Less insulation in a semi-conditioned space?

[Ryan Schultz]

In the project below, the owner's looking to condition the garage, but only to ~55 degrees. Zone 6.

As such, they think they can decrease the amount of insulation on the courtyard.

Does anyone know if there's any means, either through the IBC or IMC, that allows this?

Our AHJ requires us to use Rescheck for the multifamily project, which, if you're familiar, doesn't provide any provisions to adjust what the interior temperature will be.

 

[Enrgxprt]

Res-Check is for when the UA alternative or trade off path is being used.
Prescriptive does not need a Res Check to prove compliance as its already complaint.

If the lower than normal insulation and areas are entered in Res-Check (regardless of indoor design) and the overall UA is better, the house is a pass..
But, be sure they enter all of the homes floors above the garage in the report !

They say now they want the garage at 55... We all know that is only until the CO is issued and than the heat is set at 70....

Remember, by keeping the garage colder than the rooms above, they now are loosing MORE heat to that space from above. Raising the heating loads to
every unit above it. They save on the insulation, at the cost of every single owner living on top...

A reasonable trade off (on sunny enough days), determine how many BTU's of heat that space adds to the job (under reduced insulation levels and code design set points)
Determine how many watts of electric would satisfy that load. (3.41 watts per BTU), See if they would be willing to install Solar PV and heat that space
with electric heat pumps. A lot of the newer ones wok well at very low temps. They move BTU's from one place to the other and for MUCH less than a electric resistance, gas, oil propane etc could ever) With a warm garage, the folks living directly above wont be walking on cold floors all day... It also looks like they have plenty of roof area..

Bring to Chief building inspector or even better the DOS for an official variance.. This approach is analogous to the performance path but with a twist...

 

[ICE]

A 55 degree garage during a Wisconsin winter makes sense. Any conditioned space has to be worthy of the effort. Cutting back on insulation shouldn’t be an option. Well then, conditioning a garage isn’t done here for the obvious reason.

 

[Paul Sweet]

The ventilation required for an enclosed garage will make heating it prohibitively expensive.

 

[Mr. Inspector]

2015 IECC
C402.1.1 Low-energy buildings. The following low energy
buildings, or portions thereof separated from the
remainder of the building by building thermal envelope
assemblies complying with this section, shall be exempt
from the building thermal envelope provisions of Section
C402.
1. Those with a peak design rate of energy usage less than
3.4 Btu/h · ft2 (10.7 W/m2) or 1.0 watt per square foot
(10.7 W/m2) of floor area for space conditioning purposes.
2. Those that do not contain conditioned space.
3. Greenhouses.