I get where you’re coming from about not sealing everything up tight, but honestly, I’ve seen a lot more problems from folks *not* sealing enough than the other way around. Sure, you can trap moisture if you’re careless—like caulking a vent shut, which is a classic rookie move—but in most cases, drafts and leaks are what end up causing the real headaches. Cold spots can be a symptom, but they’re not always the whole story.
What I’ve found over the years is that people often underestimate just how much air can move through the tiniest cracks, especially around plumbing penetrations. You might check for cold spots and think you’ve caught everything, but unless you’re using something like a smoke pencil or an infrared camera, there’s a good chance you’ll miss some of the less obvious leaks. And those are the ones that’ll freeze pipes or let in enough moisture to cause mold behind the walls.
I’m not saying you should go wild with the spray foam or caulk gun—far from it. But I’d argue it’s better to err a little on the side of caution and seal up anything that looks even remotely suspicious, as long as you’re not blocking intentional vents or weep holes. If you’re worried about trapping moisture, focus on using vapor-permeable sealants or backing up your work with a dehumidifier in problem areas.
One winter, I thought I’d done a thorough job in my own crawlspace, only to find out later that a tiny gap behind a pipe was letting in enough cold air to freeze a section of PEX. Didn’t even show up as a cold spot until it was too late. Sometimes, the stuff you can’t see or feel is what gets you.
Anyway, just my two cents. There’s definitely a balance, but I’d lean toward being thorough—just with a bit of common sense about airflow and moisture paths.
One winter, I thought I’d done a thorough job in my own crawlspace, only to find out later that a tiny gap behind a pipe was letting in enough cold air to freeze a section of PEX.
Man, I’ve been there. It’s always the spot you think is fine that bites you. My trick now is to run my hand around every pipe and wire after sealing—sometimes you feel a draft you’d never see. And yeah, don’t go nuts with the foam or you’ll end up blocking something important (ask me how I know...). A little patience and double-checking saves a lot of headaches when it gets cold.
That foam can be a double-edged sword, for sure. I once sealed up a gap so well that I accidentally trapped a wire behind a blob of it—took me an hour to dig it out when I needed to replace a light fixture later. Ever tried using one of those little smoke pens to find drafts? I’ve had mixed luck, but sometimes it’s easier than crawling around on your belly in the cold. Curious if anyone’s had better luck with those or if it’s just me fumbling around...
Ever tried using one of those little smoke pens to find drafts? I’ve had mixed luck, but sometimes it’s easier than crawling around on your belly in the cold.
I’ve used smoke pens a few times, mostly in older basements where the drafty spots aren’t obvious. They’re handy, but I’ve found they can be unreliable if there’s any airflow from a furnace or even just someone walking by. Sometimes I still end up on my hands and knees with a flashlight anyway. As for foam, I learned the hard way to always double-check for wires and pipes before sealing—once had to cut open a wall after trapping a shutoff valve behind a mountain of the stuff. Not my finest hour.
Yeah, I hear you on the smoke pens. They’re great in theory, but even a draft from someone opening a door upstairs can throw them off. I’ve had better luck with a candle sometimes, but that’s not exactly scientific either. And man, sealing up a shutoff valve… been there, done that, had to explain it to my boss. At least you caught it before it was a real emergency. Stuff like that definitely makes you double-check next time.