Quick estimate of design heat load and a right‑sized boiler. (Planning aid — not a Manual J.)
Include all conditioned space (finished basement? add it).
This sets a typical BTU per square foot for your region.
Adjustment for insulation and air‑sealing.
More isn’t better — too big can short‑cycle and waste fuel.
Used to estimate pump flow. You can leave 20°F if unsure.
Adds an allowance to cover domestic hot water production.
Estimated design heat load
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Recommended boiler (input)
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Target system flow
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Based on your ΔT selection
Disclaimer: This tool provides approximate heating load estimates for space heating, with optional allowances for domestic hot water (DHW) as selected above. For safety, efficiency, and code compliance, a licensed HVAC professional should perform a complete heat‑loss calculation and system design before equipment selection or installation.