HVAC Sizing Guide: What Size System Does Your NW Arkansas Home Need?

Most homeowners assume bigger is better when it comes to HVAC. It's not. An oversized system is one of the most common — and most expensive — mistakes in residential HVAC.

What happens when your system is too big:

• Short cycling: The system cools the air quickly but shuts off before removing humidity. Your home feels clammy and cold. This is especially problematic in NW Arkansas's humid summers.
• Higher energy bills: Starting and stopping uses more energy than running at a steady pace. An oversized system cycles on and off constantly.
• Shorter lifespan: Frequent cycling puts stress on the compressor, the most expensive component. Oversized systems often fail years earlier than properly sized ones.
• Uneven temperatures: Rooms closest to the unit get blasted with cold air while distant rooms stay warm.

What happens when your system is too small:

• The system runs constantly but never reaches your desired temperature
• Energy bills spike because the system is working at maximum capacity all day
• Comfort suffers during extreme heat (94°F+ days in NW Arkansas)

NW Arkansas sits in IECC Climate Zone 3A (Warm-Humid). Our design temperatures are approximately 22°F in winter and 94°F in summer. This means our cooling loads are significant, and humidity control is a major factor in system sizing.

Here's a general guideline based on square footage. These assume average insulation, 8-foot ceilings, and standard window coverage:

Critical note: These are starting points, not final answers. A proper Manual J load calculation is the only way to determine exact sizing. This calculation accounts for your specific home's insulation, window orientation, ceiling height, number of occupants, and more.

Several factors specific to NW Arkansas homes can push your sizing needs up or down:

Insulation quality: Many older homes in Bentonville, Rogers, and Fayetteville (built before 2000) have inadequate attic insulation. Poor insulation can increase your cooling load by 20 – 30%, requiring a larger system — or better yet, adding insulation before installing new HVAC.

Window exposure: Homes with large west-facing windows get hammered by afternoon sun in summer. This can add 0.5 – 1 ton to your cooling requirement. Conversely, well-shaded homes or those with low-E windows may need less capacity.

Ceiling height: The standard calculation assumes 8-foot ceilings. If your home has 9, 10, or vaulted ceilings, the air volume increases significantly. A 2,500 sq ft home with 10-foot ceilings has the same air volume as a 3,100 sq ft home with 8-foot ceilings.

Ductwork: Leaky or undersized ductwork can waste 20 – 30% of your system's capacity. If your ducts are in poor condition, even a perfectly sized system will underperform. This is why we always inspect ductwork before recommending a system size.

Number of stories: Two-story homes often need zoned systems or dual units because heat rises. The second floor is always harder to cool than the first.

A Manual J calculation is the industry-standard method for determining HVAC sizing. Any reputable HVAC company should perform one before quoting a new system. Here's what it measures:

• Building envelope: Wall construction, insulation R-values, window types and sizes
• Orientation: Which direction your home faces and sun exposure patterns
• Climate data: Local design temperatures (22°F winter / 94°F summer for NW Arkansas)
• Internal heat gains: Occupants, appliances, lighting
• Infiltration: How much outside air leaks into your home
• Ductwork losses: Estimated efficiency of your duct system

The result is a precise BTU requirement for both heating and cooling. This number — not a rule of thumb — should determine your system size.

Red flag: If an HVAC company quotes you a system size without entering your home or performing any calculations, get a second opinion. "One ton per 500 square feet" is a rough guideline, not a sizing method.