Where Every Number Comes From
Every city-level figure on this site — spring-life bands, degree days, housing cohorts, statute facts — is computed from a named public dataset with a stated vintage, joined by county and place identifiers, and rebuilt with the site. Nothing is estimated without being labelled. This page documents each source and each join.
Which datasets feed the city pages?
| Layer | Source & vintage | How it is used |
|---|---|---|
| Climate | NOAA NCEI nClimDiv county dataset — monthly heating degree days, averaged 1991–2020 | Per-county annual and monthly HDD normals. Drives the climate band, the seasonal failure calendar, and the spring-life band on every city page. |
| Housing stock | U.S. Census Bureau, American Community Survey 2023 5-year — tables B25034 (year structure built) and B25024 (units in structure) | Place-resolved where the city matches a Census place (about two-thirds of cities), county-resolved otherwise; the page states which. Yields pre-1980/pre-1960 shares, dominant era, detached-home share. |
| Geography | Census 2020 ZCTA–county relationship file · Census 2023 gazetteers · GeoNames US postal data (CC-BY 4.0) | Joins every covered ZIP to county FIPS and coordinates (100% coverage). Nearest-city links are great-circle distances from these coordinates. |
| Statutes & licensing | State legislative and licensing authorities (e.g. California Legislative Information, Contractors State License Board) | Statute summaries carry their code reference and link the authority's root site. Nothing statutory is paraphrased without its citation. |
| Spring cycle model | DASMA technical data (10,000-cycle standard rating) · 4 cycles/day household assumption | The Cycle Gauge: rated cycles vs ~1,460 cycles/year, compressed toward the bottom of the band in high-HDD counties. A model, labelled as such — not a measurement. |
| Coverage | Live routing footprint (11,980 ZIPs · 6,363 cities · 38 states) | Coverage counts on any page derive from this set at build time. City pages exist only where routing exists. |
All federal datasets are public domain; GeoNames is CC-BY 4.0 (attribution given here).
What are the rules this site binds itself to?
Cited or absent
A number without a source does not ship. Every stat tile, table and statute block names its dataset and links the issuing authority's root site — root links, because deep government URLs rot.
No fabricated locality
This is a referral service with no local offices, and it never pretends otherwise: no invented technicians, no fake addresses, no review scores. The disclosure sits in the footer of every page.
No prices near the phone
Routing pages carry no dollar figures — pricing belongs to the licensed contractor who has seen the door. Cost-factor sections explain the drivers instead.
Models labelled as models
The spring-life band is a fatigue model (cycles × climate), not a warranty. Where a figure is derived rather than measured, the page says so.
Dated and rebuilt
Every page carries its last-review date, and data-layer changes rebuild every affected page — figures cannot drift out of sync with their sources.
Safety over completeness
Torsion-spring procedures are deliberately not documented here. Some instructions are wrong to publish, and those are the ones that maim people.