Top 10 reasons for choosing solar heat

In this column over the past few years, I have been describing the standard methods and best practices we use to install solar hydronic combisystems in the most successful systems I know. Using what I call the “New Standard” solar/hydronic strategy, our solar heated building installations have become faster to design and easier install. And, using a repeatable design configuration with an integrated control, successful results are now predictable and verifiable using remote monitoring and remote control over the Internet.

Using this approach, our solar heating and renewable energy combisystems are no longer experimental or ‘one of a kind’ customized creations. We now use more of a “cookbook” approach, combining familiar ingredients using familiar patterns and modular configurations for rapid and reliable deployment. In our experience, solar heating in buildings has never been more practical or more reliable. 

Just do it: The solar heating decision

In the construction world today, solar/hydronic buildings are still relatively rare and solar space heating seems to have become something of a lost art. But with the New Standard design methods, we have found that implementation of solar/hydronic heating has never been easier. We are always on the lookout for the low-hanging fruit, where a building project is so obviously compatible with New Standard solar heating, that it is practically ano-brainer.  
Based on dozens of successful recent installations, here is a list of the top 10 reasons why the solar heating option was chosen for these projects. 

No. 1 The climate is “sunny enough,” and the collectors will fit

In our Sun Belt climate where it is typically 85 percent sunny, an 85 percent solar heated building can certainly be achieved. But, we have also done successful solar heating projects in places like Oregon, Alaska, Rhode Island and Virginia where the annual sunshine is considerably less than ideal, but still proved to be worthwhile. In climates that may seem questionable, the only way to tell if it is ‘sunny enough’ is to model the project using local climate data. When the calculations show that a climate has enough solar energy to contribute significant fuel savings, a solar heating system is born, even in some unlikely places. 

Of course, there must be a good location for the required solar heat collectors, and Figure 77-1 shows an example from a recent installation using roof-mounted low-profile panels. There are many other ways to make solar heat collectors fit into a construction plan including roof mount, wall mount and ground mount racking systems in various tilts and configurations.

No. 2 A hydronic hot water boiler system will be there anyway.

Hydronic hot water boiler systems are easily compatible with New Standard solar hydronics. In these systems, hot water baseboards, radiator panels or fan coils are typically used for heat distribution. Also commonly included are radiant floor heat zones and an indirect domestic hot water (DHW) tank. Swimming pools, ice-melt zones and heat-storage tanks are also commonly connected to these standard systems.

Figure 77-2 shows a piping diagram of an example solar/hydronic installation using the New Standard piping configuration. The hot water boiler equipment that has to be there anyway is seen in black. Our standard solar heating configuration is seen in red. Notice that the black conventional heating equipment (that has to be there anyway) makes up the majority of the total heating equipment. You can see how the red solar equipment may optionally be added later using two-pipe stubouts on the primary loop if a solar-ready heating system is desired.

No. 3 Masonry radiant floor heat will be there anyway.

Masonry radiant floors are commonly made of concrete with PEX tubing embedded in it. Solar heat can be delivered to the concrete by circulating warm hydronic fluid through the PEX tubing. The concrete has a substantial specific heat capacity, which translates into a large heat storage capacity (a.k.a. thermal mass). Our standard control strategy uses the thermal mass of the concrete as a ‘solar heat accumulator,’ within a carefully controlled temperature range for human comfort. When the thermal mass of the building is used for heat storage like this, we can reduce or even eliminate the need for large heat storage water tanks or other more exotic and expensive heat storage systems.  

Notice that in Figure 77-2 the heat-storage tank is plugged into the primary loop in a way that makes it easy to include it or eliminate it depending on the needs of the building. Sometimes the absence of a big heat storage tank is the deciding factor that allows a project to go solar thermal.
No. 4 Heating will be a significant annual energy cost.

The average residential house in the U.S. uses about 65 percent of its annual energy consumption for combined spaceheating and DHW. This heating energy is not typically offset when photovoltaics are installed (PV: solar electricity), but can easily be offset with solar heat collectors in many types of buildings.  

