I know variants of this question have been asked before, and I’ve read many of the replies (including tons from Teddy Bear, which have all been very informative, thanks!) but I haven’t seen many that address the needs we have in Florida, where we run the AC about 360 days/year.
I’m building a large (10,000) square foot residence in South Florida and am looking for the best (least tradeoffs) way to provide some fresh air distributed throughout the home to keep the air quality high, and as a secondary goal, provide some make up air for the 400 CFM range hood and other air exhausting appliances, although realistically I will probably have enough leakage to cover the make up air.
I think we’d like to have about 100 CFM or so of ventilation air, most of the time. I am fine with there being a little more or less intermittently, I'd just like to dilute the stale indoor air with some clean air.
The original plan (suggested by the engineer) was to use a ventilating dehumidifier such as the XT205H located in the attic, however, this uses about 1,500 watts and dumps a lot of the energy into heating the supply air output. Florida is hot already and we don’t want to waste energy cooling that hot & dry air down.
Second idea (suggested by Ultra-Aire) was to use their SD-12 split system to keep much of the heat outside, however this home is spec’d to have 20 tons of A/C already (four 5-ton units), and the thought of another appliance to break down, leak, need maintenance, etc. was a concern. Plus it would likely be placed in the attic making access tougher. If we went this route, we would just use a single SD12 and split the output of this machine into the supply trunk of the 2 units that feed the bedrooms and a central area where the vent air would hopefully mix will some of the room air picked up by the other 2 handlers.
Third idea (suggested by my contractor) was doing a simple Central Fan Integrated System. Using a 6” round duct to the outside air, passing through a damper into the return trunk of a few of the air handlers. Maybe using a aircycler or similar product to choke-off the outside air when the handler has been running for an extended period, and turning on the handler for a few minutes to distribute air during periods of low use (although that is basically never in this climate).
We use properly sized, variable speed HVAC units in our current Florida house, with low-e glass & icynene sealed attic and the indoor humidity is usually 48-53% at 74 degrees (we don’t currently have any o/a intake); so I think the air conditioning can do a decent job dehumidifying the house without a dedicated machine.
So, if we maximize the dehumidifying ability of the air conditioning system by sizing the tonnage properly, using variable speed units and/or setting the fan speed of each unit to provide max dehumidification, can a Central Fan Integrated System provide some fresh air without too much humidify increase, and with a minimum of cost & complexity, or is there some magic into having a dedicated dehumidifier that will make it worth the extra maintenance?
Thanks for all the advice.
I’m building a large (10,000) square foot residence in South Florida and am looking for the best (least tradeoffs) way to provide some fresh air distributed throughout the home to keep the air quality high, and as a secondary goal, provide some make up air for the 400 CFM range hood and other air exhausting appliances, although realistically I will probably have enough leakage to cover the make up air.
I think we’d like to have about 100 CFM or so of ventilation air, most of the time. I am fine with there being a little more or less intermittently, I'd just like to dilute the stale indoor air with some clean air.
The original plan (suggested by the engineer) was to use a ventilating dehumidifier such as the XT205H located in the attic, however, this uses about 1,500 watts and dumps a lot of the energy into heating the supply air output. Florida is hot already and we don’t want to waste energy cooling that hot & dry air down.
Second idea (suggested by Ultra-Aire) was to use their SD-12 split system to keep much of the heat outside, however this home is spec’d to have 20 tons of A/C already (four 5-ton units), and the thought of another appliance to break down, leak, need maintenance, etc. was a concern. Plus it would likely be placed in the attic making access tougher. If we went this route, we would just use a single SD12 and split the output of this machine into the supply trunk of the 2 units that feed the bedrooms and a central area where the vent air would hopefully mix will some of the room air picked up by the other 2 handlers.
Third idea (suggested by my contractor) was doing a simple Central Fan Integrated System. Using a 6” round duct to the outside air, passing through a damper into the return trunk of a few of the air handlers. Maybe using a aircycler or similar product to choke-off the outside air when the handler has been running for an extended period, and turning on the handler for a few minutes to distribute air during periods of low use (although that is basically never in this climate).
We use properly sized, variable speed HVAC units in our current Florida house, with low-e glass & icynene sealed attic and the indoor humidity is usually 48-53% at 74 degrees (we don’t currently have any o/a intake); so I think the air conditioning can do a decent job dehumidifying the house without a dedicated machine.
So, if we maximize the dehumidifying ability of the air conditioning system by sizing the tonnage properly, using variable speed units and/or setting the fan speed of each unit to provide max dehumidification, can a Central Fan Integrated System provide some fresh air without too much humidify increase, and with a minimum of cost & complexity, or is there some magic into having a dedicated dehumidifier that will make it worth the extra maintenance?
Thanks for all the advice.
