Can I get some information regarding degree days and the associated cost:
My area will average 4000 heating degree days and 1500 cooling degree days but how does that translate into dollars and cents.
It would seem to me that a house “normally” produces heat from lighting, cooking, refrigeration etc. This will help a heating load but the same heat is generated in the summer adding to the cooling load.
So which is more important in my climate?
Which is more expensive, heating or cooling?
Replies
There must be a dozen other variables in that like how is the house insulated and ventilated and what type systems do you use, like all electric or electric cooling and oil heat or nat gas heat with evaporative cooling.....and what will be the cost of each alternative not only this year but five years from now.
start with your climate and house type
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Let me restate my question:
Which is more expensive heating a house in a climate of 1000 degree days or cooling a house in a climate of 1000 degree days of hot weather?
My guess is that a 1000 degrees of heat are not equal to 1000 degrees of cooling from a political stand point. Is it 2:1, 3:1, 4:1???
Well the heating degree day can be converted directly to the amount of heat that is needed to be transfered.And if using transfer systems with equal cost then it can directly relate to the relative cost.A heat pump is the only think that I know qualifies for that. While there are some differences I suspect that it would take similar kWh to move 1000 BTU from in to out as out to in. But even at that many electric rates have different summer and winter cost.But them you have the added latent heat, removal of moisture in the summer.And you have the ocupant load.A 5,000 sq ft house with only one person that only sleeps there at night will have much different loads from the occupants than a 1500 sq ft house with 4 teenagers that shower 12 hour a day, and there is a pot of soup or pasta pot going most of the day and bread is being baked every day.They you try to look at other heating eneergy soruces and their effiencies and fuel cost..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
"And you have the ocupant load."
All of which add heat. The load helps in the winter and hurts in the summer.
What fuel(s)The unit of measure to compare apples to apples is BTUsHow many to heat, how many to coolSo, if you have nat gas heat and elect cool (most common in my area, figure costs per BTU for both heating and cooling and compare1kWh = 3412btu
Remember Mary Dyer, a Christian Martyr (Thank you, Puritans) http://en.wikipedia.org/wiki/Mary_DyerMay your whole life become a response to the truth that you've always been loved, you are loved and you always will be loved" Rob Bell, Nooma, "Bullhorn"
Again - it depends on the way the house is insulated and the energy source you are using top perform either the heating or the cooling.For instance, if you are heating with oil at 87% efficiency and cooling with electricity at 100% efficiency, but paying four times as much per BTU on the electricity, then ....On the insulation/ventilation package vs climate - it ain't one size fits all. Various materials and designs and radiant barriers have their effect.I understood the 1000DD vs 1000 DD thing for the equivalency there, but you haven't mentioned any of the other variables.
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"but you haven't mentioned any of the other variables"
Your choice either
A: Natural gas heat and standard elec central AC
B: Heat Pump
Probably the 2 most common choices in this area.
Which still leaves a lot of variables open to consider.It sounds like you are trying to decide how to heat and cool your house.
How is it insulated.I think you need to be talking to the folks at your local energy store so they can run some cals with given information on their software. Be ready to answer all their questions. Bring a set of the plans with you..
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"It sounds like you are trying to decide how to heat and cool your house.How is it insulated."
No strictly a therotical discussion. In a transitional climate, I was curious as to how the most energy was expended (heating v cooling) and therefore what factors make the optimum use of a house's energy load.
Like the question of insulation -- Does it matter if you are heating or cooling to the insulation? I don't believe so.
I appreciate your responses but I was thinking in broader terms. For example, the use of glass etc
Glass has very little resistance to heat loss, but can be used for some heaat gain. The problem there is storage. Too much solar gain has to be cooled mechanically. so where you place the glass is critical.You may not believe the type of insulation is a factor whether heating or cooling but it can be.Too much detail for me to go into here tonight though.
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So ... back to theoretical.
My theory ... Insulate the heck of a building. It minimizes heat. It minimizes solar and conductive cooling loads ... but dramatically increases the affect of internal loads ... but that in my opinion is more easily controlled (as are the solar loads through windows).
Much like the earth shelter house .... well insulated, lots of mass = no energy use (or at least it is easier to control = cheaper to heat/cool.
Going back to your original question ... do you get the idea that this is a complex topic? While the concepts are relatively simple, getting your answer is not as simple as you would like it to be.
Risking some repetition (I'm not going to reread all the postings), I'll try another stab ...
1000 CDD will not give you the same result as HDD ... Solar gains could double or triple the conductive cooling load (using the simple CDD method). Internal gains also increase the cooling load. So does the latent load due to your high humidity.
So ... on the cooling side, 1000 CDD has many more added affects. On the HDD side, if you occupy the house like many people ... gone all day, stat down at night ... you would have to 'derate' the 'raw' HDD value (i.e. there are fewer HDD when you account for a space temperature variations). For example, in Spokane WA, I recall that there are 6835 HDD, but given a variation in occupancy schedules, I've recalculated HDD to be more around 4,300.
Combustion efficiency is like 70-90% ... i.e. you use/waste an additional 10-30% energy up the flue to offset the energy you calc for a conductive heat loss. On the cooling side, it may take only 33 kwh of energy to provide 100kwh worth of cooling due to the 'efficiency' of the A/C unit.
It's complicated ... did us techno energy geeks leave you in the dust?
Like the others said, the only accurate answer is "It depends".
There are modeling software programs available for a "bin" analysis. You input the details of construction, electric rate structure and fuel costs, etc., etc. The weather data for most of the planet has been extensively recorded and is available in databases for every day of every month.
In this country, approximately 3% of the energy consumed is for residential comfort cooling and about 7% is used for residential heating.
In all climates in the lower 48, cooling is optional (I'm sure there are some "heavies" and desert dwellers that will disagree with that), heating is not.
The question is really immaterial. You do not have to choose. You can have both, even in Arkansas. If you must have an answer: Cooling costs more; heating is more important.
"Cooling costs more; heating is more important."
Don't ask me that question in August! There are always blankets, sometimes a wife, or at least a dog.
faulted1
40 below? Nope heat is required to survive..
yesterday it was 90 degrees here. I didn't even turn on the A/C (nor did my wife)
It needs to get over 90 degree for several days before I feel a need to flip on the A/C
I always turn the stat down ... and then tell my wife I'm cold!! :)
In all climates in the lower 48, cooling is optional.
