A fuzzy film is appearing on the outside of these concrete planters. There is also a stain on the brick below the planters. (Reader photo)

Q: The concrete planters in the arcade of our 80-unit condo building were piped for irrigation last spring. A fuzzy film is appearing on the outside, seemingly the result of water pushing some elements of the concrete to the outside. There is also a stain on the brick below the planters that was actually black at one time. We removed the dirt from one planter and discovered three small drain holes about half an inch in diameter in the bottom, and we assume that all the planters have that same drainage. I am landscape chair of the condo association and have been given this problem to solve. What would you suggest?

Falls Church

A: The fuzzy film and stains are efflorescence, caused by water-soluble salts that the irrigation water picked up from the soil or concrete. As the water evaporated, the salt crystallized on the outside of the planters.

Although it’s possible to remove efflorescence through scrubbing and the use of masonry cleaners, it will keep forming as long as salty water is moving through the masonry. To keep that from happening, it might be enough to simply switch to water-thrifty plants and cut back on irrigation, especially if the efflorescence didn’t start until the irrigation system was installed. Salts in fertilizer can exacerbate efflorescence, so consider reducing that as well.

If that isn’t enough, investigate where the water that drains from the planters winds up. Are the drain holes simply resting on the cap of the brick wall underneath, preventing the water from draining readily and causing it to seep into the brick wall? From the picture you sent, it appears this could be the case. The lower part of the planters looks moist, there is no significant air gap under the planters, and there is a lot of efflorescence on the brick. Given all of this, if you find that there is no good way for water to drain from the planters, you might want to set potted plants in the planters, rather than fill them with soil. Set the pots on trays so that any water that drains can evaporate without having to pass through the concrete. If the pots aren’t as deep as the planters, set the pots on spacers. The added air gap will also help to keep the concrete dry.

If there is a way for water to drain and you want to keep soil and irrigated plants in the planters, consider painting the inside surfaces (after cleaning them thoroughly) with a waterproofing paint or coating. A waterproof liner would probably be even more durable. You might try using adhesive-backed, rubberized material sold as roof underlayment. Grace Ice & Water Shield is labeled as suitable for sticking to concrete and costs $138 for a roll 36 inches wide by 75 feet long at Home Depot. Cut the liner where needed so it doesn’t block the drain holes.

Q: In the 1990s, I had the windows in my 1950s house replaced with ones that are double-pane vinyl. Mold is growing between the panes in one window. I was told this was due to gas leaking. These were supposed to be lifetime windows, but the company I bought them from went out of business. I contacted a current window replacement company, and all it seems to want to do is sell us new windows. New windows are not in the budget. Is there a company that can repair just one window, without charging an arm and a leg?

Herndon

A: Yes, there are many businesses set up to replace the glass units in vinyl replacement windows. You just need to go to a glass company, not a company that specializes in replacing entire windows.

Reston Glass (703-860-2089; restonglass.com), for example, replaces “thousands and thousands” of double-pane glass units each year, said the general manager, Jacob Curtis. He estimated that it’s about half of the company’s business.

The problem isn’t gas leaking out of the windows but condensation that occurs because the seal around the edging that separates the glass pieces is never perfect. Moist, warm air inevitably infiltrates the space, and this moisture condenses as the air cools. Manufacturers add desiccant to the spacer to deal with this, but it eventually gets used up. Then the window clouds up. They are still energy-efficient, just not attractive.

Reston Glass, like many glass shops, makes service calls and will go to a house to measure and install replacement units. But it’s a two-trip process because it usually takes seven to 10 days to have the units fabricated. The price to replace a single unit typically runs $250 to $300, Curtis said, although the exact amount depends on the window size and whether you want coated glass to boost energy savings. If five or more windows need work, the price drops by 10 to 20 percent because the cost of travel time, which is worked into the price, is spread out over more windows.

You can get the price down to about $150 a window if you don’t need the company to go to your house. Curtis said many customers remove the glass unit themselves, take it to his shop to measure, then go home and reinstall it while the new unit is being made. When the new unit arrives, they return and pick it up.

Either way, the company offers a 10-year warranty against the windows fogging up. As you’ve learned, product warranties aren’t worth anything if a company doesn’t stay in business, so checking on a company’s history is always a good idea. Reston Glass advertises that it’s been serving Northern Virginia for more than 30 years.