How we research

Each diagnosis page starts from published guidance rather than opinion. Our primary references are the EPA (indoor air quality, mold, radon), ASHRAE (ventilation and comfort standards), the CDC (health effects), the CPSC (carbon monoxide and fire safety), Energy Star (efficiency), and InterNACHI inspection standards.

Ranking causes

Causes are ordered by real-world frequency drawn from inspection findings and trade reporting, not alphabetically or by drama. Each one includes a test you can complete in about ten minutes with tools you likely own.

Cost figures

Costs are US national ranges for parts and licensed labor. They shift with region, access difficulty and season, so treat them as a bracket for judging a quote — not a fixed price.

Safety first

Anything involving gas, carbon monoxide, sewage or electrical fire risk carries a warning at the top of the page telling you to leave and call for help before troubleshooting.

How we choose which problems to cover

Topics come from the way homeowners describe a symptom, not from trade jargon. A page exists because people are asking about that exact complaint — a musty smell, a cold room, a breaker that keeps tripping — and because there is published guidance solid enough to answer it. If we cannot ground an answer in a standard, an agency document or established inspection practice, we leave the page unwritten rather than filling it with guesswork.

What a page has to include

Every diagnosis page carries a severity badge, a direct answer in the first paragraph, causes ordered by frequency, a check you can finish in about ten minutes, a repair cost bracket, the mistakes that waste money, and a clear line marking where DIY stops and a licensed trade begins. If a section cannot be written with specifics, it is removed rather than padded.

Review and updates

Pages are re-checked when the underlying guidance changes, when cost ranges drift, or when readers send corrections. Each page records the date it was last reviewed. Corrections are welcome and we act on them quickly — email us and tell us what is wrong and, where you can, which source says otherwise.

Our limits

We do not inspect houses, we cannot diagnose your specific home remotely, and no page here substitutes for an on-site evaluation by a licensed professional. Treat our cost figures as a bracket for judging a quote rather than a price we can honor.