Quick Answer
STACKING MYLAR BIVYS IS POSSIBLE BUT HAS LIMITATIONS ON WARMTH GAIN. TWO OR THREE LAYERS CAN BE STACKED FOR TEMPORARY WARMTH, BUT EACH ADDITIONAL LAYER WILL REDUCE VENTILATION AND INCREASE MOISTURE BUILDUP. THE MAXIMUM NUMBER OF LAYERS SHOULD BE DETERMINED BY THE ENVIRONMENTAL CONDITIONS AND THE NEED FOR BREATHABILITY.
Choosing the Right Mylar Bivy
When selecting a Mylar bivy for stacking, look for one with a heavy-duty, waterproof coating. The thickness of the Mylar material is also crucial; 2-3 mil thickness is a good starting point. Some popular options include the Golite Bivy Sack and the Spacebrand Emergency Bivvy.
Stacking Techniques
To stack Mylar bivys effectively, start by laying out the bottom bivy, then add subsequent layers on top. Leave some space between each layer to allow for air circulation and moisture to escape. When stacking, consider using a breathable material like a silk or nylon poncho to separate the Mylar layers. This will help to reduce moisture buildup and improve ventilation.
Safety Considerations
Stacking Mylar bivys can create a humid microclimate that can lead to condensation issues. In humid environments or when temperatures are near freezing, it’s best to limit the number of stacked layers to two. If you must stack more than two layers, make sure to check for condensation regularly and adjust your setup as needed to prevent hypothermia.
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