insulation in unheated stairway

[Mr. Inspector]

2018 IRC. Failed an insulation inspection today because they only had R15 insulation in the 2x4 walls of the unheated basement stairway in climate zone 5 where R21 is required in the walls between unheated and heated areas. The insulation company claimed that the earth heats the basement, so R15 is OK. I never herd of this. Has anyone?

 

[BN4537]

The earth is not heating the basement unless there is a geothermal system installed. The earth is a giant cold ball that is sucking the heat out of the basement, it just sucks it out slower than the really cold air above grade in the winter might.

 

[BN4537]

Is this what they are trying to say?

 

[steveray]

You can probably get it to pass a res check, but they need a compliant envelope….i would ask them for a code based argument….

 

[tmurray]

So there should be no insulation required in basements. In fact, they would need to be provided with cooling.

Second the code-based argument.

 

[Paul Sweet]

In Virginia basements usually stay close to ground temperature (55 deg. or so) without additional heat. They would probably be 5 - 10 deg. cooler in Pennsylvania.

 

[SCBO1]

What R-value was on the plans, did they deviate from the approved plans and you caught em?

Earths about 55-59° so a geothermal-heat system would take that temp into consideration, can I ask what kind of heating system is proposed?

 

[Mr. Inspector]

What R-value was on the plans, did they deviate from the approved plans and you caught em?

Earths about 55-59° so a geothermal-heat system would take that temp into consideration, can I ask what kind of heating system is proposed?

R21 was shown for the exterior walls. None were shown for the basement stairway. But I never saw it shown for walls for the unheated basement stairway in my 20 years.

Heating/cooling was just the normal duct system with a basement air handler and outside condenser.

The insulation company claimed that the earth heats the basement, so R15 is OK.

Funny that they did not claim this for the insulation for the unheated garage/heated house wall which was R21.

 

[Yankee Chronicler]

2018 IRC. Failed an insulation inspection today because they only had R15 insulation in the 2x4 walls of the unheated basement stairway in climate zone 5 where R21 is required in the walls between unheated and heated areas. The insulation company claimed that the earth heats the basement, so R15 is OK. I never herd of this. Has anyone?

I'm in zone 5, and I can attest that in Winter the soil does NOT heat my basement. If I lose power for an extended period, I have to run a portable heater in the basement to prevent frozen pipes. Even if the subsurface soil temperature were at 50 degrees (which can only happen some distance below the frost line), it couldn't "heat" the basement to any higher than 50 degrees -- which is lower than the design indoor conditioned space temperature, so there's still going to be heat loss from the heated space to the unheated basement.