Research by the cubic foot (ME)

Mark Eatherton1

Some of you may remember my forays into the unknown last year with my data logger. I taped a 1" thick (R5), 1 square foot piece of XPS foam with a sensor imbedded to the side of it against an outside wall, and located a sensor outside of the house, and one inside the house. Saw some pretty interesting stuff that I couldn't interpret. R value appears to be basically a lag in time thing.

So, upward and onward. This time, I took 2" foam (R10) and made an air space approximatley 1 cubic foot. I placed one sensor in the exact center of this air space, and located another sensor hanging outside of the box, but not touching the box. I wanted to see the effects of R10 on one cubic foot of air. The XPS foam is the green colored stuff.

What I saw echoed previous findings as it pertains to time lag. But more interesting, I got a chance to see the effects of clear night sky re-radiation on my test box, as well as the effects of solar gain.

Attached please find the EXCEL data. I had the datalogger set to sample every minute. The black line is INSIDE the box, and the PINK line is outside the box.

The testing was performed in the back yard of my live in laboratory :-) and began at approx. 5:00 PM and ended around NOON the next day. The raw data is in the R_10_by_ file, and the accompanying graphs are shown for the time frames selected.

HOUR 1 shows the OSA sensor pretty much stablized, and the inside sensor sliding its way down to meet it.

19 HOUR chart shows pretty much the whole run.

10 PM to 2 AM shows some interesting temperature changes, and the beggining of the Night Sky Re-Radiation factor (NSRR) starting to kick in. Notice how the inside sensor does not shadow the Out Side Air (OSA) sensor completely.

The 2 AM to 4 AM graph shows the greatest influence of the NSRR effect on the box. The inside temperature continues to fall, even though the OSA temperature is rising

The 6AM to 10 AM graph shows the effect of solar influence. Remember, the box is a flat green color which is highly absorptive to solar radiation.

The 8 AM to 12 chart shows the greatest solar gain influence.

So, what does this tell me? It tells me that there is more to heat loss than just simple delta T driven calculations. We're taking ourselves too literally, and not taking into consideration those things that have an even greater effect on human comfort. Things like NSRR and solar gain even though there are no windows in the box.

Oh yeah, so as to not influence the testing unfairly, the infiltration factor of the box is ZERO because I tightly duct taped all of the exposed insulation butt joints.

The next step is to add some mass to the inside of the box and see what happens.

Comments welcome...

Mad Mark from the Denver Zone...

(A.K.A. ME)

EDIT: Not sure if everyone can open the .xls file, so I copied the important graphs and saved them as JPEG so everyone can see them. Enjoy!

ME

bob_44

who R you kidding

I think you are outside the box. seriously mark what are you trying to assertain? bob

Steamhead

One Question, ME

what is "Night Sky Re-Radiation"? That's a new one on me.....

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IMatEllerslie_2

very interesting stuff

thanks for sharing Mark

Christian Egli

This is bizarre

I am puzzled by what happens at around 18:20.

I find it odd that the inside temperature could ever reach lower than the outside temperature. It couldn't possibly be colder inside compared to the outside, unless...somekind of cooling mechanism is going on with the box itself.

I would first suspect the sensors, maybe they are not calibrated both as exactly. Repeat the test while crossing the sensors.

It could be that what is going on is the same thing than with a sling psychrometer. For some reason the green foam is retaining some moisture (dew perhaps) and its evaporation is cooling the box and the inside temperature. Try adding a vapor barrier (more duct tape all around!)

The radiation thing is true and your box would be a good instrument to measure it (painted in black, it would be even better) but it can't explain why the box is radiating all its heat away past below the outside temperature. If that were possible, I should be getting all hot just by sitting in front of a cold radiator.

Hot bodies radiate heat like little arrows that cold bodies absorb. If the box is colder than the outside it should be doing the absorbing. No? Is there, like, a giant ice cube near the box that could be taking radiation away from the box but that would not be big enough to change the outside temperature?

