Crochet blankets are beautiful, but due to the nature of crochet, they can have a lot of holes in them. Granny square and chevron blankets are certainly gorgeous. But I remember when I decided to crochet my first blanket, I wondered: with all those gaps in the fabric, can a crochet blanket actually be warm?
As counter intuitive as it may sound, crochet blankets are warm because of the holes in it. Air being one of the best insulators. When moving air passes you, it carries heat away from your body, making you cold. The blanket’s holes work by holding air (warmed by your body) between the yarn threads and inside the holes, stopping this air from moving away. This warm air stays next to your body, keeping you warm. This is why down jackets, down comforters, and furs are so warm. They trap warm air, and hold it close to your body.
Let’s look at this in a little more detail.
The Science Behind Crochet Blankets
As mentioned before, one of the primary ways you lose heat is when air blows past you and carries heat away from you. We all know that feeling of chill when the wind blows when you’re out on a cold day and slightly under-dressed. But this can happen inside too, on a smaller scale.
Warm air moves up. That’s why basements are usually cold, and attics get so hot. When you’re in a cold room, the air right next to you warms up. As it warms, the air rises. Cold air from the rest of the room comes in to replace it.
So your own body heat makes a small breeze that you barely even feel as it moves heat away from you.
This is convection. If you want to get really scientific: convection is the transfer of heat due to bulk movement of molecules in a fluid. Gas and liquids are considered fluids. Convection is also the fastest way heat can be lost through air. Think of a drafty room, or a room with a fan running.
But a blanket with holes keeps that warm air from moving away from your body, stopping that tiny breeze from carrying away your warmth. This leaves you with a nice toasty, stable shield of air surrounding you.
Air conducts heat very badly (mainly due to its low density as heat moves very slowly through gases like air,) but it’s a very good insulator. We normally don’t think of it as a good insulator because it’s a freely moving gas. Convection and wind often cool us down, instead of warming us up. To make air actually work as an insulator, you need to stop it from circulating and keep it in place.
This is how most insulation fibers or foam works. The insulation is provided not by the material itself, but by the pockets of air trapped in it.
Fur is one of the warmest things you can wear because the fur bends and essentially traps pockets of air against the skin of the animal, allowing some animals to live outdoors in freezing habitats.
Down jackets work similarly. Feathers are light and fluffy, which creates a lot of small air pockets.
Layering clothes is also so effective because warm air is trapped between the layers. A well layered outfit of a few moderate layers can keep you much warmer than one thick layer.
Knit and crochet sweaters work the same way – by holding air in its fibers that you warm with your body. The trapped air can’t move and carry away the heat, so you stay warm.
But if you go outside on a cold windy day without a windbreaker or coat, you’ll feel chilly even your warmest sweater. That’s because the wind would replace all your pockets of warm air with cold air.
Some even say that their crochet blanket is too hot to sleep with. This just goes to show how effective crochet blankets are! With the holes, crochet blankets might be too warm, because not only do the holes in the pattern trap warm air, but the yarn fibers themselves trap warm air.
If you bunch up a holey crochet blanket, it’ll be more insulating because the warm air is even less likely to escape.
Many crochet blanket lovers use the holes to regulate temperature. We’ve all been too hot under a down comforter. The easiest fix for that is just moving the entire blanket off you to let some of the warm air out.
But if it’s too warm under a crochet blanket, you can simply stretch the blanket more flat to become a single layer. That can let some of the heat out, but not all of it, so you’ll still stay a little toasty.
How To Make it Even Warmer
Some crocheters in super cold climates make their crochet blankets warmer by placing a blanket over the afghan to close off the air pockets.
For a more permanent solution, you can sew a layer of fleece or a sheet to one side of the blanket, to further trap air.
If you haven’t made the blanket yet but you know it needs to be exceptionally warm, consider using more insulative yarn.
What Yarn Is the Warmest?
Wool is one of the warmest yarns that’s still somewhat affordable for a blanket. The crimp in wool fibers is great for trapping air pockets. When spun into a yarn, you get a very lofty, resilient yarn that keeps you warm.
It also breathes very well, so you won’t stay sweaty in wool. In fact, wool actually uses moisture to generate heat. Water is absorbed into the center of wool fibers, where the hydrogen bond of water is broken. This way, wool can pull water from your sweat and water from the air to become even warmer.
In terms of animal fibers, qiviut is the warmest yarn there is, but it is extremely rare and can be quite expensive. Qiviut, pronounced “kiv-ee-ute” translates into “down” or “underwool” in Inuit. It’s made of the inner down of the muskox, which lives in Greenland. It’s a very lightweight fiber, doesn’t shrink, and is surprisingly very durable.
Cashmere and merino wool are other great options. Cashmere is warmer than merino, but can pill very easily. Merino is known to be moisture wicking, to some degree.
Alpaca is also very warm and soft, but is said to be more durable than cashmere. There’s also the added benefit of alpaca being hypoallergenic. Its fibers are hollow, unlike sheep’s wool, which contains pockets of air. Alpaca is also supposed to be more moisture wicking than wool.
Acrylic yarn can be pretty warm, but it unfortunately doesn’t breathe very well. This can leave you sweaty if you get too warm underneath an afghan. Rearranging the blanket can help circulate air, so if you’re not expecting to get sweaty, this can be a more affordable choice than wool. Despite this, most of the blankets I’ve made are acrylic, because it’s affordable, machine washable, and it comes in a massive selection of colors.
Cotton is really lightweight, and breathable. It’s great for the summer, but not a great choice for winter unless you run warm. It can absorb moisture to keep you dry and cool, so this is a great choice for warm days. It’s probably not the best choice for a warm winter blanket. That being said, if you need a very thin blanket for the summer, this may be something to look into.
If none of these are available, you can pick a yarn that is “hairy” or has a little halo around it. This is found in angora or mohair, and is sometimes called the “bloom.” These fuzzy fibers can help trap air. This is why some very thin, openwork lace scarves or shawls made out of animal fibers can be extremely warm, despite their design.