Hmm. a superficial look seems to point towards replacing the 19 year old gas furnace and a/c with a heat pump with new gas backup. Hope it can go in the same utility room behind the garage.

Maybe I should take my plans, and some photos, to a TRANE showroom and let them educate me a bit. Or do I hire a consultant?

lyvia

heap pump systems are a forced air system fueled by electricity rather than fossil fuel like oil or nat gas. yes, it requires a ductwork system properly sized and designed to deliver the air.

here are my specs.

these are my minimum specs for a new HP system. both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF
best matching VS air handler
full BTUs in both cooling and heating for your rated size
R-410a refrigerant(same as Puron)
scroll compressor preferred
electronic demand defrost preferred
thermostat with "dehumidify on demand" feature
staged backup heat strips
new and correctly sized refrigerant lineset

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

I would only use authorized dealers for the various brands that provide quotes. see mfg websites.

I would look at Trane/AmStd,Rheem/Rudd,Carrier/Bryant.

I would not purchase a new HP system that did not have electronic demand defrost.

it should be noted that living space over a garage known as FROGs (finished room over garage) are notorious for heating and cooling mainly due to inadequate insulation qualities, poor ductwork design/sizing and incorrect sizing of HVAC.

dual fuel-HP with gas backup seems reasonable for your area/climate. you do have nat gas service not propane? pls confirm.

your HVAC dealer should have demonstrated experience in ductwork design. request a load calculation for new addition and get this in writing.

IMO
Good Luck!

lyvia,

To clarify on the basic functionality of a heat pump ... it's an air conditioner that reverses from cooling to heating. Not literally the compressor runs backwards, but the cooling process reverses so that instead of cooling the house and pumping heat outside (cold air blows from the registers, hot air from the outside unit), it cools the outdoors and pumps heat inside (cold air blows from the outside unit, warm air blows from the registers in the house). Think of it as a window air conditioner turned around backward in the window.

The most important question is what are your electric rates. If high, upgrade the furnace and a/c to include the extra area. If low, then a straight HP is a good choice.

You should know that Seer 13 is the lowest allowed by law. Not necessarily horrible but it is the least efficient option.

Thanks so much for jumping right in! You've already given me a lot to ask the GC.

The existing furnace is natural gas.

The electric bill says 835 kWh for Dec.
distribution is 25.75,
generation is 32.66
transmission is 2.33
fuel is 23.41
plus 5.82 tax and surcharge
total 89.97

the gas bill says
82.9 therms @ $.79/therm plus $.80 for balancing is $66.29
plus distribution tax and service charges 44.08
total $110.37

Hmm. So the spec sheet doesn't say much of anything when it says a SEER 13 heat pump.

DH says the system can be in the attic with both the forced air registers and the cold air returns in the ceiling, so no chase/soffit structure. I am skeptical there. He is from Las Vegas, which is a different planet.

In TX where I'm located it's largely standard procedure that forced-air HVAC has the output registers and air returns in the ceiling, with the blower unit in the attic ... but cooling takes priority here, perhaps heating is more priority at your location.

heat pumps are surprisingly versatile and efficiently use electricity. You would be better off upgrading to highest efficiency single stage heatpump with demand defrost.

Heatpumps are not good at bring temperature back up in a quick time. Heat pumps work best at maintaining temperature.

When its sleeting/snowing out you will discover your heatpump to go into defrost alot. (if you have demand defrost). This is probably the least desirable thing about a heatpump but its part of life. If a heatpump didn't go into defrost, the outside coils would ice over. Iced over coils don't allow air to cross them and its not efficient to run. When its not sleeting/snowing out they run without going into defrost often.

I'm currently running my heatpump. Outside temperature is 22 F. Inside is 67. Vent temperature is is 86. Thats a 19 degree rise. Its running pretty constant to maintain this temperature but thats not a bad thing.

You should look into upgrading your main furnace and A/C to a 95% gas furnace and heatpump. Gas is nice for when sleeting/snowing or extra cold.

Attic handlers with registers and returns in the ceiling are fine but keeping things out of the attic is more efficient. Your best choice (IMO) is upgrade to dual fuel (NG for really cold, HP for mild) - this costs the least to run. I am in a similar climate (NC) and paid $700 total last year for heating 4000 sq ft. The estimate for using just NG was $1300. I wouldn't say that whole savings was dual fuel, but I suspect half of it was. Your prices are similar to ours although your electric is a tad more. The NG is hard to figure because there might be a $20 or so charge even if you use no NG so it is hard to figure your actual therm charge.

sounds like Lyvia isn't getting rid of gas. Getting a heatpump is always a good upgrade though.

Heatpumps don't cost much more than the same model A/C (unless the installer is taking extra profits). And heatpumps can do both heating and cooling. They are plenty efficient too. Even with very cheap gas (which won't last forever), they compete pretty well in terms of cost to heat house.

Not to mention heatpump heat is a more modern, even heat. Which heats a house evenly and thoroughly without cold spots.

"Not to mention heatpump heat is a more modern, even heat. Which heats a house evenly and thoroughly without cold spots."

modern heat,even heat, without cold spots? humm...

To answer one question, a heat pump cools just like regular A/C. There is no difference.

VA is around $.08-.10/kwh for electricity and is still regulated. It would not surprise me if it started going up some time soon.

Your old equipment is not at the end of its life, but it is getting there. It might be a wise move to include upgrading it now with this construction rather having to do it 5-yrs from now at increased cost.

You will want a variable speed blower around here. It makes a BIG difference with humidity removal during the summer. A 2-stage compressor is not really that important, or useful in my opinion.

One of the things you will need to decide is whether you want to have a single system doing the whole house (3000 sqft) or two systems. I think you should bid for both.

As Tiger suggested, you should get multiple bids from different HVAC contractors.

And dual-fuel (electricity + gas) is a Very Good Thing.

So if I get a heat pump in the attic for the rooms over garage end of the house, can I keep the gas furnace where it is (utility room directly behind garage) for backup, or does the gas backup have to be co-located with the heat pump?

I'm guessing I would need a few registers to get the heat from the furnace to the new rooms, but that would be in the garage ceiling - no biggie. And then a way to turn that zone off/on. A gas furnace downstairs with two zones - is that what we want?

lyvia

if your current system is performing satisfactorily providing good service,comfort, and operating cost, I would leave it alone.

Install a complete separate system for the addition.

In the long run, you will be better off.

IMO
Good Luck!

"modern heat,even heat, without cold spots? humm..."

tigerdunes- I'd have said this myself just a few weeks ago. We ran on just our 80% gas furnace for about 10 days while I figured out and replaced a dead HP condenser fan motor.

Qualitatively, I thought that the longer run time of the HP did a better job of keeping the whole house warm. I got a good whack of a haircut in the same timeframe and found myself wearing a knit cap much of the time to keep warm. I may have adjusted, but I haven't felt the need with similar outdoor temperatures and the HP running the past few days.

lyvia- tigerdunes gives good advice on replacing the old unit. It'll take a long time for higher efficiency to pay for the replacement cost (the Energy Star site likely has a calculator for it). With the tax breaks expired, there's not as much of a driver to replace if it ain't broke. But take a look at your utility, they may have some incentives that would sway that differently.