The Important Role of Windows Windows play a very important role in a passive solar house. To facilitate maximum solar gain, our house had to be oriented so its long side faced due south. Our south wall contains most of our home’s windows because south facing windows are net gainers, absorbing more energy during the day due to their direct exposure to the sun, then they will release at night. East and west windows are net zero, if they see the sun. They will release as much as they gain. North windows are total energy losers, which is why very few are on our north wall. High quality windows are a must. We have Simonton ProFinish ENERGY STAR qualified low E double glazed windows. While you can use either double hung windows or casement windows, casement windows have two distinct and unexpected advantages over double hung windows. Be aware that these are not your grandfather’s metal rickety and draft prone single pane casement windows. Today’s high tech casement windows are marvels. Vinyl is the material of choice for these windows. Not only are they maintenance free but they also are stable and do not expand or contract like wood or wood clad windows. The first advantage is that, because they crank open and closed, the harder the wind blows the tighter the seal becomes between the window gaskets and the window frame. The second advantage is that, since they crank open, they act as sails catching the wind from any direction and channeling it into the house. The breeze they direct can go a long way to maintain your comfort level before resorting to air-conditioning, if at all. The south windows also act as a switch to turn on and off your maximum solar gain. In the winter, the sun is low and shines directly through the glass, giving you maximum solar gain. In the spring, the sun’s height increases and reaches a high enough angle on the glass that much of the sun’s energy is refracted off the glass back outside, limiting your solar gain. In the fall the sun’s angle falls again, turning on your maximum solar gain by directly passing through the glass again. Screens also alter your solar gain. In the late fall, winter and early spring we take our screens out for maximum solar gain. When we put them in, they decrease our solar gain by about 20%, creating a simple way of keeping the house cooler as the season heats up. Eaves Regulate Solar Gain Our 4 ft. eaves also limit solar gain seasonally. As the sun gets lower in the sky towards winter, all the sun’s energy comes in through the windows. As the sun gets higher after winter, the eaves begin to increasingly block more direct light from entering our home. Around June 20 there is no direct light coming into the south side windows on the 2nd fl. and only 18” of direct light penetration on the 1st fl. Snow is Your Friend In a passive solar home, snow is your friend. On the roof it supplies additional insulation. An asphalt shingle roof is required so it will hold the snow instead of letting it slide off. On the ground the snow also helps you. The sun will refract light off the snow and through your windows increasing your solar gain. Attic in the Thermal Envelope Another advantage of having the rigid insulation on the outside of the house (including the roof) is that, even though the attic is unfinished (fig 14), it is inside the thermal envelope of the house and is therefore heated usable space. | 
