Living with High-Mass Space Heating

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Although they are extremely efficient and produce very comfortable radiant floor heating, high-mass solar thermal systems can be difficult to live with, especially at first. They require changes in habits and it may take a few years to figure out the optimal approach for your particular situation. This article will provide the background knowledge and some pointers to help you along the way.

The most important thing to understand is that it may take a year for your high-mass solar thermal space heating installation to warm up. Yes, a whole year. Depending on when it is installed, the volume of the pit under the building and the local climate, the sheer mass and inefficient nature of the storage medium means the sand can take months to warm up sufficiently to provide measurable Btus of usable heat.

The good news is that, if you complete your installation before the summer, you should have a reasonable amount of energy stored for the first winter. It won't be as good as the following years, but at least it'll do something useful!

Unfortunately, it is impossible to provide firm guidelines on when you should switch on your system, because climates and installations are all different. As a general rule, most high-mass systems operate from August through May, though many are never switched off. You will have to figure out your own schedule based on how your particular setup operates.

You may find that you switch on at the start of August for the first few years but delay the start until late August in later years, because of the leftover heat still in the sand bed. You may decide to switch on at the same time every year and just leave the windows open at night to avoid overheating in the hot months. The important thing is to gather as much heat as possible for the cold months, even if you throw some heat away in the hot period of the year.