Hmm, we had a cold frontblow through on Sunday, brought needed rain. Dew points hava actually dropped into the high 50's and low 60's yesterday and today. Will probably roll back into the high 60s for the weekend (and 'cause it always rains on the Noon Lion's fireworks show here <g>)
So, ok, in a narrow nad precise way, "cooling" is not necessary here, but dehumidifcation certainly is.
Mind you my NG bill for the entire winter was only $81; only ran the forced-air heat about 126 minutes/day excepting 6 cold snaps.
Not in the desert, but between two river valleys, and just at the edge of maritime climate from the Gulf. It's 2776 CDD and 1788 HDD per my old crib notes.Occupational hazard of my occupation not being around (sorry Bubba)
I understand where you live, I grew up not too far from there. Though not an Aggie, I am an alum of what was once the Southwest Conference. My dad still live in north Dallas (Richardson).
While cooling and dehumidification are "nice" (I would never choose to do without) and people do die from high heat (remember the summer in north Texas 1980?) it is not necessary. Without heat, humans would not survive all but the mildest winters. Building codes, as far as I know, do not mandate cooling but most if not all do mandate heating to a minimum acceptable temperature for occupancy. I can tolerate 100 degrees with some minor discomfort, but -20 would kill me.
without heat humans would not survive all but mildest winters?
tell that to the eskimo's, and while your at it sell them some ice makers.
and on the other end of your statement some people die in hot summers, but a healthy human has the ability to survive in temperatures exceeding 300 degrees, according to some experiments done at some university in an oven, i forget the details, but i can boolshlt too.
humans are one of the most adaptable creatures on the planet, humans are also the winners in a long distance foot race, will beat any other living creature on foot, if the distance is long enough. think ultra marathon.
<a healthy human has the ability to survive in temperatures exceeding 300 degrees, according to some experiments done at some university in an oven>
Yeah, I think that was at Hansel & Gretal U. or maybe at the Shadrach, Meshach, & Abednego Bible College
Forrest
i remember reading it somewhere, they had a very fit individual and gave him water and he got to wear clothes and gloves and stuff, i don't think he was in there for weeks but was able to survive it.
i personally have worked in boiler environments when after 15-20 minutes you had to back up and cool off, and then back in for more. it definitely takes a lot out of you to work in extreme heat but is very survivable.
and as to the ultra marathon champion human there are still primitive bush tribes that practice the running to death method of hunting, more as a sport than for survival but it still happens. i was amazed at how these world class runners will just jog after an animal for days and eventually the animal will collapse, then they move in for the kill with spears and knives.
i guess other animals have to devote much time to eating/drinking each day and humans can literally do that on the run so can outlast every other animal on foot.
My memory of hot work conditions is the miners in S africa who are not only in temps around 98-110, but because of the depth of th emines, under very high air pressure and humidity too, yet they put in a full shift.When I started working roofing, that first summer had a few weeks where ever day saw temps hit 113 to 119 every day and I was working next to a tar kettle where temps where even hotter.
I have also worked one day where the wind chill was about minus 86I wouldn't choose either one for fun, but it can be done.
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Eskimos have heat, what would you call a fire? The rest is BS. But you know (at least I hope you know) that.
Edited 7/2/2008 1:59 pm by Tim
Tim, you are really digging in here. The only fire the eskimos use is an oil lamp - basically a candle. They do not raise the temp of the igloos above freezing because that means no more igloo. They live most of the winter through at temps where you say humans will perish.
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You make the call.
You can have heat or you can have air conditioning, but not both.
Which one would you pick and why?
Neither, but you weren't asking about my house.PAHS works. Bury it.
I was asking about you (not you specifically) not your house.
If you have a house where you do not have to pay for energy soley to provide heating or cooling, congratulations.
Whether you pay for or it not, you would agree that you heat your home in some fashion, correct? Passive solar or some means? However comfort heat is provided in your house, it is provided. Lights, cooking, electronics, etc, all give off heat.
Our primary heat source is cooling off the house all summer. That heat's stored in the mass for winter use. Annual heat storage, passively. It's also the cooling system in this climate where everybody air conditions.
Impossible to not have both, but your question denied that choice.
Not a particularly efficient house, principally due to large glazing. We go through a lot of heating/cooling btus. Just nothing I have to do anything about. Factors you mention aren't significant here. For small super-insulated low mass, yes.
PAHS works. Bury it.
I'll take the heat, maybe.
I won't freeze ... I hate that. I've alternatives for cooling. I lived in a climate w/ cool/cold winters and sometimes very warm summer periods and had no A/C ... I was warm in in the winter.
"They live most of the winter through at temps where you say humans will perish."I don't have a horse in this race, but I will respond to that comment.Eskimos do not live at the temps you mention. They may live in the temps that Tim mentioned, but they use insulation to keep their bodies warm. IIRC, hypothermia can set in at a core temp of as high as 95°On the flip side, you can only cool so much with clothing. I can be quite comfortable in 20° temps but I guarantee I will be miserable at 120°.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
You are right - they maintain their bodies in a wrap that keeps them warm, but we are talking about interior home space - the ambient air temperature there.Now I have never lived with them, but there was a time I read several volumns of those who had about twenty years ago and remember the details of how they maintained that temp to 20-30 to avoid thaws on the ice shell.There are accounts also of early explorers going through the Straights of Magellan and seeing natives standing at the shore in a fierce blizzard who were naked for the most part.The whole point being that heat is for comfort, but people do survive without it.
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I need to pick you off on this comparison.First, remember that people die from heat exhaustion every year. The elderly and those with asthma are especially effected. I get worse asthma every year, and co-incidentally I happen to get older every year too, so while heat is not critical for me yet, I become more aware of the great "discomfort" experienced by those who cannot breathe.Second, your comparison is less than accurate. normal comfort level being about 70°F, your mention of heat at 100° is only thirty degrees off from comfort level, but your minus twenty is ninety degrees off from that level, or three hundred percent further off from comfortable. for the comparison to be valid, take fifty degrees either way. So how comfy are you at 120° vs 20°F ?
I gotta tell you that I can live at twenty without heat easier than at 120 anytime. Maybe it was the near heat stroke I had once that made me more sensitive to the heat, I don't know.The reason building codes call for some form of heat is to preserve home value. Once the pipes freeze, a lot of damage ensues. It isn't the place of the codes to dictate for comfort, only for safety and home values.
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People die from 1000 different reasons. Old people and young people. If a person were to overexert themselves in 120 degree heat, then the death would be partially attributable to stupidity. If the same person went for a walk during a Minnesota winter in nothing but boxers, the same would apply.
