Now that we’ve covered passive solar windows and floors, it’s time we got down to walls. As you know, passive solar design creates “smarter” homes that garner energy from the sun without additional operation or maintenance costs. This is because passive solar features can be built right into a home’s structure.
With walls, placement plays a big role, along with the building material used. Concrete, brick, and even water are recognized for having high thermal mass. Using such elements, your walls can absorb, store, and eventually, distribute the heat from the sun throughout your living space.
Passive solar walls can be used in direct gain systems, where the living space itself collects, stores, and distributes heat. Passive Solar Guidelines recommends the following for walls in direct gain systems:
- Unlike thermal floors, thermal mass walls can be any color.
- Use thermal mass areas throughout the space, even if they have less thickness. This is preferable to using a more concentrated area of thicker mass in one place.
- Do not exceed 6 inches of thickness for your wall.
- Fill the cavities of any concrete block used as thermal storage with concrete.
- For every square foot of south glass, use 150 pounds of masonry or 4 gallons of water for thermal mass.
The walls work in conjunction with south-facing glass, which give access to heat and light and help prevent their escape. The angle is strategic for both heating and cooling. In the summer, the sun is higher in the sky, and awnings, eaves, and foliage can help prevent the south-facing area from receiving too much solar gain. In the winter, the sun is lower in the sky, admitting more light and heat through the south-facing window.
Another type of passive solar wall falls under the indirect gain category: the Trombe wall. This 8- to 16-inch masonry wall is usually located between the sun and living space. From the outside, it often resembles a window built over a wall. The window glazing helps trap the heat. When the sun goes down, Trombe walls are known for distributing slow, even heat through built-in vents.
An alternative to masonry? Water. In fact water offers quicker heat exchange than masonry. Water walls can be integrated through containers, pipes, or tanks. One drawback is they require regular maintenance.