There have been several questions lately regarding "tightening" up a house. This image might help show how many spots in the average home are vulnerable to leakage. I'm going to touch on a couple here. More thorough information is being put together for publication later. Take a look at the attic hatch. If your hatch is leaky or poorly insulated this is an easy improvement. Most homes in Lake County IN have a piece of drywall resting on casing installed around the scuttle hole. The first action needed is to make that joint air tight with weatherstripping. The spongy type with an adhesive back is great here, install the weatherstripping to the casing in a continous loop without gaps. Now the drywall will sit tight to the weatherstripping which will limit considerably the amount of cold/hot air slipping in from the attic. Second course of action is insulating that hatch lid (the removable drywall). Use a piece of fiberglass batting, R-38 is enough, cut larger than the opening glued with spray adhesive to the backside of the drywall. Make sure the batt is slightly larger than the opening so it will fit snug to the sides of the scuttle opening. For less than $20 at the home center you should easily notice the difference. The second method is purchasing an insulated hatch cover that run about $200 dollars. I havent used one but I suspect they work a little better than the previous method.