A man came to our door and said he could install a complete solar-panel heating system on our roof for $4,500. We signed a contract and gave him a $1,000 check as a down payment. The check was cashed immediately, but no one showed up to do the installation. We tried to call the man, but his phone is disconnected, and tried to visit his office, but found that the address is nonexistent. What can we do now?

Not much. You could sue the man, if you find him, in small claims court and win, but your chances of collecting the money are slim: He probably would be broke and could not pay you back.

It sounds as if you have become the latest victim of the growing number of “green” scams, in which fly-by-night contractors or salespeople line their pockets by targeting environmentally conscious homeowners.

A number of different green scams are going on, the Federal Trade Commission says. The one you apparently fell for is popular among con artists, who offer to make energy-saving improvements but never deliver.

Homeowners should ask for references before signing a contract, call the state’s licensing board to ensure that the contractor is legitimate and contact the local Better Business Bureau.

Another green ruse is based on energy-saving audits offered by many utility companies. One or two people claiming to be from a local utility may offer a free audit. They may want to case your home for a future burglary, or one might distract you while the other steals your jewelry and other valuables.

Protect yourself by demanding to see their identification cards and then calling the utility to verify their legitimacy before letting them inside your home.

Also be wary of official-looking computer e-mails from companies, local utilities or the Department of Energy that offer free services or rebates if you fill out a form or agree to take an online survey. Many such e-mails are generated by scamsters to steal your identity, while others are designed by hackers who want to infect your computer with a virus.

We live in a townhome development. One of the directors of our homeowners association recently resigned, and the remaining board members appointed a first-class jerk to take his place instead of calling for a vote by all homeowners. Was this action legal?

Probably, although you would need to check your HOA’s bylaws. The bylaws of most associations permit their boards to appoint a replacement to a seat that suddenly becomes vacant.

Reread your copy of the HOA’s bylaws. Complain to the board if your interpretation of the rules suggests that the directors acted improperly. If you are not satisfied, contact your state’s Department of Real Estate or similar regulatory agency for help.

We accepted an offer for our home two weeks ago, after three months of marketing it for sale. Now we have asked our real estate agent to take our “for sale” sign down because people are still asking to take a tour. The agent says we should leave the sign up. What do you think?

You should probably leave the sign up for at least two or three more weeks. A proposed sale can fall apart. Keeping the sign up could help you secure a second or third “backup” offer, which would come in handy if your buyer can’t get a mortgage.

It’s rude for potential buyers to hammer on a seller’s door instead of calling to make an appointment. Ask your agent to put a small “sale pending” or “do not disturb occupants” sign atop the larger for-sale sign.