Insist on a load calculation to justify furnace fees; rule-of-thumb sizing can overshoot means

https://www.scribd.com/document/982154415/Assessing-the-Cost-of-Furnace-Installation-DIY-vs-Professional-Help-127396

Insist on a load calculation to justify furnace fees; rule-of-thumb sizing can overshoot ability, lowering efficiency and comfort.