Heres An Open Ended Question

 
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Old 02-10-2012, 01:39 PM   #1
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Heres An Open Ended Question


What is the most efficient way to heat and cool a new construction house in Iowa? Average house, r 49 in attic, r19 in walls. Geo, Natural Gas Furnace and central air, Mini Splits, Other. I am always looking for the best ways, but everyone's got their own opinion. Should be interesting

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Old 02-10-2012, 05:37 PM   #2
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Re: Heres An Open Ended Question


Have you done a heat loss calculation on the building?

I would use something that has a flame in it.

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Old 02-10-2012, 05:52 PM   #3
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Re: Heres An Open Ended Question


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What is the most efficient way to heat and cool a new construction house in Iowa?
In terms of what? Cost, labor, energy footprint, how many Nubian slaves... ?
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Old 02-10-2012, 06:31 PM   #4
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Re: Heres An Open Ended Question


Geo would be the most efficient.

How practical to install varies.
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Old 02-10-2012, 06:56 PM   #5
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Re: Heres An Open Ended Question


Geo or some way to use solar would be ideal, but seeing as there is the reality of a budget, my vote would be duel fuel, although there are some hiccups there as well.
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Old 02-10-2012, 07:37 PM   #6
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Re: Heres An Open Ended Question


I agree with flash. Wait no what no that cant be right.
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Old 02-10-2012, 11:25 PM   #7
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Re: Heres An Open Ended Question


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In terms of what? Cost, labor, energy footprint, how many Nubian slaves... ?
As far as most bang for your buck. Will Geo or solar pay for itself within 5 years, 10 years? If it would take 20 years to pay for itself I guess I would not be interested. What is this dual fuel talk? I guess I would be looking at what would be the cheapest in the long run, say 10 years or so. No heat loss calcs, just a hypothetical average home being built today.
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Old 02-11-2012, 03:10 AM   #8
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Re: Heres An Open Ended Question


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Originally Posted by TheStud

As far as most bang for your buck. Will Geo or solar pay for itself within 5 years, 10 years? If it would take 20 years to pay for itself I guess I would not be interested. What is this dual fuel talk? I guess I would be looking at what would be the cheapest in the long run, say 10 years or so. No heat loss calcs, just a hypothetical average home being built today.
Duel fuel is electric and propane running on the same system. It's also called a hybrid system.

Around here, 40 degrees and above is electric, while 39 and below the propane kicks in.

Can get mighty expensive with natural gas prices if you don't have a secondary heat source (ie wood burning stove) to offset the cold days when your around to keep feeding the fire.
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Old 02-11-2012, 03:55 AM   #9
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Re: Heres An Open Ended Question


I have heard really good responses to the dual fuel options, when natural gas is available. Our nat gas rate here is $.878 a therm. I have straight gas in my home. 1800 sq ft ranch, 1964 era, only r-11 walls, and r-30 overhead, no crawlspace insulation at all. I spent $111 for Jan, $122 for Dec, $75 for Nov. that is with a nat gas 40 gal water heater and a nat gas dryer for family of 4. My thermostat is on 74 day and night, with single pane 50 year old wood double hung windows.

We pay $.09 cents a kilowatt for power. It will be 15 degrees F here saturday night with a windchill at 0 F. It'll be 74 degrees in my house and I'll spend $5 bucks for all day.I just installed a new Ruud acheiver package unit 3 weeks ago. My nephew is an HVAC installer, and he remarked the best way to save money on heating and cooling is to quit putting the supply and returns in unconditioned space. He said attics are too hot in the summer and crawlspaces are too cool in the winter, and he said so where do they put the supply lines, in the exact worst place possible.

He has encouraged me to work on home designs that incorporate the HVAC ducting into the design, instead of leaving it like a stepchild in the building process. He remarked that they only use r-8 insulation on the ductwork now, most homes were installed with r-4.2.

If I had to guess. I would say use geothermal for cooling and for heating with nat gas helping out the geo on the heat side. To size a cooling system large enough to cool your home from say 95F to 70F is a 25 degree drop. You might not get enough heat output from that size system to get your air from -10 below to 70F in the winter. Your ground temp might be in the mid 40's in the worst of your winter up there. To capture that much heat to do the whole job with geo might use more electricity than a gas unit would use gas to provide the same gain in temp. I believe that sizing a geo system to maximize cooling in your area would give the best bang for your buck.
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Old 02-11-2012, 04:18 AM   #10
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Re: Heres An Open Ended Question


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If I had to guess. I would say use geothermal for cooling and for heating with nat gas helping out the geo on the heat side. To size a cooling system large enough to cool your home from say 95F to 70F is a 25 degree drop. You might not get enough heat output from that size system to get your air from -10 below to 70F in the winter. Your ground temp might be in the mid 40's in the worst of your winter up there. To capture that much heat to do the whole job with geo might use more electricity than a gas unit would use gas to provide the same gain in temp. I believe that sizing a geo system to maximize cooling in your area would give the best bang for your buck.

