Can't believe anyone would want to block or partially block the vents due to the damage this could cause to the system as well as risking the lives of your family. Just not worth it. I would suggest checking out all the vents thoroughly. We found tons of debris left in these, including a 4 inch round cut out from one of the openings. After cleaning these out you might want to look at which line is ducted where if you have easy access to your furnace. I would add electric heat if needed before even thinking of blocking even partially the vents.
2010 Jayco Quest G2(SOLD)
2014 Jayco Eagle 33.5RETS
2007 Ram 2500 5.9L Cummins(SOLD)
2015 Ram 2500 6.7L Cummins 4WD