Humans have inhabited the planet for 100000's of years. Willis Carrier invented mechanical comfort cooling just over 100 years ago. It was not widespread in residences before WWII. Heating is of course a different story. We've managed to live and spread throughout the world without air conditioning.
I disagree with you on building codes. Value never has or never will have much to do with building codes. Local, petty ordinances might, but national building codes are about life safety. The ability to heat and maintain a space up to 65 degF (or there abouts) is a requirement for a space to be deemed fit for occupancy. With or without plumbing, every national buidling code has a similar requirement. I have yet to see one about cooling. Have you? Safety yes, values, no.
Are you making the case that cooling is more important than heating? Or simply nitpicking my example?
Edited 7/2/2008 4:30 pm by Tim
I am not saying cooling is more important.I am saying that your reasoning is flawed and your conclusions are too
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"I am saying that your reasoning is flawed and your conclusions are too"
Thanks for the thoughtful input. You've added a great deal to the conversation.
sure thing!
I'll explain why the codes do have input on property values when you are interested in learning something. Meanwhile, I remain shocked that you are clinging to such a thin theory
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I'll abondon my very poorly constructed argument. Eskimos live in the cold and people die in extreme heat.
The question was aked, "Which is more important, heating or cooling?".
The answer is: Heating.
I agree that building codes add and maintain value. I will not agree that "adding value" is core purpose for the existence of building codes.
ah you are learning grasshopper.
We can all agree on that wording as amended;)
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I can tolerate 100 degrees with some minor discomfort, but -20 would kill me.
Well, personally, I find much over 90 to not be minor discomfort <g>
And, truth be told, anything under 0 gets to be work, too. But I know what to do in the face of cold--you add energy. But, when you have an excess of energy, you can only sweat so much, be in the shade, or what have you (and we already have too much skin showing on folks who oughtent be <g>).Occupational hazard of my occupation not being around (sorry Bubba)
Wow ... warm climate!! I'm out Death Valley way and I don't think we have that many CDD (actually 30 miles west), but I'm new in this country and my CDD value hasn't 'stuck' in my feable mind yet.
Wow ... warm climate!! I'm out Death Valley way and I don't think we have that many CDD
And that's the published data using the KCLL weather reports, which does not take into account dew points ranging from 50º to 79º (I want to remember there's a record high DP listed somewhere, and it was 81.1º--which still boggles my mind).
This morning, before leaving off for City jury duty (0730 report), it was a loverly 75º but with a 72ºDP, and that 90%RH was not at all pleasant. Stepped out of the ride at the Court and my shades almost went opaque, well under 20% acuity. Attic was already to 86º, after only 1 hour of sun exposure.
Now, for grain of salt, at least very few of the KCLL airport reports will be affected by jetwash (turboprop commuter air is the rule on our 6080' runway).Occupational hazard of my occupation not being around (sorry Bubba)
One way to look at it might be to assume that the "temperature-changing-machine" (heat pump, gas, oil, elec, whatever) had the same efficiency pushing heat into the house as it does pumping it out. Then, the only difference is the delta T from inside to outside.
Say you want it 75 inside, whether it's 95 outside or 35 outside. Your heating delta T would be twice what your cooling delta T would be, so twice the energy cost, all else being equal (not that it is!)
Forrest
" Then, the only difference is the delta T from inside to outside. "I think that the heating/cooling degree days takes care of that..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Which delta T matters?
The delta of the inside coil to inside air or the outside coil to outside air?
"Then, the only difference is the delta T from inside to outside."
"Say you want it 75 inside, whether it's 95 outside or 35 outside. Your heating delta T would be twice what your cooling delta T would be, so twice the energy cost..."This would be true only for a house that is completely shaded. In that case, delta T would be the only factor. AC load is typically much greater than heating load because insolation - the heat input directly from the sun's rays beating down on the house and windows - pumps way more heat in than outside air delta T can. That's why your AC works harder in late afternoon than after sundown, even if the outside temp hasn't changed.Think of a car parked in the sun on an 80° day versus one parked in shade. The shaded car interior will be 80°; the sun-exposed car may be 120° inside. To get those cars' interiors to 70° would take 10° of cooling on the shade car but 50° of cooling on the sun car.BruceTEdited 7/3/2008 2:55 am by brucet9
Edited 7/6/2008 1:28 pm by brucet9
Yes. All else is not equal.
Forrest
In some parts of the country, you can get someone at your electric utility company to help you understand this quite well.
So, from reading your profile, I would direct you to the Ozarks Electric Cooperative Corporation in Fayetteville.
Dontcha wish Fay Jones was still alive and could design your house for you?
View Image
"A stripe is just as real as a dadgummed flower."
Gene Davis 1920-1985
Your mention of Fay Jones
View Image
made me add one more parameters to the discussion:
Solar Gain (glass)
There are a few of Fay Jones' houses around including a few chapels in the area.
If I could have afforded his services, I would not need to worry about energy costs.
(Notice the upstairs windows -- This was his office upstairs above a local jewelry store. Can you see the models?)
Edited 7/1/2008 5:20 pm by Faulted1
FWIW In the 70's I owned a business that constructed insulating window manufacturing plants. Some would call those windows--"storm windows". I sold and installed more manufacturing plants in the southern states--where there were no storms involving snow, cold temps, etc. The need was to insulate windows because of cooling costs. I happen to have those same windows on my house in Colorado. I don't have AC but during installation on a corner bedroom with windows on two different walls I was delayed by a storm and only had one "insulating window" up. After the storm the uninsulated window was covered with ice inside (it was a #### builders window anyway). The window with the insulating window was clear as a bell.
I concluded a number of things. 1) Insulating windows work 2) People in Texas, Louisiana, etc. were willing to spend more money to efficiently cool their homes than people up north were to heat theirs. 3) That all things considered (all cost factors) it cost more to cool a home than heat it. Codes don't require cooling but in some states people are willing to fork over the bucks to cool because they can't regulate things with clothing on or off like they can to stay warm. That's about my bucks worth. Everyone (many thousands of you)please send checks to Taunton--they know where to forward them. Tyr
"2) People in Texas, Louisiana, etc. were willing to spend more money to efficiently cool their homes than people up north were to heat theirs."I'm not disagreeing, just offering an alternate explanation.Maybe the markets were all across the country but the cost-effective manufacturing was in the southern states. To say that people of the north don't care might be like saying people outside of MI don't like cars, people outside of ID don't like potatoes, or people outside of the south don't use textiles.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
Since I didn't see anything else similar to what I'm thinking ... I'll throw in my two cents.
