We have lived here for over 20 years and stuff put into the dryer at bedtime was usually still warm in the morning, even in February. This summer I noticed that the outside vent's plastic was starting to crumble so I replaced it with a similar large hood flapper with pest grill. Now if we leave the clothes in the dryer for an hour after it stops they are cold to the touch. The first time it happened I thought they were still damp but they are completely dry so I thought maybe the flapper wasn't closing properly but I checked and it is fine. Any ideas?