In Paul Turner's Blog by Paul Turner

Q:  Our parish has been worshiping in a church without kneelers, but we are building a new church. When we install kneelers with our pews,  many are asking me if they must kneel during the Eucharistic Prayer, as we have remained standing throughout it for 37 years.  They feel as though our community at prayer is more reverent when standing, than if the banging of the kneelers were to be made mandatory.
Our concern is that some will kneel & some will stand, which would be a dreadful symbol of disunity, so if we can begin doing some catechesis, it would be helpful to know what will be required.
A:  People are expected to kneel from the end of the Sanctus to after the Amen that concludes the eucharistic prayer (GIRM 43). Those rules apply to the US.