How much heat would i really be losing?

[carcajou]

I'm in the process of taking over a farm shop that was built on a 4' high 8" inch thick concrete wall, the 12' above is framed and insulated. Nothing has been added for insulation to this lower 4' concrete wall. Nothing can be done to the outside easily and i would like to leave the inside alone for the aspect of fire safety and easy clean up. The shop will be heated 4 months of the year and is located in a colder area. Am i going to spend a lot more in heating this space (40x70)? Is it worth the cost to put 2" of styrofoam sm around the building and cover it with 26 gauge galvalume or similar? Thanks in advance for your thoughts.

 

[Randy in Maine]

How long do you plan to live there?

 

[carcajou]

25 years. Likely heat it for 15 then semi retire

 

[kd3pc]

is the 4' high part above grade or below?

Long term plans to use the space often, will make the changes more affordable or at least spread the cost over several seasons of use. I am not sure that 2" will make a real difference in total energy costs to heat the building.

Were it me I would look closely at what I "need" and then form a plan.

 

[bdbecker]

Quick and dirty...

70+70+40+40 = 220 linear feet of wall to insulate (not accounting for doors)

Each foam sheet covers 8' if you lay it on its side... 220'/8' = 28 sheets

A sheet of 8' tin cut down to 4' long covers 6' of wall (2 pieces per sheet).. 220'/6' = 37 sheets of tin.

Around here, the big box cost for 4x8x2" board is $26 and the cost for a sheet of tin is $16.

28 x $26 = $728
37 x $16 = $592

So you're looking at $1320, not counting any cap/trim and taxes... call it $2000 to be safe.

4 months of heat x 25 years = 100 months

So if you think insulating will save you $20 a month on heating costs, which it very well could, then go for it.

Also, a good read that argues you might be better off doing 1" insulation instead of 2" because of the diminishing returns of additional insulation.

http://www.energyvanguard.com/blog/76941/The-Diminishing-Returns-of-Adding-More-Insulation

 

[carcajou]

Quick and dirty...

70+70+40+40 = 220 linear feet of wall to insulate (not accounting for doors)

Each foam sheet covers 8' if you lay it on its side... 220'/8' = 28 sheets

A sheet of 8' tin cut down to 4' long covers 6' of wall (2 pieces per sheet).. 220'/6' = 37 sheets of tin.

Around here, the big box cost for 4x8x2" board is $26 and the cost for a sheet of tin is $16.

28 x $26 = $728
37 x $16 = $592

So you're looking at $1320, not counting any cap/trim and taxes... call it $2000 to be safe.

4 months of heat x 25 years = 100 months

So if you think insulating will save you $20 a month on heating costs, which it very well could, then go for it.

Also, a good read that argues you might be better off doing 1" insulation instead of 2" because of the diminishing returns of additional insulation.

http://www.energyvanguard.com/blog/76941/The-Diminishing-Returns-of-Adding-More-Insulation

Thank you very much for laying it out

 

[ForceFed70]

There isn't a lot of savings there and I think you'd struggle to pay off the initial investment. If you've got other reasons for not wanting to do it then that seals the deal - don't insulate.

 

[86turbodsl]

8" thick concrete has an R value effectively less than R1. Ask me how much money i saved in the first year after i insulated my exterior foundation wall on my basement, which was exposed about 4' above grade for 30pct of my exterior wall.... go ahead, ask....

 

[acer66]

I'll bite, how much money did you save 86turbodsl?

 

[carcajou]

We're waiting!

 

[bczygan]

How much heat would i really be losing?

All of it!

Heat goes to cold, so if you turn off the heat source, eventually the heat will all go to the cold and the outside and inside temperatures will equalize.

So you are always losing heat.

The only question is how fast.

Bill

 

[carcajou]

That's so helpful lol

 

[Shiftless]

Bill is just being Bill.
But he has a good point. Theoretically, if your insulation had a high enough R value and you had total control over air infiltration with a heat exchanger for fresh air exchange, your living space or garage would stay warm with the only heat input being your lighting, spare fridge, your kegerator, a couple of neon signs, and your cordless tool battery chargers.

 

[matt_i]

If you insulate now you will not ever be able to equate the potential savings.

Also, is the 4 months of heating "on demand" or are you attempting to maintain 50F 24x7...big difference in the potential costs there imo.

You can make an "Ohm's Law Directional Analogy" with heat flow. Consider the classic equation V=IR, flipping over to heat transfer the voltage is akin to the potential difference in temperature inside to out. I = heat flow, and R is the resistance to flow or the R-value.

Not trying to defeat 100 years of heat transfer research here, just a mental tool for thinking about how the heat flows out of a system.