IDFX Cheat Sheet 2026

The 30 highest-yield IDFX facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. In space programming, the ratio of net assignable square footage (NASF) to gross square footage (GSF) is called the: → Efficiency ratio
2. Which type of HVAC system is most commonly used in commercial interior office fit-out work for individual zone control? → Variable air volume (VAV) system with terminal reheat boxes
3. Which color rendering index (CRI) value is required for retail spaces where accurate color judgment of merchandise is essential? → CRI 90 or above
4. A living wall (vertical garden, green wall) installed in an interior space contributes most directly to which sustainable design goals? → Biophilic connection to nature, potential air quality improvement, and occupant well-being
5. The 'net-to-gross' (efficiency) ratio in office space planning describes which relationship? → The proportion of usable programmed space to total building gross square footage
6. Which lighting term describes the ratio of the illuminance at the task area to the illuminance in the surrounding non-task area? → Task-to-ambient ratio
7. What is the minimum required turning radius for a wheelchair in an accessible space? → 60-inch diameter circle
8. What is the “Golden Ratio” most closely associated with in interior design? → Scale and proportion
9. Which countertop material is the most resistant to stains and requires minimal maintenance? → Quartz
10. What is the purpose of accent lighting in interior design? → To highlight specific objects, artwork, or architectural features
11. The purpose of an 'adjacency matrix' in the programming phase of interior design is to: → Systematically document desired spatial relationships between all spaces in a project
12. Per ADA guidelines, what is the minimum clear width required for an accessible single-loaded corridor? → 36 inches
13. What is the recommended monitor viewing distance at a seated computer workstation? → 20–28 inches
14. What is the minimum number of accessible parking spaces required for a parking lot with 75 total spaces per ADA Standards Table 208.2? → 3 spaces
15. For a height-adjustable sit-stand workstation, what is the typical recommended adjustment range? → 28–48 inches
16. Reference guides such as Neufert's Architects' Data are used by interior designers primarily to: → Access standardized human dimension data for space planning
17. IBC Section 903.2 requires automatic sprinkler systems throughout a building in which scenario? → Any new building of Group R occupancy that is 4 stories or more above grade
18. Which element of design is most directly manipulated when a designer uses a striped floor pattern running lengthwise in a narrow corridor? → Line — to create the perception of greater length or width
19. Which color scheme consists of colors located directly opposite each other on the color wheel? → Complementary
20. An interior designer specifies a particular brand and model number for a commercial-grade carpet. This is an example of which type of specification? → Proprietary specification
21. The 'functional reach zone' in ergonomic design refers to: → The area accessible without moving the body trunk from a fixed position
22. What does texture primarily influence in interior design? → Spatial perception and visual interest
23. Under IBC Section 303.1, which occupancy group classification applies to a public library open to general assembly use? → Group A-3
24. In stone selection for countertops, which characteristic makes quartzite preferable to marble for kitchen applications? → Quartzite has greater hardness and acid resistance than marble
25. In space planning, primary circulation paths are distinguished from secondary paths chiefly by their: → Direct connection to major activity zones and greatest required clear width
26. A 'Class A' (Class I) fire rating for interior finish materials, as tested by ASTM E 84, requires what maximum flame spread index (FSI)? → FSI of 0 to 25
27. In furniture arrangement, what is the recommended minimum clear walkway width for a primary circulation path through a room? → 36 inches
28. What is the main advantage of using ceramic tile in wet areas such as bathrooms or kitchens? → Resistant to water and moisture
29. What is the term for the minimum required vertical clearance above finished floor to the lowest overhead obstruction in an accessible route? → Headroom clearance
30. Accent lighting typically provides how many times the ambient illuminance level at the highlighted object? → 3 to 5 times