Quick Answer
A sleeping pad is not strictly necessary inside a Mylar bivy sack, but it can provide a significant increase in warmth, insulation, and comfort, especially in cold or wet conditions.
Using a Sleeping Pad with a Mylar Bivy
When using a sleeping pad inside a Mylar bivy sack, consider a lightweight, inflatable pad with a minimum R-value of 2.0. This can be as simple as a foam pad or a more advanced insulated air mattress, such as the Exped SynMat 7L, which weighs 1 lb 5 oz and has an R-value of 4.3. Place the pad inside the bivy, ensuring it fits snugly, and then add your sleeping bag.
Mylar Bivy Sack Options
Not all Mylar bivy sacks are created equal. Look for a sack with a waterproof and breathable membrane, such as Gore-Tex or similar technology, to prevent moisture buildup and keep you dry. A good example is the REI Co-op Bivy Sack, which weighs 6 oz and has a waterproof and breathable shell. Choose a sack with a decent floor space and a hood to keep your head warm and dry.
Sleeping Bag and Clothing Considerations
When using a Mylar bivy sack, prioritize a warm and dry sleeping bag rated for the expected temperature range. Choose a bag with a decent fill weight and a suitable comfort temperature rating. In addition, wear a warm hat and insulated gloves to prevent heat loss. Consider a face mask and a neck gaiter to further reduce heat loss and keep your face and neck dry.
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