Is a certificate holder the same as an additional insured?

No. A certificate holder has been sent proof that a policy exists. An additional insured has rights under the policy, and that takes an endorsement such as CG 20 10 or CG 20 37.

How long do I have to keep completed-operations coverage in place?

For as long as the subcontract says, counted from substantial completion. Because the endorsement lives on the policy in force when the claim is made, it has to be renewed each year for that whole period.

CG 20 10 and CG 20 37: which additional insured endorsement does a data-center subcontract need?

Q: CG 20 10 and CG 20 37: which additional insured endorsement does a data-center subcontract need?

Usually both. CG 20 10 makes the owner or general contractor an additional insured for your ongoing work, and that status ends when the work is complete. CG 20 37 carries it into completed operations, which is when most defect claims arrive. A subcontract that asks for “ongoing and completed operations” is asking for the pair.

What does each endorsement do?

	CG 20 10	CG 20 37
Covers the additional insured for	Your ongoing operations	Your completed work (the products-completed operations hazard)
Ends when	Your work at the location is complete	The policy that carries it is no longer in force
Applies to	The person, organisation and location in its schedule	The person, organisation, location and work in its schedule
Limited by	What the contract requires, and the policy’s limits	What the contract requires, and the policy’s limits

Why is CG 20 10 alone not enough?

On a data-center job the expensive claims tend to come after handover: a cooling loop that leaks in year two, a busway connection that fails under load. By then your ongoing operations are over, so CG 20 10 no longer gives the owner or general contractor any status under your policy.

Compliance reviewers know this. A certificate that shows additional insured status without completed operations is one of the most common reasons a certificate is sent back.

What should I look for in the subcontract?

The words “ongoing and completed operations”, or the two form numbers named outright.
Who must be named. Data-center contracts often list the owner, the general contractor and the lender.
How long completed-operations status must be kept. This is usually stated in years after substantial completion, which means renewing the endorsement on later policies.
Edition dates. Some contracts name an older edition with broader wording; ask your broker what your insurer will actually issue.

Does “blanket” additional insured wording solve it?

A blanket endorsement grants status to anyone you have agreed in a written contract to add, so you do not have to schedule each party. It is convenient, but read it: some blanket forms cover ongoing operations only, and some require a direct contract between you and the party, which a project owner or lender may not have with a subcontractor.

Sources

General information, not legal advice or an interpretation of your policy. Policy forms and endorsements control. Form numbers are © Insurance Services Office, Inc. and are cited for reference.