Being under-insured puts a co-op at risk. Insurance protects against a misfortune that strikes without warning. In a housing co-op anything can happen, from a fire - several major fires have occurred over the past few years - to a staff person or president gone missing, along with the entire capital replacement reserve.
When you get your premium notice, you should make sure that your co-op is fully covered for loss of housing charges. This term is not exactly clear. It does not refer to money lost through arrears or vacancies, but to the loss your co-op would suffer if a fire or another disaster kept you from having paying members in all your units. Because your housing charges probably rise every year, your co-op will need to increase its protection annually to reflect your current charges. So please take action to be certain you're fully insured.