HVAC balance temperature: where heat gains equal heat loss

One-line orientation

Balance temperature is the outdoor temperature where internal and solar gains equal the building’s heat loss. At that point, the building needs neither heating nor cooling.

Key points

• Definition: the outdoor air temperature at which a building’s internal heat gains (occupants, lighting, equipment, solar radiation through glazing) exactly equal its heat losses through the envelope. At this point, no mechanical heating or cooling is required.
• Below balance temperature: heat loss > internal gains → heating required.
• Above balance temperature: internal + solar gains > heat loss → cooling required.
• Typical range: approximately 55°F to 65°F (13°C to 18°C) as a textbook review range, but actual commercial-building balance points can be lower when insulation and internal gains are high. The exact value shifts based on:
  • Insulation level — better insulation reduces heat loss, so the balance point shifts lower (the building reaches thermal equilibrium at a colder outdoor temp).
  • Internal heat gains — higher occupancy, plug loads, or lighting raise internal gains, pushing the balance temperature lower.
  • Glazing and solar — more south-facing glass can lower the balance temperature in winter.
• Design / energy significance: the balance temperature defines the boundary between the heating season and the cooling season for a specific building. It is used in degree-day calculations and in sizing heating and cooling equipment.

Confusions / comparison

Balance temperature: the heating ↔ cooling threshold

The outdoor temperature where internal gains exactly offset envelope losses: below it the building needs heating, above it cooling.

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More insulation, more internal gains or more glazing all lower it. The thermostat setpoint is a separate indoor target that feeds the heat balance, so changing it can shift the calculated balance point.

Each row reads “as this factor increases.” A factor lowers the balance temperature when it either cuts heat loss or adds heat gain, so the building hits equilibrium at a colder outdoor temp.

Factor	Direction balance temperature shifts	Why	Design consequence
Envelope / insulation (more insulation)	Lower	Less heat loss through the envelope, so internal gains balance losses at a colder outdoor temp; poor insulation does the reverse and pushes it higher	Better envelope shortens the heating season and shifts where heating equipment must take over
Internal heat gains (denser occupancy, plug loads, lighting)	Lower	Larger internal gains offset losses at a colder outdoor temp; sparse activity offers fewer gains and pushes it higher	High-gain buildings can need cooling even in cool weather, driving cooling-side equipment sizing
Solar gain / glazing (more south-facing glass)	Lower (in winter)	Added solar gain through glazing behaves like extra internal gain, helping offset losses sooner	Solar-exposed designs lean toward the cooling season earlier and inform glazing/shading choices
Thermostat setpoint	Can shift the calculated balance temperature	The indoor design temperature is part of the balance-point calculation	If the balance temperature is already given, do not reuse the setpoint in that calculation

Bridge: how the balance temperature then feeds heating- and cooling-season degree-day totals is handled in thermal-building-loads-degree-days rather than re-tabulated here.

Related

→ Thermal: building load types (skin-load vs internal-load buildings) · degree days (HDD/CDD calculated from the balance temperature) · HVAC: refrigeration cycle (what provides the heating/cooling once the balance point is crossed).