HDD x U x A x 24 will give you the theoretical Btu required to heat over the period of the HDD (e.g. 4,000 per year). This accounts for the internal gains in the house as the HDD is measured at 65 degF instead of the theoretical thermostat setpoint ... 70 degF. So if you sum your U x A for all surfaces/components of the shell ... then add the conductance of your infiltration then multiply x HDD x 24 ... you have it.
HDD may change depending on whether you heat all day or only when you come home in the evening from work. HDD are measured all day long ... so if you don't heat much of the day, your HDD value will change. As someone mentioned BIN data ... you can use that to recalc the HDD based on the variations of thermostat setpoint. But that gets more complex.
Cooling degree days I believe are on the same base temp which doesn't make much sense to me ... should be at the cooling setpoint IMO ... about 75 degF more or less.
You can calculate the CONDUCTIVE cooling gain using the same formula. HOWEVER ... you've got additional factors to consider: 1) radiation of sun on the walls/roof 2) radiation gain on windows and 3) the internal gains of the building ... which SHOULD not be substantial for e.g. a residence. Unlike the winter where it MAY NOT get e.g. down to say 10 degF ... you can pretty much guarantee it will see a hot sunny day in the summer, so accounting for the sun is important.
Oh ... I forgot ... in your neck of the woods the latent heat of moisture is a big load on your cooling system (i.e. 90 degF and 80% RH can be a large load).
Solar affects on walls and roofs can be significant depending on the materials, texture, color, insulation, etc. Solar gain through windows can be catestrophic (sp?). West facing glass ... regardless of overhang can be devistating to the energy picture. Ditto east glass. South glass with a protective overhang can often be easily controlled.
Poorly oriented structure can increase cooling loads by many times ... even with relatively small glass areas facing west.
So ... HDD and CDD are largely a measure of climate temperature and can help give us some idea of heating/cooling loads ... but on the cooling side there are many other aspects to the cooling load than just CDD.
I haven't done much calcs w/ CDD and comparing the conductive calc with the magnitude of the radiation factors ... I've done a lot of radiation gain calcs and they tend to dwarf the conductive loads, I think. IOW ... you can't use HDD/CDD to calc comparisons in a valid way.
Always calc in Btu ... convert everything. Cooling is more efficient ... i.e. to TRANSFER heat from in to out can take only about 1/3 of the energy in electricity to make the transfer. On heating ... you often waste 10-30% of the energy purchased in the combustion process.
The concepts are simple ... putting it all together can get complicated fast.
If you are building new ... you have options for avoiding cooling loads and if you choose not to exercise options you choose to make less than ideal decisions.
So when is your guest appearance on the TV show--NUMBERS? I happen to enjoy that show and after I reread that rambling post of mine (broke my leg so have little to do) I think everybody (except me) has a valid point. Sorry for burning up the post. Tyr
It's all good ... just throwing in my mathematical 2 cents to try to lend some other perspective.
Very good discussion...
Is the only difference between a cold climate and a warm / hot climate is shading the glass to prevent heat gain? And the hotter the more important the shading and location of the glass surfaces?
F1
Not entirely. Cold sunny winters are good for passive solar heating. Cloudy winters you can reduce that priority to some degree.
The summer is the most important part of the design, in many respects. You will almost ALWAYS see very warm summer temps and you will ALWAYS see sunny weather accompany hot temps.
Even small glass areas on the west can let in very large amounts of solar gain ... much more than even unprotected south facing glass. The sun angle at late afternoon (usually the hottest time of the day, too) on windows is nearly vertical. The sun angle at mid day on south glass is very steep ... much less sun/solar gain. Even a fairly small overhang on the south can shade glass from the high noon sun. In the late afternoon, very deep overhangs will do you little good on west glass.
Choose glass area very carefully for the intended function ... light, sun, view. Maximize its function w/out overdoing it and you will minimize your energy requirements. Many designers and homeowners tend to 'slather' on the glazing like it is paint and then find themselves hating the result and often spending big bucks trying to fix it (e.g. $10+ per sqft on blinds, drapes, etc.).
Remeber also blinds and drapes do SOME good, but the damage is already done once the radiation comes in through the window glass ... it becomes difficult at best to get it back out (e.g. reflective blinds).
Windows are one of the most expensive components of your house ... I advocate choosing very carefully every sqft you buy. It will serve you well in the long run.
You're clearly on top of the subject, thanks for sharing. Would you also share your sources? Particularly calculations for glazing. That would help me a lot.
Not entirely. Cold sunny winters are good for passive solar heating. Cloudy winters you can reduce that priority to some degree.
The summer is the most important part of the design, in many respects. You will almost ALWAYS see very warm summer temps and you will ALWAYS see sunny weather accompany hot temps.
Actually it varies. Here, the % of possible sunshine in July and August is only 62%. We get a lot of haze from the 70.5-71.5% average rh. January % of possible sunshine is 52%. Not small issues when designing passive heating/cooling houses.
PAHS works. Bury it.
Calcs are always based on ASHRAE heat/cool load standards, but a number of HVAC manufacturers often publish other standards/methods. They are generally all based on the same methodologies. Carrier and Trane I think have always had their published methodologies. Manual J comes to mind. To the lay person, ASHRAE can be a bit daunting at times ... engineers aren't the best at writing in simple language (no offense intended).
You may have 62% possible sun in summer, but I'd guess the hottest days are the sunniest ... I may be wrong, but from a design standpoint, I think you would be wise to plan on that.
The book I use is derived from ASHRAE but written for non-engineers, very simple to use. Enter internet-available climate information, and crank out the numbers. Glazing performance I don't have the best feel for.
I actually have no problem with sun or cooling here, nor heating for that matter. Last house was sited exactly as you suggest avoiding, with large glazing facing SW. No shade or window treatments. I knew it was a mistake, client insisted. I was sure it would overheat in the summer.
I was wrong, never did. PAHS works. Bury it.
I've got a fairly good feel for glazing technical characteristics if that is what you're looking for. If you can tell me glass type, I can give you an idea of U-val, SHGC. Not sure if that is what you are looking for.
Can you share pics of the house in question? I've learned that general rules of science are often broken in actual applications ... sometimes for no reason ... until you look at some details. I've ran into this w/ moisture problems in houses/buildings. The concepts are often simple, but the results in real life can be complicated and mysterious.
