Attic ventilation is very important country-wide, but especially in the Northeast where summertime humidity is overwhelming and wintertime dryness is just as overwhelming. The change is temperature and humidity require a lot of movement of air in your attic, so mold doesn't develop. With good insulation on the floors between the joists, or sprayed on the underside of the roof sheathing itself (baffles are a must), a good ridge - vent system works well. This type incorporates a slight opening at the highest ridge of the roof, allowing warm air to escape. For this to work, it must use mechanical (electrical) fans or side -opening vents that draw in cooler, denser air. One way to add ventilation easily is to add soffit vents (eaves vents) on the underside of a roof overhang. These type allow cooler denser air to enter the attic space through the lowest point and are often slotted or meshed to keep critters out. Sometimes the soffits are very thin (less than 6 inches wide) and require special vents. Some soffit vents are circular and can be dropped into place after cutting a hole with a hole drill bit. Some come in very long strips and sometimes you can replace a piece of aluminum or plastic siding like i did with an exact sized piece that's vented with thousand of little holes. Since I didn't know the wide of each piece of aluminum siding on my soffit, I picked up two cheap (3 bucks?) vent covers and decided to do it myself. The vented panels certainly blend in a little more than these vents, but for a few dollars - it's good enough!

Things needed:

Ladder
Drill
Jigsaw
Spraypaint (if neccesary)
Stainless Steel Screws
Vents
Screwdriver
Hammer

Step 1: Remove Siding (if Necessary)

Remove siding (if you have it) or eyeball the approximate location of your vent if you have a wooden / plywood soffit. Use a stud finder to locate the wooden studs that hold the soffit in place. Approximately mark these areas, and your area to cut.

Step 2: Drill / Cut

So I then drilled a few holes in the corners that were large enough to slot the jigsaw blade into. Then I just cut along the lines and get a somewhat straight hole. It's never going to be seen by anyone, so don't waste a lot of time here. The point is to make the hole large enough to match up to the vent without going past the dimensions of the vent itself (since you have to screw it in)

Step 3: Touch - Up Paint

My original wooden soffits were painted white, and I have this personal thing about having plain plywood anywhere near moisture, so I sprayed the edges black. This can also help hide the rafters and things in the 1% chance someone glances up why walking to their car.

Step 4: Cut the Vent

Okay so now the important part - you want to position the vent (if you have siding like I do) centered on the panel. Trace gently around the vent, marking the screw holes. You don't want to cut out this line though, more like 1/4" inside the line. If you cut along the line, the vent will just fall out since you won't have anything to screw it to. Simple! My siding is vinyl on the house, but aluminum under the eaves, so using a hobby knife and SHARP scissors did the job well. Screw it using stainless steel screws for weather-protection

Step 5: The Results

Ok so here's what the finished product looks like. It does have a mesh on the backside to keep little critters out, but you get the general idea. This vent should somewhat line up with the hole you just cut and painted.

Step 6: Putting It All Back Together

Go ahead and slide the panel back into place, tap home with a gentle hammer blow or two. Use staples, nails, or screws to secure the panel back to the soffit and make sure everything is nice and lined up. Reapply the trim molding, clean up your work site, wipe down the paneling for dirt and fingerprints and caulk the sides with waterproof sealant if you'd like.

Step 7: Finished Result

Here's the finished result. I probably spent more time climbing the ladder up and down than it took to install. Now the attic can have cool fresh air in it, and life is good. While you're up there, check the conditions of your shingles and gutters, seal any leaks, etc.