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Old 03-31-2016, 05:17 PM   #1
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calculating the BTU's you need to stay warm

So i have been researching to find out what a good R value for a schoolie would be for full timing it. i ran into this calculation to help me, hopefully it can help you as well.


take the area of the wall, floor or ceiling, multiple by the difference of the schoolies internal temp(or the temp you wish to maintain) and the current temperature outside then divide that total by the r-value of each surface.

Example: and 8 ft x 10 ft wall = 80 sq ft, the temp inside the bus is 70 and the outside temperature is 30 or a 40 degree difference, the R value we will call it 14 for this "wall"

(80 * 40)/14=229 btu's are required to maintain 70 degrees for that wall

a better example would be

24 ft by 3 feet for wall 1 and 2

(72 * 40)/14=206
206 * 2 as the both walls will be the same
so 412 BTU's for those walls

now lets assume you have a 26 ft by 10 feet wide roof/ceiling

(260 * 40)/14 =743 btu's

and for ease of math we will assume the floor takes up as much space so we just double that.

743 * 2 = 1,486 Btu's

1486 + 412 = 1898

1,898 BTU's needed to maintain the temp of 70 inside your schoolie when its 30 degrees outside with r 14 insulation. i grant these are brick and mortar numbers and you would probably need to add 10-15% more BTU's based on heat loss from windows and general heat loss. But it is still extremely manageable at 2,300 BTU's. A Mr. Heater portable buddy on 4k btus covers that easily with a box fan to move the heat around a bus.

How Insulation Works, What R-Value Means, and How to Calculate Heat Loss/Gain for your house | BrainStuff

is where i got my numbers.so hopefully this will help you plan and stay warm and toasty in your schoolie in the winter.

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Old 03-31-2016, 05:58 PM   #2
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so hopefully this will help you plan and stay warm and toasty in your schoolie in the winter.
This is how I plan to stay warm and toasty in my skoolie-

(And, IMHO, Rachel Nichols looks sooooo much better as a redhead)
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Old 03-31-2016, 06:07 PM   #3
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This is how I plan to stay warm and toasty in my skoolie-

(And, IMHO, Rachel Nichols looks sooooo much better as a redhead)
well you cant argue with that lol
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Old 03-31-2016, 06:41 PM   #4
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Scooter's plan looks very hot and very expensive.

i used the btu calculator found here:

Home Heat Loss Calculator

if i recall, i used a (-20) for my outside temp and (70) for an inside. my 30' bus needed about a 30K btu furnace.

i have 2" of spray foam insulation that was about R4.
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Old 03-31-2016, 08:04 PM   #5
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That's all the R value there is from 2" of spray foam?
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Old 03-31-2016, 08:17 PM   #6
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its been awhile since i did it.... perhaps that was R4 for each 1" of foam.
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Old 03-31-2016, 08:35 PM   #7
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Foam board is higher in R value, isn't it? I thought the R value of spray foam was better than that, especially considering the expense.
Perhaps the main idea of spray foam is how it does a good job of reducing the sweating because of its direct contact with the metal.
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Old 03-31-2016, 10:11 PM   #8
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Foam board is higher in R value, isn't it? I thought the R value of spray foam was better than that, especially considering the expense.
Perhaps the main idea of spray foam is how it does a good job of reducing the sweating because of its direct contact with the metal.
it depends on the board, the r-10 value is 2 inches thick, the r-4 value is 1-1.5 in thick. they were solid foam board, Spray foam is a different beast, but i believe they calculate the R value for each inch of insulation added that way. so initial r value of 3 for one inch, 6 for two inches and so on. Each spray foam will have information on how the R-value is calculated on the manufactures website. That is always the best source of information and also most of the time the most detailed.

side noted once you calculate the area once you wont have to ever do it again nor will your r value change. so the only thing that changes is the temp difference. But you can just go worst case scenario. which -20 would work lol.
664 x 90/14 =4,269
4,269 with 15% added heat loss
4,910
man 14 r value is kinda boss...
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Old 04-01-2016, 11:54 AM   #9
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This is per Secret Agent Google:

Closed-cell spray foam provides a higher R-value per inch (6.5) than less expensive insulation types like cellulose and fiberglass (3.5 to 3.7). Most spray polyurethane foam is called "two-component" foam.

