The hebrew word has can mean that Noah was
physically blameless, as many respectable scholars hold due to the previous mention of fallen angels (the sons of God) interbreeding with the daughters of men. The idea is that Noah's flesh and human physicality was untouched by the inpurity, and therefore made him a good candidate for repopulating the earth. That's the natural way it reads to me, because the flood isn't brought on specifically because of sin, but because of the interbreeding. Watch-
Gen 6:4 The Nephilim were on the earth in those days, and also afterward,
when the sons of God came in to the daughters of men, and they bore {children} to them. Those were the mighty men who {were} of old, men of renown.
Many scholars believe that demons were trying to corrupt the mankind as a race entirely, because it would disable the solution of God to send a redeemer as promised at the fall. Thus God needed to wipe all of them off of the earth in order to get rid of the physical impurities.
Gen 6:5
Then the LORD saw that the wickedness of man was great on the earth, and that every intent of the thoughts of his heart was only evil continually.
If you noticed, the verse starts off with "then". Then is in reference to what was stated in the previous verse, about the interbreeding. God saw the wickedness and evil going on (the interbreeding) and decided-
Gen 6:7 ... "I will blot out man whom I have created from the face of the land, from man to animals to creeping things and to birds of the sky; for I am sorry that I have made them."
But then in comes Noah-
Gen 6:8 But Noah found favor in the eyes of the LORD.
That is, God chose Noah to stay alive and repopulate the earth because of this-
Gen 6:9 ...Noah was a righteous man, blameless in his time; Noah walked with God.
Noah was righteous, pure, and walked with God. So God chose Noah to repopulate the earth.
Van will have you believe it was merited. I say, all of the qualites that Noah possesses are only bestowed upon one by the grace of God in the first place. And according to this text, it seems that Noah was saved even before God decided to wipe man off the earth, which means God bestowed His grace upon Noah because God chose Noah in the first place to be who he was and to fulfill God's purposes, NOT because Noah was righteous on his own.