CG,
"When building a new house, we only have speculative information. We have formulas that estimate what the heating/cooling loads SHOULD be, but we have no actual, definitive, raw data."

Um yeah we do have data. We can add up the insulation, loads etc and know what loss will be at a given temp. These are fixed not speculative. Weather and fuel prices may be, but not heat loss.

Todd, you continue to employ poor arguments.
" Let's say your boss tells you three years hence that your position has moved to Houston so maybe you should, too. You borrowed an extra $14,000 to install geo. Will you get that money back in your sale price? I dunno"
Let's say you borrowed $200K for the new built house, will you get that back in your sale price?
I dunno. If you happened to build in MI in 2008 definately not. Ergo the whole house was a bad idea not just the geo.

Two proposals prepared today against propane.
1) $2.19 Gallon propane vs .110 kwh geo- all heating/cooling hot water with propane $2,819.....geo $922 install ~$17,000. 30% tax credit and yada yada. More modest home and higher electric rate so savings not as terrific.

2) $2.39 gallon propane vs .075 kwh- all heating/cooling/ hot water with propane $4,593....geo $1,166. Install cost ~$18,000. Larger home and lower electric rate and more hot water users, I'm thinkin' no brainer.

Real numbers (retrofits not new builds). Customers are asked not to tell me current costs until I have my calculations done, so we presume if I am close to their current usage then the geo predictions are close.

Real world calcs. Crossed checked against current usage at current utility rates. It will be compelling to my customers or not.

You guys can continue to obsess about the choice of presentation by us unwashed mechanic types, but there is a reason this stuff sells.

j

Those who cannot remember where they put their Bartlett's book of quotations are condemned to repeat them.
Oh, wait. That's not what what Santayana said.

You're so vain, you prob'ly thought that post was about you.

Posted By TechGromit on 05 Jan 2011 03:41 PM
Another thing to consider that has nothing to do with energy costs is the comfort factor. Geothermal systems do not have the kind of temperature fluctuations many systems have in an effort to reduce heating or cooling costs. It's generally more efficient to leave the thermostat alone and let the system run, instead of turning it down every night. Also it's a gradual heating method, there's no blast of hot air when the system switches on, so it dries out the air a lot less than say a Gas system would.   

Agree!

@ Joe ...you said Um yeah we do have data. We can add up the insulation, loads etc and know what loss will be at a given temp. These are fixed not speculative. Weather and fuel prices may be, but not heat loss.,"

Even heat loss is a close estimation BEFORE the house it built. From the way you speak, it sounds like any estimation BEFORE construction means that's what will actually be AFTER construction, meaning that there A) will be no changes during construction, and B) that the construction will always flow smoothly, everything will be installed or built 100% correct with no variation. If the plans call for 1/8th of an inch gap, rest assured, they won't be 5/32 of an inch, which would allow more air to flow through. All those things add up. And in the case of ICF walls, do the models take into account the various sub contractors stripping away the insulation to make room for things like wiring, pipes, outlets, etc? How about any gaps around electrical boxes, canister lights, etc.? Every model makes certain assumptions. And every insulation product is tested for certain temperature ranges, sometimes well within the extremes that can happen. And certainly any measuring equipment has it's own tolerances, or a certain precision. So yea, even heat loss is a guess....an educated, calculated guess, even precise (to a degree) but certainly not exact. And if you believe in the scientific method, certainty is truly a perspective issue, dependent on how precise you want your measurements, assumptions and results to be. Case in point, the rule of thumbs that we all hate....years ago, the industry made a rule of thumb for heating load based on the square footage of the house...mainly because your average local heating guy could not perform the high level math required to accurately size the system, and if he could, without even a calculator, it would take a very long time for those calculations to be completed. Certainly these days, we all scoff at the idea of estimating heating load by square footage, because our measuring tools are more accurate, our computers have programs to make the calculations for us in a matter of milliseconds rather than days or weeks, and certainly the local hvac guys are more knowledgeable on what affects the sizing of the system. A side note, you don't often see hvac installers putting duct work in unconditioned spaces much anymore, because of the losses associated with that, however, at one time, the professionals that had been in the business for a few decades would laugh at you if you wanted the duct work elsewhere.

So, again, estimates are just that, estimates. Estimates are guesses, based on reason. As you design a building, the heat loss is still an estimate. Before you tell me again that it is not, that there all sorts of numbers floating around to make your estimate decently close to actual, realize that the thing you can control (Customer's final billing) is also an estimate when you bid the job and is likely to change slightly by the end of the job. If you can't nail down your own costs perfectly (and there are so many variables, it is understandable as to why final billing might be different than up front estimate or even bid), you can't logically tell me that the actual construction of a project and any variations (no matter how small) doesn't change the actual heat loss of a building from the pre construction estimate. It might still be within tolerances, but it is a different value.

