Product Info for Western Mountaineering Hotsac VBL Sleeping Bag Liner

The HotSac vapor barrier liner (VBL) is your most important companion for technical winter trips. A VBL works by stopping heat loss from evaporative cooling. Vapor barrier liners also prevent your body vapor from degrading your insulation. This is most important during extended stays inside your bag, particularly if it has a laminated outer shell fabric. Our HotSac VBL goes one step further by stopping radiant heat loss with its reflective gold backing. An elastic draw cord at the top of the HotSac cinches about your neck to prevent convective heat loss. This proprietary fabric was specifically developed as a two layer lightweight ripstop with a reflective ultra-thin film designed to block moisture vapor transfer. The HotSac weighs only 3.5 ounces (101 grams), so light and compact it can be carried in a day pack for use as an emergency bivouac sack.

Features of Western Mountaineering Hotsac VBL Sleeping Bag Liner:

Light enough to carry as an emergency bivy
Stops heat loss from evaporative cooling
Prevents body vapor from degrading insulation
Reflective metal coating
Draw cord closure
Convenient foot pocket for compact stowing
Color may vary according to fabric availability

Package Contents:

Western Mountaineering Hotsac VBL Sleeping Bag Liner

Customer Reviews for Western Mountaineering Hotsac VBL Sleeping Bag Liner Read All (1)

Helpful Positive Review

Perfect for deep winter adventures.

by Trodger, Verified Owner from CT, United States Updated on January 3, 2025

An absolutely necessary piece of equipment in a sleeping system for sub-zero temps. Moisture management is crucial for comfort and safety on any trip more than a day or two long at freezing temps. Keeping insulation dry is very important. The WM vbl is nicely made to fit their bags and adds considerable warmth and insulation protection from body moisture. I have used mine for s...
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Would recommend: Yes

7 of 7 people found the following review helpful.

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