In the closing days of 2020, the federal government approved one of the largest renewable energy spending bills in over a decade. 

When designing hydronic circuits, most of us focus on what’s necessary for that circuit to absorb thermal energy at a heat source, carry it along like a conveyor belt and release that energy at one or more heat emitters. 

I don’t know about you, but after more than 40 years of working in the HVAC industry I find myself a bit overwhelmed trying to keep up with standards, codes and other well-intentioned regulations, issued by “authorities having jurisdiction,” or sometimes by “authorities” not having jurisdiction, but looking to cash in by grabbing the steering wheel on some of the latest trends in HVAC technology.

I’m sure everyone reading this column has heard the adage “a picture is worth a thousand words.”  

The classic way of estimating heating load in smaller, envelope-dominated buildings is to assume the rate of heat loss is proportional to the difference between the inside and outside temperature.

In last month’s column, I presented a “template” for a system that provides space heating, cooling and domestic water heating using a cold climate air-to-water heat pump as the primary heat source, and the sole source of chilled water for cooling. 

For decades, fossil-fueled boilers have dominated the market for hydronic heat sources.

Most hydronic heating systems that have renewable energy heat sources, such as solar thermal collectors, an air-to-water or geothermal heat pump or a biomass boiler also have an auxiliary heat source. 

Most of the modern hydronics technology used in North America for residential and light commercial buildings is for heating.