I am having a heating system put into our building as we speak.

I had a manual J done, used it to size the radiators, I know at best it is an estimate and that actuality will be different, but you need to base your system on something. I will be interested to see how far my guesstimates will be from reality.

Assuming you are putting in a system for the long term then the cost of fuel used will exceed the capital cost quite comfortably, usually.

We are all guessing at future fuel prices, they are going to go up, but which one will go up most?

(If this was my new house I would put the money in design/insulation, not fancy heating systems)

@Como...exactly...that is my point, that we have to estimate...and we can't do that without making certain assumptions or without a certain amount of guesswork, or, in comparing various alternatives for the same solution, we need to speculate on some things. It's certainly understandable that the actual does not come out with the exact same numbers as the models suggest, I just got my panties in a bunch when some people suggest that speculation doesn't happen. Estimation is an art...based on speculation of the future. The very definition of "estimate" suggests that the final product (be it insulation factor, cost, heat transfer, etc.) will be slightly different.

Good luck with the install of your new system. Hope everything goes smoothly.

CG,
I glazed over trying to read your lengthy rebuttal, but am I to understand that your position on why a heat loss based on a blue print is speculative is because others may not follow the plans?

That's silly.
j

Posted By Cgallaway on 29 Jan 2011 07:51 PM
@ Joe ...you said Um yeah we do have data. We can add up the insulation, loads etc and know what loss will be at a given temp. These are fixed not speculative. Weather and fuel prices may be, but not heat loss.,"

Even heat loss is a close estimation BEFORE the house it built. From the way you speak, it sounds like any estimation BEFORE construction means that's what will actually be AFTER construction, meaning that there A) will be no changes during construction, and B) that the construction will always flow smoothly, everything will be installed or built 100% correct with no variation. If the plans call for 1/8th of an inch gap, rest assured, they won't be 5/32 of an inch, which would allow more air to flow through. All those things add up. And in the case of ICF walls, do the models take into account the various sub contractors stripping away the insulation to make room for things like wiring, pipes, outlets, etc? How about any gaps around electrical boxes, canister lights, etc.? Every model makes certain assumptions. And every insulation product is tested for certain temperature ranges, sometimes well within the extremes that can happen. And certainly any measuring equipment has it's own tolerances, or a certain precision. So yea, even heat loss is a guess....an educated, calculated guess, even precise (to a degree) but certainly not exact. And if you believe in the scientific method, certainty is truly a perspective issue, dependent on how precise you want your measurements, assumptions and results to be. Case in point, the rule of thumbs that we all hate....years ago, the industry made a rule of thumb for heating load based on the square footage of the house...mainly because your average local heating guy could not perform the high level math required to accurately size the system, and if he could, without even a calculator, it would take a very long time for those calculations to be completed. Certainly these days, we all scoff at the idea of estimating heating load by square footage, because our measuring tools are more accurate, our computers have programs to make the calculations for us in a matter of milliseconds rather than days or weeks, and certainly the local hvac guys are more knowledgeable on what affects the sizing of the system. A side note, you don't often see hvac installers putting duct work in unconditioned spaces much anymore, because of the losses associated with that, however, at one time, the professionals that had been in the business for a few decades would laugh at you if you wanted the duct work elsewhere.

So, again, estimates are just that, estimates. Estimates are guesses, based on reason. As you design a building, the heat loss is still an estimate. Before you tell me again that it is not, that there all sorts of numbers floating around to make your estimate decently close to actual, realize that the thing you can control (Customer's final billing) is also an estimate when you bid the job and is likely to change slightly by the end of the job. If you can't nail down your own costs perfectly (and there are so many variables, it is understandable as to why final billing might be different than up front estimate or even bid), you can't logically tell me that the actual construction of a project and any variations (no matter how small) doesn't change the actual heat loss of a building from the pre construction estimate. It might still be within tolerances, but it is a different value.

And the point is....? The purpose of the heatloss calcs is that your select a system size which is best fitted for the house, heat pumps usually come in 1 ton increments. Based on that number one can use the performance and weather data and give an estimate about the energy consumption. Now, the energy needed will be the same, whether it is a geo or a conventional system.

And the OTHER option would be???

Ignore the plans and install however big a system will fit through the mechanical room door?

