I just received my power bill. Now, I don't want anyone to get the wrong impression; I really do appreciate the work and service provided by PP&L, as well as the gas company where I purchase my propane. But as that famous song so aptly puts it, "Good golly, Miss Molly!" That's just a little too much. Let me tell you about my dream house, because it would incorporate a feature that would help me out in this situation. That feature is called passive solar.
What is passive solar, you may ask? (Well, isn't that just amazing, how great minds always run in the same... the same... ahh heck, where do great minds go?! Because I think that my mind must already be there without me!) There are two generic solar systems. (Now don't go there, because I know that there are more than just two solar systems!) One is active solar and the other is passive solar. For example, an active system, such as an active solar water heating system uses five different components to work: a collector to capture solar energy, a circulation system to move fluids between the collector and the storage tank, a storage tank, back-up heating system, and a control system to regulate the overall system. There are also active solar space heating and many other systems. Passive solar uses thermal mass to collect and disperse the collected energy, or possibly uses a simple transfer system to accomplish the same. Okay then, are you confused yet? No? Way to go! Now let's look at the passive solar system, because, well... because I said so.
It's best to plan for using passive solar during the planning phase of your next home. (Important note: There is a lot of information on passive solar available to us, so what you will read is basically going to be biased towards what I have experienced and seen. I would suggest that you avail yourself of the myriad of information to decide for yourself what is and what is not so good.) The key to a good passive solar home is being able to have the light of the sun access the collectors when needed, for the collectors to be able to store the heat and for the collectors to release the heat in a slow and comfortable manner.
There are two terms to remember: K Value--the ability for mass to quickly absorb solar heat gains anl later release it; R Value--the ability to resist heat loss. How well a solar home works then, is determined by these two simple values. What I mean is that: The floors and walls of your home need to be constructed of high thermal mass so that heat gain can be quickly absorbed and later released as needed. When a home does not store heat (or if it has a low K Value), then the constant radiant heat loss means that the heat stored will be inadequate for your heating needs, as it will release heat throughout the day, instead of when you really need it released, like at night.
Now, just because an item has a high R value, like straw bales, wood, drywall and insulation, this does not mean that it can be used in thermal storage because it has low to no K value. When the heat is stored in a home's furnishings and a thin coat of stucco, then mechanical heating systems are needed to heat the home. This is why thermal mass is so important. You can get heat, but you need to store it. Now there's another problem in my opinion, there is really only one good medium for passive solar storage, and that is concrete masonry. So don't go building your home with straw bales, logs, wood or even the foam foundation blocks, and expect it to be truly passive solar. The problem with foam foundation blocks is that the insulation is on both sides of the concrete. Insulating the exterior wall of your home is a good idea, buy why insulate the interior, and not allow the heat stored up in the mass to go into your home? It defeats the purpose of passive solar. Logs, even though they may have respectable R Values, have low K Values, and are also unable to store heat, which prevents them from being the solar system of choice. We'll continue with this next week.
Until then, see ya'!
Originally published in the Daily Courier March 23, 2000