My house really has nothing to do with this thread. But click on my name, there's a link to a page on my house put up by a guy promoting passive heating/cooling dialog. You'll learn I had little idea what I was getting into, but it worked. Several photos. My roof's 240 tons (for 1600 sq ft), and is only a small part of the house mass. The client house, that didn't overheat, is substantially more.
Now that I have a very good idea how my place works, I was hoping you'd have a better web site for dealing with window properties than I've found. As you mentioned, not only are windows a major cost item, but for me they are by far the largest heat factor. Both coming and going.
Your mention of conductive and radiative gain got my attention. U and solar energy transmittance are what I've dealt with. No specific glass in mind currently, though that will change when we get the FEA on an Atlanta PAHS (passive annual heat storage).
The building permit there requires a PE stamp, cannot accept my numbers to show that it works. I only know of one PE able to do the modelling, in Seattle. None in Georgia that they could find.
Sometimes it gets interesting. No hoops like that here. PAHS works. Bury it.
I was hoping you'd have a better web site for dealing with window properties than I've found.
Tom, not sure what properties you are researching...but I have found this to be an interesting site concerning solar heatgain:
http://www.susdesign.com/windowheatgain/index.php
If your location is not listed the author may give you cloudiness data if you email him.
I found it very interesting that a climate like Atlanta will net more heat gain thru a north facing window in June than thru a South facing window.
Thanks, that link is more or less what I was looking for, and maybe the author will share methodology. You're correct, extremely limited locations. And possibly worthless unless the author did account for things like % of possible sunshine, all readily available.
Are you aware that Amory Lovins measured a net gain through a north-facing window in the Colorado mountains? Not glazing I'd be paying for, but fascinating.
You hit on a major drawback to a program like that. Doesn't seem to answer the question you should be asking: why? I'll play with it, then ask the author.
What I want to know is... everything.PAHS works. Bury it.
Also, remember "official" temperature is always measured in the shade. Therefore, the "actual" sunny day temperature is always higher than the official temperature. This would under report cooling days and over report heating days.
I disagree. From a design standpoint I've accounted for the affect of solar radiation separately. Sensible temperature is just that ... the temperature of the air w/out the affect of radiation. Sure radiation affects our situation, but it is a separate component.
Based on your theory, the sun will increase the sensible temperature CDD. I suppose it could increase the HDD, too, but that is an illusive item as many cold or HDD days have a tendency to be devoid of sunshine, too. Doesn't really matter. While your theory is appreciated it is not how we calculate loss/gain.
I suppose it could increase the HDD, too, but that is an illusive item as many cold or HDD days have a tendency to be devoid of sunshine, too. Doesn't really matter.
The offical temperature is taken at a location "devoid of sunshine" (shade to us commoners).
My point is that HDD and CDD does not take into account sunlight. Unless your house is all in the shade.
Sensible temperature doesn't either (take into account the radiation). Without doing hourly calcs you can't really take into account the radiation affect on a surface. So for the CONDUCTIVE heat flow, the HDD approach is quite valid. The radiation affect associated with the heating loss calc is generally considered small, I think. The exception, of course is passive solar designs that account for radiation gain through windows that contribute significantly to the heat gain. I think most people doing calcs will calculate the radiation separate from the conduction ... a different methodology.
"I found it very interesting that a climate like Atlanta will net more heat gain thru a north facing window in June than thru a South facing window."
Anyone care to explaining that to the novice?
West and East window appear to have very similar value, but practical experience )and Clewless1) tell me that West windows are bigger heat gainers.
Does this program not take into account the daily variation of temperature as it relates to sun position during the daylight hours (for example - it is hotter in the afternoon than the morning.)
""I found it very interesting that a climate like Atlanta will net more heat gain thru a north facing window in June than thru a South facing window.""Look at the sun path.During the summer it it will rise north of east and set north of west.http://www.physicalgeography.net/fundamentals/6h.htmlhttp://www.phy6.org/stargaze/Sunangle.htm
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
During the summer it it will rise north of east and set north of west.
But for how long is the sun greater than 30 degrees north latitude as opposed to the time at less than that angle.
And how intense is the heat during the time it is "north" of Atlanta?
(Not to mention the angle of the sun to a north facing window.)
It may well be right, just doesn't make sense to this design novice.
Yes, of course the sun will set/rise well north of west/east ... question is will it go far enough north to produce more solar gain on the north window than a south facing glass. Due to the low angle to the horizon and what I thought was a relatively brief time frame north of west/east, I thought the solar gain couldn't compete w/ south. The low sun angle itself is a tough one, it seems to me as the sun is passing through MUCH more atmosphere than at high noon.
ALL: the calculator does say verify using other methodologies. I've no reason to question it one way or another. I suppose it is correct and my spot check revealed nothing surprising. In the lower states apparently the sun must set farther north ... or the south angle is too steep to make up for the difference (high noon at lower latitudes means a very steep sun angle on the south side ... higher latitudes means it is less steep at noon). We need a sun angle calculator.
I used the site for the calc ... In the more southerly latitudes there appears to be more gain per day on the north side. I speculate that this is because the sun sets farther north in Atlanta GA in the summer than in Duluth MN ... where, by the way solar gain on the north side is lower than the south ... all conditions being equal.
I'm a bit skeptical, still. I've done a lot of analysis in my day. The extreme sun angle on the north side and the distance the sun must go through the atmosphere will combine to reduce the gain. The other side of this is that maybe you have more hours of exposure on the north side (2-3 in a.m. ditto p.m.) and the south side sees a fairly quick window of sun mid day say 10:30-1:30.
West windows are a big focus not because there is more solar gain (there isn't), but because it is also the hottest time of the day (e.g. 4-6:30 pm typically). Also, cooler morning air that is higher in humidity will likely see somewhat less solar radiation (but we ain't splittin' hairs, here or heirs). In commercial applications, I've heard the concern is with the early morning solar gain boosting the heat gain of the building way early on. I'm on the fence on that one ... haven't really studied it like the guy who told me that.
My sense is that the website is a pure solar radiation calculator ... nothing else. It doesn't offer much in the way of documentation and detail for us solar geeks. I've never used clearness factors in calcs ... always % possible sunshine (and I don't know how they may relate to each other).
"I've learned that general rules of science are often broken in actual applications "
In theory, practice is the same as theory. In practice, it isn’t…
good one!
I've used a similar book ... ASHRAE methodology simplified.
