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# Stone wall R value question...................(Starch)

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Member Posts: 7
Just didnt want to sound argumentative. I dont do hydronics for a living, just am interested in it alot and learned alot from yer posts.

Makes sense...I think you are saying that the 55 deg temp I see is sort of the "best" the stone wall can "produce" so to speak.

Not to hijack, Brad, but are you using Monitor's O.Reset unit-seem to remember you were going to get it. Mine works well, but doesnt use the 2nd stage of the MZ 40 in DHW mode..wondering if that were normal. I get plenty of hot water, but swmbo sometimes will kill the 60 gall.tank on one of her home spa nights...
Also, love to hear what you all think-could I run low temp water (140 max) through a Modine type heater with blower to heat my woodshop?
(It's 1200 sq/ft) using the spare capacity I have in the mz. Wondering how to select one of these heaters in terms of btu output, using lower water temps than the 180 they want. Shop will have decent insulation. Thanks for any input.

• Member Posts: 626
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Trying to put a proposal together.....

....for a very old historic building here. My question is how to figure the r value for the walls. They are approximately 16" to 18" limestone, with plaster applied directly to the interior of the stone. The mortar joints appear to be in pretty good shape, but I'm admittedly lost on the r value.

Anyone????

Starch
• Member Posts: 2,398
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Sitting Down, John?

Overall R value is about 2.6 and the inverse (u) factor is about 0.3846.

This includes R values of:

Interior Air Film =0.68 (Still Air)

Plaster, 3/4" = 0.47

16 inches Stone (Lime or Sandstone 0.08 R per Inch)= 1.28

Exterior Air Film = 0.17 (15 MPH Wind)

I used these factors on a renovation at Princeton University (East Pyne/Chancellor Green) a few years ago. Tried and tested

"If you do not know the answer, say, "I do not know the answer", and you will be correct!"

• Member Posts: 626
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Now how did I know....

...that you'd be the first one to respond, Brad?

Psychic, I guess!!!!

Thanks, brother.

Starch
• Member Posts: 1,935
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just what i've

been waiting for, i have a stone basement, around 12-14 inches thick. not limestone but mine rock. I used R1 as in concrete and pooped my pants, basement had larger heatloss than entire poorly insulated house! half of the basement is walkout, that kills the heat.

maybe I'll use R2 or 2.4.
• Member Posts: 2,398
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What you really need

is a new house and a change of shorts.

A greenhouse made of low E glass has a better R value.
"If you do not know the answer, say, "I do not know the answer", and you will be correct!"

• Member Posts: 1,935
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Mr Grenjeans

well now you can call me mr greenjeans. the house i speak of is getting remodeled and insulated.

this weekend I wired up my PV panels at the current dwelling, lights for the first time in 3 yrs!!!! passive solar too,almost as good as a greenhouse.
• Member Posts: 477
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Yah, but...

Don't discount the thermal mass time-lag effect. If that stone wall was subjected to day-night temperature swings, the actual heat transfer through it is a dynamic average of the temperature fluctuations. Heat loss through a heavy mass wall is not an "instantaneous" effect. But I quibble, all heat loss calculations are a good estimate at best, unless you have access to high end building thermal modeling software.

If there was a way to add insulation to the outside of the heavy mass walls, then the mass would retain the indoor temperature and you could vastly downsize the heating system. The stone basement walls will provide free air conditioning to the basement in the summer. If you insulate the inside of them, you'll likely need mechanical cooling there.

But, yeah, if those stone basement walls are in direct contact to the earth, and you are in a heating dominated climate, well, it's a problem. In new construction it's much better to insulate the exterior of the basement wall to keep the thermal mass on the warm side.

Infiltration around windows and other building openings may be a bigger issue in an older historic building.
• Member Posts: 626
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I hear you, Geoff.

Normally, I would suggest adding insulation to the walls, but that won't be possible in this case. It's an ooooold stone building, around 150 years old, I think. It was built to house the lighthouse keeper, long before my town was a town.