I'm going back to bed now, but I am still puzzled. You did a nice job with the data acquisition.

Mark Eatherton1

NSRR...

is the process by which bodies give up their heat. At night, during a cloudless night, clear sky re-radiation can actually sub cool surfaces emmiting a substantial amount of heat to the super cold extremely overbearing btu sucking black hole we call, the sky...

I know of an engineer in the mountains who has two 14 story twin tower hotels being operated off of one physical plant. If it's cloudy, he can get by on one boiler. If it's clear, he HAS to fire both boilers or will get complaints from the guests...

I first met it back in the middle 70's working on large solar arrays. The absorbers in the collectors always cooled down to temerature that were considerably less than the lowest ambient temperatures seen over night. Like by 20 to 30 degrees...

It's cool:-)

ME

Mike T., Swampeast MO

unless...some kind of cooling mechanism is going on with the box itself

That's the night sky re-radiation.

Is there, like, a giant ice cube near the box that could be taking radiation away from the box but that would not be big enough to change the outside temperature?

Quite literally that "ice cube" is the upper atmosphere and perhaps, dare say, "stuff" in the vacuum of space--Mark's in Colorado high country so he's a bit closer than many... His box is highly emissive and since it's made of foam doesn't have much specific heat. It's giving up its heat more rapidly than the other objects (including the air) around it. While we consider air transparent to radiation, such is convenience--not fact. The same thing tries to happen on cloudy nights, but the clouds intercept and reflect some of the energy back to the surface.

Mike T., Swampeast MO

Lag in Time Thing

R-Value equals "Fahrenheit degrees x hours x square feet per Btu" so time is a very important factor--even if the number we see is based on "hours" with a value of 1.

jp_2

more questions

got a picture of the experimental green box?

what was the barometeric pressure? or your elevation?
boiling point of water where you live?

so, what do you consider is your radiant body, the moisture contained within the air, the air itself or the cube of insulation?

the box was initially at 70F, wondering what the amount of moisture was intitally in that box?

I really like the idea of swapping sensor and re-testing, please let us know if you do this.

jp_2

still more questions

Ok, interesting stuff for sure!

what is the resolution of your temperature sensors, or the a/d converter they hook to?

I think you need some curve smoothing software here, I see from 3;30 to 4:16 outside temp rose and fell 4F? what do you make of this?

I would like to see a ground sensor, say 1/4" to 1/2" in the ground, after all, its the ground that are giving off these long waves!

jp_2

still more questions

Ok, interesting stuff for sure!

what is the resolution of your temperature sensors, or the a/d converter they hook to? so, I'm asking what is the error of your equipment?

I think you need some curve smoothing software here, I see from 3;30 to 4:16 outside temp rose and fell 4F? what do you make of this?

I would like to see a ground sensor, say 1/4" to 1/2" in the ground, after all, its the ground that is giving off these long waves!


""So, what does this tell me? It tells me that there is more to heat loss than just simple delta T driven calculations. We're taking ourselves too literally, and not taking into consideration those things that have an even greater effect on human comfort."""

here I disagree a bit, other than say water to ice phase change, I think we always see/feel delta T with energy gain/loss. when I walk into my cold cabin, my face "sees" delta T associated with woodstove radiation, but nothing behind me.

bob_44

Might check your

definition of R mike. Sounds like some mysterious secret thermodynamics going on here. Don't let the cat out. Maybe Schrodinger's cat? If mark is outside of the box how does he know what's really going on inside the box. If he opens the box will the knowledge within collapse? bob

Christian Egli

The Eupatheoscope and hot bodies

Ah ha! your machine has a name. It turns out, someone in Britain, a long time ago, wanted to measure the heat loss of a simulated human being.

The eupatheoscope resembled humans in every way... It was a large stove pipe-like copper vessel filled with, I guess, blood-colored water. It had a heart in the shape of an electric coil. The whole thing was heated to a simulated body temperature of 75 F, then heat loss was measured while placing the gadget in various environments or in front of various radiators and sticking a sensor on its forehead.

