Enfield sits in a cold-severe climate band, and that's not a marketing phrase, it's the difference between a seal that flexes with temperature swings and one that just cracks. Vinyl and rubber both stiffen hard once the mercury drops, and a stiff seal stops following the slab underneath it. Add in the fact that most houses in this service area were built between 1938 and 1986, with the typical build year landing around 1969, and you've got fifty-plus winters of frost heave working under slabs that were never poured to today's spec. The concrete moves a little every freeze-thaw cycle. The door frame, bolted to a house from that era, doesn't move the same amount. Over decades that gap between the door bottom and the slab stops being flat and starts being a slight wave, sometimes barely visible, that no factory seal is shaped to follow. That's before you even get to the jamb itself. A lot of the 1960s-70s stock across this area used dimensional lumber that's shrunk with age, so the top and side seals are pressing against a frame that's a little narrower or a little bowed compared to the day it went in. Cold makes a bad fit obvious. It doesn't cause the gap, but it turns a small one into a whistle you can hear from the kitchen.
The draught you feel isn't usually one bad piece of rubber, it's three small failures stacking up: a bottom astragal that's stopped matching the slab, side seals compressed flat from age, and a top seal that was sized for a jamb that's since moved. On a house from the 1938-1986 build range that's common here, none of those three failed on the same day. They drifted slowly, so nobody noticed until a cold snap made the gap impossible to ignore. The other part of the problem is that a lot of these doors are original to houses built well before double-wall steel and foam-core panels were standard, so even a perfect seal is sealing against a panel with almost no insulating value of its own. You can chase the draught with new weatherstripping and still feel cold radiating off the door itself. Fixing the seal helps the air leak. It doesn't touch the heat loss through the panel, and those are two separate problems that get lumped into one complaint.
The common mistake is buying a universal seal kit and pressing it into the same track without checking whether the track itself is still square. On a door bolted into a frame that's shifted with fifty years of freeze-thaw, a new seal pushed into an out-of-true track will look fine for a season and then start gapping again in the exact same spot, because the underlying geometry never changed. People also tend to seal the sides and top and skip the bottom astragal, assuming the door's own weight handles that gap. In this climate band, ice under the door edge is common enough that a worn astragal lets meltwater and cold air in at the same point every time. The other error is treating every draught as a seal problem when sometimes it's a level problem: a door that's racked slightly on its rollers will never seal evenly no matter how many times you replace the rubber, because one side is closing tighter than the other. We won't sell you a third seal kit for a door that needs the track adjusted first.
A draughty seal on its own won't wreck a door. It'll cost you heat and let in enough cold air to make the garage itself uncomfortable, and if the garage is attached, that cold air finds its way past the interior door too. What it can lead to, given the age of framing common in this area, is moisture getting into a jamb that's already a little soft, and moisture in cold-severe conditions means freeze cycling inside the wood itself, which is a slower and more expensive problem than a $30 seal. We'll say plainly that not every gap needs a service call. If you can see daylight under the door in a straight, even line, a seal replacement you do yourself on a Saturday will probably fix it. If the gap is uneven side to side, that's a track or hinge issue, and no amount of new rubber solves that one.
Cold-severe conditions stiffen rubber and vinyl seals, so a gap that was minor in October becomes obvious once temperatures drop. On older frames common in this area, built mostly between 1938 and 1986, the jamb has also shifted slightly over the decades, so the seal is pressing against a slightly different shape than it was designed for.
It stops the air leak but not the heat loss through the panel itself. A lot of doors on houses from the 1960s-70s stock common here are single-wall steel or original wood with no foam core, so even a perfectly sealed door still radiates cold. Seals and insulation are two separate fixes.
An even, straight gap under the door usually means the astragal is worn and needs replacing. An uneven gap, wider on one side than the other, points to a door that's racked on its rollers or a track that's shifted. Replacing the seal won't fix that; the track has to be brought back to level first.
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