It is hard to know where to start here. The flow rate (cfm) is determined by the uprising velocity of the cooking plume effluent and the aperture area of the hood, and not to first order by the BTUs. I would start at 90 times the area in square feet. Baffles will not separate grease from the air at really slow air speeds, so if one intends to go as low as possible, then a mesh that is routinely cleaned is probably better. However, mesh hoods typically have undersized apertures, so capture is degraded at the hood periphery. In other words, the hood is smaller than listed. Baffles will at any speed provide fire blocking, their other purpose. All fans have fan curves, including those made from magic lungs. The fan curve plots flow rate versus pressure drop across the fan, which results from duct friction, duct transition flow disruptions, mesh or baffle restriction, lack of MUA, etc. Typical fan curves are slightly convex, with cfm on the abscissa and pressure on the ordinate. When the pressure drop reaches some maximum, such as an inch or two of water column, the flow reaches zero. At zero pressure drop, the flow is (should be) the rated flow. The pressure drop is never zero in situ. VAH may be counting fan and hood, which can also be the rating used by some others at some times. It depends on whether the rating is for the hood with fan or for the fan only. The VAH rated flow certainly does not include the losses from the ducting and duct transition to the cap at the outside. Unfortunately, unless susceptible to a calibrated measurement, code enforcers will look at the fan rating and not actual flow for enforcing MUA rules. Ideally, they would test for negative house pressure vs. what combustion appliances present are not allowed to exceed without risking back-drafting. The relative loudness and ugliness of outside fans has to be compared to the relative social ugliness of loud inside fans. YMMV. I would not, however, duct to my neighbor's door. Some other path should be adopted. kas

If you are buying Carrier equipment, then it is best to buy from a factory authorized dealer. They are supposed to install the equipment to your satisfaction or remove it and refund your money. They should also have better training than the typical Carrier dealer. The Comfort series is Carrier's entry level product. I would be a good idea to upgrade to the Performance equipment. It is a little better built and quieter. I think upgrading to the 2-stage Infinity furnace is expensive, but worth the money in my opinion. I hope your upgrade price includes the Infinity controller. The ECM motor is reliable, but is expensive to replace if it ever goes bad. If you get a labor warranty get it through Carrier. I have the Carrier warranty and I am not forced to have maintenance. But you do have to take care of your equipment and not abuse it. I suggest having maintenance done once a year. You should not pay more than 10% of the total price for the labor warranty. You are already covered by a 10 year parts warranty.

It is hard to tell from this one drawing how the supplies and returns are connected. Is the main supply located in the attic? Are the supply vents 4 feet X 1 inch? If so then why so many and so narrow? I am not used to seeing these type of vents. Is this typical for new builds in Florida? Are the fours vents at the top supplies or returns? The supplies should be near the big south facing window, and supplies on the east and west wall, with the returns on the north wall. The 90 degree turn in the main duct needs to be rounded. If it is built as drawn there will be increased air turbulence and noise. If the duct work is in the attic then is should have R-8 insulation.

Austin Air- Can you have a filtered return as well as a filter on your furnace/indoor unit? We do have filters on the unit itself but it seems like a filter at that spot would be good There are many ways to filter HVAC, some designs will leave the return unfiltered and have a larger 4 or 5 inch media filter right before furnace. From there (where the return(s) are sized well it proposes options of incorporating a pre-filter. (cheap see thru filter) on the returns before the larger 4 or 5 inch wide media filter. I don't suggest you incorporate a two filter set up on your own. Because of the 2 filter restriction problem will cause more problems that that type of set up will cure. The problem with the 4 or 5 inch media filter at the furnace design is that the returns will become laden with dust in time. The dustier the home (typically more foot traffic, either people or pets) it won't take long for a clean return to become filthy. Dust contains dust mites. Small little creatures that feed on that dust. The whole reason to put a filter at the return entry is to prevent that, capture the dust at the filter change monthly. The 4 or 5 inch media filter typically you get away with 1 or 2 filter changes per year. Most returns are undersized. So when you place a filter at the filter return grill and then another at the furnace the HVAC becomes choked for air. This ramps up static pressure, utility bill costs, makes the AC & furnace have to work much harder than what they would have to otherwise. AC really needs 350-400 CFM (cubic foot per minute per ton) --- if you have a 5 ton AC that's around 2000 CFM. If you only provide 1600, the 5 ton is a 4 ton... yet you are paying for 5 tons as most are single speed systems. The reason why most returns are undersized is mostly due to cost / cutting corners OR possibly over sizing equipment. This is a part of design as much as everything else. An easy way to see if your return is too small is with the system running in AC mode place your filter in the return, the filter should not be sucked in... should be loose fit with only a slight pressure draw into the return grill. An inward bulge of the filter as it becomes filled with dust is an indication to change it, not a function of how it should be the minute you put a clean filter in the return grill.