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For commercial greenhouse operators in Ontario, winter is not the slow season. It is the season that separates well-run operations from ones that are one mechanical failure away from a significant loss event. A heating system that worked perfectly through October can fail at 3am on a February night, and by the time staff arrive in the morning, the damage is done.
The crops inside a heated greenhouse in January represent weeks of growing time, significant input costs, and in many cases, committed forward sales contracts. Protecting that investment requires treating your heating system with the same seriousness you apply to any other critical business asset.
The consequences of a heating failure in an Ontario winter greenhouse depend on the crop, the temperature at failure, and how quickly the problem is identified and corrected.
For most fruiting vegetable crops, temperatures below 10 degrees Celsius cause chilling injury that affects fruit quality and plant health even when the plant survives. Below 5 degrees, most greenhouse crops begin experiencing tissue damage. Below 0 degrees, most crops in an unheated greenhouse environment are lost within hours.
A single overnight heating failure in February can represent a loss of tens of thousands of dollars for a mid-sized operation. For a large commercial grower, the numbers climb higher. This is why backup heating, remote monitoring, and a planned response protocol are not optional extras but fundamental parts of a serious winter heating program.
Gas-fired unit heaters are the most common primary heating system in Ontario commercial greenhouses. They are relatively low-cost to install, effective for heating large air volumes quickly, and straightforward to service. The main limitations are uneven heat distribution at floor level and the lack of thermal mass to buffer overnight temperature drops.
Boiler-based hydronic systems distribute heat through overhead pipes or in-floor tubing, providing more even temperature distribution than unit heaters. The thermal mass of the water in the system buffers temperature swings better, and separate distribution zones can be controlled independently. For larger or higher-value operations, a boiler system is generally the preferred approach.
Many Ontario greenhouse operations use a combination of boiler-based distribution for steady background heat and unit heaters for peak demand or rapid recovery after a cold event. This combination provides both efficiency and flexibility.
The question is not whether your primary heating system will ever fail. All mechanical equipment fails eventually. The question is whether a failure means a crop loss event or an inconvenient service call.
A backup heating system does not need to be identical to or as large as the primary system. In most cases, a backup capable of maintaining frost protection temperatures, roughly 8 to 10 degrees Celsius, is sufficient to preserve the crop until the primary system is repaired. This is a significantly smaller equipment investment than the full primary system.
Options for backup heating include:
The best approach depends on the size of the operation, the crop value at risk, and the distance from emergency repair service. Alpine can help greenhouse operators assess their specific redundancy requirements and design a backup solution proportionate to the risk.
A backup heating system only helps if someone knows the primary system has failed. Without remote monitoring, a heating failure at midnight may not be discovered until staff arrive at 6 or 7am, by which point temperatures inside the greenhouse may already be below critical thresholds.
A building automation system with temperature sensors throughout the greenhouse and alert notifications sent to staff mobile devices changes this picture entirely. When temperature at plant level drops below a set threshold, an alert goes out immediately. The response window is measured in minutes rather than hours.
Alpine installs open-protocol BAS systems in greenhouse operations that provide continuous temperature and humidity monitoring with configurable alert thresholds. Remote access from any device means growers can check growing conditions from anywhere at any time, and response to an alert can begin before anyone has left the house.
The best time to find a problem with your heating system is before the first hard frost arrives. A thorough pre-season inspection in September or early October should cover:
Alpine offers pre-season greenhouse heating inspections for operations across the Niagara Peninsula and Golden Horseshoe. A two-hour inspection in September is far less expensive than an emergency service call at 2am in January.
How do I protect my greenhouse from frost in Ontario winters?
Frost protection requires a combination of reliable primary heating, a backup heating system sized to maintain minimum safe temperatures, continuous remote temperature monitoring with alerts, and a documented response protocol for heating failures. The weakest link in most operations is the monitoring gap, where a failure is not discovered until temperatures are already critically low.
What is the minimum safe temperature for a heated greenhouse in Ontario winter?
For most fruiting vegetable crops, the critical minimum is approximately 10 degrees Celsius to avoid chilling injury and 5 degrees to prevent tissue damage. However, operating at minimum thresholds is not a growing strategy, it is a survival strategy. Normal growing operations target significantly warmer temperatures. The backup heating system should be designed to maintain at least 10 degrees even under primary system failure conditions.
How often should a greenhouse boiler be serviced in Ontario?
Commercial greenhouse boilers should receive a full annual service before the heating season begins, typically in September or early October. This includes combustion analysis, heat exchanger inspection, burner cleaning, safety device testing, and controls calibration. Operations with older equipment or high-use systems may benefit from a mid-season inspection as well.
What backup heating options work best for Ontario commercial greenhouses?
The most reliable backup approach is a second boiler on an automatic standby circuit that starts immediately on detection of primary system failure. For operations where a second boiler is not feasible, a staged system of propane unit heaters on a separate fuel source provides effective emergency frost protection. The backup system should be tested under load before the heating season, not when you need it.
Can a building automation system monitor a greenhouse heating system remotely?
Yes, and it should. An open-protocol BAS with temperature and humidity sensors throughout the growing area, connected to a central monitoring platform, provides real-time visibility from any device. Alert thresholds set for low temperature at plant level trigger immediate notifications to responsible staff, regardless of the time of day. Alpine installs and maintains these systems for greenhouse operations across the region.
