Hydronic Baseboard

Hydronic Baseboard

Hydronic Baseboard Radiator.
Hydronic Baseboard Radiator. Photo courtesy of Slant/Fin Corp

Hydronic means hot water.  These traditional fin style baseboard units are very common and very effective.  They use high-temperature water (160-180ºF) from a boiler (also called a hydronic furnace) that is fueled by oil, gas, or wood pellets  (or, less commonly, cordwood boilers.)

Keep in mind that many electric baseboard units can look pretty similar to hot water (hydronic) baseboard.  If you don’t have a boiler in your basement or utility room, you’ve probably got electric baseboard.

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Panel radiators that work with high or low water temperature. Image courtesy of Myson

Air to water heat pumps and geothermal heat pumps achieve energy savings by working with low water temperatures (120ºF+/-) hydronic baseboard. Low-temperature hot water systems require more surface area to emit an equivalent amount of heat.  Some companies market larger panels and columns that work with either high or low temperature water.  See also panel radiators and fan convectors.

Heat Loss

The two variables of of heat loss are a) geographic location, and b) building performance. Together they will determine the quantity of heat needed to maintain comfort.

Geographic location drives the building's “design day." Your design day is the difference in temperature between the inside and outside of your house on the theoretical coldest day of the year; so in the northeast we calculate a day that is -10ºf outside and comfortable 68ºf inside. This is referred to as the “delta-T” value. A typical delta-T for the northeast is 78º.

Building performance is the big one because there’s nothing we can do about geographic location. Today we can build a really tight thermal envelope, but most of our heating pollution comes from the millions of homes built over the last 100-150 years. We are getting better at buttoning-up those old buildings with insulation and weather sealing but weatherization is still  never going to be enough to overcome the heat loss from a 78º delta-T. That means we need heating systems that can quickly put a whole lot of heat back into those old houses on the days that are really cold.