When crafting the perfect home, choosing a trusted general contractor to help design and build your home is not the only decision you will have to make. Today, you must also consider the style and sustainability of your home. If you are interested in a home that reduces energy costs, is easy to maintain, and lacks the bulkiness of traditional energy-saving devices, a double-envelope house may be perfect for you.
What is a “Double Envelope House” and how does it work?
A double envelope house gets its name from its structure, which consists of an outer and inner shell. When sunlight hits the building, warm air is drawn in from a greenhouse moves between the inner and outer shell, and spreads into the insulated foundation of the home.
Essentially, the structure creates a pocket or “envelope” of warm air that surrounds the entire inner shell and maintains the warmth of the home. This pocket of warm air also acts as a buffer to the cooler air outside of the home.
However, during the night, this cycle is reversed. When light is no longer being absorbed by the glass on the building of the greenhouse, the air within the pocket slowly begins to cool as the warm air is forced up and out of the building. As a result, a comfortable temperature can be maintained throughout the day and throughout the year. More than simply another ‘green option’ you can add to the design of your eco-friendly home, the envelope house is in and of itself a holistic sustainable solution that is growing in popularity for those concerned about their carbon footprint.
Though a double envelope house certainly does make the most of its design, there are still a variety of pros and cons to consider, before you choose whether or not to decide on a double envelope home.
Pro: Energy Conservation
One of the biggest advantages that the double envelope house offers is the amount of money that can be saved on energy bills. The design of the home, which includes the greenhouse and sub-floor cooling tubes, ensures that a comfortable temperature can be maintained. In other words, this particular design allows energy, in the form of heat, to be collected and stored during the winter whenever the sun is shining.
However, this design does not only collect warmth but can also ensure that the home stays cool during the summer seasons –– all it takes to cool down the home is to open the windows on the upper part of the house. By opening the windows, the hot air is forced out of the building, keeping the home cool.
Essentially, the design of the home harnesses the natural energy of the sun to maintain the temperature of the home year-round. This envelope house can drastically cut energy costs because it is energy efficient in summer and winter, ensuring that you can enjoy a comfortable temperature home all year round.
Pro: Envelope Homes are Aesthetically Pleasing
Because the envelope home’s energy-saving abilities are found within the structure of the home, there is no need for additional bulky systems that may not match the aesthetics that you prefer. For active systems, such as solar panels, it is necessary to install a device to harness the energy from the sun. These devices are usually expensive, large, bulky, and extremely noticeable. If you are looking for energy saving that is a bit more discreet, then an envelope home may be more ideal than one that is covered in energy-saving devices.
Pro: Envelope Homes Are Not High Maintenance
There are many non-solar heating options, such as forced air and hot water systems; however, these active systems require regular maintenance on their complex systems of pumps, pipes, and collectors. A hot water system works by moving hot water from pipes to baseboard convectors in a loop. Forced air systems function by moving either heated or cooled air to specific areas of the home. Each of these systems has a high amount and variety of parts that require maintenance, and could potentially fail. As a result, these systems could cost a lot of money to maintain.
However, unlike these systems, the envelope house does not require much maintenance. For an envelope house, the system is built into the house’s design. Because of this, envelope houses cost much less to maintain.
While there are plenty of pros to the double envelope style house, there are a few cons as well. You’ll want to carefully weigh the following factors before you commit to this unique design for your custom home.
Con: Envelope Homes Are Not Suitable for Every Climate
Passive heating systems like the envelope home are best suited for moderate climates, where the temperature of the surroundings does not drastically change from season to season. For climates that are extreme, the double envelope house is not for you. In order to be used in a hotter climate, the design of the double envelope house must be altered and given extra attention in order to remain cool during the summer months. For example, it may be necessary to add window shades, additional vents to expel the excess hot air or a roof overhang.
Unfortunately, for those who live in colder climates, a passive heating system like an envelope home will not be able to heat the home properly. For colder climates, it is necessary to have an active system that will be able to heat your home and maintain the inside temperature of the home.
The envelope home is ideal for moderate climates, such as California, the Southeastern United States, and mild European climates.
Con: Envelope Homes Hold Heat for Less Time
Unfortunately, the double envelope house’s passive system cannot store heat for the same amount of time as the active system. The envelope house relies on sun exposure to collect and store heat, so long periods without adequate sun exposure could result in a reduction in heat storage. For the double envelope house, energy can be stored for an estimated 72 hours.
While this energy storage is limited by a short period of time, active systems can store energy for longer periods because of their ability to store energy in devices such as battery banks. In places where direct sunlight is scarce, active systems are more reliable to regulate and maintain your home’s temperature.
Con: Temperatures of Envelope Homes Are Often Inconsistent
Because of the design of the double envelope home, hot and cool air is constantly circulating around the house. As a result, there is a possibility that there is a variation in temperature throughout the different areas of the home. In addition, the design of the home interacts directly with the amount of sunlight that is touching the building.
This means that it is the sunlight and energy harnessed from the area that influences the temperature of the house, not a control panel or a smart-home app where you can easily adjust the temperature of the home. For someone who desires consistent control over the temperature of their house, the double envelope design may not be a perfect fit for you.
Choosing the perfect home requires careful consideration of the positive and negative aspects. If you are looking for a home with a low-maintenance solar energy option and live in a place with moderate temperatures, a double envelope home is worth considering.