it was recommended by a LPE to add a vent cap to my chimney to prevent rodents,debris, etc from clogging the stack openning ( carbon monoxide buildup. The box warns of ice and snow buildup in freezing cold weather. This should be checked daily in the winter and during snow storms. my question is as this house was without one for many many years, should I be more concerned with an uncovered chimney or one that is covered that may clog in bad weather?
Most people do not have chimney caps. There are 2 advantages to having them.
1. Keeps the rain out.
It's not a lot of water since no water flows towards it. The water that gets in will usually be absorbed by the flue but some will go straight down to the bottom.
2. Keep animals out. They won't block the top but could get in and once in they can't figure out how to get out and can wind up at the bottom to die. Or birds could sit on the top and be overcome by the fumes and then pass out and fall to the bottom.
The cover WILL NOT clog from ice and snow. Plus, if your heater is connected to it it will continually send up heat.
Chimney hoods come in steel and stainless steel. Stainless steel is a few bucks more but it won't rust so get that one.