For your HVAC system to function at its peak efficiency it is necessary that the insulation is done properly. If after installing the best heating and cooling system in your house you find out that you are not able to achieve a comfortable temperature then the efficiency of the unit decreases and you will end up paying more amount for energy. Bad insulation is the culprit for inefficient cooling and heating. If your house is under construction then it is not an issue as you can get the insulation work done without any extra cost but if you have an old home and if it is not properly installed then it is going to cost you a lot of money. More over the renovation work is not going to be easy for you.
If your attic insulation is less than six inches then you will have to add an extra 6 inch fiber glass or any other material to heat the room more efficiently by doing so the rooms below the attic will be heated much faster. You also have to add 6 inch additional insulation on top of the crawl space to keep the floors warm. It is also very important to insulate the rim joist for the basement to prevent heat leak. Most of the time those who are doing the insulation forget about closing the ceiling gaps which results in hot air leak. Another area where insulation is ignored is around the plumbing pipes and heating ducts. Make sure that such areas are insulated properly to prevent hot air from leaking.