1st choice 95+% eff two stage var speed furnace with high eff AC

2nd choice 80% eff two stage var speed furnace with high eff heat pump

Tell us about your new home-design, layout, size

Don't like the selections your builder has suggested.

R8 ductwork insulation with correctly sized supply and enough return air.

IMO

Likely to need 4 units! How big is this house? Can you give a general description and size of each level?

In general builders and general contractors know very little when it comes to HVAC. They are also going to spend the least amount of money possible since most home buyers don't know a good system for a bad one. The money goes into the kitchen and bathrooms.

It sounds like you are investing in upgrading the insulation. When you get the Manual J calculation review it carefully. If it doesn't make sense to you it is likely to be wrong. Most contractors don't do a Manual J calculation and even fewer are prepared to discuss it with the homeowner.

I recommend staying away from any builder's grade equipment such as the Carrier CA16NA. The Atlanta summers are hot any you want equipment which will hold up to a lot of use. The 59TP5 furnace is good, but it is not have a variable speed blower. The variable speed air flow will help lower humidity and increase comfort. I would suggest looking at the Infinity 59TN6 furnace, or other manufacturer's variable speed furnaces. In the Carrier line my recommendation with be the Performace AC or higher. I am a fan of the 2-stage condensers with a variable speed furnace. It gives the best humidity control. It would also be the way to go if you incorporate zoning in any of you systems.

Thanks Tigerdunes.

The house is approximately 6,000 square feet. Approx 2800 on first floor and 3200 on second floor making use of some space over garage. Only part of basement will be finished (exercise room and office). House will be easy to divide north/south with hallway on both levels splitting the house. Initial thought was to have two units per floor. Three can likely be similar size and the forth may be slightly bigger to account for space over garage too. Not sure what to do about basement yet but likely its own unit. Not only is it easy to split north/south but that line naturally splits space used frequently versus not as often.

One question is if it's a total waste to have one "nicer" system for the part of the floor we use most often with the other one a step down. Part of me thinks since the spaces are so close together and won't be sealed off completely from each other is it's either all or nothing.

My understanding is because of the foam insulation, we'll need to use 95% eff furnace so the only question there is variable speed or settle for multi speed.

Thanks!

You could do zoning controls one system for second floor. Straight two stage high eff heat pump with VS air handler would be fine. Dealer though must have demonstrated experience with zoning and good ductwork design.

IMO

I'll leave most of your questions to the pros, but we recently installed 2 Carrier Infinity systems. We are in the Houston area and had 109 temps with no AC, but its been raining off and on since they were put in. We've gotten a good test of the humidity control. I think you'd like it. You can set the thermostat to cool to temp or to make humidity control the priority, but in either case, you have that low speed fan running all the time and never feel or smell a blast of warm air when the unit cycles on -- something I hadn't really thought about until I found I wasn't missing it at all. The Performance was our other option, but if you're building a home at that level, I'd go up to the Infinity.

Keep in mind that each unit adds thousands to the cost which each ton only added about $400 in my case.

My initial thoughts would be two systems, one with each floor. Each floor would be split into two zones. In this situation I would spend the extra money on modulating furnaces with 2-stage AC condensers. The basement could be a third zone of the first floor if you want to have good temperature control, but I am not sure it is necessary. I can't imagine ever having to provide heat to the basement given the mild winters of Atlanta. It should also be cooler then the first floor so no cooling should be required.

This is a big house so it merits careful planning. I would want the HVAC systems in the basement.

The amount of zoning and zoning controls is up to you and your budget.

Correct sizing, equipment selection, good ductwork design are paramount.

However, the most important is finding a qualified dealer with demonstrated experience in zoning, zoning controls, ductwork sizing and design.

I personally believe Carrier/Bryant have the best integrated residential zoning in the marketplace.

I normally agree with Mike but I would prefer the second floor system to be attic located rather than in basement. Ductwork would require R8 insulation or better.

While modulating furnaces are nice, I think they are overkill for Hotlanta location/climate where average winter temp is around 40 degrees.

IMO

Tigerdunes,

The reason I suggested a modulating furnace is to decrease the chances of problems with zoning. It may work with a 2-stage variable speed furnace. This is where a contractor with zoning experience can guide the customer.

I don't like the idea of duct working baking in an attic in Atlanta. This house is big enough to build a utility room on the first floor, so that may be another option.

Thanks for the thoughtful and detailed responses and personal experiences. I heard so many negative thoughts about zoning that I honestly never considered it. Given the comments, I'm going to make a renewed effort to learn more about the zoning experience of the folks we're talking to. Also - because of the foam in the attic, hopefully the ductwork won't be baking up there.

For Hotlanta, I would forget a furnace/AC combo for upstairs and consider a straight high eff HP/air handler system with zoning controls.

I think the key to satisfaction is the equipment selection and sizing, the zoning controls proposed, and a dealer who knows what the heck he is doing.

IMO

With a foamed attic, no problem with ductwork located there. Still like the idea of a two stg HP for upstairs system.

Downstairs can be 95% eff 2 stg vs furnace with high eff AC or 80% eff furnace with AC or HP.

Atlanta can have brutal summers and moderate winters usually with a couple of cold blasts.

Obviously this home will have excellent building and insulation properties.

Now is the time though to do your homework on HVAC.

IMO

I always hear the expression "Hotlanta", but is it really that hot? According to The Weather Channel the average high temperature in the summer is 89 degrees. Compare this with Newark NJ were the average summer high is 86 degrees. That's a 3 degree difference yet you don't think of Newark as being oppressively hot.

Either there are big swings in the summer temperatures which make the average look reasonable, or the humidity is constantly high which makes everyone uncomfortable. Whatever the reason you want a properly sized HVAC system.

This post was edited by mike_home on Mon, Jul 22, 13 at 8:20

Mike

Suggest you go to Atlanta in July and August and report back.

Yes it is quite hot there...and humidity is terrible.

IMO

Mike,

"I always hear the expression "Hotlanta", but is it really that hot? " And Atlanta's annual rainfall is 50" compared to 38" in Seattle. ;-)

People must be feeling a high heat index caused by the temperature and high humidity.

I am looking forward to seeing the Manual J calculation on this house.

Thanks to everyone who helped with this thread. Just received the first set of J calcs. To avoid duplicate threads (and to attract others who may not have looked at this one) I'm posting a new thread with the results attached and would appreciate any insight on something that doesn't look right. Thanks again.