I've been planning (hoping) that the roof ribs with 3/4" of plywood furring strips will = 2" depth. Sound reasonable?

Also, I have to point out that the green energy solution is almost always the most expensive choice.
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Old 04-01-2016, 12:32 PM   #10
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Originally Posted by Scooternj View Post
This is how I plan to stay warm and toasty in my skoolie-

(And, IMHO, Rachel Nichols looks sooooo much better as a redhead)


Daaaammmn, she's hot. I like redheads.
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Old 04-01-2016, 12:33 PM   #11
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Originally Posted by dan-fox View Post
This is per Secret Agent Google:

Closed-cell spray foam provides a higher R-value per inch (6.5) than less expensive insulation types like cellulose and fiberglass (3.5 to 3.7). Most spray polyurethane foam is called "two-component" foam.

I've been planning (hoping) that the roof ribs with 3/4" of plywood furring strips will = 2" depth. Sound reasonable?

Also, I have to point out that the green energy solution is almost always the most expensive choice.

"Closed-cell foam is the most effective, with an insulation value of around R-6.2 per inch of thickness. Open-cell foam cells are not as dense and are filled with air, which gives the insulation a spongy texture. Open-cell foam insulation value is around R-3.7 per inch of thickness." there are different types of spray foams, make sure that you get the closed cell if you want that maximum return. as you said the high grade closed cell is double that of open cell.

Spray Foam Insulation: Open and Closed Cell | GreenBuildingAdvisor.com

I think 2 inches is a reasonable hope for ceiling space after the roof is removed. but you will only know for sure after you measure.
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Old 04-01-2016, 12:37 PM   #12
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If I am not mistaken (which I often am)...open cell foam will absorb and hold moisture, no mon ami?
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Old 04-01-2016, 12:40 PM   #13
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Quote:
Originally Posted by Azuleslight View Post
So i have been researching to find out what a good R value for a schoolie would be for full timing it. i ran into this calculation to help me, hopefully it can help you as well.


take the area of the wall, floor or ceiling, multiple by the difference of the schoolies internal temp(or the temp you wish to maintain) and the current temperature outside then divide that total by the r-value of each surface.

Example: and 8 ft x 10 ft wall = 80 sq ft, the temp inside the bus is 70 and the outside temperature is 30 or a 40 degree difference, the R value we will call it 14 for this "wall"

(80 * 40)/14=229 btu's are required to maintain 70 degrees for that wall

a better example would be

24 ft by 3 feet for wall 1 and 2

(72 * 40)/14=206
206 * 2 as the both walls will be the same
so 412 BTU's for those walls

now lets assume you have a 26 ft by 10 feet wide roof/ceiling

(260 * 40)/14 =743 btu's

and for ease of math we will assume the floor takes up as much space so we just double that.

743 * 2 = 1,486 Btu's

1486 + 412 = 1898

1,898 BTU's needed to maintain the temp of 70 inside your schoolie when its 30 degrees outside with r 14 insulation. i grant these are brick and mortar numbers and you would probably need to add 10-15% more BTU's based on heat loss from windows and general heat loss. But it is still extremely manageable at 2,300 BTU's. A Mr. Heater portable buddy on 4k btus covers that easily with a box fan to move the heat around a bus.

How Insulation Works, What R-Value Means, and How to Calculate Heat Loss/Gain for your house | BrainStuff

is where i got my numbers.so hopefully this will help you plan and stay warm and toasty in your schoolie in the winter.

