Construction Products, Windows, Doors & Fenestration worked example

Fenestration Warranty Reserve at 110% share of units included in this reserve: a worked example

What does the result look like when share of units included in this reserve reaches 110%? The full calculation is worked below with real intermediate numbers. setting warranty accruals and comparing product risk by family

The inputs for this scenario

  • Shipped fenestration units under warranty reserve: 4,200 units (unchanged)
  • Warranty reserve accrual per unit: 18 $ / unit (unchanged)
  • Share of units included in this reserve: 110 % (raised for this scenario; the documented default is 100)
  • Fixed service campaign and claims administration cost: 15,000 $ (unchanged)

Working through the calculation

  • Applying the documented formula (Variable warranty reserve = shipped fenestration units under reserve × warranty reserve dollars per unit × warranty reserve scope included) to the inputs above produces each figure below.
  • At this operating point the engine returns 98,160 $ for total fenestration warranty reserve, the number this scenario is built around.
  • At this operating point the engine returns 23.37 $ / piece for warranty reserve per unit.
  • At this operating point the engine returns 83,160 $ for variable warranty reserve.
  • At this operating point the engine returns 15,000 $ for fixed service campaign and claims admin cost.

How this compares with the baseline

  • Against the tool's baseline example, where share of units included in this reserve sits at 100% and the headline result is 90,600 $, this scenario comes in 8.34% above the baseline at 98,160 $.
  • A figure at this level is achievable when share of units included in this reserve is genuinely sustained, not just peaked for a shift. A flat per-unit accrual assumes claims are spread evenly; a single systemic defect (a bad seal lot) can blow past the reserve, so stress-test against your worst historical claim event.

Results at a glance

  • total fenestration warranty reserve: 98,160 $ (headline result)
  • warranty reserve per unit: 23.37 $ / piece
  • variable warranty reserve: 83,160 $
  • fixed service campaign and claims admin cost: 15,000 $

Run it with your numbers

  • Every input above is editable in the live Fenestration Warranty Reserve calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.