Your client's house ... SW windows w/ no shading ... at all? (no overhang, no trees?). The earth shelter approach gives you lots of mass in your climate. Really helps temper the space temp. If your night temp typically drops, you will have a tendency to charge/discharge the mass daily to some degree.
It appears you have plenty of shading in your own house. What kind of glass information are you looking for?
Wasn't it you who pointed out the futility of overhangs to prevent summer overheating? Anyhow no, no overhangs, none of my trees. I expected the direct gain to overwhelm the mass' absorbtion capacity. I was wrong, didn't happen.
The client was unconcerned. Had a back-up plan.
PAHS has little relationship with typical high mass houses. The key element is an insulating umbrella that covers the entire house mass, extending 20' beyond the house perimeter. Diurnal air temp fluctuations have almost no effect. We're doing annual heat storage, not short-term. Major difference.
An interior temp swing of 3º in a day is huge, only occurs with direct gain in the winter and rarely then. This time of year we vary 1º.
If you're curious, an excerpt: http://www.earthshelters.com/Ch_1.html My houses have greatly under-performed the original one. Still pretty comfy. Aesthetic demands trumped maximum performance, though I'm getting better through my heat loss/gain calculations. The key is understanding what's going on. Glass is the major one.
PAHS works. Bury it.
I only said futility (overhangs) for east/west windows ...
none of your trees what? .. missed what you were trying to say.
Aesthetics need to come into play. Energy is a game of balancing science w/ art. You have to like what you see/design. Function w/out art is just not what real design is all about. Take your scientific rules ... apply them, but don't seel your soul to them ... add a little art/creativity and you've got something worthwhile.
Sounds like some great results and generally a formula for reasonable success. Hats off to you.
none of your trees what? .. missed what you were trying to say.
None of my trees. As in: he has none. No point, just no shade.
PAHS results are very good, thanks. Far as I can determine, applicable to about any climate. With an FEA on the Atlanta project, I'll be able to better predict. Not that I haven't done well with heat gain/loss calcs.
Had yet another tour today. She could hardly believe there wasn't a hidden ac unit here somewhere. Then we got into air changes, blew her sox off. PAHS works. Bury it.
"The sun angle at late afternoon (usually the hottest time of the day, too) on windows is nearly vertical. The sun angle at mid day on south glass is very steep ..."
On the day the sun is at its highest (in the northern hemisphere), June 21, the azimuth at 8 am or 4 pm is 35 deg (above the horizon) and 73 degrees at noon.
"blinds and drapes do SOME good" Light colored blinds will reflect 33% of directly incident solar radiation, when used with clear glass.
35 degrees off the horizon is a lot more vertical to the glass than 73 degrees. Also earlier than 8am and later than 4 pm ... the sun gets even more vertical to the glass.
A particular blind may reflect 33% of the incident solar, but that reflected radiation may have difficulty going back out the window as it is now infrared ... the basic reason why the greenhouse affect occurs in glass houses.
Personally, I don't consider 33% reflectance a very good perfomer anyway. If the glass has to be clear for it to happen, you have just sacrificed much of what tinting and mirror finishes could prevent in the first place (i.e. blocking the solar energy before it passes through the glass). I'd rather spend a buck or two a square foot to have tinted/mirrored glass than to spend $6-15 on quality blinds. Better yet, design my windows so I don't need to do it at all (keeping in mind that it isn't always practical to avoid the sun ... you have to balance the solar science with the practical uses of the windows (view, ventilation, light, aesthetics etc.).
IMO The best strategy for solar control is to prevent it from hitting the glass. I encourage people to carefully choose the glass areas and make sure it is doing everything they need.
Also, if you graphically layout your solar angles for LATE afternoon and mid day, you will quickly realize how difficult it is to prevent sun from hitting west glass (i.e. with e.g. an overhang) and how relatively easy it is to use an eave to protect the south glass.
"HDD x U x A x 24 will give you ..." Nothing useful. Same with CDD. The heating degree days and cooling degree days are comparative climatic data only. Not useful in any sort of engineering calculation.
"conductance of your infiltration" You'll have to explain this one a little further.
"HDD may change depending on whether you heat all day or .." No, it doesn't ever change based on personal habits, thermostat setpoints or anything else. Like ARI conditions, HDD and CDD may not accurately represent every actual operating condition, they do represent a consistent coparitive number. If I heat my house to 65 and my neighbor heats theirs to 75, we still experience exaclty the same HDD.
"BIN data ... you can use that to recalc the HDD" No you can't. See the paragraph above. You can use bin data to run a detailed day by day energy use analysis, which isuseful only in complex systems, such as thermal storage and peak shedding systems.
Uh, no. While CDD calcs are clearly incomplete and only deal w/ the conductive aspect of the cooling load, you can use the information in calcs (although I've really not used the CDD calcs much).
HDD calcs can be used ... and HDD depends ultimately on the thermostat setpoint. HDD weather data is based on the 65 degF base, but you can base it and calculate it on any temp you want.
The [simple] HDD calcs would be accurate if the house was occupied and heated continuously. Most houses, however are not ... we go to work and set it back ... ditto late night sleep. But you can use BIN data or hourly data to recalculate heating degree days based on the variations in the thermostat setpoint.
I've been doing this kind of thing for over 27 years and have worked with many in this field. I've recalculated HDD for many situations and occupancy schedules to estimate more accurately the heat loss throoughout the year. With all due respect and no offense intended, you are mistaken about this.
Edited 7/7/2008 10:27 pm ET by Clewless1
I take no offense.
"While CDD calcs are clearly incomplete ..."
"The [simple] HDD calcs would be accurate if ..."
'nuff said. In doing "your kind of thing", incomplete and "would be accurate if" might be acceptable. I work to a different level of accountability. SWAGs, rules of thumb and rough estimating procedures cannot be employed here.
I will admit that I have used HDD and CDD data as you have mentioned previously. I have also compared those rough estimates to rigorous energy analyses and found the errors to be no less than 20%. That is just my personal experience. At least they are quick. You have many people impressed.
Depending on the purpose of the computation, the rough guess you method you employ may be acceptable. With all due respect, and no offense intended, for jobs that require a little more than you are used to providing, you should enlist the services of an engineer.
Assuming I calculate HDD appropriately ... accounting for internal gains and the scheduled occupancy and setpoint of the building, I can recalc HDD fairly accurately and come well within 20% accuracy. Considering the occupancy, variations in temperature, wind, internal gains, etc. being sometimes +/- 30-50% of predicted and all that happening sometimes independently of each other, I condsider the accuracy quite acceptable.
