Can the addition of a bivy make my three-season tent usable year-round?

I have a Marmot EOS 1 tent that I love for three-season camping in Colorado. I would like to use the EOS occasionally for winter camping, but I wonder how well the EOS would protect me from blowing snow. Would it be a wise investment for me to purchase a bivy to use inside my EOS for those few times I may camp in the winter? Sherry Parker, Colorado


Yeah, that’s a good point. Three-season tents such as the otherwise excellent Marmot EOS 1 ($225; often have too much mesh to be good winter tents. But it does have a full-coverage fly, so that should help quite a bit. If you’re camped on snow, for instance, you can heap some snow around the perimeter of the fly to form a better seal. That will prevent wind from blowing up between the fly and the tent body, bringing snow with it.

Outdoor Research MicroNight Bivy

MicroNight Bivy

Certainly, taking some sort of bivy bag or sleeping bag cover wouldn’t hurt. But I wouldn’t get a fully bivy bag; it’s too heavy and expensive. Outdoor Research ( makes just the right thing: the MicroNight Bivy. It’s made with Pertex Endurance fabric, which is very light, breathable, and water repellent. It’ll nicely shake off any snowflakes that find their way into your tent. Cost is $119, and weight is less than 20 ounces. REI ( also makes a no-frills bivy, called the Minimalist Bivy. It’s made from REI Elements, a proprietary waterproof-breathable material, so it would offer a lot of moisture protection. Price is $89.

Myself, I’d worry a bit more about temperature than moisture. It’s gonna be chilly in that well-ventilated EOS 1, particularly seeing as it’s a solo tent so there’s no one else generating any body heat. I’d pack an extra sleeping pad (a lightweight foam pad such as Cascade Design’s $35 Z-Lite is perfect). And certainly, use a sleeping bag with a rating that matches your anticipated low temperatures.

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Filed To: Tents
Lead Photo: courtesy, Outdoor Research