Foundations: Common Questions

Modeling a Walk-Out Basement

Question: How do I model a walk-out basement in OptiMiser?

Answer:
Please refer to the attached detailed instructions for guidance on modeling walk-out basements or other complex foundation areas.

Partial Foundation Insulation

Question: In a full basement, the foundation wall is half insulated with fiberglass in the finished portion and not insulated in the unfinished portion. I want the improvement to be insulating the rest with foam board. How do I input this? 

Answer:

There are two different partial insulation scenarios, and each requires a different approach:

1. The insulation does not cover the full height of the wall (e.g., insulation only goes from the top to 2 ft below grade).

   • This can be modeled by selecting the closest matching configuration under Set Configuration (found to the left of the Insulation Loc control in detailed mode).

2. Only a portion of the wall perimeter is insulated (e.g., a partially finished basement with an unfinished, uninsulated utility room).

   • This can be modeled by following the instructions in the attached workbook.

Handling Crawl Spaces in OptiMiser

Question: I want to insulate a crawl space wall and rim joist. The Condition control does not seem to differentiate these properly. What is the correct approach?

Answer:

• If the Condition control is set to "Conditioned crawl", the Cont Insul control switches to "Found Insul", representing insulation applied to the crawl space wall.
• Rim joist insulation can be specified separately using the Rim Jsts popup.
• However, rim joist savings are not analyzed separately in the model.

No Spray Foam Option for Crawl Spaces?

Question: Why is there no spray foam option for crawlspaces? It appears as an option for basements but not crawlspaces.

Answer:
The options available depend on the selection made in the Condition control (Conditioned or Unconditioned):

• If the crawl space is unconditioned, insulation controls apply to the floor above the crawl space. Spray foam is available as an option in Cavity insulation.
• If the crawl space is conditioned, insulation applies to the crawl space wall. The only insulation option for conditioned crawl spaces includes spray foam as an option.

Vented Crawlspace with One Wall Opposite Conditioned Space

Question: How do I model a vented crawlspace with one wall opposite a conditioned space?

Answer:

• Model the wall between the conditioned space and crawl space as an exterior wall under the Walls tab.
• Since the crawl space is unconditioned, the thermal barrier is at the insulated floor above it, meaning this change does not impact the crawl space itself.

Follow-Up:

• If the home has both a crawl space and a conditioned basement, or if the conditioned space is the lower level of a split-level home, you may need to clarify how you want insulation applied.
• If one crawl space wall is adjacent to a conditioned space, this can be modeled as a partially insulated exterior wall.