Insulation, Radiant and Vapor Barriers - Attic insulation

OK I have read a little but I think that I have a specific question that warrants a new thread. I need to add insulation to my attic. I live in the Detroit Metro Area, R=39 is recommended, and my house was built in '42. There is some existing insulation up there that looks like it is in black bags. My roof has no soffits and therefore no soffit vents. My plan was to blow in cellulose insulation over what is in there now. My question is should I do this or first remove what is in there now and start fresh? Do I need to add a vapor barrier or would the existing insulation (if I decide not to remove it) perform that duty? Since I have no soffits do I need to add baffles near the edges for air flow? Is cellulose the preferred material for insulating whether I am adding to existing or starting out new? Sorry for such little info on the existing insulation.

Thanks in advance

You could add cellulose over the existing insulation. The advantage to doing it this way is that it is less expensive and easy to do. Removal of the existing insulation does have it advantages too. The most obvious is that it exposes any electrical or cable wires in the floor. This allows you to replace those old wires and even lets you add more, such as telephone, cable TV and add electrical outlet and switches to rooms below.

If you don't have soffit vents there is no need to install baffles. But you still want adequate free venting. The way to accomplish this without remodeling your home is to install low and high vents on the walls of the attic. Assuming you have gabled ends. The walls of the attic or gabled end resembles a triangle. Install vents at the 3 points of the attic or gabled walls. Or if you prefer the 3 points of the triangle on both walls in the attic.

I posted this same question in roofing but thought that it might go here as well. I have a guy that says he can install a ridge vent and something like a soffit vent. He says the can cut into the roof above the gutters and install a vent that runs the length of the house like a soffit vent. I was wondering of anyone has heard of this and if anyone has any comments on this. Good idea? Bad idea?
I am seriously considering this because I have read (and please correct me if I am wrong) that a ridge vent with soffit vents are the best way to ventilate and attic.

Thanks for the help

What he intends to do is usually done on Cape Cod homes where the facia board is cut or lowered to allow air to enter the attic for ventilation. This is quite common and is used widely. In these cases, the gutter is slightly below this cut and attached to the facia, Roofing shingles are then installed to drape over this opening into the gutter. This way water that runs off the roof does not go into the opening in the facia. The 2 most common problems with this is when the gutter overflow, especially if there is ice in them. Moisture finds its way into the home through this opening in the facia. The other is squirrels. Once they find out there is a place for them to best for the winter, they will make that opening bigger.

The ridge vent is there to allow air into the attic during the winter to dillute any heat and moisture that manages to get through your insulation. The problem I have with ridge vents is when they are covered with snow in the winter. This sometimes makes the attic warmer because the vents are covered and ice damming occurs.

What I like about the example of the vents on the gable is that none of the aforementioned problems exists with them.

Thanks for the input. I didn't even think of the squirrel problem and we have a lot of squirrels in our neighborhood so this is a major concern. I will ask the contractor these questions and see what he has to say.
If I don't go with this option I will go with 3 or 4 of more cans lower on the roof and then open up the gable vents.

Thanks again

OK I really need some input here because I just spoke to the roof venting guy and it turns he does not want to do the vent just above the gutter thing but he will actually cut into the roof about 3 feet above the gutter and install the vent there. Does this make any sense to anyone? He says that he prefers to do this because it handles drainage better and you don't have to take off the gutters. I am just a little bit worrled about cutting into the roof as opposed to cutting into the facia.

Ridge vents and roof vents can provide you with adequate free venting. The problem that I have with either is that when it snows both vents get covered and when you need the ventilation the most, you have the least. Another is when ever you cut a hole in a roof, you only increase the chances that the roof will leak. My first post in my opinion is your best option. Because it is the least intrusive and expensive.

Your other choice with the facia vents is to build out the facia. Before installing the roof remove the old facia. Install 1 x 2 inch wood blocks on your rafter ends. Install plywood to cover top and to extend roof and then facia and gutter. The space or gap at the bottom of the facia is now your vent. You have to screen this area. A lot more expensive to do.