Codes & Standards
Federal HVAC rules, efficiency standards, permits, tax credits and rebates, with effective dates and citations checked against the eCFR and Federal Register.
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Duct Insulation: R-Value Requirements by Location, and Why Sealing Comes First
Duct insulation rules by location under the 2018 IRC and 2021 IECC, read from state code text, with a worked attic heat-gain example, the condensation physics and the…
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Refrigerant Leak Detection: Methods Compared, A2L Sensors and the Federal Rules
Refrigerant leak detection methods compared from maker specs and EPA’s own definition, plus what A2L leak sensors do and which federal leak rules actually apply.
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AC Disconnect Box: Code Rules, Fused vs Non-Fused, and the Live Side
An AC disconnect box must sit within sight of the outdoor unit under NEC 440.14. The condenser nameplate decides fused or non-fused, and the line side stays live…
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Industrial Ventilation System: How LEV Works and What OSHA Requires
Local exhaust or dilution? The five parts of an LEV system, why capture velocity collapses with distance, and the OSHA welding and spray booth rules a commercial HVAC…
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HVAC License Requirements by State (2026): 15 States Verified at the Source
A source-verified table of HVAC license requirements in the 15 most populous states: licensing body, statewide or local, license name, experience and exam, plus the federal EPA 608…
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One in Five US Homes Is Poorly Insulated: Insulation, Drafts and Windows by the Numbers
EIA data: 20% of US homes are poorly or not insulated, 13% drafty most of the time and 35% single-pane, falling steeply with newer construction.
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HVAC Permit Requirements: When You Need One and What Happens If You Skip It
Most jurisdictions treat an HVAC equipment replacement as permitted work. Here is what the permit buys, which jurisdictions exempt in-kind swaps, and what unpermitted work costs at resale.
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Home Energy Audit: What the Blower Door Measures and How It Changes HVAC Choices
What a professional home energy audit measures, what CFM50 and ACH50 mean against the IECC limits, who can issue a DOE Home Energy Score, why the 25C audit…
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Carbon Monoxide Detector Placement: The Code Rule, the Clearances and the Numbers
Where CO alarms go, what IRC Section R315 actually requires, the clearances manufacturers specify, the UL 2034 alarm thresholds, and the federal death data behind the rule.
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Garage Ventilation: What the Codes Require for an Attached Garage
An attached garage is a ventilation problem for the house. Here is what CPSC, EPA, the IRC and ASHRAE 62.2 actually require, and where the 70 cfm exhaust…