Have you checked to see if there’s a draft at the bottom of your entry door? Drafts, no matter how small, can mean inefficiency in cooling and heating your home because they allow air to enter and escape. It is, therefore, very important to find out if there is a gap between your door and its threshold. If you do find a draft, it’s time to raise the threshold and eliminate the gap. Here’s how to do it.
Using a screwdriver and straightedge, such as a framing square, adjust the threshold height by turning the screws and using the straightedge. Periodically close the door and check to see if any light is visible between the door and the threshold. If so, continue adjusting the screws to raise the threshold until until no gap can be seen. Read here for more tips.