The first real bite of winter settled in to Northern New Mexico for the past week or so. Last week lows were in the single digits to low teens and highs were in the 30’s and 40’s. Looks like Thanksgiving will be chilly with possibly the first sub-zero lows of the season. By most American standards these temperatures mean some heating is required to keep your home comfortable. The low in the house so far since this cold snap has been 67. The house heats into the 70’s during the day. These interior temperatures at face value are not particularly remarkable since most people under normal circumstances would keep their homes in that temperature range. In fact, in our Alaska homes where we had to run heat almost year round, we kept our thermostat at 62 most of the time. What makes these temps in our home remarkable is the fact that we have no heating system. Specifically, we have no traditional furnace powered by electric or fossil fuels.
Passive solar design – when done right – has almost no user involvement or moving parts and the house just keeps itself warm. The design is pretty basic. The low winter sun heats the house through south facing windows much the same as it would heat your car interior. Thermal mass inside the house (concrete, flagstone, adobe walls, etc.) stores the heat. A well insulated shell and roof and thermal blinds over the windows that you close at night keep it from escaping at night. We do get cloudy spells and once in a while, usually in late winter/spring, the house gets cool enough to use the wood stove. Last winter was a little colder than average and we burned less than half cord of wood to heat an 1100 square foot area. The same super insulation and interior thermal mass keeps wood stove heat going long after the fire is out.
This is a change that can make a real difference and have real impact on the amount of fossil fuels used for space heat. It boggles my mind why local and even state wide building codes don’t require new construction to incorporate passive solar designs. Sure it cost more up front but the savings in energy over the long term will dwarf the initial up front increase of passive solar design and pay for itself many times over. Sadly, even in progressive Northern New Mexico county local building codes do not require new homes or buildings to meet any substantial passive solar design principles. Passive solar design is really just simple and sensible science and shouldn’t be part of an ideological or political debate, but sadly it is.