The International Residential Building Code (IRC) is the predominant single-family residential building code in the United States. Vented attics are the “default” construction practice recognized by the IRC. Changes to recent editions of the IRC have introduced unvented (sealed) attics as an alternative. Deciding which approach to take should include consideration of issues such as ease of installation, ability to troubleshoot after the fact, performance, upfront cost and return on investment.

https://www.roofingcontractor.com/articles/89247-vent-or-seal-the-attic