Building a custom home - HVAC options - could use a bit of help please!

[ameliasolis]

Hi!

We are in the process of building a 3200 square foot custom home in North Carolina. We have been approached by the HVAC contractor and given three options for the systems we can choose (he has estimated a 2.5 ton system upstairs and a 3.5 ton system downstairs). They are all Trane systems and are:

Option #1: The XB1000 air conditioner (10 SEER) with the XE80 gas furnace for approximately $12,000***OR***
Option #2: The XR12 air conditioner (up to 13 SEER) with the XR90 gas furnance for approximately $15,000***OR***
Option #3: The XL14i air conditioner (up to 15 SEER)with the SV90 gas furnance for approximately $18,800.

Our questions are:

1. In light of the upcoming regulation changes, what would be the mininum expected requirement for a custom home?

2. What are the real differences in comfort one might feel in the different systems (I am more sensitive to heat and humidity versus cold)?

3. We are not on a gas line, therefore, we will be on propane and option #3 includes a two-stage gas furnance. What kind of savings can we expect to see with a two-stage system?

4. We have a fairly open floor plan; however, there were no deisgned-in locations for the return ducts. Our contractor has proposed two locations within 7 feet of each other (no barrier walls involved) for the first floor. Will this be sufficient to adequately draw air?

5. He has also presented the option of an electronic air cleaner at a cost of $1495 - are these worth that expense? Do they really help with dust?

Our general contractor has not offered the option of getting other "bids" to verify fair pricing and the HVAC company is ready to start working now. Any help, advice or guidance offered would be most appreciated.

Thanks!

 

[duffer]

I've built 8 new houses in my life. I've always used "the best" option for HVAC. Never go on the cheap.

Based on the options your builder has given you, I'd seek out another quote on your own from another HVAC contractor. Carrier or Trane are both good systems. 15 seer is lower than I would go. They make equipment up to 20 seer now. Higher the seer the more efficient it is. I have 17 seer. Very efficient and low utility bills. And with you being on propane, the more efficient the better.

Also, you should be able to get a "zoned" system. One AC condensor, one furnace with 2 zones of ductwork. It's what I have in my home now. Works great. Separate thermostats for each zone. Costs a little more for ductwork installation, but lowers the overall costs on 2 condensors and furnaces.

And putting both return ducts 7' apart is mal-practice IMO. I'd never put them that close together. Contractor is trying to make it easy on himself (jeeze...there's a surprise).

And remind your builder whose house it is, and who is paying the bills. If you're not satisfied with his HVAC contractor he can easily find another for you. He just doesn't want to.

 

[ericm979]

I'd want to see the Manual J load calc and Manual S sizing that the HVAC contractor did. (or some alternate method other than guessing or what's in the warehouse). 6 tons for a modern well insulated and sealed 3200 sq ft house seems like a lot.

Where you are (not too cold) heat pumps or even mini splits or small ducted systems may make sense, especially if your electricity rates are low compared to propane costs. Or even better if you have or plan to have solar.

Ducting (for a ducted system) is really important. Our house built in the '80s came with just one return. We had one added which took some fancy custom metal work for a plenum and it helped the system's performance. Make sure the ducts are large enough.

These days I'd want a variable speed/output furnace. It's more comfortable than the temp going up and down with a single speed/output setup. I wish our AC did that. That's one of the advantages of mini splits and other inverter based heat pumps, they can run longer at less output to keep the temperature more stable.

Your contractor should not rush you on this. If he didn't start you on making the decision far enough in advance that's his fault not yours.

 

[Roadworthy]

For answers to all your questions I suggest getting an evaluation and bit from a second HVAC contractor. They are NOT all the same. HVAC generally falls under the purview of a mechanical engineer. Finding one of them may be a wise investment. If your contractor doesn't offer the option of other bids is there anything to prevent doing so? Is the HVAC contractor in collusion with the general contractor? Perhaps a consultation with an attorney regarding your contract is in order.

 

[JM7500]

Another thing to consider is the ductwork material. It should be wrapped hard duct with only a short run of flexible duct (>5') to the register. 10 SEER is to low. In 2005, I put a 14 SEER 5 ton heat pump with a variable speed supply fan on a 3000 sq ft house. I agree with ericm and using the Manual J to size the units. This is a code requirement in some jurisdictions. Most major brands (Trane, Carrier, York) are good and manufacture most of the secondary brands.

 

[JDAOWNER]

I HAVE A 2500 SQ.FT HOUSE, HAD A 15 SEER -3 TON-HEAT PUMP/AIT CONDITIONER INSTALLED LAST YEAR AND LOVE IT. HEAT DOWN TO ABOUT 35 AND AIR WHEN IT HOT. I HEAT WITH FUEL AND THE HEAT MODE HAS SAVED ME A LOT OF FUEL. I HAD 5 OR 6 QUOTES FROM 15K TO 6K.

 

[WM75Guy]

We have a comparable size all-electric home, 3200 square feet on 1 floor with a Trane 3.5 ton for the living areas and Trane 2.5 ton for the 3 bedrooms. They were installed in 2009 and are 14 SEER. The entry way which has 17' ceilings has ducts from both systems feeding it as it has a dormer and gets the west sun. We have auto season thermostats set from 68 - 72 degrees year-round. The house also feeds the barn which has a mini-split system in the tack room. Between the 2 buildings there are 4 refrigerators, 3 hot water heaters, and 2 laundry rooms. We have average billing which is running around $250/month on coop electric at $0.105/KWH.

I would go with the best system you can afford but also put your money into insulation. We also have R15 blown insulation in the walls, R44 blown in the attic, and double pane insulated windows. The deck sheeting on both the house and the barn is the reflective sheeting which prevents radiant heat coming into the attic, similar to LP Techshield as an example. Along with good ventilation the attic stays tolerable even in the summer, lessening the amount of heat radiating into the house.

 

[WM75Guy]

Here is a picture showing the reflective deck boards. It is installed with the foil side down. If you zoom in you can see the instructions saying that.

 

[JimRB]

I believe the past 2 issues, or maybe three issues of Fine Homebuilding will answer the questions you should be asking. One issue talks about leaky houses and controlling air. I am pretty sure one of the issues talks about SEER. In days of old you could go to the library to look at magazines. Not sure if libraries do that anymore. They may have digital magazine subscriptions.

I have a geothermal system in my house. I love the not hot heat. I mean the heat comes on and warms things up and turns off. When it turns off you do not feel like you walked from standing in the sun to standing in the shade. Of course some of that could just be my mother's leaky slab house versus my not as leaky house with a basement.

 

[jk96]

I believe the past 2 issues, or maybe three issues of Fine Homebuilding will answer the questions you should be asking. One issue talks about leaky houses and controlling air. I am pretty sure one of the issues talks about SEER. In days of old you could go to the library to look at magazines. Not sure if libraries do that anymore. They may have digital magazine subscriptions.

I have a geothermal system in my house. I love the not hot heat. I mean the heat comes on and warms things up and turns off. When it turns off you do not feel like you walked from standing in the sun to standing in the shade. Of course some of that could just be my mother's leaky slab house versus my not as leaky house with a basement.

Geo uses a lower air volume as well and makes for a very quiet system. Usually never even know if ours is on or off.

If you get a chance do a blower door test prior to sheetrock to help with air sealing.