A few weeks ago I posted several photos of attic problems in my blog Fight The Cold!, and said I would come back to them in a later post with explanations. Here we go!
This photo shows a bypass to the attic space around a furnace flue. The square piece of metal is not sealed to the drywall, and there is a fair amount of air leaking into the attic space from this gap. I brushed the insulation away to show the gap for the photo. The insulation has turned black because of the air leakage – as the warm air passes through the insulation, the fiberglass acts like a filter and collects the dust / dirt particles in the air. Any time you see darkened insulation, you can bet there is air leakage occuring. This is often confused with mold because it looks similar.
In this photo the gap around the plumbing vent is allowing air in to the attic. Notice the dark insulation? An easy fix would be to fill the gap with expanding foam. 
This photo shows several holes that wires pass through to get to the attic. These holes could easily be sealed up with expanding foam. I didn't move any insulation to find these holes – this is exactly how the insulation looked when I climbed in to the attic, so there is obviously missing insulation here too. The recommended insulation depth for loose fill fiberglass is 18", but the silver areas have no insulation at all. 
This is another attic space in desperate need of more insulation. Someone probably moved the insulation away to install a ceiling fan, but never bothered to put it back.
There is a major attic bypass around this furnace flue, and this is one of the most common bypasses that I find. You can clearly see the walls on the floor below, and you can even see the basement ceiling from this opening! To correct this bypass, the owner will need to install a large piece of wood, metal, drywall, or any other material that air won't pass through, and caulk all of the joints to make it airtight. This wasn't obvious just by looking, but I always make a point of pulling the insulation away around furnace flues to look for bypasses. The fiberglass batt on the right side of the photo was sitting on top of this opening.
Hopefully these photos have helped to illustrate exactly what attic bypasses are and how to correct some of the issues.
Reuben Saltzman, Structure Tech Home Inspections – Email – Saint Paul Home Inspector
