There can be many factors to lead to an inefficient ventilation system, such as: old windows, poor set up of duct work, leaks at various places in the home, or (the biggest one) improper attic insulation and venting.
If not properly sealed, vented, and insulated, the attic can become a huge issue with home heating/cooling efficiency. As you can see from the picture to the left, there are many areas one can easily miss if not aware. Your hard-earned money slipping out of unsealed vents and exhausts, or possibly over heating an attic due to improper venting making temperatures soar upwards to 175 degrees F. When temperatures get that high, not only does your condenser work harder to keep the house cool, but condensation then begins to form due to temperature variants, which lends itself to another whole host of problems such as: mold, mildew, and wet nesting bacteria, which I dare say is another blog post entirely… But as you can see, attic insulation must be maintained to have a cost efficient healthy home.
After going through your attic and using the proper sealant around possible leaks, its then time to focus on your insulation and its level. In the photo to the right, you can see proper insulation levels. You will also notice in the picture that the ductwork is also enclosed inside the insulation. This helps maintain temperature stability to reduce issues with water forming and causing issues down the road. Attic insulation should be R-8 value for maximum efficiency, and if your ducts are not insulated, waste no time in doing so , just remember to keep the water barrier to the outside of your ducts. Did you know that you can also get tax credits for doing upgrades such as this to help home efficiency.
All you have to do is keep all papers/receipts pertaining to the improvement on the home and when tax time comes around then go to: https://www.energystar.gov/about/federal_tax_credits/insulation.
There you can see how to qualify for potential money back.