They noticed how wind chill and radiation had very significant effects on comfort.

Then the tests were repeated in America and it was found that a simulated human body temperature of 82 F was more realistic... I measured myself this afternoon and got 96.1 F under the arm. Either your green box and sensors got my blood boiling, or the eupatheoscope needs a simulated brain.

Honestly, I believe the tests were going for the human skin temperature and allowances had to be made for simulated clothes we all wear. Maybe, the foam green jacket is just the thing in fashion today?

The green box you made measures the radiation effect which turns out to be astonishingly large. I am still in awe of how much you found, and this proves the point we all know: that forced hot air heating schemes are severely defective on both issues of radiation and wind chill.

There is one main difference between the green box and the eupatheoscope: your box is lifeless-no heart-no heat source. So, it does not get fresh gobs of energy to radiate, which means it should keep getting colder and colder.

With that in mind, should we not expect the gap between the two curves to be widening over time? not even just a little? how quickly should we reach steady-state? I think I see a gap that is fairly constant all the way, except for in the morning when the sun comes out. There, we clearly see a broadening gap, and this shows that the foam has the insulating capability to resist to such a difference.

I am still looking for the giant ice cube. The great galactic outdoors seems so far away, but I agree it is there. Getting a measurement for the ground is a great idea. What if the thermocouple (I am assuming you used a J, K, ... thermocouple) is the source of cold? Thermocouples do remove heat in tiny measures which they convert into tiny electric voltages.

I don't know where I am going with these thoughts. It might that I am turning into a simulated hollow copper pipe. I can sure sound like one.

Has anyone ever seen the handy dandy comfortstat in use? Apparently they should be stuck to the wall or the ceiling and be the size of a tennis ball. It sure seems like a much smarter way to measure comfort and not just temperature. Did it really work as good as hoped? I joined a sketch to this post.

Hey, tonight, I hope we'll all get to cozy up under a great blanket of clouds, or else it'll be cold tomorrow.

Goodnight

Mark Eatherton1

Assertaintion...

NEW WORD, 50 bonus points:-)

bob, the only thing I was trying to acheive was to find out what happens to the air temperature inside an R10 foam insulated box with no internal heat available. I'm still trying to get a good "picture" of R value. I know what it is supposed to be theoretically, but I want to "see" what it looks like. Kinda like trying to see what a btu looks like if you get my drift...

Still looking for R :-)

ME

Leo G_99

Ice

cubes in the dessert. or is that desert?

Leo G

Leo G_99

Good,

cause we all know where ME is!!!

Leo G

jp_2

box location?

where is the box located?
on the ground or suspended?

I agree with super cooling(not sub cooling by the way), but why would an "insulated" box give off heat faster than surrounding air?

wouldn't that dismiss insulation as insulation?

this thread could go on a long time.

Mark Eatherton1

Some answers

I'll take a picture and post it later. Not really much to see though. Just a box made out of EPS foam, taped at the lap joints, with a small hole, just large enough for the 3/16" sensor to fit in, and the sensor lowered into the very center of the box, with the penetration hole taped tight. The OSA sensor sits on top with the actual sensor hanging over the side so as to see air temp.

I have no idea what the barometric pressure was, and as far as I know it would have no effect on air temperatures. I believe we were under the influence of a high pressure cell at the time due to the clear sky situation, so for what its worth, baro pressure was probably high.

Elevation ASL = 5,280 feet give or take a few hundred feet. I'm slightly higher than the capitol which IS 5,280 feet ASL, so say 5500 feet. Don't know what relevance that has to do with the findings either, but there it is.

Boiling point of water is 2hundred (208-210??) and something. Less than sealevel for sure. Not sure what relevance that has to do with the findings either. Results were no where near boiling.