@joe, in a sense, yes, the heat loss calcs done before the house is built won't be identical to the actual heat loss of the house. I was trying to say that the calcs done before hand can not possibly take into account every little detail that could change during construction. Think of this situation, you plan to build an ICF house. The heat loss models expect all the foam bricks to be left intact. During construction, your electrician removes a 1/2 inch wide by 10 ft long by 1/2 inch deep section to install conduit. The conduit has a much greater heat loss value than the closed cell EPS blocks. He essentially just changed your heat loss calc with a volume of 30 cubic inches. Imagine all the wiring throughout the outer walls of the house, and the small value adds up to a lot. Your actual heat loss will be greater than the estimates you came up with prior to building the house.

@doc and engineer.....I'm not suggesting to do it another way. If you read earlier, someone (Doc, I think it was either you or Joe, I don't remember who) said that speculation wasn't needed. My whole point is that to compare the life costs of various systems, that speculation of future fuel costs was necessary. Then it was brought up that the heat loss calcs aren't speculation. So I am now arguing that every estimate is speculation. We speculate, that is what we do when we can't take every variable into consideration, or we ignore certain possible differences between design and as built.

I didn't want to sound like a complete jerk on the measure, but I guess to prove a point, here it goes.

Speculate:

transitive verb
1
: to take to be true on the basis of insufficient evidence : theorize

From: http://www.merriam-webster.com/dictionary/speculate?show=0&t=1296939001

Any and every computer model makes certain assumptions. With respect to HVAC, assumptions could be made about altitude, for example. The computer programmer that writes the codes knows that altitudes vary throughout the country, so he writes the program to assume altitude at sea level and then tells the user to use a conversion factor. In other words, the programmer did not have sufficient evidence to code for a specific altitude, so he took the assumption of sea level to be true in his calculations. Another good example would be the estimation of soil resistivity for heat loss calcs in a basement. We estimate those numbers (or assume or theorize or speculate) based on what we see in the ground as a particular soil type. I don't think any builder actually takes measurements of soil resistivity, composition, moisture content, etc. prior to building the house. I would expect a knowledge on the area and a vague definition of if it is 'sandy' or 'clay' or 'dirt', but to what degree is anyone's guess.

So, to sum up my argument, I am being a grammar nazi, my argument is not about how the calcs are done so much as on the definitions of words people throw around to suggest that any estimate prior to construction is exactly what the post construction attributes of a building will be. Estimations are made, speculations are made, the final attributes of the house will be different (no matter how slightly) from the pre construction computer calculations. That is inevitable. That is ok, there is a reasonable degree of accuracy. But don't tell me that's it's nailed down to a gnat's ass, because it isn't.

Posted By Cgallaway on 05 Feb 2011 04:08 PM

Speculate: transitive verb

1 : to take to be true on the basis of insufficient evidence : theorize

From: http://www.merriam-webster.com/dictionary/speculate?show=0&t=1296939001

Nihilism: noun

1b: doctrine that denies any objective ground of truth ...

From: http://www.merriam-webster.com/dictionary/nihilism

But don't tell me that's it's nailed down to a gnat's ass, because it isn't.

Who gives a rat's rump about a gnat's ass? Were you planning to
write a special order for a 3.234-ton heat pump? ...sheesh!

Actually new builds are usually about 10% within projected loads, which is what we need for sizing. The biggest variables for heating estimates is actually the use pattern of the owners, some set the thermostat to 62 F, some to 74 F. Some take 20 min showers with their 5 faucet shower system, draining down a 120 gal tank. But those would be the same issues with a conventional system.
What does not change is the percentage of savings versus a conventional system.

Now retrofits, I admit, is a different story, because there it is a guesstimate at best.

CG,
first, do you work somewhere that you are paid by the word?
look up brevity in your word research.
second to suggest that I am guessing because others may not follow a plan remains silly.
on a recent set of prints I calculated the load. they changed their design and I recalculated to match the new design.
fact remains with known parameters I can predict (not guess) the load. for some reason it is important to you to continue to suggest that someone may change the "known" parameters and therefore my predictions are guesses.
not so. we know that one and one are two. if someone adds a three then one and one and three are five. not difficult to understand for most.
J

I second the "sheesh"

We are not designing the space shuttle here - we have very discrete whole and occasionally half tonnage heat pump sizes to choose from. It is not uncommon to find a house and system mismatched by a factor of 50% or more. No sane person sweats a missing foot of caulk or a fistful of removed ICF block foam.

If I can reduce a 50-100% sizing error to 10-20%, I've performed a real service with measurable improvements in operating cost and comfort.