If you are building your home from low-cost, eco-friendly materials, like earthbags, you should consider integrating passive heating into your design. Here are some things to consider when you take your earthbag home to the next level in eco-friendly living.
Consider Earth Floors and Earth Furniture
Passive heating requires two elements: sun to heat the inside of your home and thermal mass to hold the heat. An earthbag home is constructed of great thermal mass. However, depending on your insulation choices, the walls may leak heat to the outside or not efficiently store heat. Also, walls that are far away from your windows will do a poor job of storing heat since they are not being hit directly by sunlight.
To get the most out of your southern facing windows, you should consider installing thermal mass in direct sunlight. The easiest way to do this is to make a tamped earth floor. These floors can save you money, as you will already have most of the earth material necessary to make them at the building site. They can also be glazed to create a polished surface with a rustic look.
If you already have a different type of flooring in mind, you could install a window seat or similar piece of furniture, made from earthbags, directly beneath your window. Not only would this be a pleasant place to sit, but it would work as a small heater throughout the evening and night.
Increase Your Southern Window Exposure
Passive homes require the southern wall to have a large window area. The square-footage of windows you will require depends on the amount of sun your area receives during the winter and the size and shape of your home. The standard guideline is that your southern facing wall should contain windows equal to 7-12% of your total floor area in your home, while other walls should have less than 4%. Since most earthbag homes are round, it can be difficult to get enough southern sun exposure in the home.
While you are designing your home, you may consider an oval as opposed to a circle. This can increase the length of your southern facing wall. Additionally, you can select a mixed-material building method as opposed to a full earthbag home. Consider using timber supports for your south facing wall as opposed to building earthbag columns. This can increase the surface area for windows you are able to install without compromising your structure's stability. If you decide to use earthbag columns that are less than 4' long, you should be ready to reinforce them with rebar or create solid buttresses.
Make the Most of Your Roof
Earthbag homes require large overhangs on their roofs to protect the walls from rain damage. This makes them ideal for passive heating as you will need to protect your home from overheating during the summer. However, you may need to adjust the angles of your overhangs to allow for southern sun exposure during the winter and prevent it during the summer.
Purchase Quality Windows
One of the most attractive qualities of an earthbag home is that it is affordable for many families. Many earthbag builders recycle old timber and source their earth from the building site, making building costs next to nothing. They also tend to install small, recycled windows to reduce the costs of timber and glazing. However, windows are not an area that you will want to skimp on if you are integrating passive solar heating.
You should consider new double or triple glazed windows. While you are window shopping, you should look for windows that have a low U value, which is the amount of heat that the window allows to pass through it, and a high Solar Heat Gain Coefficient (SHGC), which is the amount of light it allows to pass through it. This combination allows sunlight to enter your home and heat thermal mass but does not allow heat to leave your home through the thin layers of glass.
Making a round earthbag home adhere to passive heating standards is slightly more difficult than rectangular homes, but the comfort and energy savings are well worth the extra time and design costs.Share
15 April 2015
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