I would consider the first order of radiant body to be the actual cube itself. I think the air temperature inside the cube is basically following the cube, slowed by the R value of the cube, but eventually following it.

As for starting temeprature, I allowed the box to "normalize" inside my heated dwelling for an hour prior to throwing it outside. I had it hooked up to my PC and when the inside of the box equaled the outside of the box, I dragged it outside and the test started. Simple as all that.

The two sensors came to within 1/2 degree F of each other prior to my starting the test. I see no value in swapping the sensors. We're not talking miles of difference here, were talking millimeters as it pertains to the picture as a whole. As for color, a flat green surface has an emmisivity that equals or betters flat black. If flat black were a better color, mother nature would have made trees black instead of green... Roll with the flow.:-)

ME

rb_6

stuff

Thats why when SIM system are modelled we look at cloud cover before, during and after a snowfall.

But here's a toy for you guys to play with, its a comfort data logger:

Mark Eatherton1

More answers...

The sensors are pretty darned accurate. If memory serves me correctly, they're accurate to within 1/2 degree F, and +or - 1 degree over the whole range. It's an Onset Hobo 4 channel recorder. I've checked it against my brand new infrared non surface contact thermometer, and it appears to be dead on.

As for up and down temps, we were on the leading edge of a cold front pushing in form the southwest, This generaly has wind included, and up slope winds cause warming conditions called Chinooks. Not untypical for this time of the year.

I'm not sure what the ground temperature has to do with all this, but the next time around I will measure it too. I suspect it will shadow the box. Anything that is warmer than outter space will be emitting heat, including the green box with no heat being generated inside of it. Remember, heat flows from hot to cold until both are equal.

According to my ASHRAE Fundamentals book, section 3.10 on Heat Transfer, "Radiation exchange by opaque solids is considered a surface phenomenon. Radiant energy does, however penetrate the surface of all materials" blah blah blah blah blah blah blah. (Beers Law). Hence, a cooler inside of the box than outside due to the night sky absorbing all potential energy through the opaque material.

What the heck do I know, I'm just a hot water plumber from Denver:-)

Here's where I disagree with your assetion. If you walk into a cold cabin with a hot stove, your back side "see's" cold and doesn't like it and tells your body to turn around to warm it up before it freezes. It's what I call the rotissary effect. ;-)

Night sky reradiation pulls heat from all surfaces, regardless of their orientation. So long as the surface can "see" the night sky, it WILL give up its heat to that body, thereby creating a cooler internal surface that OUR bodies in turn see and begin giving up (unwillingly) thermal energy to that surface, thereby creating a condition of thermal discomfort that is not associated with the normal means of conductive energy transfer associated with conventional heat loss calculations. (Did I just say that???) Trust me, there are people here who know MUCH more about this subject than I profess to...

I can only hope they will step up and swat me down if I'm out of line, and I suspect I am:-)

I'm not trying to rewrite the laws of thermal dynamics here. I'm just posting what I found doing a simple experiment...

In search of the big R :-)

ME

Mark Eatherton1

Location location location...

It was setting atop my 1975ish barnwood red lumber picnic bench which serves as my dogs sun bathing deck during the day when we're not here. They know better than to get on the table when we're here, but I've snuck home during the middle of the day and caught them up there tanning themselves.

The box gives up heat to the night sky because its a perfect color for high heat emmitance, that color being a flat green. There is NO heat being generated on the inside of the box. The only "mass" of the box is the insulation itself, which doesn't stop the flow of thermal energy, but only slows its transfer down.

Sub cooling, super cooling. Whats the difference? Semantics?

Thanks for playing:-)

Still looking for R..

ME

Mark Eatherton1

Bedouins I believe...

made ice in the desert with nothing more than water and dark surfaces. Hiya Leo! Wanna make any bets on the Stanley Cup this year??? ;-)

ME

Mark Eatherton1

Jeez Christian...

I wanted to stimulate your thinking process, not constipate it:-)

Good questions tho, I'm gonna have to sleep on it too...

