How Do Insulated Lunch Bags Work?

Unlike the good old plastic or brown lunch bag, insulated lunch bags can keep your food warm or cold for much longer and prevent it from going stale. Insulated lunch bags are even better than classic lunch boxes at retaining heat and preserving freshness due to their embedded insulation. But how do they work? The short answer is layers.

How Do Insulated Lunch Bags Work?

Most insulated lunch bags come with multilayered insulation. They usually have an outer layer, a lining, and a middle layer which offers the insulation. The most important is the middle layer as without it, a lunch bag wouldn’t be any better than your average lunch box.

While thermoses and insulated lunch boxes rely on a vacuum created between the outer layer and the inner layer to prevent energy dissipation, insulated lunch bags keep food and drinks warm or cold thanks to a core layer made of dense foam. The thicker and denser the foam, the better the insulation.

The foam layer prevents heat from seeping to the outer layer and keeps the surrounding cold or heat from reaching the bag’s contents. You might notice that insulated lunch bags’ exterior doesn’t heat up when filled with heated items as the heat is prevented from dissipating in the surroundings. (Most lunch bag’s outer layer is usually made of non-woven fabric, vinyl, or heavy fabric.)

As an extra layer of protection, many insulated lunch bags come with an inner layer or a lining made of foil, heavy vinyl, or plastic that is waterproof and heat reflective.

Being heat reflective means that the bag’s foil-like inner layer reflects the food’s radiated thermal energy back, rather than absorbing it and allowing it to escape the bag. As a result, the food inside retains its original temperature, flavor, and moisture for longer than it would do in a regular bag.

This means that an insulated lunch bag will also prevent food from going stale just like tin foil does but to a much larger extent.

This is why insulated lunch bags are a must-have for people who love to pack their own lunch while on the go, for kids taking homemade lunch to school, and anyone on the go who would rather consume a hearty homecooked meal than playing Russian roulette with their health when ordering takeout or fast food.

How Long Can an Insulated Lunch Bag Keep My Food Warm/ Cold?

There’s no easy answer to this question. The time food can be stored in an insulated lunch bag varies depending on several factors:

● Type of bag

● Whether or not there is a heated or frozen gel pack in the insulated bag

● Temperature outside.

As a rule of thumb, without added gel packs, food in an insulated lunch bag should be still warm after two to three hours if it’s hot, and four to five hours if it’s cold. A heated or a frozen gel pack can buy you three to four extra hours.

But these numbers largely depend on the quality of the bag and surrounding temperatures. So, it is best to test your insulated bag at home before taking it out for lunch.

Beefing Up Insulated Lunch Bags’ Performance

Here are a handful of tips if you want to keep your food warm or cold for longer in an insulated lunch bag:

- Place a cold or warm source in the bag, such as a heated gel pack/ water bottle if the food is warm or a frozen gel pack/ water bottle/ juice box if the food needs to stay chilled.

Reheat the food just before packing or pack the chilled food directly from the fridge or freezer into the lunch bag.

- Wrap the food in aluminum foil for an extra layer of insulation; afterwards, you can wrap a tea towel around the food to further prevent heat from dissipating.

Don’t open the lunch bag before you need to actually consume the food to prevent thermal energy from escaping the bag.

- Place the lunch bag in places with air conditioning (your car trunk on a hot summer day is not an ideal location for a lunch bag if you want to keep its contents chilled)

- Use the right sized lunch bag for your needs; a partially filled insulated container is less effective than a jam-packed one.

Keep hot items and chilled items separated, even if some items are inside the bag while others are outside.

Check Out Tote Bag Factory’s Best-Selling Lunch Bags

Tote Bag Factory prides itself on having some of the best insulated lunch bags out there at the most competitive prices. Regardless of whether you need a lunch bag for your kid, yourself, or for a giveaway, we’ve got you covered. Here’s our top-selling items in the category.

Promotional Polyester 6-Can Cooler Lunch Bag

This sturdy square lunch bag has been a best-seller ever since its introduction, and for a good reason. It is sturdy, stylish, and roomy enough to fit 6 drink cans. It also comes with a handy side pocket and can be easily folded up and tossed in a handbag or backpack when empty.

Deluxe Polyester 6-Pack Cooler Lunch Bag

Here’s another heavy duty insulated lunch bag that can easily accommodate six beverage cans or your lunch. The Deluxe Polyester Cooler Lunch Bag is made of durable but low maintenance 600D poly and a heavy vinyl lining. The adjustable web strap allows you to throw this bag over your shoulder for enhanced portability.

Promo Wholesale Lunch Cooler Bag

The wholesale price of this quality insulated lunch bag makes it a great prop for promotional events and giveaways. This promo bag is made of heavy duty 600D polyester outer layer and a reflective inner layer to ensure peak performance and durability. It also has a zippered front pocket, black web handle, and a generous imprint area. There are five colors to choose from.

Economical Lunch Bag Cooler

This large insulated lunch bag (6" W x 12" H x 5"D) is one of the best options for multiple users or for storing and keeping multiple items fresh while on the go. It comes with a hook and loop closing system, a large imprint area, and a poly-web handle. The thick 420D nylon is easy to spot clean, durable, and water resistant. Learn about the difference between water resistance and waterproofness here.

Insulated Polyester Cooler Bag 
(with Side Pockets)

Here’s a sturdy insulated lunch bag that is best for picnics, hiking trips, and other short outings. This bag’s outer and inner layer are made of heavy duty 600D polyester and heavy vinyl material respectively. It comes with two zippered side pockets and a front pocket for extra storage.

The top zippered closing system makes this bag more effective at retaining heat or keeping things cold inside even if you have to open it multiple times before lunch break. Its design also makes a great cooler bag for cold drinks.

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