The same envelope value lives in three documents at once
On most projects the fenestration U-factor appears in the window schedule on the drawings, the performance section of the specification, and the compliance report. Three documents, usually three different people, and no automatic relationship between them.
The drift is a coordination problem rather than a knowledge problem. Everyone involved knows the required value. The schedule gets revised, the specification does not, and the compliance report was produced against an earlier revision of both.
Plan review catches it. By then the set has shipped, the correction runs through an addendum, and the schedule absorbs the delay.
Nobody owns the relationship between the three documents, because it was never anyone's task to maintain it.
Read all three sources together
The window schedule, the specification section and the compliance report get read as one set rather than as three separate documents, so a mismatch surfaces as a mismatch.
Carry the citation
Every value reports the sheet, section and revision it came from. A discrepancy names both sides, so the coordinator resolves it instead of hunting for it.
Leave the judgement with the professional
The output identifies where the numbers disagree. Which value governs stays a decision for the licensed professional on the project.
Why do U-factor values drift between the drawings and the specification?
The same value is maintained in three places by three people, and no automatic relationship links them. A revision to the window schedule does not update the specification section or the compliance report, so a set can hold three different values for one assembly without anyone acting incorrectly.
What is the difference between U-factor and R-value on a window schedule?
U-factor measures the rate of heat transfer through the whole assembly, so a lower number performs better. R-value measures resistance to heat flow, so a higher number performs better. Fenestration is normally specified by U-factor for the assembly, which is why a schedule carrying R-values for glazing is worth a second look.
Can this replace an energy code compliance review?
No. The work identifies where documents disagree and cites both sides. A licensed professional still performs the compliance review and decides which value governs.
How much of your bidding lives in one person's head?
The Standards Gap Test asks 40 questions about your symbol library, your assembly rules, and the conventions nobody wrote down. You answer from memory in 15 minutes, then you count how many answers only one person can give.