The first factor in how much insulation you need is where you live --

you'll need a higher R-value if you live in the Northeast than if you live in Southern California. The R-value basically determines how much heat or cold it can stand, or in other words how effective it is. The higher the R-value the better insulating properties. The Northeast faces more severe weather conditions than Southern California, thus if your home is located there then you would need an insulation appropriate for the weather conditions. If you live somewhere in between then you would need a value in between. If you are concerned about the R-value for your area, then ask an expert. When in doubt go with a higher R-value.

The next factor you need to consider is the age of your home

(if your home is more than 10 years old, you likely need more). Older homes were not built with as good of materials generally. Increases in technology and material quality make it so you do not need as much insulation. Older homes may have deterioration etc and require more insulation. You want to make sure that you consider the age carefully when determining how much insulation you need.

The third thing to consider is how your home is built --

for example, is it a single-level or multi-level structure? Do you have vaulted ceilings? Is there a basement or is your home built on a slab? Do you have an attic, etc.? The height of ceilings and the whether or not you have a basement will play a great role in the amount of insulation you need. Having your attic insulated and your basement will greatly reduce your utility bills. So, if you have these items in your home, then you should highly consider insulating them for the best results.

Next, consider the ways in which you heat and cool your home --

do you have a furnace, a central air conditioner, or a heat pump? These too will play a part in how you want to insulate, and thus how much insulation you need. Basically the better insulated your house is, the better. Your home will be more comfortable, will keep the desired temperature longer and cost less to keep it at a comfortable setting.

The Recommended Levels of Insulation

If you want to have the minimum amount, but not more than that you can always look at the department of energy's recommendations. The U.S. Department of Energy has recommendations and minimum R-values and it is relatively simple to find these recommendations. You can look online or ask your area building codes.

So Why Add More Than the Minimum?

Adding fiber glass and rock and slag wool insulation above minimum requirements helps:
Increase energy savings , it provide greater noise control, and control moisture which helps your house and roof last longer. Savings may vary, find out why in the seller's fact sheet. You can also access information about specific financial incentives being offered in your area. Simply select your state from the "Incentives" list on the right to learn more.