But before I do, heres some data I retrieved from the same system on NSRR using the same system. The NSRR sensor was located on a clear plastic bottle. The sensor was "lamp blacked" with soot from a candle. The ambient air sensor was the conventional metallic color. The intent of this research was to come upp with a sensor that could determine when the sky was clear, and when it was cloudy. A "solar gain" anticipator if you will. If the logic detects a clear sky, it would ignore a call for heat from a east of south facing windowed room if that call came within 4 hours of the room seeing solar gain. Avoiding compounded solar input, and allowing for Better Thermal Utilization (BTU) of the FREE solar energy.

Enjoy, and sleep tight:-)

ME

bob_44

ME's butt mrt sensor

Mark, you indicate you have ASHRE Fundamentals. If you look at how they calculate surface conductance they use an emissivity of .90 facing a virtual black-body at the SAME TEMP as the ambient air. The night sky at altitude on a clear night is probably much colder (background radiation of the big bang?) I don't know. Inside a building your butt sensor only sees MRT in the direction it's aimed. As for your quest for R here's my take. All the heat transfer factors k,C,f,a, and U tell you HOW MUCH heat goes through R tells you how HARD it is for heat to go through. Take care of your sensor. bob

chilly

what you're really measuring

I believe what you're really measuring is black-body radiation. At night as you point out if the sky is clear the Earth radiates energy back into space via IR band. During the day the Earth stores incoming solar radiation or insolation via shorter UV and visible light. At night if it's cloudy the IR is reflected back by the H2O and CO2 in the clouds since that's where they absorb and radiate back to the Earth. The Earth doesn't cool down as much. There is the other edge to this sword that if it cloudy, thhe sun's energy is reflected back into space so we don't get that hot.

Also in Denver you're average un-adjusted atmospheric pressure is about 850mb. The elevation of Denver puts about 1/2 of the weather generating atmosphere below it. As the amount of air above you decreases then the amount of H2O and CO2 decreases as well. In Denver you have less atmosphere to radiate through than say New York (disregarding the urban heat island effect). So you can get some great swings in temperature.

I would suggest suspending the box if possible. Placing 1 sensor inside, 1 outside not touching the box and try to suspend the box about 2 meters off the ground. This is where offical National Weather Service temperatures are taken. You would be amazed at the difference in temperatures during radiational cooling by measuring air temp at 2meters vs 2 cm above the ground.

If your box is truly sealed from outside air, then you would have the inner box gain heat via solar radiation and it should cool more slowly than the outside air on a cloudy or cool night. However since the only heat gained in the box I assume is from the sun the experiment will only be valid on a 24 hr clear period.

I just wanted to add my 2 cents.

Mike T., Swampeast MO

That simple definition came from a Google of "define: r-value"

Here's a link to some actual formulas:

Heat Flow Through Object Formulas

The r-values we see for insulation materials are based on resistance through one square foot over a time period of one hour so they are easily expressed in BTUs per hour.

JohnWood1

Heat and R factor


Mark;

Was thinking about yer little experiment and it came to me that R factor is a resistance to heat flow. No real quantity of heat in the small amount of air in yer box, so therefore it should track the outside temp with some lag. Try the experiment with something with some decent specific heat involved, such as water. Or even better in my mind would be a constant heat source of known input. Small incandescent lamp comes to mind. Then use the hobo and two sensors for the same experiment and see what the results are. Should give some realistic results of what the insulation really does or does not do.

I do enjoy yer experiments! Got a simple one going on with my own home as I have limited my heat input to 5kW just to see how cold the outside needs to get before it runs continually. So far we have had -8 and still cycling! this in a 2000' moho. We have some -19 coming tonight. Will be interesting to see if it can keep up 68F then.

I have always felt that we oversize the heck out of our heating plants even using man J.

Boilerpro_3

I have brought this night sky radiation to customers attention

It adds new importance to proper attic ventilation. It helps keep the attic warmer on cold clear nights.

