Hi ionized and thanks for your reply, Our original house was not built without cooling, our home is in the final stages of framing for an addition out back and moving of walls/major renos in the front portion. Prior to our large addition/remodel we had forced air heating and AC. The HVAC contractor has almost finished up the in floor hydronic heat which will replace the forced air. He started to work on the AC a few months ago, and to our shock installed large 9-10 inch main trunks in our great room and dining room (I posted about the issue at the time and I think you kindly responded). The contractor then explained for the first time we would have lots of these ducts all over the main level. The contractor stopped the progress as we wanted a new AC plan that would minimize the drop downs (contractor went on to some other jobs, and we focused on other aspects of the build as well). We definitely need AC here, our weather would be like Michigan or Buffalo -- lots of brutally hot days for 3-4 months per year. As per the mini-splits we are definitely still considering using them (or ducted mini-splits too). We have heard mixed reviews about mini-splits. I think the main draw back we have been told is the mini-splits need replacing say every 10 years or even sooner, so they don't last as long as central air (hence seen as a less permanent kind of AC). Also, if we go ductless, it will be harder to tie in the HRV unit. Not sure if these warnings are justified or not. The architect and HVAC contractor were down on the mini-splits so made as weary. Cost may also be high with mini-splits, but so is making a conditioned area in the attic I am discovering (not sure yet which is a higher priced solution). A high velocity unit might also be worth investigating. Carol

Can't really improve upon tigerdunes minimun specs above, efficiency performance dehumidification (if sized correctly..)staging electric strips. R-8 should be for all ductwork supplies and returns. All connections should be mastic..not foil or duct tape but paint on mastic and/or mastic tape. load calc to show how much air is needed and how to distribute air.(duct sizing & design) I'd invest in the room by room load calc and see how they plan to size the ducts and lay them out. you don't mention where ahu & heaters will be located. one in crawl space the other in attic? both in conditioned space with ductwork in attic and crawl? one thing to know going in is that sheet metal duct is best under houses. animals love flex duct, while you can usually deal with mice in attics..coons, possums can wreak flex duct. also sheet metal duct ( I call it hard pipe) leaks air at all connections. in addition to screwing duct together all joints and seams should be mastic sealed...before duct is wrapped. duct wrap should be stapled, and taped with duct tape (fsk tape) 80 years ago we built houses for ventilation. tall ceilings, balloon framed walls. to add central air to these homes is to change the dynamic of the house. in my area we usually foam floors with closed cell as it is the most cost effective way to both air seal and insulate the floors. here is a link to LaHouse (LSU Baton Rouge, La) about insulating floors: http://www.lsuagcenter.com/NR/rdonlyres/D33F711D-DC4B-4E4C-9ED6-A97DCE9DB026/79806/pub3187insulatingraisedfloorsHIGHRES.pdf you'll have to cut and paste for it to work.. if ductwork is in attic, another option is to foam the roofline and keep ductwork in a conditoned space. this will minimize problem areas like recessed lights that are not air tight, which allow attic air and insulation particles to enter the house. we use open cell installed in rafter bays and covering the face of the rafters. in my experience with older homes you have to fix the house in terms of air leakage and insulation for the central installs to provide comfort, dehumidification and savings. otherwise you just throw more tons of a/c at a leaky structure. insulating floors and attic would be to your benefit. air sealing the house is a good investment. there are lots of energy raters in Texas. you should talk to a few and get more information before spending so much for a/c. unlike a lot of audits an energy rating unbiased information that provides a blue print for efficiency, recommendations specific to your home and performance & install verification. best of luck.

breakeroff, You can get a restrictor plate that will reduce the amount of flow into the room that is too cold. If you restrict the air at the outlet, it creates turbulence-induced noise. So the restrictor plate is put on the supply end of the supply duct, right where the 2" duct branches off of the main trunk or plenum that comes off your air handler. The actual restrictor plates are easy to install and quite inexpensive. You may already have one on that line, it may simply be too large in that it is allowing too much flow into the room. I have tweaked the airflow through the plates by applying aluminum tape to the UPSTEAM side of the restrictor plate to limit airflow to somewhere between two commercially available sizes. If there is no restrictor plate currently installed, I'd certainly get one and give that a shot. If you have one installed, you can try to stop it down on your own. If you have more than one outlet in the room, try to treat them the same so you get equal airflow through them...unless the room has non-standard needs, like more cooling over a warmer spot, for example. Mongo

I have a 1930's colonial and am also in NJ. I had a conventional system installed in 2009 and my only regret is that I didn't do it sooner. I received 4 estimates - 1 from a company that only installed high velocity systems, 2 from places that installed both high velocity and conventional and 1 from a company that only installed conventional. Three of the 4 recommended high velocity systems. Most of the estimates per pretty close in price, about 12K. Surprisingly, all of the companies that install the HV system told me they would have to make holes in wall of the staircase to run the hoses to my family room addition. One company suggested that I install a split system in the FR. The conventional a/c installer was able to feed the flexible ductwork through a 2nd floor closet into the FR ceiling. All bedrooms, bathrooms and 1st floor rooms have at least one vent in the ceiling. I lost some closet space in the bedrooms and in the coat closet, but it is a minimal loss. Before deciding on which type of a/c to install, I posted on the "ask the pro's" section of the hvac forum - http://hvac-talk.com/vbb/forum.php They were decidedly pro conventional system and explained the pros and cons of each.