Stay Warm on the Road: The Best Long Underwear of 2025 | I Heart RVing

When RVing in cooler weather, staying warm is key to enjoying the journey. The best long underwear (or long johns) can make a big difference in your comfort—whether you’re hiking mountain trails, walking your dog through the campground, or just enjoying a cozy campfire. These base layers are key to helping regulate body temperature by wicking away sweat while adding insulation to keep you warm.

For RVers, long johns offer a lightweight, packable solution for staying warm without adding bulky outer layers. They’re perfect for layering under hiking pants, lounging around the RV, or even sleeping on frosty nights. With all that in mind, let’s explore the best long underwear options for men based on warmth, breathability, comfort, durability, layering ability, and price.

What to Look for in Long Underwear

The fabric or material your long johns are made of greatly affects their performance. The most common options include Merino Wool, which is known for its exceptional warmth, moisture-wicking, and odor resistance. Merino wool is a favorite for cold-weather gear, especially when it comes to your base layer. Plus, it’s soft and breathable, making it ideal for extended wear.

Materials like polyester, nylon, and other synthetic blends are durable, moisture-wicking, and quick-drying. They’re often more affordable. However, they can also sometimes retain odors.

Another popular option is silk. Lightweight and smooth, silk offers decent warmth and is nice for layering. However, it’s less durable and doesn’t wick moisture as effectively as other materials. It can also be expensive.

While you can find long johns made of cotton, this isn’t the best option, especially in cold conditions. Yes, it adds a layer of insulation, but unfortunately, it also absorbs and retains moisture, which can leave you feeling cold, damp, and uncomfortable.

When shopping for long underwear, you’ll want to be aware of the key features, including:

• Warmth: Look for a high warmth-to-weight ratio for cold-weather activities.
• Breathability: Essential for avoiding sweat buildup during active pursuits.
• Comfort: Soft, non-itchy materials with flat seams and a good fit enhance comfort.
• Durability: High-quality fabrics and construction can withstand the wear and tear of RVing adventures.
• Layering Ability: Look for slim fits that work well under other clothing.
• Price: Consider your budget—there are great options at every price point.

The Best Long Johns for Men

In any outdoor store, you can find a range of long underwear types and brands. Here are some of the top choices:

Best for Warmth and Comfort: Smartwool Classic Thermal Merino Base Base Layer

Material: 100% Merino Wool

Features: Soft, breathable, and naturally odor-resistant, this midweight base layer is perfect for cold-weather activities. Flatlock seams and a great fit enhance comfort.

Price: $115

Why It’s Great for RVers: This base layer is perfect for RVers who enjoy both active outdoor adventures and quiet evenings at the campground. The odor resistance means you can wear it multiple days without washing, making it ideal for extended trips with limited laundry facilities. Its midweight construction offers versatility in layering, so you’re prepared for fluctuating temperatures.

Best for Layering: Patagonia Capilene Thermal Weight

Material: Recycled polyester with HeiQ Fresh odor control

Features: Lightweight yet warm, it wicks moisture quickly and layers well under any outerwear.

Price: $99

Why It’s Great for RVers: Patagonia’s commitment to sustainability and durability makes this a favorite for eco-conscious RVers. The lightweight fabric takes up minimal storage space, while the moisture-wicking properties keep you dry during active pursuits like hiking or biking. Its layering ability makes it adaptable to a range of weather conditions.

Best Budget Option: Uniqlo HeatTech

Material: Synthetic blend with a brushed interior for extra warmth

Features: Affordable, lightweight, and available in a variety of styles.

Price: $29.90

Why It’s Great for RVers: For RVers who want functional base layers without going over budget, Uniqlo HeatTech provides surprising warmth for its price. Its lightweight design makes it easy to pack several pairs, ensuring you’re covered for various temperatures. It’s best for casual wear around the RV or for layering under everyday clothes.

Best for Odor Control: Icebreaker Merino 200 Oasis

Material: 100% Merino Wool

Features: Lightweight and breathable with superior odor resistance. Perfect for multi-day wear.

Price: $105

Why It’s Great for RVers: Icebreaker is a fantastic choice for RVers on long trips with limited laundry stops. The odor resistance allows you to wear it multiple days in a row without worry, while the lightweight fabric ensures you stay comfortable whether you’re hiking, driving, or relaxing.

Best for Durability: Carhartt Force Midweight Base Layer

Material: Polyester with FastDry technology

Features: Tough, moisture-wicking, and odor-fighting, designed for heavy use.

Price: $35

Why It’s Great for RVers: If your RV adventures involve rugged activities like chopping firewood or working outdoors, Carhartt’s durable base layer is built to last. The moisture-wicking technology ensures you stay dry even during high-effort tasks, while its toughness can handle wear and tear from rugged outdoor activities.

Best Value for Performance: REI Co-op Midweight Base Layer

Material: Polyester and spandex blend

Features: Warm, stretchy, and moisture-wicking with a snug fit for easy layering.

Price: $55

Why It’s Great for RVers: REI’s midweight base layer offers a balance of performance and affordability, making it an excellent choice for RVers who need versatile, durable gear. The stretchy fit ensures comfort during long drives or active outings, and the brand’s reputation for quality means these will last for many trips.

Best Hybrid Option: Helly Hansen Lifa Merino

Material: Merino Wool exterior with synthetic Lifa interior

Features: Combines the warmth of wool with the moisture-wicking capabilities of synthetic fabrics.

Price: $100

Why It’s Great for RVers: This hybrid base layer provides RVers with the best of both worlds: the warmth and comfort of merino wool and the fast-drying capabilities of synthetic materials. It’s a great option for those who split their time between active and leisurely activities.

Caring for Your Long Underwear

To get the most out of your long underwear and ensure they last through many RV adventures, it’s important to care for them properly. Start by reading the manufacturer’s care instructions on the label.

Some materials, like merino wool, require gentle handling. Always use a gentle cycle with cold water and a mild detergent. And avoid fabric softeners, which can coat fibers and reduce performance.

Odor-resistant materials like merino wool can go multiple wears between washes. This reduces wear and tear. While it may seem counterintuitive, it’s best to wash less. When you do wash, remember to avoid using a dryer and instead lay flat or hang on a drying rack to air dry. It’s especially important to avoid high heat, which can shrink or damage delicate fabrics.

Finally, you’ll want to store your long underwear properly. Fold or roll your long underwear neatly and store them in a dry, ventilated space to prevent odors or mildew.

By choosing the right pair and taking proper care of them, you’ll stay warm, dry, and comfortable on every RV adventure—no matter how cold it gets.

Source: https://iheartrving.com/blog/stay-warm-on-the-road-the-best-long-underwear-of-2025/