If you have many possessions—but precious little room to store them at home—chances are you’ve considered renting a storage unit.

However, in some cases, those items could be at risk if you fail to rent a climate-controlled unit. Climate control keeps temperature and humidity levels constant.

“Temperature and humidity control can prevent damage when items are stored for a lengthy period of time,” said Tim Dietz, a spokesman for the Self Storage Association.

Climate control in the self-storage industry can be defined in various ways, said Diane Piegza, vice president of corporate communications at Sovran Self Storage Inc., a REIT that operates the Uncle Bob’s Self Storage chain.

“It’s everything from temperature control to humidity control,” she said. “In some cases, it’s the best of both worlds.”

Piegza said climate control has become more common in self-storage in recent years. She estimates three-fourths of newly built facilities now offer this feature.

Watch the video to learn more about when you need to use climate-control, and other amenities to look for when you book a self-storage facility:

The Advantages of Climate Control

The climate can wreak havoc on stored items in many regions of the U.S. In parts of the South and West, daytime temperatures regularly reach scorching highs during the summer.

“Clearly, that kind of heat is just not good for a lot of items,” Piegza said.

By contrast, customers in Northern states may own items that are vulnerable to temperatures that regularly fall below freezing in the winter.

Temperature extremes can be tough on everything from wood and leather to pictures and videotapes. Some items may crack or warp. Others may yellow, while documents may become unreadable over time.

Other items that may be susceptible to damage without climate control include:

  • Bedding and mattresses.
  • Sports equipment.
  • Metal appliances.
  • Books and other paperwork.

Climate-controlled storage reduces these risks by using heating and cooling units to keep the storage space at a safe temperature, usually at a level above freezing and below 90 degrees, Dietz said.

Humidity: The 55 Percent Mark

Units that also offer humidity control keep humidity levels around 55 percent, Dietz said. Humidity is particularly dangerous to a variety of items, said Tom Maxfield, national operations director at Move It Storage Management in Dallas.

“High humidity can cause photos to stick together, or wood furniture to warp, or leather goods to crack,” he said.

Electronics, artwork and items such as pianos also may sustain damage from too much moisture in the air, Piegza said.

If you own an item that’s especially sensitive to humidity, search for a storage unit that actively dehumidifies the air. Units that simply cool the air with air conditioning may not bring moisture levels low enough to protect all items, Piegza said.

“The true sweet spot for items that are truly sensitive to high humidity levels is around 55 percent,” Piegza said.

The cost of renting self-storage with climate control varies widely—anywhere from 20 percent to 50 percent higher than traditional storage. “It’s all based on supply and demand,” Piegza said.

Maxfield said the extra cost of climate control—often referred to as the “climate control premium”—typically adds up to 35 percent to 50 percent. A standard 10×10 storage unit with climate control might cost $140 a month to rent, he said, while a unit without climate control could cost $90.

Do You Really Need Climate Control?

Not everyone needs climate control, Piegza said. “I don’t want to totally discount traditional storage,” she said. “In many cases, that will suffice for people.”

People who plan to store items for short periods of time probably can stick with traditional self-storage, Piegza said.

“Climate control does rent for a premium,” she said. “Clearly, the benefits outweigh the cost factor. But don’t believe climate control is the answer to everything.”

Still, anyone storing expensive or irreplaceable items—especially if they hold sentimental or historical value—should consider climate control, Maxfield said.

“The monthly rental rate is not significant for these customers,” he said. “A secure, clean, dry and temperature-controlled environment is essential.”