What is radiant solar high mass heating?

Solar high mass heating collects the heat from the sun in solar panels and transfers it for storage into an insulated sand bed via fluid filled tubes. As the hot fluid passes through a network of tubes buried in the sand, the heat dissipates into the sand where it is stored. This stored heat warms the building by convection and can provide as much as 70% of the buildings heat needs. High mass systems are turned on in late summer to begin heating the mass.  With a solar high mass heating system, an adequately insulated building will never freeze. 

At Lamar, a 16-inch sand bed under the basement floor holds seven zones of tubing. Outside, an array of ten 4' x 10' panels creates an absorbing field of 370 square feet. A photovoltaic panel attached to the array powers a small pump which circulates a diluted antifreeze called propylene glycol. Propylene glycol is preferred for this closed loop system because it is non-toxic, can withstand high temperature, and lasts a long time. Propylene glycol is also used in ice cream to prevent it from hardening.

Collector output varies seasonally depending on the number of daylight hours and daily depending on cloud cover. In September, the system at Lamar collects an average of 32,000 BTUs per hour. In November, when days are short and overcast, the average output is 19,000 BTUs per hour. Radiant solar energy is virtually 100% efficient while heating sources that depend on combustion operate at significantly lower efficiency. Boilers, for example, have combustion efficiency of about 85%. 

Delete this para: On average, the panels collect 1100 BTUs per square foot per hour for a total of 407,000 BTUs per hour. The average length of the collection day in the Midwest is 3 hours in the winter. Thus, this system collects an average of 1, 221,000 BTUs per day. The furnace for an average home provides about 50,000 BTUs per hour and heats for about 10 hours per day for a total of 500,000 BTUs.

Although systems are ordinarily installed in new construction, the solar system at Lamar is a retrofit that was accomplished during renovation of the lower level. 

Why choose radiant solar heating?

Radiant solar high mass heating is a low maintenance, long lasting system. The system itself has a life of at least 30 years; the antifreeze should be changed every ten or fifteen years. Radiant solar offers homeowners reliable heat with little involvement.

Solar systems reduce the need for fossil fuels, which makes them friendly to the environment and also the economy.

Over the long term, solar systems are cost effective. Although they have high initial installation costs, they have extremely low operating costs. As concerns for the availability of fossil fuels increase along with their rising costs, radiant solar offers a reliable and cost effective source of heat.