Accumulating snow can create ice dams, block vents

• Image

John M. Steiner / The Sun A man cleans snow from a roof Monday in northeast Jamestown while another uses a snowblower to clear the white precipitation.
• Image

John M. Steiner / The Sun Ice dams form at the bottom edge of a roof when heat escapes from poorly insulated attics.

Talk about it

Accumulating snow on roofs in the Jamestown area can cause ice dams and other problems, local officials warn.

An ice dam forms when snow melts and runs down the surface of the roof, said Lance Brower, Stutsman County NDSU Extension agent. As the melted snow hits cooler parts of the roof, near the eaves, it refreezes. This process continues and eventually creates a dam of ice.

As more snow melts the dam stops the water, which freezes and makes the dam bigger or backs up the melted water and allowing it to leak under the shingles into the attic spaces or eaves. This can lead to water stains in the ceiling and structural damage and mold growth inside the home, Brower said.

Heat in the attic is the major cause of snowmelt on the roof forming ice dams — the greater the heat, the greater the snowmelt. That’s why having the proper insulation amount is a good way to prevent excess snow melt, he said.

Carl Pedersen, NDSU Extension energy educator, said attics in our region need to have roughly 18 inches of insulation.

“The ability of insulation to stop heat loss depends on the type and thickness, but attics in northern climates need roughly 18 inches of insulation to be properly insulated,” Pedersen said.

Improper ventilation is another cause of snowmelt on the roof. Allowing heat to leave the attic through vents is a good way to get heat out of the attic, Brower said. Residents should make sure the attic’s insulation does not block the air flow from the vents.

The easiest and most affordable way to prevent ice dams from forming is using a roof rake to remove the snow from the lower portion of the roof so melting snow can run off.

“However, removing snow from the roof can be dangerous, so avoid getting on the roof by using a roof rake,” Pedersen said. “You also need to take care to avoid overhead power lines.”

Jerry Bergquist, Stutsman County emergency manager, said he doesn’t want to see people on roofs with shovels and recommends a roof rake from a local hardware store.

“People need to use common sense when removing the snow from their roofs,” Bergquist said.

He also recommended that people work in pairs in case something does happen.

Bergquist also said that snow on the roof can lead to vents getting frozen over and the build up of toxic gases.

“Toxic vapors in sewer gas can be a serious hazard,” said Jim Reuther, fire chief.

Sewer gas consists of methane, which can cause asphyxiation. It normally escapes a home through vents on the roof. If those vents get blocked, the gasses are forced into homes through drains and toilets.

Rotten egg odors or drains not working properly and having a gurgling sound are signs that methane is building up, Reuther said.

He spent his Saturday clearing his own roof of snow and said there was six to eight inches of snow up on top.

The measurement at the North Dakota State Hospital boiler plant shows 13 inches of snow on the ground.

“It causes a lot of weight load on the roof that really shouldn’t be there,” Bergquist said.

Sun reporter Ben Rodgers can be reached at 701-952-8455 or by e-mail at brodgers@jamestownsun.com

Tags: local news, news, ice, snow