Read the day count, then the precautions
This is the clause to read twice. An Aviva seasonal comprehensive form excludes loss "caused by freezing during the usual heating season: (i) within a heated portion of your dwelling, if you have been away from your premises more than 4 consecutive days; but you will still be insured if any of the following precautions have been taken: arranged for a competent person to enter your dwelling each day you were away, to ensure that heating was being maintained; or shut off the water supply and had drained all the pipes and domestic water containers; or if your plumbing and heating system is connected to a monitored alarm station providing 24-hour service; (ii) within an unheated portion of your dwelling."
That is the whole structure in one sentence. There is a day count. Then there are three ways to stay insured once the count expires. And there is a flat exclusion for unheated parts of the building.
The day count varies by form. Four days in that Aviva form. Ten days in Sandbox Mutual's H252, which keeps the same three escape routes and names "a 24 hour monitored low temperature alarm system" specifically.
Fourteen days in Red River Mutual's seasonal broad form, after which a competent person must enter "daily after the initial 14 day period."
For contrast, the TD principal-residence wording uses seven days. If your cottage sits as an extra location on a policy like that, check which clock applies to it.
Four, seven, ten, fourteen. There is no national standard, which is exactly why you read your own. The Insurance Bureau of Canada's coverage guide describes the common baseline as more than four days away in the heating season, after which you "must drain the plumbing or have your home checked regularly or daily to ensure that heat is maintained."
Heat maintained or shut off and drained
Those are two different strategies, and each has its own way of failing.
Heat maintained means the furnace, baseboards or heat pump keep running and someone confirms it. None of the wordings we read sets a minimum temperature. They say only that "heating was being maintained." Insurer guidance fills the gap: TD suggests 10°C to 15°C for a heated cottage, and Square One suggests around 16°C and never below 12°C for an empty home. Pick a number, set it, and photograph the thermostat. The condition fails if the power goes out, the fuel runs dry or the heat source trips, and nobody is there to notice.
Shut off and drained means the water supply is closed and every pipe and domestic water container is empty. That includes the water heater, pressure tank, toilets and traps. The condition fails through incompleteness. A single low spot holding water, a tank left half-full, or a line nobody knew about can all breach it.
For a three-season cottage with no winter heat source, draining is usually the only route available. For a four-season place, you choose. And if you choose heat, you are signing up for the inspection condition below.
The sprinkler and "unheated portion" traps
Two details catch people who think they did everything right.
First, the sprinkler system. The SE Mutual form's freezing exclusion names "any part of a heating, sprinkler, air conditioning or plumbing system." Square One describes a denied claim where an Ontario couple shut off their water but left a code-required sprinkler system live. The sprinkler line froze and burst, and the claim was denied because every water-bearing system should have been dealt with. A fire sprinkler in a cottage needs its own plan, agreed with your broker, not a guess.
Second, the unheated portion. In the Aviva wording, freezing "within an unheated portion of your dwelling" is excluded outright, with no day count and no precautions. A crawlspace, an unheated addition or a plumbing run through an uninsulated bump-out can fall outside cover even while the main rooms are warm. The same Bureau guide also lists freezing outside the home, snow and ice movement and frost heave among the standard exclusions.