New Build HVAC advice - Gas, Heat Pump, or Hybrid?

pbx2_gwSeptember 27, 2012

Our new build will be blown door tested, energy rated & certified by Earthcraft.

* Located in Central VA - Midatlantic region.

* Usually get mid-40's winters & 90's late spring to mid-August.

* 2x a decade we will get a blast of artic air stringing together several 0 degree days (thinking this year -LOL!).

* I hate humidity - am the polar bear in the family; wife hates cold.

* 2900 sf house

Builder say most of the HVAC contractors bidding for our build are recommending Heat Pump in the 18+ SEER & 9.5 HSPF.

Questions:

1) Read the HP are great a higher temps but worse below lower temps - true?

2) Can a high efficient HP only provide the performance each of us needs?

3) Would a HP + Gas backup be more optimal?

4) Would #2 be more costly I'd imagine? By how much?

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tigerdunes

Natural gas service is available?

Any budget constraints on new HVAC?

Sgl story or two story?

Post back.

IMO

    Bookmark   September 27, 2012 at 1:56PM
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david_cary

NG available = hybrid if you really care about cost and future proofing.

I am not sure I agree with Seer 18 on a well designed house. In a new house, you are better off putting the money into design than seer 18. A well designed house takes very little to air condition so the payoff for high seer is never.

In NC, this summer was $300 to a/c. Total season. I have 20 unshaded East windows. Designed better and that total would be $150 (or when the trees grow up). Seer 18 could save $20 a year....

Today - no heatpump can touch NG for cost when it gets below 30 degrees. A well designed house doesn't need much heat above 30.

The sweet spot in your climate (IMO) is seer 15 or 16 with NG hybrid system. But if you design right, then seer 13 is actually the most cost effective.

    Bookmark   September 27, 2012 at 3:14PM
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pbx2_gw

Hi tigerdunes:

Natural gas service is available?
YES

Any budget constraints on new HVAC?
I'm sure that the builder does have a budget in mind as part of the total price of the project but what that number is we haven't discussed in detail.

Sgl story or two story?
1.5 stories - with upstairs being 2 bedrooms & 2 baths.

    Bookmark   September 27, 2012 at 3:21PM
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pbx2_gw

Posted by david_cary (My Page) on Thu, Sep 27, 12 at 15:14
NG available = hybrid if you really care about cost and future proofing.
This is a objective for sure.

I am not sure I agree with Seer 18 on a well designed house. In a new house, you are better off putting the money into design than seer 18. A well designed house takes very little to air condition so the payoff for high seer is never.
Interesting, would I see a big drop in pricing if I went down to a SEER 17 based on the scale I've seen referenced here: 15 (good), 16 (better), 17 (best) plus a 9.5 HFPS?

In NC, this summer was $300 to a/c. Total season. I have 20 unshaded East windows. Designed better and that total would be $150 (or when the trees grow up). Seer 18 could save $20 a year....
I see what you are getting @.
Our house is longer rather than wide or a 4 square box.
So sun rises in the back & sets in the front.
With the main side facing south & the auxiliary side facing north.
These last 2 sides have the most windows 11-12 (again house is longer than wide) while upstairs have 3-4 at most.

Today - no heatpump can touch NG for cost when it gets below 30 degrees. A well designed house doesn't need much heat above 30.

The sweet spot in your climate (IMO) is seer 15 or 16 with NG hybrid system. But if you design right, then seer 13 is actually the most cost effective.

It seems I can some upfront savings by shaving off a couple tiers off the SEER since our house is well placed for cooling but not so sure the below 30 days can be accommodated by just the HP with electric radiator backup.

More costly to do hybrid HP/NG correct?

    Bookmark   September 27, 2012 at 3:41PM
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pbx2_gw

** to add - we are basically on a lot with NO mature tree shading on any side.

    Bookmark   September 27, 2012 at 3:43PM
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weedmeister

If you have gas (not propane), then the HP/NG is the way to go.

As to good/better/best, let me exaggerate a bit. If good is $1000, better is $2500 and best is $10,000, then which would you chose? The more cost effective would be 'good'.

What you will see with SEER vs price is that the delta price will increase between each level of SEER. But the percent decrease in electrical usage will be the same. Hence you will take much longer to make back the money you would spend for higher SEER, if ever.

    Bookmark   September 27, 2012 at 4:32PM
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david_cary

There appears to be some confusion.

If you have NG (and you do), you would never use electric resistance backup. Sure it will cost more money but probably about the stepup from seer 16 to seer 18.

I think it was about $1000 more to do NG backup than electric strips in my situation.

    Bookmark   September 27, 2012 at 4:52PM
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pbx2_gw

Posted by david_cary (My Page) on Thu, Sep 27, 12 at 16:52
There appears to be some confusion.
If you have NG (and you do), you would never use electric resistance backup.
My statement should have been read as - for my bidded options of HP alone, the 'fail-over' is the electric radiators.

Sure it will cost more money but probably about the stepup from seer 16 to seer 18.
Contextually, it appears I can negate some of the added cost of a hybrid backup system by 'stepping down' from 18 to a 15 or 16 SEER HP...just what I wanted to hear. :)

I think it was about $1000 more to do NG backup than electric strips in my situation.
Sounds manageable & maybe even bettered if I can get the SEER savings by stepping down a level or two.

Thanks for your feedback D_C!

    Bookmark   September 27, 2012 at 5:31PM
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pbx2_gw

Posted by weedmeister (My Page) on Thu, Sep 27, 12 at 16:32
If you have gas (not propane), then the HP/NG is the way to go.
As to good/better/best, let me exaggerate a bit. If good is $1000, better is $2500 and best is $10,000, then which would you chose? The more cost effective would be 'good'.