Generally Geo's are sized to the heating load. A 2 stage Geo is often used, so that it can help keep the humidity low enough during the cooling months.

In this area, most Geo's are set up that if they have strip heaters, the thermostat has to be manually switched to emergency heat for them to come on. And it only has to be done if the heat pump has a failure. Other wise the Geo heats the house to set temp, even when the outside temp is below 0.

The ground/well temp does drop below 40, but there is still plenty of heat for the Geo to use to heat the house.
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Old 02-11-2012, 04:34 AM   #11
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Re: Heres An Open Ended Question


Would it matter if the unit was in say the gulf coast area vs. say Iowa or the Dakotas. I had always thought that you sized for the smallest temp range you needed and then supplemented with the next available cost effective energy source to cover the gap. I was trying to show the OP that putting a smaller geo unit to cover cooling and then using what heat it could make to help keep the nat gas use to a minimum. I felt like he was looking at overall total cost of installation, equipment and fuel for the long run. I was under the impression that geo was the most expensive upfront. So thats why I thought about just a smaller set up for the cooling.

But I learn something new everyday. I am just starting to explore the benefits of comfort from the ground. Where I am at in Tennessee we have nearly constant ground temp of 60F year round if you get below 6 feet. But with cheap electric and for now cheap nat gas, I only hear about 4 or 5 well coupled units being installed. I am becoming more familiar with them as time goes on.
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Old 02-11-2012, 05:09 AM   #12
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Re: Heres An Open Ended Question


Ground/soil type determines the number of wells, or length of slinky a system needs. From there, you basically can size the system the same way.

While your ground temp may be 60 after a depth of 6 foot. Once a geo is removing heat from it, it will drop quickly, and becomes a matter of how quick the well heats back up to temp. Thats why well depths and number of wells required vary per are.

One area may need 1-250 foot deep well per ton, while another area may only need 1-450 well per ton, while another area yet may only need 1-500 foot well per 2.5 tons.

The well/wells are the most expensive part of the install.

Your Jan gas bill would be considered a high bill for a Geo system total electric house in the 2600 to 3000 sq ft range. At an electric rate .12 cents per KWH.

Your area has both cheap electric and gas. So installing Geo is a flip of the coin. Its the utility rate that determines how practical Geo is or isn't.

The larger the home, the more practical it is usually.
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Old 02-14-2012, 08:48 AM   #13
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Re: Heres An Open Ended Question


I will have to check into the dual fuel thing a little more. What about hydronic in floor heat? Would that only make sense if it was supplied by a geo unit?
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Old 02-14-2012, 04:07 PM   #14
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Re: Heres An Open Ended Question


In floor radiant makes sense for oil, or gas fueled systems. Many Geo's won't supply enough heat for certain types of radiant installs. Such as staple up systems.
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Old 02-14-2012, 05:53 PM   #15
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Re: Heres An Open Ended Question


I was thinking more along the lines of in slab heat in the basement with the geo unit also providing forced air heat in the upper floors.
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Old 02-14-2012, 06:36 PM   #16
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Re: Heres An Open Ended Question


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I was thinking more along the lines of in slab heat in the basement with the geo unit also providing forced air heat in the upper floors.
If the Geo is sized large enough.
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Old 02-21-2012, 06:42 PM   #17
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Re: Heres An Open Ended Question


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As far as most bang for your buck. Will Geo or solar pay for itself within 5 years, 10 years? If it would take 20 years to pay for itself I guess I would not be interested. What is this dual fuel talk? I guess I would be looking at what would be the cheapest in the long run, say 10 years or so. No heat loss calcs, just a hypothetical average home being built today.
To answer your question you need to look at the cost of energy, your climate, what credits/grants etc are available for the different technologies. And finally what fuels are available to use.
These are the factors that will determine how long the payback on a system is.
For information on solar etc incentives see www.dsireusa.org
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Old 03-01-2012, 10:55 PM   #18
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Re: Heres An Open Ended Question


You propose a well insulated house, but with no details. How big, what is the heat loss. The solution will vary based upon your replies. The vast majority of home heating systems are grossly oversized. Given the insulation spec, you may be in a very low load situation, but you need to help us out.

BTW, I checked the BIN numbers for Ames. Under 20f you have 498 heating hours. Above 20, you have 4709 heating hours.
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Old 03-01-2012, 11:19 PM   #19
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Re: Heres An Open Ended Question


Seems to me if you start off air sealing and insulating more than the "average house" you could get by with a much smaller system so the cost to do geothermal wouldn't pan out
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Old 03-03-2012, 08:54 AM   #20
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Re: Heres An Open Ended Question


I question the whole geothermal thing.. I am sure it is great when things are working well. But, one needs to factor the "what if". Finding qualified geo-thermal techs is likely hard to do, and, I can imagine someone really screwing things up. That's why I believe that in general, one should go with a setup that is commonly used.

Don't get me wrong, I would love to get into the solar and alternative energy thing. But, for the most part, most people want a system that "just works" without any drama.

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