We are south of Houston, so we have hot and humid summers. A/C is used from April until October. Heat is only on for about 2 months. Our house is single story, built in 1984, about 1980 sq ft and poorly insulated but we have added attic insulation. We have single pane windows but hope to change these within the next few years. We're choosing to replace HVAC first because of it's age and some issues we had last summer...not sure if it will last through another season and can't swing both financially. The ducting is falling apart so we're looking at complete replacement. The existing pad is in good condition but elevating it would be more of a hurricane flooding precaution, although this neighborhood has not had a flooding problem and we didn't flood from Ike.

He gave us 3 options since I asked about the tax credit and super efficient models.

Installation of a Lennox 4 ton 14 seer single stage air conditioning system (R410a refrigerant) with single
stage gas heat and replace all supply ducting.
14ACX-048-230 Lennox 4 ton condensing unit
CH33-50/60C-2F Lennox evaporator coil
91M02 Lennox expansion valve kit
ML180UH090P48B Lennox gas furnace
Honeywell Pro8000 digital thermostat
Sheet metal supply and return plenums
Replace all supply ducting with R-8.0 flex duct
Auxiliary drain pan and drain line connections with over flow float switch
Flush refrigerant line set and make connections
Install supply vent with ducting in master close
Enlarge return grill to a 20w x 30h for better air return
High and low voltage connections
Concrete condenser pad with blocks
Double wall flue piping connections
Gas line connections
Remove and discard all old equipment and materials
WARRANTY: 20 years heat exchanger, 10 years parts, 1 year labor.
Materials and Labor Sales Tax
6705.69

ALTERNATE #1: Installation of a Lennox 4 ton 15.50 seer (12.00 eer) 2-stage air conditioning system
(XC16-048 condenser) with 2-stage variable speed gas furnace (SL280UH090V60C) installed as above:
WARRANTY: Same as above
Total Price $8,863.69
NOTE: The condenser and furnace on this system
qualify for $350.00 in rebates from Lennox if installed by 6/3/11. The furnace used in this system qualifies for
a $50.00 federal government tax credit.

ALTERNATE #2: Installation of a Lennox 4 ton 17.70 seer (13.20 eer) 2-stage air conditioning system
(XC21-048 condenser) with 2-stage variable speed gas furnace (SL280UH090V60C) installed as above:
WARRANTY: Same as above
Total Price $10,662.00
NOTE: The condenser and furnace on this system
qualify for $500.00 in rebates from Lennox if installed by 6/3/11. The system also qualifies for a $300.00
federal government tax credit.

Thanks for any guidance!

Additional info, we currently have a 4 ton unit and 100,000 BTU furnace.

2) how long do you think you will be in the home?

3) is there a reason you are not looking at heat pumps?

4) The quality of the installer will be the most important factor in you satisfaction and life of your system. Are you considering other bids?

5) Is flex duct common in an installation such as yours in your area?

6) are you close enough to the ocean to look at coil coatings to help avoid corrosion?

On the whole, I like the second option best of these 3. The staging gives you better filtration options and humidity control capability. Best bang for the buck IMHO

1)why flushing? I suppose it's cost savings but I'd have to ask. I'll speak to him about that.

2)not planning on moving within the next 10 years but who knows what's down the pike. DH works for railroad and seniority moves are possible, especially when the kids are older.

3) Consider heat pumps? I've read very little about them. Not a commom installation in my area but that doesn't mean anything when you're talking builder grade. We have NO idea what's involved in installing that.

4) Quality is definitely a consideration for us. This company is local, in business for a long time, and used throughout my community, and highly recommended. I've contacted other companies, but they did not show up for appts. It sounds lazy, but I'm glad SOMEONE thought my business was worth keeping their appt.

5)Flex is very common. We're soley attic installation due to slab only foundations and past building practices. Have never been in a house with soffits for duct work, not that it isn't used somewhere.

6) We're about 25 miles away. Judging by the state of our current system, corrosion isn't a big issue.

Humidity control is a huge issue here. For the record, our current unit does a fine job of that and it's single stage and OLD. I've never felt uncomfortable when it's running and I'm a big wimp as far as that's concerned. Grew up in Missouri and not a fan of the summers here, especially since I'm a human space heater. Lived in KCMO before we moved here for DH's job, as a matter of fact. I miss home!

Thank you for your opinion. I really like the idea of 2-stage for the efficiency and weather here.

On the lineset. Technically they can be flushed out, and when done correctly this will pose no problem. But if you can easily get to the space to put in a new one, I feel that offers some peace of mind. Now if they simply can't get to it easily, then you will have to trust them to flush it out.

I would feel that with 10 years you will get the return on investment on any of these systems.

Heat pumps basically use the AC "in reverse" flow to pull heat from outside and use it to heat the house during mild cool weather (65-40ish). It is more energy efficient than running a furnace, Some dealers just don't like them as they are more complex, some areas have such cheap gas heating costs that they are not worth it, and they do cost slightly more than AC alone. Also you state or utility energy programs may vary on rebates or electric rates depending on what you install.

You will like the humidity control with these systems.

And I have to get on my soapbox for a bit, and ask if you have changed out your lightbulbs to CFLs from incandesants. The CFLs use less energy, and put out less heat so that means you need less cooling. We changed ALL our lightbulbs, and got a new AC heatpump last May. Our June and July bills were HALF of the previous year!

I just read a bit on heat pumps. It sounds fantastic except for the "back-up" you need in case of malfunction. Ummm, fireplace? That's our back up if the furnace goes, or hotel. Ground source sounds like the ideal, but I'm not sure that will be feasible on our lot.
The last two winters have been a bit cooler. There were several nights in the 30's with a few of those 32 or 31. Climate is wacky all over. Would we need a system in place to supplement a heat pump? I'm hot-blooded, but DH and children are sensitive to cold.

I worry that the heat pump won't be able to keep up with the summer heat/humidity here. This is based on nothing but ignorance on my part, however.

I would so jump on the CFL bandwagon if they didn't contain mercury, require specialized disposal (have a pile waiting for our recylcling program to figure out what to do with them) and emitted a decent colored light. I have some, but I'm not a fan. You would be happy that our kitchen and laundry is almost exclusively flourescent and those are the lights that are on most. If we ever remodel, I'm hoping LED has progressed enough to offer pretty lighting or something else has been discovered.

A heat pump works as an a/c as good as any a/c only system. I have no issues with cooling.

The backup is usually electric strips (in your climate) or can be a gas furnace. If you are talking power outage, no forced air system will work. The best system is hybrid where you have a gas furnace and a heat pump. Yes the cost is more but you have the best of both worlds. If you electric is high, then it is hard to justify even the extra small cost of a heat pump.

Now if you think the electric rate problem will get fixed or you get different rates with a heat pump, that might change the math. It is about $500-1000 to add a heat pump since it is just a reversing valve and some sensors.

Thanks for your help Julie. We really like the second option best, too.