Sources & evidence
Every number on a OurHomeSays page traces to a source (or is arithmetic over sources and your inputs). We rank evidence by how much we can trust it for the claim it’s making.
Tier 1 — official (13 facts)
Government agencies, fire services, utilities, building codes, and official manufacturer manuals. These back our safety guidance.
Tier 2 — standards & extension (21 facts)
Standards bodies (NFPA), certification bodies (InterNACHI), and university extension services. These back most lifespans and intervals.
Tier 3 — industry estimates (14 facts)
Cost surveys from contractor-lead publishers. We use these only for cost ranges, always mark them as estimates, note the commercial bias, and date them.
What community posts can and can’t do
Forums, Reddit, and autocomplete tell us which questions real homeowners ask and how they phrase them. That’s all we use them for. They never stand as evidence for a price, a safety threshold, a code, or a repair step — those require an official or standards source.
Keeping sources fresh
Each fact records when it was last verified. Stable references are checked automatically; prices and specs only ever open a proposal for review; and safety, code, and diagnostic guidance is changed by hand, never by an automated job.