{"uid":"cap_Cc2Bt-gdbn0HbRSVyCAeU","slug":"home-energy-calculators-heat-loss-e118fdff","name":"Home Energy Calculators – Heat Loss","description":"Heat loss of a building in BTU/h and watts from surface areas and R-values plus air leakage, and yearly energy from degree-days.","url":"https://home-energy-calc.x402tookit.com/heat-loss?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["surfaces","indoorF","outdoorF"],"properties":{"indoorF":{"type":"number","description":"Indoor temperature in F, 40 to 90"},"outdoorF":{"type":"number","description":"Design outdoor temperature in F, -60 to 130"},"surfaces":{"type":"string","description":"Lines name:areaSqFt:Rvalue separated by semicolons, for example 'walls:1000:13; windows:150:3; roof:1000:38'"},"volumeCuFt":{"type":"number","description":"Heated volume in cubic feet, for air leakage (with airChangesPerHour)"},"airChangesPerHour":{"type":"number","description":"Air changes per hour, 0.05 to 5 (a tight house is about 0.2 to 0.5)"},"heatingDegreeDaysF":{"type":"number","description":"Heating degree-days (base 65 F) per year, for annual energy"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"source":{"type":["null","string"]},"deltaTF":{"type":["null","number"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"totalKw":{"type":["null","number"]},"verdict":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"surfaces":{"type":["array","null"],"items":{"type":"object","properties":{"ua":{"type":["null","number"]},"name":{"type":["null","string"]},"rValue":{"type":["null","number"]},"uValue":{"type":["null","number"]},"areaSqFt":{"type":["null","number"]},"btuPerHour":{"type":["null","number"]},"sharePercent":{"type":["null","number"]}}}},"totalTons":{"type":["null","number"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"totalWatts":{"type":["null","number"]},"infiltrationCfm":{"type":["null","number"]},"totalBtuPerHour":{"type":["null","number"]},"annualHeatNeedKwh":{"type":["null","number"]},"totalUaBtuPerHourF":{"type":["null","number"]},"annualHeatNeedMMBtu":{"type":["null","number"]},"annualHeatNeedTherms":{"type":["null","number"]},"conductionBtuPerHour":{"type":["null","number"]},"infiltrationBtuPerHour":{"type":["null","number"]},"infiltrationSharePercent":{"type":["null","number"]}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_NcUHdI66U-Jah2T7Zh0US","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Calculates building heat loss in BTU/h and watts from surface areas and R-values plus optional air leakage, and estimates yearly energy from degree-days.","exampleAgentPrompt":"Calculate the heat loss for my house: walls are 1200 sq ft at R-13, windows are 180 sq ft at R-3, and roof is 1100 sq ft at R-38; indoor temp is 70°F, outdoor design temp is 10°F, heated volume is 14000 cubic feet with 0.35 air changes per hour, and we get 5500 heating degree-days per year.","exampleUseCases":[{"title":"Sizing a furnace for a new home","prompt":"I'm building a 2000 sq ft house and need to size the furnace. Walls are 1400 sq ft at R-15, windows are 200 sq ft at R-3, roof is 2000 sq ft at R-49. Indoor temp is 68°F, outdoor design temp is 5°F, heated volume is 18000 cubic feet at 0.3 air changes per hour. What's the total heat loss in BTU/h?"},{"title":"Comparing insulation upgrade savings","prompt":"My current attic is 900 sq ft at R-19 and walls are 800 sq ft at R-11, with 100 sq ft windows at R-2. Indoor is 70°F, outdoor design is 15°F. I have 4800 heating degree-days. Can you calculate the heat loss and annual energy so I can see how much upgrading the insulation would save?"},{"title":"Diagnosing a leaky older building","prompt":"I have an older drafty office — 2000 sq ft of walls at R-8, 300 sq ft of single-pane windows at R-1, 2000 sq ft roof at R-20. Indoor 70°F, outdoor design -5°F, volume is 25000 cubic feet with 1.2 air changes per hour and 6000 heating degree-days. What's the total heat loss and which surface is losing the most heat?"}],"resultDescription":"Returns a per-surface breakdown including area, R-value, U-value, UA product, BTU/h loss, and share of total heat loss; plus totals in BTU/h, watts, and tons; air infiltration loss if volume and ACH provided; estimated annual energy if degree-days provided; and a plain-English summary with disclaimer.","failureModes":["Missing required surfaces, indoorF, or outdoorF parameters returns an error","Malformed surfaces string (wrong delimiter or missing fields) causes a parse error","R-value of zero causes division-by-zero and likely an error or infinite result","Temperatures out of range (-60 to 130°F outdoor, 40 to 90°F indoor) may be rejected","Providing volumeCuFt without airChangesPerHour or vice versa omits infiltration calculation","Providing heatingDegreeDaysF without valid surface data will not produce annual energy output"],"whenToPreferThis":"Use this endpoint when you need a physics-based, per-surface heat loss calculation for a building — especially when you have specific R-values and surface areas and want BTU/h results suitable for HVAC sizing or energy auditing. It is more detailed than a rule-of-thumb estimator and handles both conductive and infiltration losses plus annual energy from degree-days, making it ideal for design, auditing, or insulation upgrade analysis.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-29T13:14:22.972Z","isFirstParty":false,"canonicalSlug":"home-energy-calculators-heat-loss-e118fdff"}