Around 50 people on Monday protested briefly outside the building over elections to the parliament, which were held years late and marred by violence and allegations of fraud.
"While we're here, people are outside and are criticizing our presence in this room and everything that happened that led us here," said Andris Riche, president of the Senate.
Still struggling from a 2010 earthquake that killed more than 250,000 people, Haiti's parliament was belatedly dissolved in January last year.
A first round of legislative elections was held on August 9, more than three years behind the constitutional schedule because of a crisis between the executive, led by outgoing President Michel Martelly, and the opposition.
Voting was canceled in nearly a quarter of the country's constituencies because of violence.
Twenty-six seats for senators and six for deputies are being contested in a partial second round of voting scheduled for January 24.
On the same day, Haiti will hold the runoff vote in the presidential election, which has also been deeply controversial.
Opposition candidate Jude Celestin goes up against government-backed rival Jovenel Moise.
Celestin refuses to take part in the second round without sweeping reforms to electoral oversight.