Now that the temperatures have finally climbed back to more normal levels and summer is on the way, a question among some people is if it also means the return of out-of-state firms coming into the area to make sales pitches for "radiant barrier" insulation.

The item came up for discussion last year at a meeting of a local group of residents as some people in that group were invited to a free lunch at a local restaurant and an opportunity to learn about the so-called savings from the barrier, which is something like a shiny aluminum foil that causes radiant heat to bounce off. The events were never published in any local newspapers, perhaps so as not to draw scrutiny; instead direct mail invitations went out, usually to elderly people.

Our group consists of a retired physics teacher, a contractor and other knowledgeable people that questioned the benefits of this. Although we concluded there were none, our suspicions have been confirmed recently.

Last month, the Minnesota Department of Commerce's Division of Energy Resources issued an alert to consumers who are considering the purchase of radiant barriers in their attics. The alert warns that the barriers are not cost-effective ways to reduce heating or cooling loads in Minnesota.

Radiant barriers consist of reflective film, usually aluminum, laid over the top of attic insulation in existing homes. They cause radiant heat to reflect back, thus reducing the heat reaching a house.

Although they may help in homes with no or little insulation in Minnesota, their main benefit is in warm climates, such as Miami, Fla., or Houston, Texas, where the barriers could reduce utility bills by as much as $150 per year.

However, in cooler climates, such as Minnesota, which doesn't need as much air conditioning, the savings drops to $10 to $40 per year. If there are no ducts or air handlers in the attics, the savings are much less.

So, that means an investment of $2,000 or so for a radiant barrier would take 100 years to pay back if the savings is $20 per year.

The U.S. Department of Energy agrees with the Minnesota Department of Commerce that implementing air sealing and adding conventional attic insulation would be considerably cheaper and more effective for saving energy than installing a radiant barrier.

The issue was also covered recently in the Star Tribune newspaper's whistleblower column by Jane Friedmann. She contacted utility companies, which were unimpressed with the value of the products for cold-climate customers.

If you think about it, that makes sense just on the basis of radiant barriers not being eligible for rebates. Utility companies really want to reduce energy use and only list products that they feel will make a substantial reduction in demand for energy.

Whistleblower's findings with the Better Business Bureau were mixed. That's because the products do have some value in southern states and also because the BBB gauges how companies respond to complaints, not necessarily the validity of claims.

Local people that attended the sessions said the presenter was pleasant and not pushy. However, one person that followed up on the pitch said the company representatives that came to her home offered her a deal and kept emphasizing that it was for a limited time only because their crew is so busy that it would be moving to another area shortly.

The push to get people to make up their mind in a rush about spending substantial money on a product should always arouse suspicion.

The local homeowner also had trouble finding information about the company. Although there was much documentation, supposedly using scientific principles, to sell the energy savings for their radiant barriers, there was little information about the ownership or even location of the company's headquarters, another red flag for consumers.

You don't need to be an expert in physics or construction to understand if something like this doesn't seem right. There are clues - and it is always wise to seek the advice of people in the know. A good place to start is to have a home energy assessment through your utility company, which will recommend cost-effective energy improvements.

Those jumping into a project based on the presentation during the meal will find that their free lunch turned out to be quite expensive in the end.