Is the bank sanction letter alone enough proof of funds for the visa, or do I also need to have money in my bank account as a basement of the loan in Ireland?

No, a bank loan sanction letter alone is not enough for an Ireland student visa. You must also show that the loan amount is available to you - typically by providing recent bank statements confirming the funds have been disbursed or are accessible in your account.

Visa authorities want proof that you can immediately cover tuition and living expenses. Make sure your bank statements are recent, clearly show your name, and explain any large deposits if needed.