No, but it’s common that they do. Gravity furnaces weren’t terribly efficient so wrapping either the ductwork in asbestos, the furnace itself, or both, was something done regularly. This allowed the system to retain more heat. At the time, this greatly enhanced the efficiency of the furnaces but it wasn’t until later that we became aware of just how carcinogenic and dangerous asbestos could be.

Knob and tube wiring is an older type of electrical wiring that's no longer used and generally not considered safe. However, some homes still have it, or may have a knob and tube wiring system that was incorrectly modified or rigged to work with a modern electrical system. Knob and tube wiring may contain asbestos insulation, but the only way to know is to have the material professionally tested.

Since DIY asbestos removal isn’t the best option to save money, there are other steps that you can take to help cut costs when dealing with this project. After speaking with your asbestos removal expert, discuss if encapsulation is an option. If it is, you can save between 15% to 25% on overall project costs over demolition and disposal. In addition, when speaking with your professional, discuss if there are any tax credits available for your removal project. Finally, check with your homeowner’s insurance to see if any removal costs might be covered. However, be aware that this is usually only applicable if the asbestos is due to a covered incident, like a tree falling into your roof.  

Asbestos itself does not typically leak from a roof. However, if an asbestos-containing roof is damaged or deteriorated, it can release asbestos fibers into the air. This can occur when the roof is disturbed, such as during maintenance or repairs, or due to weathering over time. Exposure to airborne asbestos fibers can be harmful to health, so it is important to address any damaged asbestos roofs promptly and safely.