Legislation to create the new rent cap system has been sent to President Higgins for signature.
The Seanad passed the laws without a final vote being called.
Senators also passed a motion asking President Higgins to sign the legislation earlier than ordinarily allowed, so that the caps can be introduced immediately.
The laws passed after the Seanad voted down moves from Sinn Féin and Labour to link the cost of rent to inflation.
Labour's Kevin Humphreys says the bill is otherwise unfair.
"Nobody, certainly in the private sector, will see their salaries increase by 12% over this period because the wage inflation is very slight in the private sector," he said.
During the Seanad debate, Fine Gael Senator Paudie Coffey denied his party is a "landlord's party".
"It has been charged against my party that we are a landlord's party, and I certainly don't agree with that", he said.
"The legislation that the Minister [for Housing Simon Coveney] is bringing forward proves in fact that we are working hard to bring certainty to renters around the country that their rental accommodation is sustainable."