Is your unit sweltering, even on the coldest days? We can help.

If you live in a particular type of building, you can be forgiven for keeping your windows cracked, even during the Polar Vortex. In older units, with equally ancient steam heating systems, regulating your apartment temperature can feel nearly impossible.

Blame central heating, and that hulking (probably ancient) boiler in the basement. Here's how it works: the heater burns fuel to heat water, which then turns to vapor and rises up through all of the building's radiators. The heat of the steam pushes cold air out of pipes and individual radiators through air valves (the little metal thing that sticks out of one side).

Single valve heating system.

Once an air valve reaches a certain temperature, it closes with a clicking noise, allowing the radiator to cool off. When the steam valve cools, it opens up again to let out more cool air. This in turn draws the hot steam up. The left-over water droplets sink to the bottom of the radiator and drip down the pipes back to the boiler in the basement, where the water is reheated.

Interestingly enough, the system was designed to force you to open your windows.

"The Spanish influenza epidemic, which took place during the winter of 1918–19, had a dramatic effect on the way heating engineers sized radiators," explains Dan Holohan, author of several books on steam heat and founder of "Central heating was relatively new then and the world had never seen anything as horrible as the Spanish flu, which caused an estimated 50 million deaths. Because the flu was airborne, the Board of Health started a campaign the following year that urged (more like demanded) people to keep their windows open so fresh air could enter the rooms."

In fact, engineering manuals from the 1920s dictated that radiators and boilers be manufactured large enough for "the coldest day of the year, with the wind blowing, and the windows open."

Fast-forward to the 1970s, when many apartment buildings began installing double-pane windows, further exacerbating the overheating problem. By then, the aging systems themselves—when not properly maintained—had already collected 50 years worth of mud and gunk in the pipes, meaning heat distributes unevenly in the building. Many landlords "fix" this problem by turning the heat up even more, so that the cold apartments were a comfortable temperature and the hot apartments unbearable.

This is the situation we’re dealing with today: a perfect storm of over-sized radiators, double-pane windows, and landlords that refuse to spend the time or money to clean out the pipes.

Never fear though. Here are some DIY tips to regulate your apartment's heat.

Cover Your Radiator

My covered radiator.

A radiator radiates heat (obviously), so if you cover it, it’ll radiate less. Depending on your situation, a cover can be as thin as a sheet or as thick as a blanket or two. Holohan says that back in the day, there were special "radiator cozies" that tied at the top, so you could regulate how much of the radiator was showing and therefore how much heat it gave off. Covering your radiator is completely safe. "Radiators only get as hot as about 215 degrees," Holohan says, "which isn't nearly hot enough to start a fire." However, be careful not to use certain synthetic fabrics (like fleece or polyester), which might melt. I’d recommend sticking with cotton or wool.

Close the Air Vent

My closed air vent.

If cool air can’t get out of the radiator, there’s no room for hot steam to come in. As the steam turns into water and cool air, and the water flows back down the pipe, all you’re left with inside the radiator is cool(er) air, which effectively turns off your radiator.

To close the air vent, I usually use a piece of tape or a sticker to cover the hole on the top. I've found that first-aid waterproof tape works best. But before you run to your radiator, a warning: Don't burn yourself! The air vent gets pretty hot, so use an oven mitt. How do you know if you’ve successfully blocked the air valve? Open valves hiss when letting out air, so if the hissing is gone, you're golden!

Preparing for Next Winter

Once spring comes and the central boiler gets turned off, there are a number of things you can do to help alleviate your apartment's temperature problems next year.

  • Twist off your air vent and boil it in vinegar to clear out any residue inside.
  • Get a thermostatic radiator valve to better control temperature (single-pipe systems only). TRVs cost about $30.
  • Holohan recommends looking into Radiator Labs's new invention, a radiator cover/temperature regulation system that you can control remotely via smartphone app.

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