Despite the wide proliferation of PV panels and exciting advances in zero energy building techniques, these technologies have not made a dent in the heating energy consumption in buildings which represents a huge opportunity for efficiency improvement. Since most of us live and work in buildings that require significant amounts of heating energy, it makes sense to use a proven technology that we have on hand to offset conventional heating fuel consumption whereever we can.

No. 5 The local cost of conventional heating fuel is high.

When the cost of fuel is high, the savings from a solar heating system becomes more valuable as well. Many of our clients who depend on propane, fuel oil, diesel or electricity (from the grid) for their conventional heat have determined that the savings from solar/hydronic heat provides a very attractive cash flow improvement. The steady supply of solar heat over the years may be considered a kind of insurance against the rising cost of heating fuel over time as well.

No. 6 There are other alternative sources of hydronic heat.

The New Standard solar/hydronic piping configuration allows multiple heat sources andheat loads to be centrally connected and intelligently controlled. So, the system can accommodate other multiple heat sources, beyond the example seen in Figure 77-2 where there are three common heat sources: boiler, solar heat collectors and heat storage tank. 

In some past installations, we have included other unconventional heat sources, such as a wood-fired hot water coil, ground source heat pump, waste heat recovery from an engine generator and heat recovered from a refrigeration air-conditioning system. Sometimes the New Standard hydronic configuration is chosen because it can seamlessly mix and match a wide variety of renewable heat sources.

No. 7 There is a large heated water feature.

It is not unusual for a facility with a large water heating load to look to solar heating as a way to manage the heating fuel consumption. A commercial water heater at a hotel or a car wash, for example, is always worth considering. Also, a heated swimming pool or large hot tub is easily included in the heating loads connected to a New Standard heating system. 

A large pool may benefit from solar heat even at times when nothing else in a standard system needs any heat, thus extending the usefulness of the existing solar collectors. Any large hot water heating load that is persistent throughout much of the year is a candidate for regular and substantial fuel savings from a properly designed solar heating system.

No. 8 Green motives: carbon offset, near zero energy goals.

Some building projects are guided by green objectives, such as a high LEED rating or a small carbon footprint as seen in net zero ornear zero energy designs in buildings these days. Since solar heat is capable of offsetting large amounts of combustion fuel, it is therefore capable of preventing large amounts of combustion products from being generated, specifically large volumes of CO2. Sometimes this can be a strong motivating factor for a ‘Green’ end-user to choose hydronic solar heating. 

No. 9 Self-reliance or emergency preparedness.

Some of our most interesting solar combisystems are installed off-grid, or are designed to operate normally off-grid during outages and emergencies. Solar heat and other alternative heat sources can go hand in hand with off-grid PV electric power, generator backup, wood boilers and other technologies commonly used in self-sufficient installations. The New Standard hydronic heating configuration can be applied to off-grid self-reliant installations and is sometimes used for that purpose.

No. 10 There are tax rebates or other financial incentives.

Sometimes the final decision to install solar heat is inspired by rebates and incentives. State and federal incentives are summarized most conveniently on the “DSIRE” website at In many instances, the same financial incentives often associated with PV systems are available for solar heating equipment, as well.


These 10 reasons apply equally well to new buildings, retrofits and remodels. Not all 10 need to apply for a positive decision to go solar thermal. In fact, if three or more of the top ten reasons apply, then a solar heating system probably makes sense.

Final notes

These articles are targeted toward residential and small commercial buildings smaller than ten thousand square feet. The focus is on pressurized glycol/hydronic systems since these systems can be applied in a wide variety of building geometries and orientations with few limitations. Brand names, organizations, suppliers and manufacturers are mentioned in these articles only to provide examples for illustration and discussion and do not constitute any recommendation or endorsement. 


Bristol Stickney has been designing, manufacturing, repairing and installing solar hydronic heating systems for more than 30 years. He holds a Bachelor of Science in Mechanical Engineering and is a licensed mechanical contractor in New Mexico. He is the chief technical officer for SolarLogic LLC in Santa Fe, New Mexico, where he is involved in development of solar heating control systems and design tools for solar heating professionals. 

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