💧 Glycol by Volume
⚙ Pump & Flow Penalty
Property Corrections at This Concentration
Full Calculation Table
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How to Use the Glycol Concentration Calculator
Pick propylene glycol unless this is a fully closed industrial loop with zero risk of contact with people, pets, or potable water, in which case ethylene glycol gives marginally better protection.
Enter the lowest temperature you need to protect against, usually your local winter design temperature with a margin. Use the Canadian city quick-fill buttons for common provincial design temperatures.
Click Calculate Glycol Concentration to see the required percentage by volume, along with the viscosity and specific heat penalty this concentration adds.
Use the flow penalty shown to increase your design flow rate before sizing pipe and pumps. A glycol system needs more flow than water to deliver the same heating or cooling capacity.
Sizing Glycol Systems for Canadian Winters
Glycol protects a hydronic system from freeze damage in unheated mechanical rooms, rooftop equipment, outdoor piping, and any other location exposed to sub-zero temperatures. The tradeoff is that glycol changes the fluid's properties enough to affect pump sizing, pipe sizing, and heat transfer capacity, so a glycol system is never a simple drop-in replacement for water at the same flow rate.
Picking a Concentration
Concentration is driven entirely by the lowest temperature you need to protect against, with a margin for safety. Most Canadian commercial and residential systems use a freeze point target a few degrees below the local winter design temperature, not the average winter low, since a single cold snap is what causes freeze damage. Going well past your actual requirement adds unnecessary viscosity penalty and cost, so this calculator targets the concentration that protects against your entered temperature with normal margin already built into typical freeze-point tables.
Ethylene vs. Propylene Glycol
Propylene glycol is the default choice for nearly all HVAC applications because it has low toxicity, which matters anywhere a leak could reach people, pets, soil, or groundwater. Ethylene glycol offers slightly better freeze protection and lower viscosity at the same concentration, but its toxicity restricts it to closed industrial process loops with no realistic contact pathway. Canadian commercial and residential hydronic systems, including snow melt, solar thermal, and chiller loops near occupied space, should use propylene glycol unless there is a specific engineering reason and proper containment for ethylene glycol.
The Hidden Cost: Viscosity and Specific Heat
Glycol is more viscous than water, and that viscosity increases further as the fluid gets colder, which raises pump head requirements and reduces flow through the same pipe size. Glycol also carries less heat per litre than water because of its lower specific heat, so a glycol loop circulating at the same flow rate as a water loop delivers less heating or cooling capacity. Most designers compensate by increasing design flow rate by roughly the percentage shown in this calculator's flow penalty, then re-checking pipe size on the pipe sizing calculator and pump head on the pump head calculator using the corrected flow rate.
Where Glycol Shows Up in Canadian HVAC
Common Canadian applications include outdoor air handling unit coils, rooftop chiller loops, snow melt systems, solar thermal collector loops, and any hydronic piping running through an unheated attic, parking garage, or exterior wall cavity. Refrigeration applications sometimes use secondary glycol loops as well, governed under CSA B52, the Mechanical Refrigeration Code, when glycol serves as a secondary heat transfer fluid around a primary refrigerant circuit.
A Note on Accuracy
This calculator uses published freeze-point and property tables for ethylene and propylene glycol at standard concentrations for estimating purposes. Actual glycol products vary slightly by manufacturer additive package, and inhibited glycol formulated for HVAC use behaves somewhat differently from automotive antifreeze. Always use HVAC-rated inhibited glycol, never automotive antifreeze, and verify final concentration against the specific product's data sheet.
Frequently Asked Questions
Propylene glycol is the standard choice for any system where a leak could contact people, pets, food, or potable water, since it has low toxicity. Ethylene glycol gives slightly better freeze protection and lower viscosity at the same concentration, but it is toxic, so Canadian practice generally limits it to fully closed industrial or process loops with no contact risk. For most residential and commercial hydronic systems, including those near domestic hot water or food service areas, propylene glycol is the appropriate choice.
Glycol is more viscous than water, and viscosity increases further as temperature drops, so a glycol mixture resists flow more than plain water through the same pipe and pump. Glycol also has a lower specific heat than water, meaning it carries less heat per litre for the same temperature change. Both effects mean a glycol system usually needs a larger pump, larger pipe, or higher flow rate to deliver the same heating or cooling capacity as a water-only system.
No. Automotive antifreeze is formulated with corrosion inhibitors designed for engine block materials and is not approved for HVAC piping systems, which use different metals and operate under different conditions. Always use glycol specifically inhibited and labelled for HVAC or hydronic use, since the wrong inhibitor package can accelerate corrosion in copper and steel piping over the system's service life.
If every section of piping stays inside heated space with no exposure to outdoor temperatures, attics, parking garages, or exterior walls, glycol may not be necessary. However, many systems have at least some piping in a vulnerable location, like a rooftop unit connection or an outdoor air handler coil, and a single unprotected section can still freeze and cause damage even if most of the system is indoors. Review the full piping route before deciding glycol is unnecessary.
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