Choosing the right ductless HVAC system isn’t just about picking a brand or price point — it’s about finding the right size for your space. Go too small, and your home won’t stay comfortable. Go too big, and you’ll waste energy and money.
At AirZone HVAC Services, we help Ottawa homeowners every day decide how many ductless zones they need, what capacity works for their square footage, and when to consider a multi-zone system. Here’s how to figure it out.
What Is “Sizing” in Ductless HVAC?
Sizing a ductless system means choosing the right BTU (British Thermal Unit) output and the correct number of indoor heads based on the layout of your home. The goal is to ensure each space is heated and cooled efficiently — no more, no less.
Ductless units typically range from 9,000 to 24,000 BTU per indoor head, and are matched to room size and insulation quality.
Quick Rule of Thumb for Ottawa Homes
Here’s a rough guideline for estimating BTU needs per room:
- Small Bedroom or Office (100–300 sq. ft.): 9,000 BTU
- Medium Living Area (300–500 sq. ft.): 12,000–15,000 BTU
- Large Open Concept Room (500–800 sq. ft.): 18,000–24,000 BTU
But don’t stop there — Ottawa’s weather and your home’s layout make a big difference. Homes with older windows, poor insulation, or open staircases may need more output per zone.
Single-Zone vs. Multi-Zone Ductless Systems
Single-Zone System
Perfect for heating or cooling a single space — like a new home office, in-law suite, or top-floor bedroom.
Multi-Zone System
Ideal for full-home comfort without ducts. These setups include one outdoor unit and 2 to 5+ indoor heads, each independently controlled.
AirZone frequently installs multi-zone ductless systems for:
- Older downtown Ottawa homes with no existing ductwork
- Split-level homes where zoning is essential
- Additions, basements, and garages that need their own climate control
Learn more about our ductless split air conditioners and how they can be tailored to your layout.
Sizing Example: Typical Ottawa Two-Story Home
Here’s a typical zoning layout we install in Ottawa:
- Main Floor (Living/Dining): 18,000 BTU
- Primary Bedroom: 9,000 BTU
- Two Other Bedrooms: 9,000 BTU each
- Finished Basement: 12,000 BTU
Total: 57,000 BTU, using a multi-zone system with 5 indoor heads and one outdoor condenser.
We’ll customize this setup based on insulation, layout, and comfort goals.
Why Proper Sizing Matters
- Comfort: Undersized systems can’t keep up on -25°C days. Oversized units cycle too quickly and don’t dehumidify properly.
- Efficiency: A well-sized ductless system keeps your hydro bills down year-round.
- Rebate Eligibility: Some rebate programs may require professional sizing documentation.
- Longevity: Proper sizing reduces stress on the equipment and extends lifespan.
Don’t Rely on Online Calculators — Use Local Expertise
Most online “mini split calculators” are generic and don’t account for:
- Ottawa’s extreme winter lows
- Home age and insulation types
- Ceiling height and window exposure
- Room orientation (north-facing vs. south-facing)
That’s why AirZone HVAC offers personalized in-home assessments from our trained ductless installation team. No guesswork — just the right system for your home.
Ready for a Sizing Quote?
Whether you’re heating a single room or looking for a full-home ductless solution, we’re here to help. We handle everything from product selection to installation — all done by our in-house licensed team, never subcontractors.
- Request a Free Sizing Quote
- View our current specials and financing options
- Learn more about our ductless offerings
