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3 Ways to Boost Radiator Performance

These cast-iron relics from the early days of central heating are still remarkably good at keeping a house warm and cozy. If radiators are part of your home, TOH’s Richard Trethewey explains how you can improve their operating efficiency

Shown: TOH plumbing and heating expert Richard Trethewey replaces the old valve on a hot-water radiator with an orange-capped thermostatic valve that allows homeowners to fine-tune the heat output of an individual radiator.

  1. Add an outdoor reset control. This device signals the boiler to gradually heat up or cool down, based on changes in temperature outdoors. That can save about 15 percent on fuel and eliminate the big swings typical of thermostat-controlled systems. “Installing an outdoor reset is the single best thing you can do to improve radiator efficiency and overall comfort in the heating season,” Richard says. You’ll need an HVAC pro to wire the control to the boiler, connect an outside temperature sensor, and set minimum and maximum boiler water temps based on how cold it gets in your area.
    Install thermostatic radiator valves (TRVs). These devices limit the amount of steam or hot water that comes into a radiator, turning it into its own zone. Richard says, “Equipping individual radiators with these valves can reduce energy use by about 5 percent and eliminate the discomfort of overheated rooms.” Most any DIYer should be able to install a TRV for a steam radiator: Just unscrew the old vent attached to the radiator fin and screw the TRV into the same threaded hole. Adding a TRV to a hot-water radiator requires special tools and fittings; this is a job for an experienced plumber.
    Get an air eliminator. Every time water is added to a hot-water system, it introduces microscopic air bubbles that will eventually form big bubbles inside the tops of radiator fins, limiting their heat output. Regularly bleeding the air out of a radiator restores its full function for a while, but that chore becomes a thing of the past with a pro-installed air separator, like the one made by Spirovent (starting at $93; Just one of these, fitted near the boiler downstream from the radiators, expels microbubbles from the entire system before they have a chance to collect in your radiators.