TradesQuote Blog
- 16 Jun, 2026
AC Tonnage by Room Size: Sizing Chart and How to Calculate It
How to size AC tonnage by room or house square footage. A square-footage-to-tonnage chart, the 20 BTU per sq ft rule, climate adjustments, and why room-by-room sizing beats rules of thumb.
- 16 Jun, 2026
Fan Laws Explained: How Blower Speed Affects Airflow
The three fan affinity laws relate blower speed to airflow, static pressure, and power. Why a 10% speed increase costs 33% more power, with worked examples.
- 13 Jun, 2026
What Is CFM and How to Calculate It
CFM is the volume of air your HVAC system moves per minute. What it means, how to convert CFM to tons, the formula to size airflow per room, and how to measure it.
- 11 Jun, 2026
Refrigerant Overcharge vs Undercharge: How to Tell
How to tell if an AC is overcharged or undercharged using superheat and subcooling, the symptoms of each, and why airflow must be verified before touching the charge.
- 10 Jun, 2026
How Many BTU Do I Need? AC Sizing for Every Room and Home
The right BTU for any room or home - the 20 BTU rule, adjustments for climate, ceiling height, sun, and insulation. Includes a quick-reference size table and worked examples.
- 09 Jun, 2026
Manual J vs Rule of Thumb: When to Use Each
Manual J is a room-by-room load calculation; rules of thumb estimate tonnage from square footage. How each works, why oversizing hurts, and when each is appropriate.
- 03 Jun, 2026
What Size Heat Pump Do I Need? A Guide for Cold Climates
Size a heat pump for both cooling and heating with balance-point analysis for cold climates, climate zone factors, and when to add backup heat.
- 27 May, 2026
Furnace Sizing Guide: What Size Furnace for My House?
Find the right furnace BTU for your home by climate zone and insulation with AFUE adjustment, worked examples, and why oversizing is the most common mistake.
- 20 May, 2026
HVAC Delta T: Normal Range and What a Bad Reading Means
What Delta T is in HVAC - the temperature split for AC and furnaces - the normal ranges, how to measure it, and what high or low readings tell you about a system.
- 13 May, 2026
Superheat vs Subcooling: A Field Guide for HVAC Techs
What superheat and subcooling mean, how to measure each, normal target ranges for TXV and fixed-orifice systems, and what readings tell you about refrigerant charge.
- 06 May, 2026
SEER vs SEER2: What Changed and Does It Actually Matter?
SEER2 replaced SEER as the federal efficiency standard in 2023. A side-by-side comparison chart of what changed, how to convert between them, and whether the difference matters when buying.
- 29 Apr, 2026
Is a 95% AFUE Furnace Worth the Extra Cost?
Compare 80% vs 96% AFUE furnaces on fuel cost, payback period, and 15-year total cost. Worked examples for cold and mild climates at different gas prices.
- 15 Apr, 2026
Markup vs Margin: How HVAC Contractors Should Price Jobs
The difference between markup and margin, why most HVAC contractors underprice jobs, and how to calculate the right selling price to hit your target profit.
- 08 Apr, 2026
HVAC Static Pressure: How to Test It and What the Numbers Mean
How to measure total external static pressure (TESP), the normal range for residential systems, and how high or low readings point to specific duct and equipment problems.
- 31 Mar, 2026
Mini-Split vs Central Air: Which Is Right for Your Home?
A direct comparison of ductless mini-splits vs central air - upfront cost, operating efficiency, installation, comfort control, and which wins in each scenario.
- 24 Mar, 2026
HVAC Duct Sizing: Manual D vs Rules of Thumb
How to size HVAC ducts using the Manual D friction rate method and simplified rules of thumb, with duct velocity limits and why wrong sizing causes comfort problems.
- 10 Mar, 2026
HRV vs ERV: Which Recovery Ventilator Does Your Home Need?
Heat Recovery Ventilators vs Energy Recovery Ventilators - how they work, what each recovers, which climate conditions suit each, and how to size them.
- 24 Feb, 2026
Heat Pump vs Gas Furnace: Which Is Cheaper to Run?
Side-by-side operating cost comparison of heat pumps and gas furnaces by climate, electricity rate, and gas price. Break-even analysis and when each wins.
- 10 Feb, 2026
ASHRAE 62.2 Ventilation Requirements: What Your Home Actually Needs
The ASHRAE 62.2 whole-building ventilation formula, why tight construction requires mechanical ventilation, and how to size an HRV, ERV, or exhaust fan to meet the standard.