Gear Review

Thermarest Prolite Pads

1. significantly warmer
2. thicker, extra comfort
3. heavier

Obviously Thermarest's four-season Prolite 4 inflatable sleeping pad is warmer than the three-season Prolite 3.

The question is: how much warmer is it, and do I need that extra warmth?

According to Thermarest, the Prolite 4 provides an R-value of 3.2 (a construction-industry measurement of insulation), which is a point above the Prolite 3's 2.3 R-value. I've had the opportunity to snow camp using both 3 and 4-season Prolite pads. In my experience, there is a big difference.

In my opinion, the Prolite 3 provides inadequate insulation when camping on snow or significantly cold ground (especially damp earth in near-freezing temperatures).

In contrast, I've found that the Prolite 4 does indeed offer enough insulating value to keep your body warm, even when sleeping directly on snow.

Losing body heat into the ground is a huge concern in winter—and it can easily defeat even a 0° sleeping bag, as your body weight compresses the insulation beneath you.

For truly cold applications, I'm still going to recommend bringing a small foam pad to double with your Prolite 4 underneath your core (torso). On its own, however, the Prolite 4 will at least be adequate, and warm sleepers may find it downright luxurious.

The only real liability to switching to a Prolite 4 (compared to the three-season pad) is the extra weight. In terms of bulk, the Prolite 4 is marginally bigger, but still rolls up nicely into a stuff sack that will fit easily in your pack. As for weight, the regular length adds a modest four ounces (24oz total). The short weighs 16 ounces—three more than the Prolite 3 short.

Frankly, that's not a great deal of extra weight. If you're uncertain about how much warmth you need, erring on the side of warmer versus colder isn't going to break your back.

A possibly unexpected perk of the Prolite 4 is its extra comfort. The Prolite 4 is thicker, which makes it feel more like a mattress underneath you, adding up to an easier night's sleep. As with the Prolite 3, you get a micro-dot textured surface to help keep the pad from sliding around beneath you as you sleep.

Winter camping is a subject in and of itself, but I will mention that when taking an inflatable pad into very cold weather, the threat of a valve failure or puncture should be taken seriously. A punctured Prolite 4 offers very little insulating value, which could quickly become dangerous in the wrong conditions.

For that reason, winter campers should bring a repair kit (available from Thermarest) as insurance. Also, I'll again recommend bringing a small foam bivy pad as a safety backup.

If you're wondering, do I really need a heavier Prolite 4 for winter, the answer is no. Individual metabolisms and body fat percentages vary greatly. Some people sleep colder and some warmer. Pairing a three-season Prolite 3 with a good foam pad (like a RidgeRest) will be acceptable for many winter users. That said, the extra warmth of the Prolite 4 makes it the more weight-efficient choice when warmth really matters.

» Bottom Line: More warmth than Prolite 3, but snow campers may still want a foam underpad

» More Sleeping Pad Reviews