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Basement Insulation question

1K views 5 replies 5 participants last post by  EricBrancard 
#1 ·
City of Minneapolis has a basement finishing handout that states that "as an alternative, insulation need not be in installed in basement finishes". I'm questioning why and asking for opinions on why they give you the option to NOT insulate. (In case you guys are wondering, Minneapolis requires minimum R-10 foam if insulating.)

After doing some research, my ASSUMPTION is that insulating basements can be complicated due to moisture infiltration which is almost bound to happen sometime down the road. Even if you do insulate with rigid foam, moisture will ultimately seep through and get trapped between rigid foam and concrete wall. This can cause mold on concrete. Also if enough moisture gets through concrete wall, it can drip down causing moisture damage to basement finishes. Choosing not to insulate allows walls to breath and solve the moisture issue. Also basements are below ground and that itself aids in keeping heat/cold out of home.

What are you opinions on this?
 
#4 ·
Do not worry about the freezing and deterioration baloney. If the Minneapolis code office says it is OK get a note thay your plans are OK.

Concrete has a problem with many, many, many alternating cycles - In the thousands of cycles for questionable concrete. You will only have a few cycles annually at the worst. Your average temperature at about 4' deep is not lower than 54F with no heat escaping your basement shell. If there is appreciable snow cover it is much, much less.

There are many that recognize the true mechanics of heat flow and even RECOMMEND no insulation except if it for "creature comfort" inside. The concrete wall is a "heat sink" the promotes uniform temperatures and even conducts it from the deeper soils and the basement floors.

The mythical "frost depth" is simplistic number for the depth to avoid frost heaves in the next 100 years or so to avoid structural damage and does not address the freeze/thaw cycles since the cycles are minimal. It is ode requirement for heaving and soil. Actually, if the soil under a footing is "non-frost susceptible" it does not have to be as deep as the cook-book "frost depth" that is used in codes to make code writing and enforcement easier.

I worked doing some surveying about 200 miles north of Minneapolis and the moist soil was only frozen about 6" deep with 12" of snow cover after 2 months of morning lows of -10F to -45F and most highs not above 5F. - The soil is a great transmitter of heat to make it much more uniform and milder than air temperatures.

Above grade is a different scenario.
 
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