The local historical society is looking for a way to heat and cool the place. Heating will be done mainly in the "shoulder" seasons, but they want to try and maintain 45-50° in the winter. Lots of challenges to figure the best installation without losing too much of the asthetics.

I'm thinking high velocity system in the attic, using an air-to-air heat pump, but it's early in the process.....

Starch
• Member Posts: 2,398
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Starch- I agree with Geoff

that mass is your only friend here, conductivity aside.

Still, what do you think about doing some radiant here? Cheating the MRT and all that. The occupants will thank you and the energy use will be less for the effect especially at lesser indoor temperatures... just a thought.
"If you do not know the answer, say, "I do not know the answer", and you will be correct!"

• Member Posts: 626
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I would love to.....

...but I think the physical challenges, along with asthetic considerations, will make radiant a no-go.

This is a non-profit group, so funding will be an issue whatever I do.........
• Member Posts: 7
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My own house is also historic,all stone, plastered right onto it. Its about 2000 sq. ft, and biggest gas bill was bout 475 last year in February.
After using both the wirsbo and hvaccalc software, I somewhat disagree with the engineering worlds R value assessment of stone.
Granted, I am running an MZ, and have spray foamed the formerly incredibly leaky (air infiltration wise) roof, but still..inside surface temps on the plaster exterior walls hover around 56 degrees on design day.
• Member Posts: 1,935
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a puzzling thing

i agree, lots of mass and high conductivity make stone walls puzzling?

you'd think if they have low R values, heat would pass right through....

I did fire the basement wood stove for several hours the other day, to no avail, the basement was in the 20's and not bugging. early in the winter it would warm up, now its going to take a ton of wood.
• Member Posts: 2,398
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56 degrees confirms it, Jesse

The R value assessment was made in a laboratory hot box and confirmed over the years empirically. Your inside surface temperature of 56 degrees is roughly the inside temperature of my double-pane windows with inside storms (triple pane actually), which has an R value about the same as your stone wall.

The thermal mass (specific heat of stone) is high enough to bank the heat given, meaning time to cool off but also as much time to heat. With good solar exposure even in winter, this will slow the losses on those walls perceptably.
"If you do not know the answer, say, "I do not know the answer", and you will be correct!"

• Member Posts: 7
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Not trying to question your answer, but my gas consumption to me is not that of what would basically be a glass house, if I read you right. Dont get much solar gain in either season to speak of..I also get that same mid 50 deg wall temp in many other houses (framed ones) as well using my laser thermometer.
I understand to a degree the mass effect, but after a month of being very cold here I would think thats negated, right?
• Member Posts: 1,935
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curious?

and how does that compare to the \$475 fuel bill?

it is surprising how warm you can stay by just putting on a windbreaker over a light sweatshirt. points to infiltration as a big loser.

have you done a heatloss on paper?
• Member Posts: 7
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Using heatcalc, it's just over 100k. (been a couple years)Granted, my infiltration has been improved (foaming the roof saved me 20% easy a month). I also was able to turn the water temp down to 140 max by toying with the outdoor reset curve and we're comfortable(not sure if that's a helpful tidbit or not)
• Member Posts: 2,398
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Jesse,

No harm in questioning any of my answers, I have much to learn myself.

"I also get that same mid 50 deg wall temp in many other houses (framed ones) as well using my laser thermometer. I understand to a degree the mass effect, but after a month of being very cold here I would think thats negated, right? "

I agree, many framed portions (non-insulated portions of an otherwise uninsulated wall) will get you mid-50's surface temperatures. My double-pane glass has interior surface tempratures in the 40's and with another interior storm, the mid-50's. No surprises there. By contrast, my insulated portions are within (below) a degree or two of the indoor setpoint temperature. The difference is the indoor air film (an R value of 0.68) which the IR thermometer negates because it reads the surface temperature itself.

But your last sentence about a month of cold weather negating the effect?

Only if your heating system cannot keep up. Remember, your heating system has been working more or less in proportion to the cold weather and as continuously as it has. If it were not, only then your wall temperature would drop. Does that make sense?
"If you do not know the answer, say, "I do not know the answer", and you will be correct!"