There are many different types of sleeping bags. Each bag is suited to different conditions, temperatures, and purposes. Sleeping bags can be made out of different materials, insulated with different fillers, and take various different shapes.
An envelope sleeping bag is a sleeping bag that is rectangular in shape. This rectangular bag has a zipper along two sides, generally down the length and across the width of the bag. This article will discuss the benefits and drawbacks of envelope sleeping bags, as well as discussing their characteristics in further detail.
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Characteristics of an Envelope Sleeping Bag
An envelope sleeping bag is a rectangular bag. It can accommodate one person or two people if it is a couples sleeping bag. These sleeping bags are considered regular or typical sleeping bags and are the most common type of sleeping bag available for purchase.
Rectangular sleeping bags can be fully unzipped to take the form of a blanket. Rectangular bags also provide for more room than other types of sleeping bags. However, because of their roominess, they can lose heat more easily.
Rectangular sleeping bags can have different temperature ratings and be designed for different seasons. Generally, rectangular sleeping bags can be suited to summer camping, winter camping, or three season camping. Three season camping describes a sleeping bag that can be used during fall, winter, and summer.
A summer rated sleeping bag is a lighter bag with less insulation. They are often lightweight and highly compressible, making them suitable for backpacking and hiking. Winter sleeping bags are rated for cold temperatures. They are heavily insulated, resulting in a bulky sleeping bag.
Envelope sleeping bags may be rated for winter conditions but they are often not the warmest. Due to their roominess, they aren’t the best at trapping heat.
In addition to the seasons that each bag is optimal for, the sleeping bag will also have a temperature rating. Usually, the temperature ratings will be can be found on a scale attached to the bag or one of its tags.
The scale displays the tested lower limit on one end, and the upper limit on the other end. The optimal comfort rating is located somewhere in between these two extremes.
The lower limit, also sometimes classified as the extreme limit, is the coldest temperatures at which the bag can safely be used. If you are using your bag in temperatures at the very lowest limit, you may feel slightly cool. Using the bag in temperatures contained in the extreme category or below is not recommended as it could result in hypothermia.
The upper limit is the warmest or highest temperature in which you would want to use the bag. At these upper levels, your sleeping bag may feel a bit too warm, in which case you would want to unzip it for ventilation.
As the name suggests, the comfort rating found in between the cold and warm extremes is the optimal temperature in which you should use your sleeping bag. At this temperature, your sleeping bag will feel the most comfortable.
A rectangular sleeping bag can be filled with down or synthetic insulation. Each type has drawbacks and benefits.
Down is a natural form of insulation. It is composed of the downy feathers from geese and other fowl. Down sleeping bags are extremely warm and have excellent insulative properties. One of the downsides, no pun intended, is that it is not waterproof.
Synthetic insulation is created from fibers that mimic the properties of down. They are often very warm and cost less than natural down insulated bags. Synthetic fill is typically waterproof. A drawback to synthetic is its bulkiness and weight when compared to down.
The shell of rectangular sleeping bags can vary as well. Sleeping bag shells can be made of polyester or nylon, and rarely of cotton.
Nylon is the material more often selected by serious and frequent campers. It is highly durable while still being lightweight. Nylon can also be conditioned to repel water.
Nylon shells treated with Gore-Tex, a waterproofing solution, can be more expensive. However, waterproof bags are treated on multiple levels to be resistant to liquid including a sealed fabric and “seam-tapping” so water will not seep through the stitching. If you are taking your bag into the backcountry, especially if you are canoeing or kayaking into your campsite you will want a waterproof sleeping bag.
Polyester shelled bags are usually not waterproof but perfectly fine for occasional campers and those who will not be exposed to the elements while sleeping. Because of their lack of specialization, they are typically more affordable.
Though available on the market, cotton bags are not advisable. They soak up water and take a long time to dry. Even though they can be found for a steal, you will likely regret your purchase.
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How Does it Compare to Other Sleeping Bags?
There are two other types of sleeping bags predominantly used instead of rectangular bags. These sleeping bag shapes are mummy or semi-rectangular.
Mummy sleeping bags are touted for their warmth and insulation in extreme conditions. Mummy sleeping bags have a sarcophagus shape and are tapered towards the feet. Mummy sleeping bags also cover the head and usually have a drawstring feature so it can be tightened around the face.
A mummy sleeping bag is great for small spaces and getting the most out of your sleeping bag in extreme conditions. However, because of their confining shape, they may be too restricting for some campers.
Due to their tight, body-hugging shape, mummy sleeping bags are very warm. They trap heat against your body and contain insulation suited to cold conditions. Even though they have a high warmth factor, they usually are lightweight and compact, making them easy to carry.
Half-rectangular bags or semi-rectangular are a compromise between envelope sleeping bags and mummy sleeping bags. A semi-rectangular bag has some of the warm and insulating properties of a mummy bag but also a bit more room to spread out.
The Pros of an Envelope Sleeping Bag
There are quite a few benefits to envelope or rectangular sleeping bags. The strengths of rectangular bags lie in comfort and versatility.
If you are someone who rolls or thrashes in your sleep, you will likely find that an envelope sleeping bag is more comfortable. Rectangular sleeping bags offer more space than mummy sleeping bags and are less constricting.
In a mummy sleeping bag, you typically have to sleep on your back due to its body contouring shape. In an envelope sleeping bag, you can sleep in almost any position you like. The sleeping bag can also be couples sized so that more than one person can sleep in the bag at a time.
Envelope sleeping bags have a zipper down two sides, running the length and the width of the bag. This means that they can be unzipped. You can either unzip your bag for ventilation if you are feeling too warm or completely unzip your sleeping bag and use it as a large blanket.
Rectangular sleeping bags are a popular choice among car campers. If you are not worried about carrying your sleeping bag into your campsite, rectangular bags are a warm and spacious choice for families and car campers.
Envelope sleeping bags are also cost-effective. Mummy style sleeping bags are valued for their high performance and cold temperature ratings, making them typically more costly than rectangular sleeping bags. You can usually find a quality envelope sleeping bag in a variety of sizes, insulation types, and shell materials for a reasonable price.
The Cons of an Envelope Sleeping Bag
One of the biggest drawbacks to a rectangular sleeping bag is its weight and bulkiness. Because of its shape, it does not compress easily. Therefore, it is not preferred by those who have to hike or travel by water into their campsite.
Rectangular bags are more spacious but this means that they are heavier than other sleeping bag shapes because of their increased area and volume. Envelope sleeping bags will provide you with more sleeping space but at a price.
The additional space of an envelope bag can also affect its warmth. Because these bags are roomier they are not as efficient at trapping heat and keeping you insulated. There are a few envelope sleeping bags rated for winter or extremely cold weather conditions, but they are not optimal for arctic camping.
Some sleepers may find their feet getting cold in a rectangular bag. The extra space at the bottom allows for air circulation, sometimes resulting in chilly toes and extremities.
Is an Envelope Sleeping Bag Right for You?
Ultimately, the decision about which sleeping bag shape to purchase depends on your camping style, conditions, and sleeping preference. If you are planning on camping in very cold conditions or having to hike or canoe into your campsite a rectangular sleeping bag may be too cold and too bulky. If you are a car camper, looking for a warm, versatile, and spacious bag that won’t break the bank, you would probably be happy with an envelope sleeping bag.