While I much appreciate calculations that are theoretically 'more accurate', I found out a long time ago that accuracy is important, but for the vast majority of time precision is rarely warranted. I've used other methodologies many times (e.g. modified BIN methodology and DOE2.1 series, etc.). There is a time and place for everything. Calculating precise energy use in great detail to achieve e.g. 90-95% + accuracy is quite often akin to taking great pains adjusting my lawn mower to cut my lawn to 'precisely' 1 and 13/32 inches high (they do this kind of stuff on golf courses, however).
I'm not advocating HDD method of heat loss estimation over any other method, just saying that it is a relevant and reasonable method. This assumes you understand the basic limitations and either make adjustments for them in the calc or realize that your energy use estimate will be [too high].
As for CDD methodology, I'd take a lot more care. CDD is a MUCH smaller piece of the cooling energy estimation and you need to accomodate all of the other cooling related factors or you will be significantly off. You have to account for: 1) radiation affect on opaque surfaces and windows, too 2) in many areas account for the latent load of higher humidities and 3) account for internal loads of people, lights, and other equipment.
I've seen plenty of engineers in my day that do not have a clue about how to use energy modeling software ... particularly DOE2.1. Most people assume that if DOE2.1 was used that it must be right. Generally, I'd agree to enlist the services of an engineer, but good engineers that can really model energy use well are very rare, in my 27 year experience. I'll take a seasoned energy consultant any day over a design engineer for this type of thing.
In my opinion, design engineers are good for sizing a system and the components, but not much else ... AS A GENERAL RULE ... if you are an engineer that doesn't fall into this category, you already know you are above this and no offense intended. Few have the skills and knowledge to predict energy use over time ... OK, they do have the aptitude, it's just not what they are trained and experienced (and often interested) in.
But we are digressing a bit ... we started talking about 'simple' residential type energy use calculations. Are we leaving the OP in the dust? Is he rolling his eyes?
We are indeed digressing. We have adressed the OP's questions, ad naseum.
I agree with the reality that design engineers seldom get the whole picture "right". I do not agree that they, as general rule, are even particularly adept at sizing equipment and/or components correctly. In my present role, I "assist" (or more often correct) design engineers in their equipment and system selections. I see many commercial designs and am favorably impressed by few.
I learned this trade (HVAC design) from an old timer (that looked at computers with disdain) by performing all calculations by hand. Cooling loads were performed for each room at 8 am, 10 am, 12 pm, 2 pm and 4 pm. Short cuts were not permitted. I greatly appreciate the software I use today (Trane Trace). I am intimately familiar with all aspects of heating and cooling load determination. I would further add that by utilizing a more complex method does not generate better results. Better results comes only from the experience and judgement of the user. For instance, I would adjust some of the factors I use in determining loads if I know a specific GC will be involved. Sloppy construction and insulating practices can greatly affect the perfomance of the HVAC system(s).
I have also modeled energy use by various manual methods including utilizing HDD and CDD in various forms. With the understanding of the limitations (as you clearly have) and the application of the additional factors required, the errors associated with simplistic methods can be mitigated, but then the additional efforts make these methods not quite so simple.
I am curious, as you have entered no profile information, as to where you live and what you do with all of this stuff, for 27 years and counting.
Edited 7/9/2008 9:03 am by Tim
I admit it ... I was giving the engineers the benefit of the doubt. My opinion tends to parallel yours in terms of engineering quality and attention to detail. I see a lot of engineers wearing their holsters very low on the hip. There are plenty of good engineers out there, but there are also some that are 'less than attentive'.
I don't know how to enter profile information ... when I try to do it, it doesn't let me. With some computer things I'm inept. Maybe I missed something (likely very obvious, I'm sure). Professionally, I was 'raised' in the Northwest starting to work for a very intelligent engineer ... much like you describe. While I love the benefit of computers, I tend to be skeptical of the black box syndrome and have learned that the use of software is as much of a skill as learning to do it 'the long way'. My primary experience is energy modeling and on-site energy auditing.
My background (education) is in architecture, but I have strong HVAC influence in my experience. I am currently near Death Valley providing consulting services in energy/resource management. I generally consider myself holistic when it comes to buildings and energy ... I look at the entire picture and don't get caught up on one aspect as many do, due to their focus on one aspect or another (e.g. lighting, HVAC, etc.).
Just checked some calcs comparing some conductive and solar loading. Solar gain on glass can be several times the combined conductive gain and radiative gain on the rest of the building.
Bear in mind, depending on the orientation, shading, and sqft of glass, this value can vary greatly. A well designed structure can just about make conductive/radiative (opaque) gains about the same as solar gains on the glass only. Poor orientation and lots of glass area can increase the disparity by double.
Check out the post entitled "Mission Accomplished" gives you an idea of what can be done to avoid solar heat gains. A little attention to details and you can make a BIG dent in your A/C bill.
"Check out the post entitled "Mission Accomplished" gives you an idea of what can be done to avoid solar heat gains. A little attention to details and you can make a BIG dent in your A/C bill."
I couldn't find it ... can you give me a better idea of where to look (folder?).
Thanks!
mission accomplished
Goal<!----><!----><!---->
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The following is ‘most’ applicable to mixed humid climates. My climate is north central <!----><!----><!---->Texas<!----><!----> and I have 4,000 sq. ft. of conditioned space.
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I set out to build a house that was relatively cheap to air condition, without spending a lot of money on the AC equipment, and not requiring a lot of non-conventional (expensive) building techniques.
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Results <!----><!---->
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I have my thermostat set to 74 degrees and 42% humidity. I do not hear the AC going on or off. The house stays at a constant 74 degrees and the humidity between 39% and 43%. The average high for my last electric billing period was 96 degrees. Keeping my house at that temperature and humidity cost me about $60 for the month – at 14.5 cents / kwh.
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We can set the thermostat where it is the most comfortable and not worry about the electric bill.
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The AC equipment consists of a 14 SEER two ton heat pump for the whole house, and a 19 SEER mini-split for the master bedroom only. With the mini-split turned off, the two ton heat pump will cool the whole house down to 70 degrees on a design day – 98 degrees outside with the dew point at 68 degrees. The mini-split is used to keep the master bedroom at 70 degrees for more comfortable sleeping, but is not needed otherwise.
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The house is close to standard frame construction with 2x4 walls, cellulose insulation, and polyiso sheathing on the walls.
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Due to the slope of the land, and some very desirable trees, we used pier and beam construction. The resulting ‘crawl space’ is conditioned with a stepped concrete floor and a ceiling height that varies between 6 and 10 feet.
