Heat Loss

{
  "annualHeatNeedKwh": 13571,
  "annualHeatNeedMMBtu": 46.3,
  "annualHeatNeedTherms": 463,
  "asOf": "2026-10-11T14:31:35.646Z",
  "conductionBtuPerHour": 8234.8,
  "degraded": false,
  "deltaTF": 40,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "infiltrationBtuPerHour": 7200,
  "infiltrationCfm": 166.7,
  "infiltrationSharePercent": 46.6,
  "notChecked": [
    "thermal bridging through studs, which lowers a wall's effective R-value (see /insulation-r-value)",
    "solar gains, internal gains, ground contact and unheated-space buffers",
    "…2 more"
  ],
  "reasons": [
    "Conduction = area x temperature difference / R; infiltration = 1.08 x CFM x temperature difference, where CFM = air changes per hour x volume / 60.",
    "Largest loss: walls (19.9%).",
    "…1 more"
  ],
  "source": "computed locally",
  "summary": "At a 40 F difference the building loses about 15435 BTU/h (4523 W): 8235 through surfaces and 7200 from air leakage (166.7 CFM). Over 5000 degree-days that is about 46.3 MMBtu of heat a year.",
  "surfaces": [
    {
      "areaSqFt": 1000,
      "btuPerHour": 3076.9,
      "name": "walls",
      "rValue": 13,
      "sharePercent": 19.9,
      "uValue": 0.0769,
      "ua": 76.923
    },
    {
      "areaSqFt": 150,
      "btuPerHour": 2000,
      "name": "windows",
      "rValue": 3,
      "sharePercent": 13,
      "uValue": 0.3333,
      "ua": 50
    }
  ],
  "totalBtuPerHour": 15434.8,
  "totalKw": 4.52,
  "totalTons": 1.29,
  "totalUaBtuPerHourF": 385.87,
  "totalWatts": 4523,
  "verdict": "COMPUTED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://home-energy-calc.x402tookit.com/heat-loss?airChangesPerHour=0.5&heatingDegreeDaysF=5000&indoorF=70&outdoorF=30&surfaces=walls%3A1000%3A13%3B+windows%3A150%3A3%3B+roof%3A1000%3A38%3B+floor%3A1000%3A19&volumeCuFt=20000'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://home-energy-calc.x402tookit.com/heat-loss?airChangesPerHour=0.5&heatingDegreeDaysF=5000&indoorF=70&outdoorF=30&surfaces=walls%3A1000%3A13%3B+windows%3A150%3A3%3B+roof%3A1000%3A38%3B+floor%3A1000%3A19&volumeCuFt=20000' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fhome-energy-calc.x402tookit.com%2Fheat-loss
const res = await pay("https://home-energy-calc.x402tookit.com/heat-loss?airChangesPerHour=0.5&heatingDegreeDaysF=5000&indoorF=70&outdoorF=30&surfaces=walls%3A1000%3A13%3B+windows%3A150%3A3%3B+roof%3A1000%3A38%3B+floor%3A1000%3A19&volumeCuFt=20000");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://home-energy-calc.x402tookit.com/heat-loss?airChangesPerHour=0.5&heatingDegreeDaysF=5000&indoorF=70&outdoorF=30&surfaces=walls%3A1000%3A13%3B+windows%3A150%3A3%3B+roof%3A1000%3A38%3B+floor%3A1000%3A19&volumeCuFt=20000")
    print(res.status_code, res.text)