Mineral wool wraps are the most affordable and effective insulation for crawl space ducts. They are easy to cut, last for a long time, and healthier for humans. Meanwhile, fiberglass wraps are cheaper but more hazardous and difficult to handle. If you do choose to use a fiberglass wrap, make sure you are wearing long sleeves and wear proper protective gear.

Yes, cold walls are a common indicator of poor or inadequate insulation, especially if the walls feel significantly colder than the air in the room. This suggests that heat from your furnace is escaping rather than being retained. The issue could be that the walls have no insulation, or that the existing insulation is old or has been damaged by water, moisture, or pests. Your best course of action is to hire a professional to investigate. An insulation contractor can determine if you need to add or replace insulation and can often perform the work without creating large holes in your drywall. If you suspect the problem might also be related to your heating system's performance, an HVAC technician can take a closer look.

Installing sheets of plywood over attic insulation is a popular choice, especially in storage spaces. That said, insulation works by trapping hot air—so it needs extra space to expand and be effective, or you might reduce the energy efficiency of your home. 

It’s important that you never compress the insulation by installing flooring directly on top of it. In many houses, you’ll need to install a subfloor before putting plywood over insulation in your attic.

Insulating your home's exterior walls can realize up to a 20% reduction in your monthly energy bills. This means that regardless of how much the project costs, it can begin to pay you back immediately. Additionally, adding spray foam and other high-end materials can increase the selling value of the property.