Let’s start with the basics. For the purposes of our conversation, there is a fairly wide array of insulation on the market. There is no best insulation. Each insulation has its pros and cons. Here are the most common ones and their R-Values.
Remember though the insulation is only as good as the air sealing that is done in the house. A VERY COMMON MISTAKE is for people to add insulation in their attic but not do any air sealing. You can have 20 inches of fiberglass insulation which you would expect to give you R-60 but if the insulation is installed poorly or if you have not air sealed the attic well, you will end up with an “effective” or actual R-value of around R-14 for that 20 inches of fiberglass. We see this happen all the time. Air sealing and Insulation always should happen together.
Like the winning combination of a warm sweater and a great windbreaker your insulation will keep that heat in your house, keep you comfortable and keep your heat system from working so hard.
Consult with an energy consultant or home performance professional to help you decide which insulation is the best for you, your values and what you are trying to achieve.