DEAR GEAR MAVEN:

My question concerns condensation in a tent whilst winter camping.

This past weekend my friend and I spent the night on Mt. Clay (Presidential Range, NH). The temp was somewhere above 20 degrees and it snowed throughout most of the night. The rainfly was on the tent and the two doors and sky window were closed, both on the tent itself and the fly.

The tent is a Moss Stardome II 4-season tent. We woke up at 4am and the inside walls of the tent were soaked with condensation. Not only the tent walls were soaked but also our down sleeping bags! Thankfully we were only spending that one night up there b/c the bags were really wet. Is this normal? What can I do to reduce the amount of moisture inside the tent?

Oh yeah, we did not, repeat, did not cook inside the tent. Only sleeping.

Annie's Answer:

	Ask the Expert Annie Getchell Gear expert Annie Getchell believes the key to happiness is buying quality gear and treating it with tender loving care. Meet Annie Answer Archive Gear Forums

From your classy grammar, I'd guess you're a walking British Thermal Unit. But your question gives you away entirely. You and your friend didn't know it, but you were a veritable Petri dish for condensation analysis.

Conditions were perfect: transitional temperatures (around freezing), precipitation, altitude. Toss in some wet gear and a couple of burly guys zipped into toasty down bags emanating some BTU's and voila! You have created the perfect condensation chamber.

All the more so when you're entombed in a Moss tent, whose designs are known for keeping the weather out — and the hiker microclimate in.

Just because you're snoozing doesn't mean your respiratory system is. All those dreams and exhaled breaths hit the wall and drip, drip, your superfill is saturated. Solution? Ventilate! Certainly keep the fly closed during wet, low-pressure nights, but absolutely open the top third of both front and rear ports of the tent body. Or, try venting one door low and the other high for maximum circulation. Not sure about the stargazer window-you'll have to experiment.

Also, make sure the rainfly is well-guyed away from the tent walls - - if the fly sags onto the tent proper, the resulting evaporative cooling makes condensation worse.

Finally, down bags are always risky at such temperatures, especially in New England or boreal forest. Better bag makers use water-resistant shell fabric on their down bags. Synthetic fills are inherently water-resistant. If you're reluctant to invest in a synthetic fill bag for wet conditions, consider a simple waterproof-breathable bivy sack, which will extend your camping options in many ways.

Now here's my incredibly cheap trick: Zip your techy raincoat around the leg-foot area of your mummy bag. Let me know how it works.

P.S. Congrats for choosing not to cook in your portable domicile: You are a good, obedient camper who has read all the warning labels. You get a gold Star.