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Chimney and Flue Sizing: NFPA 211, Draft Calculation, and the 3-2-10 Rule
How to size chimney flues for fireplaces, wood stoves, and gas appliances. NFPA 211 requirements, draft calculations, the 3-2-10 rule, and liner selection.
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Mini-Split Efficiency & Cost Calculator
Is your mini-split cheaper than propane right now? Enter your electric rate and fuel prices to find the exact outdoor temperature where your heat pump stops saving money and your backup heat wins.
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Heat Load from Bills Calculator
What size furnace or heat pump do you actually need? Skip the $300 Manual J - estimate your home's BTU/hr heat load from your gas, propane, or electric bills. See how your home compares by age and climate zone.
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Heating Bill ROI Calculator
Will a heat pump pay for itself? Enter 12 months of heating bills to see payback period, annual savings, and NPV analysis. Uses HDD regression and real COP curves for accurate projections.