BushwalkBushwalkAn underquilt is used with a hammock to reduce heat loss to the air under the hammock. Underquilts are made out of the same insulation material as a sleeping bag and hang beneath the hammock. The idea is to create an insulation layer underneath the sleeper that does not get crushed under body weight. Since crushed insulation is far less effective than expanded insulation, keeping body weight off the insulation material provides a far more effective insulation layer for hammock users.
Some hammock users carry sleeping mats to give them more options. For example if they camp somewhere with no hanging points, they can use a sleeping mat on the ground, where an underquilt would provide very little value. Most hammock sleepers find underquilts lighter, warmer and more comfortable then a sleeping mat in most situations.
Similar to sleeping bags, some of the key features to look out for when selecting an appropriate underquilt include the following.
The two main material elements to consider for a hammock underquilt are the outer shell, which will be subject to dew and condensation from being out overnight, and the insulation.
The shell of a hammock must be durable and water repellent. Ideally, select a hammock with a material that is non-rip (e.g. Ripstop material) to protect the underquilt from tears. Select materials with some sort of durable water repellent coating.
Just like sleeping bag insulation, underquilt insulation is either synthetic or down. Down has the advantage of a great weight to warmth ratio and compacts well. Synthetic insulation tends to work better if it gets wet and is bulkier.
An underquilt should be well fitted to your hammock for maximum insulation. Size differences in underquilts generally relate to the length and width of the hammock, so check that these dimensions match the hammock you typically use. Select a size that insulates well but not so tight that it restricts your movement in the hammock.
Weight is obviously a factor for comfort in overnight hiking. Underquilts range in weight from as light as 210 grams (e.g. Thermarest Slacker Hammock Warmer) through to 400 grams (e.g. the Revolt) and more.
There is generally a trade-off with weight – the lighter it is, the more expensive it is! Light can also indicate that the temperature rating is not as high as heavier ones made from same materials, so make sure to check this out also.
Hammocks work well in a broad range of temperature conditions and follow a similar temperature rating scheme to sleeping bags. Seek an underquilt that is rated to below conditions you’ll typically be using it in.