The colder it gets outside, the cozier we want to be inside. That’s especially true when it’s time to curl up for bed. One of the most important things to getting a rejuvenating night’s sleep is being comfortable. And when it comes to staying comfy and cozy all night, pajamas play a big role. But PJ’s are for more than just quality sleep. We often spend a good deal of time lounging around in them. Here is an UpWest guide to selecting the most comfortable PJ’s for you.

Maintaining Temperature

According to Lindy Deal, UpWest’s Curator of Comfort, there are two categories of pajamas: Warm-Handed to keep you warm in the winter and Cool-Handed to keep you cool during those dog days of summer. Warm-Handed include flannel, fleece, sherpa, and wool, while Cool-Handed fabrics include cotton, rayon, and linen.

Turns out, the body absorbs and loses heat by what science gurus call infrared radiation. Actually, about 40% of heat transfer happens this way at room temperature, according to New Scientist.

Pajama fabrics trap a varying amount of this infrared radiation. The more Warm-Handed, thicker and textured a fabric is, the more infrared radiation is trapped within the fibers and the warmer you’ll be. The more Cool-Handed a fabric is, the more breathable and easier to release the infrared radiation. Cool, huh?

Unrestricted Movement

Relaxation expert (yes, that’s a thing), Dr. Sophie R. Kaufman, who’s an Adjunct Associate Professor at Pace University’s College of Health Professions, says loose-fitting, natural fabrics, that feel soft on the skin and don’t constrict movement are the best pajamas for restful sleep regardless of the season.

The right fit will help you fall asleep quicker, sleep longer, but also have deeper, better quality sleep. And as Kaufman points out, more restful sleep can make you more effective in inserting that appropriate pause between a stressor and your reaction to that stress, and better at practicing mindfulness.

Minimizing Sensitivities

Kaufman teaches a Mindfulness-Based Stress Reduction course at Pace. She says dressing in layers is key to comfort, especially at bedtime. “Body temperature varies at different times, even during [a short period of time],” Kaufman explains. “I am partial to natural fabrics and softness. As we explore body sensations in mindfulness practice, I find an increased sensitivity to the sensation of various fabrics on the skin.” Softness is key to minimizing sensitivities.

Deal says the UpWest team tests pajama fabrics for levels of softness and sensitivities, as well as physical and emotional responses to each. “We put everything through the Comfort Test,” she adds. “We make sure everything UpWest feels like a hug to your body, mind and spirit.”

Functional Fashion

Layering is the perfect way to blend fashion and function. While the latest “excessive layering” runway trends might be a bit much, we can dig the idea of winterizing your summer loungewear with layering or doubling up the knits for extra warmth.

Layers can add fun textures and colors to a look, but it’s also easy to peel away a layer to keep you the ideal temp. Deal says that’s easy with UpWest’s Cozy Up Waffle Henley Tee, Fireside Flannel separates, sherpa robe and even a faux fur sleep mask. “My favorite is the Fireside Flannel PJ Set,” Deal adds. “It’s brushed, washed, peached and glorious. Seriously, the softest flannel you’ve ever felt.”

Don't Forget the Feet

Researchers say feet play an important role in regulating body temperature, especially when sleeping. Feet have specialized blood vessels and nerves that connect to the thermostat in our brain, so our body temps can be accurately controlled through the temperature of our feet. No wonder they creep out of the covers while we're sleeping!

For a leg up on comfort while sleeping, don’t forget about winter-ready socks and slippers. Deal suggests the UpWest Cable Knit Snuggle Socks, Sherpa Booties, Fireside Slippers, or the Leg Warmers with an open heel and toe for added breathability and function. Deal also says THE Legging has a rad cinch design that takes it from a cropped pant to a long pant covering the foot, like a built-in sock. “I know if my feet are comfortable, the rest of my body is too,” Deal laughs. “And that’s what UpWest is all about — comfort head to toe — literally, in this case.”