Methodology
Last updated November 9, 2026
Every number on this site is either sourced or labelled as an estimate. This page explains the difference, and how a claim gets from a source document to a published page.
1. Primary sources first
Code and safety claims follow NFPA 211 and the locally adopted mechanical code. Liner claims follow the product's UL listing and the manufacturer's installation instructions: liner type, insulation, appliance category and the flue size it is listed for. Inspection findings are described as a sweep reports them, and the page says when a claim depends on an on-site measurement we cannot make.
2. Cost models show their inputs
Installed cost is modelled from visible inputs: the material or equipment price, the labour and access scope (excavation, drain, electrical, permit), consumables, and a reserve for service or repair. We do not present a single "average cost" as if it were a quote; the range and what it includes are stated on the page.
3. How options are compared
We compare options on appliance compatibility, listing and insulation, expected service life, and what the job does to the flue's cross-section. A liner earns a recommendation for a stated appliance and flue; no manufacturer can buy a place in a comparison.
4. What we have not tested
We do not run a laboratory or a crew, and we do not carry out every job we write about. When a claim comes from a manufacturer document, an adopted code, a certification listing or a contractor report, we say which. We do not imply first-hand testing we did not perform.
5. Sources we work from
| Source type | What it decides | How it is cited |
|---|---|---|
| NFPA 211 | Clearances, inspection levels and chimney construction requirements | Section cited |
| UL 1777 liner listings | Which liner is listed for which appliance and fuel | Listing and product named |
| Manufacturer installation instructions | Insulation, sizing, support and termination | Document and product named |
| Certification directories (chimney sweep bodies) | Whether a sweep holds a current credential | Credential and directory named |
| Published US price guides | Installed cost bands | Band with the month it was checked |
When two sources disagree, the page says which one it followed and why. A figure that cannot be traced to a document is labelled an estimate, and an estimate is never presented as the price of a specific job.
6. Listings and directory data
The service-area directory is compiled from public business records: the firm's own website, its published address and phone number, and the state or local licence register named on the city page. A record is marked verified only when the name, address, phone and licence have been checked against those sources and the date of the check recorded; everything else is labelled. Where a source does not publish a ZIP code or a website, the field is left blank rather than guessed.
7. Corrections
If a code, a specification or a listing changes, we update the article and its "last updated" date. Emailcontact@chimneylab.com with the page and the correction.