"Heating and cooling services are one of the fastest-growing areas today," he said. "Many baby boomers have incredible accumulated wealth and they're looking for convenience and comfort. But we don't have the people we need to provide the service."

And that's because the industry isn't attracting young people to the skilled trades. There was a time when vocational and technical schools were the "dumping grounds" of North America, he said; kids wanted high-profile, big money jobs like those in computer programming.

"We lost a generation of people moving into this industry," he explained. "We need to sell the industry to these kids. People don't decide on their career when they are very young; they only know what they don't want to do."

For example, he cited an exhibit currently at the National Building Museum in Washington, D.C. -- "Celebration of the Building Arts," -- where families can give kids a hands-on experience with construction.

Lack of skilled labor will result in a change to the industry, Trethewey noted. He sees using a manifold approach to everything, a more plug-and-work approach to accommodate the skill levels of future plumbing and heating contractors.

He also sees service trucks equipped with Web cams so employees out on the job who run into problems can get direction from a seasoned pro back at the office.

Can The Past Influence The Future?

"Back then, the plumber was a magician because he was going to bring water into the house," he said.

And plumbing and heating contractors had to pipe and size everything correctly. Today, it's too easy to over-size and over-complicate things, Trethewey said.

"What made us so stupid?" he asked. "Electricity! Look how much has changed over the last 100 years; what will the industry look like in the next 100 years?"

One of the trends he sees in the future is the use of emerging technologies for water conservation and emissions control.

"Water conservation is the next offering in the skilled trades," he said. "With the lack of drinkable water and the cost of using water today, we need to provide our customers with this service."

Even "This Old House" has profiled a house with rainwater collection, he said. In Europe, there are several alternative methods used to conserve water and he sees that happening in North America over time.

He believes that hydronics will gain in popularity; again, he cites the European influence, as well as fuel economy.

"As fuel prices continue to rise in North America, the fuel-efficiency benefits of hydronic heat will become apparent to consumers," he said.

The bottom line is that with the dwindling resources of the planet, it is important that we keep looking for new materials to build our communities, such as engineered lumber or foam or plastic, and conserve what we have left.

Trethewey also talked about his years on "This Old House" with old host Bob Vila and current host Steve Thomas. Audience members were treated with outtakes from his new show, "Ask This Old House."