Boilerpro

jp_2

inside experiment

first off thanks for all the replies.

I was tired and hungry yesterday and off on the wrong foot about forming ice that was contributing to your readings, but i was heading in the wrong direction.

your experiement should be transferable to inside, if you were to put the box near a radiator it should heat more than the room air? if super/sub cooling take effect so can warming. I propose!

ps I've super cooled water to -25F without it freezing, my winter time experiments! nothing added to the water by the way.

one last point, the reason I'm curious in ground surface temps. this is where the long waves originate, the ground temps should lead air temps when changing.

Boilerpro_3

I have brought this night sky radiation to customers attention

It adds new importance to proper attic ventilation. It helps keep the attic warmer on cold clear nights.
Also another good reason to uselight colored shades on windows at night, I belive it will reduce this radiation heat loss effect.

Boilerpro

Christian Egli

Wild entertainment watching the thermometer

Hi Mark,

Thanks for the neat thing you've done. I've learned a new trick. I had never realized how much radiation does beyond the massive doses you get out in the sun or in front of a radiator.

At lunch, today, I made my own eupatheoscope (It's a fun word, no? it comes from a Greek root, EU for good, PATHOS for feeling, SCOPE for seeing, so the gadget measures the right feeling and not just the right temperature, that's for smart dictionaries)

Your green box totally fits that definition. Here's how I made mine.

I used a digital indoor outdoor thermometer which I have on my desk. I brought the outdoor sensor back in and checked the two sensors side by side for a same reading. Then I placed the outdoor sensor inside a coffee can which I closed tight again.

Then I made myself some coffee... I spent the afternoon keeping an eye on the thing. Here is what happened.

I left both units on a table in a rather cool room at 44 F (I would say everything in that room was at the same temperature walls and all, no heat, no light, no draft, no sun and no sky) Things stabilized, and the coffee can was colder by 0.6 F. Isn't that something?

The can still has its dark brown label around it. Later in the afternoon, I insulated it on the outside with a black scarf and provided as little contact possible with the table. The can remained colder by 0.6 F.

I have no explanation. I plan on checking out what happens in front of a radiator and in front of a hot air register, and out in the sun...

You're on to something.

Thanks for all the fun.

jp_2

pls explain

boilerpro, aren't you saying the opposite of what mark is saying? you say the attic is gets warmer, marks little attic gets cooler??????

warm attics lead to ice dams around here, guess I need a data logger in the attic to see whats up. I've always assumed ice dams are created in the day time, interesting!

jp_2

more entertainment

take your thermocouple and dip it in water, alocohol, gasoline,etc....
watch the temperature dip as the liquid evaporates! it may amaze you with the low temps they reach!

Tim Doran

Good Stuff

Great test Mark! There is as far as I can find a great deal of validity to the clear night sky thing. Steffan Boltzman looked at this when working out his laws(calculations) for radiant transfer. This adds another dimension to skylights doesn't it?

Tim D.

Mark Eatherton1

Super Secret Pictures...

As promised, here are some pictures o fthe box. 2 of it naked, and two of it with a Duncan Wilson treatment:-)

I reloaded the HOBO and set it outside for the night with the Wilsonizing intact. It is a great clear night, and it's supposed to dip down to around 11 degrees tonightm so we'll see what the net effect, if any Wilsonizing has on the insulation.

For those of you that are avid hunters, I included a picture of a herd of elk I came across today whilst running a service call. This is part of the Mt. Evans herd, wintering at Cold Springs Ranch. Technically speaking, they're not called a herd, but instead are referred to as a gang.

What do you think THEY think aboout night sky re-radiation...

Enjoy,

ME

Christian Egli

How big is the hole in my wall, it's a size R10

We all see how a boiler just rams the BTUs, by the car load, into a house. We know also that the BTUs have an irrepressible urge to escape like convicts from a prison. We make it a maximum security prison by wrapping the home in insulating foam. Very clever...

