R-value is a measure of the material's resistance to conductive heat flow. The heat flow is measured in terms of its thermal resistance(R-value). The higher the R-value, the more effective the material is at retaining heat inside your home. These values will be already calculated for you by the manufacturers. It's a good idea to take your wall and ceiling insulation into account as well because it covers over 70% of the surface area of your home. Badly accounted window insulation will result in warm air slowly escaping to the outside through surfaces such as windows and insulation materials.
If you'd like to learn about the technicalities, continue reading on below.
The R-value depends on the material type of insulation, thickness, and density. Additionally, for some materials, the R-value depends on temperature, aging, and moisture accumulation.
When installing more insulation in your home, the R-value is increased and the resistance to heat flow. A general rule of thumb is the insulation thickness size will proportionally increase the R-value. However, there is a catch. As the
What is insulation? Insulation acts as a barrier between the air, moisture, etc. in your house and the air, moisture, etc. out of your house. This is what helps houses maintain their temperate for longer periods of time. Without it, air-conditioning wouldn't be as effective as air would escape outside and your air-conditioner would have to do more work to keep your home cool. Additionally a home without insulation increases the stress on your air conditioner which means its prone to fail more quickly.
The energy.gov(https://www.energy.gov/energysaver/insulation) website has compiled a list with how much you should be looking for in your Zone. We'd recommend to additionally consult with a contractor as they will be more capable to provide the best R-value given the context of your home—areas humidity, moisture, etc.