What attic insulation R-value do I need in my home? This question is asked all the time. The short answer is to go by the building code in your area. The correct answer may be something else. Here is why. Number 1 reason is the building code is MINIMUM. This means that you can put more insulation in your home but the code says at least this much. The codes are changing rapidly for the next few years compared to when they changed before. The reason is the government agencys have realized that the country has been wasting a tremendous amount of energy heating and cooling homes. They are now in the process of raising the R-values that is required in homes. So now do you want the minimum amount of insulation up there or would you like enough to meet future code? The 2012 code says you should have R-49 in our area in the attic. This is reasonable enough although we have been installing R-60 more than R-49 for the simple reason that it costs little more to go the extra amount. Someone is blowing it up there anyway so it takes little to hold the hose a little longer and material costs are not much more. And it will save you Energy and Money!
Another thing to consider is how much space is there to blow insulation in. It is arguably better to have a ventilated roof if you have shingles on it. This means you should have an air gap above the insulation. In older homes there is sometimes hardly any room to put any kind of insulation in the attic over the top plate. Then you or your insulator has to figure out the best way to do the job. Air sealing is also critical to ensure that you are not leaking air through your ceiling. A lot of insulation without proper air sealing can rot the roof deck out from under your roofing in a few years.
There are differences in the cost of insulations. You should weigh the differences in these costs when combining air sealing and R-value. Most new homes are built with an energy heel on the trusses which enable you to get more insulation out over the top plate. For example, with a 12” energy heel you can get R-26 in that space with loose fiberglass while you can get R-39 in that same space with cellulose. If you use the Blow In Blanket System you can get R-50 there. Foams have different R-values so you need to check them out carefully. I would not recommend fiberglass batts at all as they are the least effective insulation in filling a cavity without holes or voids. The bottom line is, to go beyond R-60 is not cost effective unless the rest of your home is very well insulated also with good windows and doors and is well air sealed. The next step beyond this would be a super insulated home like a Passive House.
You need to find an insulator that can explain all these things to come up with the best solution. We are here to help and answer your questions. Call 715-364-2805