And yet, the buggers, they still escaped. You see, there was a hole in the insulation. The manufacturer did warn us by telling us the R-rated size of the hole. We could have figured it all out.

Pressurize your home, make a hole in the wall and feel all the air coming out. More air will come if either the hole is bigger or the interior air pressure is greater. You would measure this flow in cubic feet per minute. You would also get the pressure difference in PSI. And since a plain hole is easy to see you could just measure its diameter.

The same relation works for heat. The temperature measured by the thermometer relates to pressure level, and heat transfer relates to air flow. The flow is measured in BTU per hour and the delta T temperature difference in degrees.

And since the hole is not plain to see, you can't really get a simple diameter, instead you co-mingle all the units together. Also, to make the whole thing scalable to an entire wall surface, you add a per square foot dimension that allows you to assume that if there is such a type hole per square foot, you'll find the same for every other square foot of wall.

And here we are, measuring stuff in BTU per h, per degree, and per square foot. This value is U, the heat transfer rate, thus

U = (BTU/h) / (deg F * ft2) = (BTU) / (h * deg F * ft2)

R is simply the inverse of U, 1 / U,

1 R = 1 (h * deg F * ft2) / (BTU)

It is inversely proportional. The bigger the R number, the less heat leakage. It does not seem as intuitive as the U value which shrinks with less leakage, but in a world of marketing, I guess bigger is always better.

Finally, this is how the BTU mystery escape unravels for each square foot of wall:

If you know the R-value and the delta T, you can compute the BTU/h rate.

If you know the BTU/h rate and the delta T, you can compute R.

If you want to shrink the BTU/h heat leakage you can either decrease the delta T or increase the R value, or both.

To reduce your fuel bill, you can either lower the thermostat (decrease the delta T) or wear a jacket (increase the R value).

If you increase the R value and proportionally increase the delta T, you will not have changed the BTU/h rate at which heat leaves your home.

In the hot summer, while keeping R the same, the delta T will reverse itself which means the BTU/h flow will reverse itself, hence the need for AC cooling.

You can really knock yourself out, like I just did.

Thanks for reading and I hope this helps. Thanks again, Mark for making me peep through the hole.

By the way, the coffee can test is fascinating, so far, and we've run out of coffee.

Christian Egli

Elks

Nice bugs you have around your place. It's beautiful where you are.

I think I see one elk with a green box, it must be up to something...

jerry scharf_2

just for grins

Mark,

I've got a fun thing to try. Build another one of your cubic foot frames, and cover this one with aluminum foil, shiny side out. It should reduce the radiation effect, but I'm more interested in the lag. I'm wondering what the net mass/R value of the foam has over something that can be thought to be massless other than the inside air.

You're really should check out the 1-wire temp sensors from Maxim Semi. At $4 each and a trivial bus setup to collect data.

jerry

Mark Eatherton1

Beatchatuit Jerry...

It's in the anti-microwave oven I call my backyard collecting data as we speak. To appease those non belivers, I switched probes too.

ME

bob_44

Complexifacation

Mark, because you have chosen to use a six sided box the calculations get involved. Each side probably sees a different radiant target. The R factor for each surface is different depending on orientation ie the R factor for the green box horizontal surface is .61 for the top and .92 for the bottom and .68 for the sides this is just still air surface conductance. For the druncan wilsonized box it's, top 1.32, bottom4.55 and sides1.70 this is all plus the R value of the foam. these numbers are based on radiation to a black-body at ambient air temp. You can see Mark that ASHRAE has to make some assumptions or this gets way to involved for what we do. Heat loss calcs can be an exact science but it ain't practical. How many jobs that you have installed haven't heated because you made a bad assumption about nsrr. bob

ScottMP

Mark

I am but a slow student sitting in the back of the class trying to keep up, but ...

Thanks for doing this. I "think" I am learning something here. I have nothing to add, just that there are some of us who are following along.

Scott

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