Frequently Asked Questions

Please note that the answers given are abbreviated in order to be "short and to the point". The answers are meant to provide a starting point towards further understanding. Further research into these questions is encouraged, or feel free to call CCE. Some books may be referenced elsewhere in this webpage for further information.


How much carbon will a system prevent from entering the atmosphere?
To calculate your "carbon offset" (for, in this example, natural gas heat), determine yearly BTU heat load of the dwelling (including both heating load and domestic hot water usage). Take 75% of this BTU value (approximate portion of heat provided yearly by sun in a well designed system), divide this number by 100,000 (number of BTU's in a "Therm" of natural gas; look on your monthly bill for present # of therms used). Take resultant number and multiply it by 11.64 (lbs CO2 in one Therm natural gas) to get yearly carbon offset. (OR; just call CCE, and we'll calculate this!)

How much of my annual heat load can be satisfied by solar heat?
The answer depends on numerous factors. The answer can be anywhere between 0-100%! Factors to consider when making this calculation are: What type of climate/microclimate is the house located in? Was house designed with passive solar heating principles in mind (see question/answer below)? How well insulated is the house? What type of heat delivery system is used (radiators, baseboard, air handlers, radiant floor, etc.)? How much space is there on the roof for the collector array? Is there adequate space inside the mechanical room for a large storage tank? With a reasonably well designed house, a good, affordable goal may be about 75% of annual fuel replacement cost.

What's all of this hype about "radiant floor" heat?
Radiant panel heating refers generally to heat tubing (PEX) laid down in a poured concrete/gypcrete floor, usually during new construction. Since the entire floor surface is the "heating element", your feet feel very comfortable, which makes the rest of you feel good! Also, much lower temperature water can be used to heat the home, which offers two further advantages: It works wonderfully with solar heat systems, and it takes advantage of the high efficiency provided by the newer, more efficient modulating/condensing boilers, by operating them in their low temperature (most efficient) range.

Will I need a boiler in the house to provide backup heat in case the sun doesn't shine?
In almost all cases, yes. Typically, a modulating/condensing boiler is used for backup. When heat in the solar storage tank is depleted, the radiant (typically) system will automatically switch over to the boiler to provide the balance of floor heat necessary to satisfy the home heating load. The modulating/condensing boiler will only come on when the sun can't keep up with the load (mostly in December/January, and decreasing in the "skirt" winter months). Generally, from March thru early October, most of the heat (home heat and domestic hot water) will be provided by the solar system. When it is called upon, the mod/con boiler, which is designed to operate in it's "sweet spot" for efficiency, will use much less fuel than a typical "traditional" boiler.

What about using baseboard or radiators with solar heat?
It can be done, but at lower efficiency than when radiant flooring is used. This is because all of those other types of heat transfer devices (baseboard/radiator) operate at higher temperatures than a masonry/radiant floor system. Baseboard/radiators generally operate at about 160-170 degrees, which is rarely available from a solar system. Staple up type radiant floor systems are OK, but operate at a higher temperature (perhaps 115-135 degrees) than masonry based radiant, which can operate as low as 85 degrees (or even lower in some cases, such as a garage floor). For example, comparing staple up (with, say, an average heat requirement of 125 degrees) to "slab type" radiant (with a requirement of, say, 90 degrees), consider this: the staple up based system will switch over to boiler when the solar storage tank temperature is drawn down to 125 degrees, whereas a "slab type" radiant floor can draw down the storage tank temperature to 90 degrees before the boiler takes over the heat load! Additionally, when the storage tank is drawn down to a lower temperature (in the case of the slab radiant system), it will "grab" more heat the next day from the solar collectors, because the solar collectors operate most efficiently with a large heat differential (between storage tank water and collector absorber plate temperatures)!

What's the difference between evacuated tube and flat plate collectors?
Flat plate collectors have been in use for over 100 years. They are the ones that look like large skylights. They are tough and reliable (when installed properly!). Evacuated tube collectors are glass tubes about 7 ft. high, stacked vertically to form arrays. They are more efficient in colder and cloudier conditions (as with some higher altitudes here in Colorado). They cost more, but are also easier to install in high places (one person can lift the parts onto a roof by themselves).

How do you store solar heat collected during the daytime for later use?
The heat can be stored in a large (300-400 gallon, typically) hot water storage tank. The hot water from this tank is then pumped into the heating system later at night when it's most needed. Alternatively, the heat from the panels can be pumped directly into a high mass floor. Each system has it's advantages, and the choice of methods depends on many factors in the building design, as well as how the homeowner wants the heat distributed.

What type of system is best; drainback or glycol?
Neither is "best"; the topology chosen depends on the building design, collector orientation, pipe chase locations, whether the array is ground mounted, etc. Drainback systems are more efficient in collection, and don't have overheating issues that are associated with glycol in the summertime. However, they are susceptible to freezing if not installed by an experienced professional.
Glycol based systems allow more flexibility in pipe runs, and minimize concerns about running pipes through unconditioned (unheated) spaces. They can also be powered with PV powered circulators, for a true "zero energy use system", which is harder (though not impossible) to do with a drainback system. Despite which type of system design is chosen, they should be installed by, or in consultation with, a professional solar installer, as there are many "gotchas" that can cause serious damage to your home if not proactively addressed.

What is the difference between "passive" and "active" solar heating?
Passive solar heating refers to architectural design features in the home that capture the sun's heat during daylight hours (and hopefully retaining this heat through the nighttime hours). Passive design features include: energy efficient south facing windows, thermal mass (masonry floors/walls/etc), well designed eaves on the house that allow sun in the winter but block it in the summer, home orientation on the property (to capture sun, and avoid cold winter winds), tree and shrub placement, etc. Passive solar design is the "low hanging fruit" of solar heating, and should be the first consideration in any heating system design.
Active solar heating systems utilize collector panels and circulating pumps to "actively" collect and store the sun's heat, and then move it around the home for use when/where needed. Active systems augment heat provided by passive systems, and can boost total solar heat generation to satisfy as much as 95% of heat load in the case of some well designed homes!

How much does a solar heating system cost?
Cost varies, and depends on the answers to such questions as: New construction? Retrofit in existing dwelling? System size/number of collectors, storage tank type? House design (how easy it is to install the plumbing/mount the collectors). With those questions answered, you can call CCE for an estimate.