Boiler System Freeze Protection — Complete Guide

Published: July 21, 2026 — CANRO Heating & Cooling — Greater Vancouver, BC

Antifreeze Additives

Boiler antifreeze (propylene glycol) can be added to the system water to prevent freezing in unheated spaces. Antifreeze costs $200-500 for a typical system plus professional injection. It reduces heat transfer slightly and requires periodic testing of concentration and inhibitor levels.

Winterization for Unoccupied Homes

For vacant homes: drain the boiler and system completely (if no antifreeze is present), or maintain minimum 15°C thermostat setting, or add antifreeze. Draining is safest but requires professional refill and recommissioning when the home is reoccupied.

Pipe Insulation

Insulate all boiler pipes in unheated spaces (crawlspace, garage, attic). Use pipe insulation rated for temperatures up to 95°C. Insulate the condensate pipe with thicker insulation — this is the most freeze-prone component.

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Safety Reminder

If you smell gas, suspect carbon monoxide or believe there is an immediate danger, leave the property and contact emergency services or the appropriate gas emergency authority. Do not remain inside — exit the building immediately and call for help from outside.