DT is in the upstairs living area, then as mentioned above, a bath fan in the basement and a means of dehumidification for the living space air for IAQ.
--Now as far installation and cost. If your basement has exposed central ducting, preferably return air, then installation would cost as much as if the ducting was mostly concealed. If the installation area has readily available power for the dehumidifier would be another factor of cost also. Ducted dehumidifiers can be purchased many places,
Amazon even has some that are Prime 2-day shipping eligible. If the ducting is easily accessible, and there is a sufficient power supply nearby, and if you are a fairly handy with tools the installation could be done yourself for probably $1500 or less (average price I found online for reputable Ducted DH was $1000). If the basement area only has one power circuit (plugs) the power usage of the DH and a couple heaters in the grow-out tanks/ sump would likely be too much. Which normally I install at least one new dedicated branch circuit (plug) to sump and DT areas (vacuum cleaners and tank heaters=tripped breaker).
--Your area service install rates - In my town the average Service Call hourly labor rate is $90 however 45 minutes west the average hourly rate is $125, so the same install we do wold likely be 25-40% higher a city over!
-- On average, houses with plenty of access area (basements and 3-4ft high crawl spaces) with readily available power outlet, to set the machine, install drain line, duct into the system, and install a humidistat (if the current thermostat isn't dehumidification capable) the installation would be $3200.
--Most reputable companies would give you a written proposal/ estimate for the installation, although many companies will likely only want to use machine they provide and install. Some may would price the install both ways also, your machine installed= X, or their machine installed=X. Which if your state is like NC, the total installation of their provided machine job would be sales tax exempt since it is equipment connected to your central HVAC system. If you purchased the machine they will charge you sales tax at purchase of the DH, and the labor/ materials for install would likely be taxed also, again depends on local tax codes. Form 589-CI is used here when replacing/ adding equipment to a residential house.
Im sure Ive forgot something, will add as remembered.