What you will see with SEER vs price is that the delta price will increase between each level of SEER. But the percent decrease in electrical usage will be the same. Hence you will take much longer to make back the money you would spend for higher SEER, if ever.

Great example. I think the upfront cost benefit to go to a higher SEER level vs. return in cost savings is not worth it.
I think sticking with a good/better SEER & using those savings to do what I have read you all suggest now & in prior threads gives us the biggest bang for the buck.

Thanks for the feedback!

    Bookmark   September 27, 2012 at 5:40PM
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Britney80

Not sure if this will help you, BUT if you are thinking about going with a high effiency unit, I would not, I had one and had SOOOO many problems with it, I ended up going with an American Standard I think it is called, same as Carrier and all the big names its jsut a lot less money to pay.

    Bookmark   September 28, 2012 at 2:34PM
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pbx2_gw

Posted by david_cary (My Page) on
Thu, Sep 27, 12 at 15:14

NG available = hybrid if you really care about cost and future proofing.

I am not sure I agree with Seer 18 on a well designed house. In a new house, you are better off putting the money into design than seer 18. A well designed house takes very little to air condition so the payoff for high seer is never.

In NC, this summer was $300 to a/c. Total season. I have 20 unshaded East windows. Designed better and that total would be $150 (or when the trees grow up). Seer 18 could save $20 a year....

Today - no heatpump can touch NG for cost when it gets below 30 degrees. A well designed house doesn't need much heat above 30.

The sweet spot in your climate (IMO) is seer 15 or 16 with NG hybrid system. But if you design right, then seer 13 is actually the most cost effective.

So our builder came back with a dual fuel system option from Trane (not sure which model/config) that essentially takes our his original 18 SEER & reduces it to 16.25/9.0 + Dual fuel backup for about $1k more.

Or we could go down to 14.75/9.0 for no upcharge.

Any thoughts based on my Central VA/MidAtlantic weather & my super tight home?

    Bookmark   October 1, 2012 at 10:30PM
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david_cary

I'd do the 14.75/9.0. But what is the efficiency of the NG component?

I have a 90% because of a basement location - it was actually cheaper. I have been in the house 3 years and have used about $500 in gas so the 80% would probably cost $15 a year more to run. (5000 sqft house)

You should know that "energy rated" does not at all mean that the house is being built with best practices. My biggest regret is not doing a better wall system - just adding an inch of rigid foam would really futureproof your house but payback is likely 15 year range. Of course, dropping to seer 13 and using the savings here will be a better long term financial decision. With NG costs right now, it is really hard to justify much $$ invested on the heating side without a long outlook.

Mature trees are nice but you can get window coverage pretty quickly with planted trees. Sounds like West is the front. What I find works well is a flowering tree planted fairly close to the house centered on a window bank. You can crop the lower branches as it grows so the window view is not blocked and the house is still visible - but within a few years, you get a great reduction in the heat gain from that window bank.

    Bookmark   October 2, 2012 at 6:05AM
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pbx2_gw

Thanks for chiming in again david_cary.
Cooling wise - our west facing front porch is covered from the sun for most of the day.

We anticipate landscaping with a small pear tree in the front but that's about it.
The long southern side where I mentioned has 11-12 windows will provide some ancillary heating from the sun but here's where we stand:

Heat Pump Only (SEER/HSPF: 18/9.5)
Pro's
Great Efficiency
Great SEER/HSPF
Low operating cost
Con's
Could feel cold below 32

Heat Pump+Gas Backup (SEER/HSPF: 14.75/9.0/95 or 16.25/9.5/96.7)
(Split System)
Pro's
Above 32 good efficiency
Gas heat can be used any temp
Warm air feel
Con's
Less efficiency than above
$1K more than only HP @ this ratings =>>> 16.25/9.5/96.7

    Bookmark   October 2, 2012 at 11:07AM
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pbx2_gw

Adding some additional model info - would appreciate any feedback.

HP only (18.0/9.5): Trane XR16
Split Higher Efficiency (16.25/9.0/96.7%): XR16 with XV95 furnace; $1K upcharge
Split Lower Efficiency (14.75/8.5/96.7%): XB14 with XV95 furnace (XB14 functionally equivalent to XR15 per Trane rep); no upcharge.

    Bookmark   October 2, 2012 at 1:52PM
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weedmeister

I'm not sure about using a 95% gas furnace due to the extra up-front cost. You might want to ask for a bid on an 80% furnace.

With the dual fuel, you will have an outdoor temp sensor. You will adjust the thermostat control temperatures for when the gas is used (below a certain temp) and the HP is used (above a certian temp) based on comfort and your electric rates (these temps will overlap). VA rates aren't that bad right now (~$0.08/kwh) but I'm sure will climb in the future.

    Bookmark   October 2, 2012 at 3:31PM
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pbx2_gw

Good point weedmeister.
The efficiency builder we are contracted with likes those big E numbers.

However, it does appear he's willing to sacrifice the Heat Pump somewhat for essentially a part-time component & it's big 95% #.

    Bookmark   October 2, 2012 at 3:53PM
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weedmeister

What I meant to say is that if you were doing a gas furnace only, then the 95% would be the way to go. With a HP along side, a less expensive furnace would be fine since you would not be using it that much and the cost savings in gas of the 95% vs 80% wouldn't amount to much.

But you might want to also check out any rebates that you might get from the gas and electric company. This would also figure in.

    Bookmark   October 2, 2012 at 6:00PM
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