DUDE! You are overthinking everything. You will be paralyzed before you get anywhere. How is this R factor going to affect your illegal honey moonshine while you are trying to outrun Johnny Law as you are crossing state lines attracting the attention of the BATF. You might need to trade that civic for a blown charger with a hemi.
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Old 04-01-2016, 12:41 PM   #14
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If I am not mistaken (which I often am)...open cell foam will absorb and hold moisture, no mon ami?


Man...you speak French too.
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Old 04-01-2016, 12:42 PM   #15
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If I am not mistaken (which I often am)...open cell foam will absorb and hold moisture, no mon ami?
if what i have read is true 50/50 with the internet. Both versions of spray foam absorb water. The open absorbs more water, however does not hold onto it as well. and can/possibly return to its original shape without warping.
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Old 04-01-2016, 12:44 PM   #16
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DUDE! You are overthinking everything. You will be paralyzed before you get anywhere. How is this R factor going to affect your illegal honey moonshine while you are trying to outrun Johnny Law as you are crossing state lines attracting the attention of the BATF. You might need to trade that civic for a blown charger with a hemi.
the original post was about BTU calculations, my other post "odd question" was about mead transportation and production while crossing state lines lol...wait, you are joking aren't you -.- well i fell for that one lol
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Old 04-01-2016, 12:53 PM   #17
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the original post was about BTU calculations, my other post "odd question" was about mead transportation and production while crossing state lines lol...wait, you are joking aren't you -.- well i fell for that one lol

Yes I was joking. I just happened to read two of your posts back to back. My point being don't make things too complicated. AND DON'T GIVE US MATH PROBLEMS! You make me feel like I'm back in high school and I have homework.
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Old 04-01-2016, 12:57 PM   #18
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Yes I was joking. I just happened to read two of your posts back to back. My point being don't make things too complicated. AND DON'T GIVE US MATH PROBLEMS! You make me feel like I'm back in high school and I have homework.
lol i totally fell for it, i was in both posts as well. I had to double check by leaving the post and going back into it lol. Well i see it this way, if i plan correctly now, it will go smoother when i implement it, granted i can respect the "nope, that aint going to work" factor as well lol. The military instilled having a plan of action XD. As for the math problems, im sorry, please forgive me...*grovels humbly* lol
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Old 04-01-2016, 02:31 PM   #19
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Azule: you're calculations are two-dimensional. You're not trying to maintain the temperature of a wall. You're trying to maintain the temperature of the whole space. You need to be calculating volume, not surface area.

Figure the inside of a bus is 7.5 feet wide, by however long, by an average of 6 feet tall. If you want to get really technical, you could subtract, let's say, 50% of the volume for the cabinets and other spaces that don't really need to be climate controlled.

Heat distribution is going to be the big thing, which is what I've been playing with in my head for a while now. I'm debating using 2 heaters instead of one due to the length of the area I want controlled. I've also been thinking about some creative ducting to limit the heat to where I will be during the day and at night.
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Old 04-01-2016, 03:06 PM   #20
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Azule: you're calculations are two-dimensional. You're not trying to maintain the temperature of a wall. You're trying to maintain the temperature of the whole space. You need to be calculating volume, not surface area.

Figure the inside of a bus is 7.5 feet wide, by however long, by an average of 6 feet tall. If you want to get really technical, you could subtract, let's say, 50% of the volume for the cabinets and other spaces that don't really need to be climate controlled.

Heat distribution is going to be the big thing, which is what I've been playing with in my head for a while now. I'm debating using 2 heaters instead of one due to the length of the area I want controlled. I've also been thinking about some creative ducting to limit the heat to where I will be during the day and at night.
Hmm, volume is basically doubling the space overall yes?

It is still manageable as empty spaces go. the heat retention from the added wood would only make my requirements better. But you are right i was suppose to double the space basically. But numbers dont mean crap in the end. real life trial on a freezing night will tell the truth lol.

I plan to keep it simple for the day and just add a box fan. it works currently in my apt with the ground heater i have. i only use it on 600w and half power and my 12x14 room becomes a suana.
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