David, I live in dry CA and honestly have not done any research on how it affects humid environments so my experience can't offer you much help. Did it work? It helped reduce my electric usage immediately and the air temp differential from a vent dropped by about 3 degrees immediately. I didn't test much after that, but the before/after differential was done two days apart at the same time of day. I was keeping my thermostat between 81 and 83 (damn sweaty hot) and still had a $400/mo pge bill (~1700kwh) and after the RB I kept it at 77 and the bills were between 10 and 20% lower. The bills compared year-to-year were so much lower over 12mo period (20%?) that the utility gave me some kind of automatic refund. I bought my stuff from Horizon (savenrg.com). They are in Phoenix AZ where the climate is a bit worse than mine, but similar. They aren't a flashy company, obvious from their site, but their material made so much sense when I confirmed from other sources. It's not cheap. The owner also helped teach me the DIY w/duct sealing: making sure all joints are tight (ties/metal straps), lathering on tons of mastic on them, and applying metal backed tape where needed. Dust is the #1 killer of a radiant barrier. Their site explains it and how multiple layers of reflectivity, when separated adequately (scrim), keep the RB working even when dusty on the top layer. The RB on the floor, above the insulation, is triple layer. The ducts are wrapped with their ducting RB which is double layer and I put the triple layer on the top-parts where the dust might collect. Either way, I'm not taking chances as I'm having my roof replaced and afterward I'm going to cleanup & dust where it's easy to do so. After the 15 months I went back up to check out dust and it was very minimal, except directly under the dormer vents where a handful of smaller leaves/dirt had dropped. Ducting: That's existing flex ducting (r4/5 don't recall) wrapped w/multi-layer RB. RB under Roof I'm not sure it will help all that much to put RB under the roof when it's already on the attic floor + ducting like mine. Their site also talks about this. IMO I'd be creating an oven situation, but in reality I don't know if it matters. I currently have shake roof w/stick frame so it slightly breathes there and through the ventilation at night. However, once it goes to OSB w/composite shingles, I'm relying on the vents anyway. The roofing salesmen say "sure it helps, anytime you can prevent heat from entering the attic in the first place is good" as they try to sell the OSB w/tiny bit of foil on the bottom of it. I don't know if that works w/out creating conductive heat transfer that then radiates in the attic. As far as whacky CA rules, yeah no kidding. I honestly think in certain parts of CA they should've left the R alone and just suggested RB properly installed. I was hoping bluelogic would've been subscribed to his original thread and could tell us what happened with his project.

Thanks Tigerdunes. Yeah I only looked at the Infinity condensor as 1 possible option. The thinking is replace the compressor/coil now and then later when money is not so tight, add the matching Carrier furnace. The tech mentioned that the coil would swap in easily enough without having to reconnect or evacuate the lines again. But I am not loving the idea of breaking this down into two parts. Seems like the less we handle the coil, the better. Not to mention additional labor costs vs whole system replacement at once. Here in the Southeast we have been having a very mild but wet summer. I think I might just hang on for 2 or 3 more weeks, save my pennies and re-evaluate in the spring. If money/economy is still a problem, then I can decide to go with A/C components only. The wife and kids have all been trained to bang on the outside fan housing to get it working on start up LOL. The rebate situation is unclear- not sure if Carrier will extend it next month (Sept.) or not. TigerDUnes you mentioned the Fed energy tax credit for the Infinity 17 system that you spec'd. What kind of $ savings and how does that work or can you give a link? I emailed the Carrier rep yesterday to add whole system quote and revise the a/c quote to reflect keeping the fiberboard plenum and factor in the cash discount but have not heard back. Thanks a "ton" for your voice in the middle of darkness.

FWIW, I just had AC installed this summer. It's a mid-60's 2-story in CT with HWBB heat, no existing ductwork. We had options for single system, 2 systems, and high velocity (Unico). I decided to go with the 2 systems: 1st floor system installed in the basement, 2nd floor in the attic. The reasons were the ability to "zone" the system, not having to give up space to build a chase, and less cutting of drywall. We had an interesting problem getting A/C to the family room, which is on a slab on the 1st floor behind the garage. Due to the layout, we could not get ducts from the basement to the family room, so instead it's fed from the 2nd floor system, with the ducts run through the garage and into the family room attic. In practice, it works very well, as the family room stays within 1 or 2 degrees of the upstairs, and the comfort level is excellent. So here's a vote in favor of 2 separate systems.

First thing I would do is unplug the current duct and verify it is getting good air flow. You want to make sure the original duct was not disconnect further back towards the air handler. You also want to observe if there is an noticeable decrease in air flow to the other supply vents. If the air flow is good, then I suggest running a 6 or 8 inch hard duct to each bathroom. If you have to use a flexible duct then use an 8 inch diameter. The air flow in a flexible duct is not good as a hard duct so it is best to use a larger diameter. These are small bathrooms and you should have sufficient air flow to keep them warm or cool. You should not have a problem if your system was properly designed and has good air flow to the other supply vents.