With the cold sting of winter on its way, many homeowners are starting to think about their furnace.

To save money and ensure that their homes are comfortable, they will want their furnace to run as efficiently as possible.

Jerry Kennihan, service manager at Kennihan Plumbing, Heating & Air Conditioning in Middlesex Township, said most of the time, when there are efficiency issues, the furnace works fine but the rest of the system needs to be improved.

“The furnace is capable of doing the job. The house isn’t letting it do the job,” Kennihan said.

Ken McDonald, owner of Kenneth McDonald Plumbing Heating and Air Conditioning in Connoquenessing Township, said that a variety of items could cause these issues.

“They vary so much,” McDonald said.

Kennihan said the entire system needs to be considered.

“How do we make what you have work the most efficiently?” Kennihan asked.

He said most systems only retain 57 percent of the hot air they make.

“The rest of it leaks out,” Kennihan said.

One common cause of leaks are recessed can lights. Because of the heat these lights generate, they are not allowed to touch insulation, leaving open spaces.

To solve this, Kennihan said homeowners can buy covers.

He said doing this can cut a heating bill by 25 percent.

Another issue are rooms that do not have return air ducts. In many houses, there is only one return air duct. Without these, air does not have anywhere to go.

If return ducts are installed in every room, furnaces will not have to run as much. Kennihan said many customers are surprised how well their heating systems work when such ducts are installed.

Sometimes, he said, the furnace may not have been installed correctly in the first place. In these cases, the most common issues are duct work or filter assemblies that are too restrictive.

He recommends a media filter, which cleans more air and allows the furnace to breathe more easily.

“You just have to tweak what you have,” Kennihan said.

Holes in duct work also are common problems. McDonald said that holes can be sealed easily, often by the homeowner.

He said that chimney flues should be free and clear of debris.

He also recommends changing the filter as needed. If a system has both heating and air conditioning, he recommends changing the filter twice a year. This will keep the air clean.

“The blower doesn’t struggle as much to keep up,” McDonald said.

As a safety measure, McDonald recommends people owning gas or oil heating systems have a carbon monoxide detector.

“That’s probably the biggest thing,” McDonald said.