The R-Value measures the thermal resistance of a sleeping mat: how much insulation it provides against the cold from the ground.
In ultralight hiking, the ground is the main source of heat loss, so an insufficient mat will leave you cold even with a good sleeping bag. The R-Value is cumulative and quantifiable, making it an objective reference for making the right choice.
As a technical reference:
R-Value 1–2: summer, mild nights, warm ground
R-Value 2–3: three seasons, general UL use
R-Value 4–5: cold, mountains, late spring or fall
R-Value >5: winter, snow, or frozen ground
The main difference lies in how thermal insulation is managed. In a traditional mummy-style sleeping bag, the insulation surrounds the entire body, but the bottom part gets compressed when lying down and loses much of its insulating capacity. In practice, that area provides little warmth.
The quilt eliminates that unnecessary bottom insulation and relies on the sleeping pad for insulation against the ground. This allows for:
reducing weight and volume
improving thermal efficiency per gram
adapting the system to different conditions by regulating ventilation
In exchange, the quilt requires:
a sleeping pad with an appropriate R-Value
good control of air drafts
a bit more experience in adjusting the system
In ultralight terms, the quilt is not a “less warm” solution, but a more efficient and modular way of managing insulation when the system is well balanced.
Down offers the best warmth-to-weight ratio and compressibility, making it the preferred choice for ultralight gear. At the same temperature, a down sleeping bag weighs less and takes up less volume than a synthetic one.
Synthetic insulation performs better when wet and is more forgiving of careless use, but it compromises on weight, volume, and long-term thermal durability.
In ultralight philosophy, down is the most efficient option as long as moisture is properly managed. Synthetic makes sense in very humid environments or for users who prioritize robustness and simplicity over weight optimization.
The temperature range of a quilt is based on its superior insulation capacity, as there is no compressed insulation under the body. This means the system heavily depends on the sleeping pad (R-Value), the quilt's fit, and the clothing worn while sleeping.
For quilts, the indicated temperature is usually a comfort limit temperature for an average user, not an absolute guarantee. Sleeping warmer or colder depends on metabolism, wind, humidity, and how tightly the quilt is closed around the body.
In ultralight, it is common to choose a quilt with a safety margin of 5°C below the minimum expected temperature, optimizing weight without compromising rest.
The choice depends on the actual minimum temperature you'll be sleeping in and how well-tuned the rest of your system is (sleeping pad, clothing, shelter).
0 °C → Suitable for mild three-season use. Ideal if you usually sleep in temperatures above 2–4 °C, with a good pad and without seeking extra margin. It is the lightest option.
−6 °C → The most balanced option for most mountain routes. Offers a safety margin, tolerates occasional cold nights, and is the most versatile choice for ultralight hiking.
−12 °C → Designed for constant cold, high mountains, or people who easily feel cold. Provides a lot of thermal security, but with a clear penalty in weight and volume.
In ultralight quilts, it is not advisable to cut it too close: choosing a slightly warmer model allows for better sleep, compensates for errors (wind, humidity, fatigue), and extends the use of the equipment over more months of the year.
In a quilt system, the sleeping pad is as important as the quilt itself. Without insulation on the underside, all the protection against ground cold depends on the sleeping pad.
The key factor is the R-Value, which measures thermal resistance:
R ≈ 2–3 → Summer use or mild nights. Insufficient with quilts in cold conditions.
R ≈ 3.5–4.5 → Three seasons. The minimum recommended for quilts from 0 °C to −6 °C.
R ≥ 5 → Cold, high mountains, or winter. Essential for quilts from −6 °C to −12 °C.
A sleeping pad with a low R-Value causes heat loss through conduction, making the quilt “perform worse” even if its nominal temperature is correct. Therefore, in ultralight design, the system is considered as a whole: quilt + sleeping pad + shelter.