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Method<!----><!---->
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All the windows are shaded during the summer. The only exceptions are three very small windows that start to get some sun at about <!---->6pm<!---->. They are very low E glass. The other windows get zero sun during the summer months. This was done by situating the house properly, 3 foot overhangs on the roof, and large porches.
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All of the HVAC equipment and duct work is in conditioned space. Mine is in the ‘crawl space’. Because it is in conditioned space, the duct work does not have to be insulated.
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Air tight construction. I put a lot of personal effort into the air-tight drywall approach. The house is very tight.
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Extra insulation. R49 blown in cellulose in the attic. Cellulose in the walls of the main floor. 2†of polyiso sheathing on all of the exterior walls.
Thanks, Paul!
It's in the energy section/folder.
Did I read an implication that your roof structure was inexpensive? Also you said the roof was 240 ton rated ... not sure what you mean. If you have 4" concrete deck, you've got about 30+ tons in concrete (if my calc is right). If you have 28" of dirt, that'd roughly be 240 tons +/- (VERY rough calc).
I like the roof structure ... I've always seen the concrete planks used for earth shelter ... nice ... but tends to be expensive. The concrete and steel is conventional construction and lighter weight.
Did you insulate the roof and then put a membrane over that?
That would be me, not Faulted1. I suppose we're sort of still talking about heating and cooling costs...
That's my roof, if you substitute a small amount of dirt for the weight of the steel. Yes, very inexpensive. I had an engineer design cast-in-place tee beams for my loads, turned out to be incredibly expensive. Went back to him to make sure I wasn't making a major error somewhere. Nope, he told me that's why it's rarely done. Steel's the answer.
Well, thin-shell might be cheaper. Was not with Cloud's Monolithic method (we had a long discussion), but I'm pursuing another approach that he's totally dismissive of. I think he's wrong, but haven't built one yet.
My roof is what you see on commercial buildings everywhere. The Atlanta client (CPA) had already settled on that before we crossed paths. It's common due to its economy. The difference: more steel for the higher loads. As you may know, steel is sold by the pound. But larger steel is cheaper/lb.
I was shocked at how little more 40' 600 lb bar joists cost than my 30' 400 lb ones. The steel company I originally bought from misled me, turns out they can only deliver 30' on their straight truck. I've never had tractor-trailer access.
Did you insulate the roof and then put a membrane over that?
Sort of. From the nominal 4" roof slab up: scrap carpet, 6 mil poly, scrap carpet, dirt, scrap carpet, insulation umbrella (multiple layers alternating 6 mil poly and xps), scrap carpet, dirt. Quite a bit of detail involved, I'll spare y'all. No water-proofing or foundation drains needed.
BTW, the client house appraised 50% higher than it cost to build (ignoring the energy features, comparing it to stick built here). The shell wasn't the only reason of course, but a substantial part. We were worried, no idea how the appraisal would turn out. Instant equity! And a new car.PAHS works. Bury it.
Heating is a fairly simple direct process - electrical power heats an element, or fire heats the air, either directly or indirectly.
Cooling is not such a simple process - it is more indirect, using compression/expansion cycles, for example. You can't just unburn a fuel and get colder air. You have to figure out the efficiency of the cycle being used. And if you want to be practical about it, you have to consider humidity. All of my heat transfer and thermo books are in the basement, along with the ASHRAE handbooks, in a box, where I hope they stay. I hated Thermodynamics. And I hated Heat Transfer.
That said, I'm sure there are typical examples posted all over the net, because this can't be such an unusual question.
While my head hurts trying to follow all the "what's more important" arguments. ;-)
Here's a good approach to figuring the cost.
http://www.hvacopcost.com/
Faulted1,
In an attempt to answer your original question, it might be useful to look at the data. Here is a quote from the November 2006 of Energy Design Update:
"According to the most recent available data (the “2001 Residential Energy Consumption Survey†from the US Energy Information Administration), the average American household uses 2,263 kWh of electricity per year for air conditioning; at 12 cents per kWh, that would cost $271 annually. In contrast, the amount of energy used by the average American household for space heating -- 44.9 million BTUs -- is almost six times higher than the energy used for air conditioning. On average, families heating with natural gas use 55.4 million Btus annually for space heating; at $1.36 per ccf, that costs $753 per year. Families heating with oil use somewhat more energy: on average, 70.2 million BTUs (507 gallons of oil) per year. With oil priced at $2.45 per gallon, the average family that heats with oil pays $1,242 per year for space heating."
Obviously, energy prices have risen since the article was written. But the basic point remains: Americans spend much more on heating than on cooling.
Edited 7/11/2008 5:41 am ET by MartinHolladay
Although at the risk of using averages across such a vast geographic area with very wide variations in climate, Mr. Holladay points out some very good key items. This reinforces the notion that simple CDD calcs are woefully inadequate for TOTAL cooling loads and the resultant radiation loads CAN be (and on average, are) very significant.
Not sure if I missed something here or not. You said for heating the average use is 44.9 MBtus ... not sure how this would translate upwards to the higher values you used for various fuels. 44.9 MBtus of use is just that, no more, no less. If it is USE (rather than load), then taking into account all the different energy sources and efficiencies, the average use is 44.9 ... just as the KWH use accounts for the efficiency of the cooling system.
Using your values, indeed, the cooling energy consumption is only 7.7 MBtu and the heating is 44.9 ... a big difference.
W/out knowing the ratio and average efficiencies of the various heating fuel sources, you really can't back out of the equation to find the other values.
To the OP ... sorry for the complexity. The problem w/ the average value is that it may not apply to you in Arkansas. I'm guessing the heating/cooling load disparity in the southern states could easily be just the opposite of the northern states. I'm in SOCAL and the heating load/consumption here is relatively low. I think I spend very little for heat in the winter and a LOT for cooling in the summer.
Thinking out loud ... if I theoretically shade my house from all direct/indirect solar radiation, could I use my CDD calc? The answer I think is yes ... but I still haven't accounted for the latent loads of e.g. the SE ... not sure what those might be relative to conductive heat gain. I suspect it may be fairly significant. But few houses might see this theoretical condition even if surrounded by dense, tall trees in the woods (they would have to fully shade the roof as well).
Didn't think of it until now ... w/ high gas and diesel prices these days, what is the current fuel oil prices? If diesel for cars is $5/gal, isn't fuel oil going to be pretty high, too? Anyone know the answer?