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What is a Building Shell?

By B. Turner
Updated May 17, 2024
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A building shell, or envelope, includes all components that separate the interior spaces within a structure from the surrounding exterior areas. The shell may be composed of many different features, including walls, windows, doors, roofing, footers, and foundations. While the building shell may be made up of various material, it will typically be made from some form of wood, stone, metal or concrete.

The building envelope helps to protect the interior spaces in the building from exterior elements such as rain, wind, and snow. It also acts as a barrier to keep out noise, insects, and intruders. In addition to its role in protecting the interior of the building, the shell provides structural stability for the remaining building components. It also plays a major role in temperature control, while allowing occupants to regulate air pressure and humidity levels within the building. Finally, the building shell acts as a security feature to protect occupants and assets.

A building shell is often categorized as open or closed, and these designations can have a major impact on the energy efficiency of the structure. Older buildings will generally have an open shell, which means they are loosely constructed. This also means that wind, moisture, and pests can enter and exit the building through cracks and other openings in the shell. Modern buildings are typically constructed more tightly, or closed. This means that it's harder for air, moisture, and insects to enter the space, making it easier to control interior conditions.

Both tight and loose building shells require a careful balance between energy efficiency and air quality. Tight buildings let less air escape, making them cheaper to heat or cool. At the same time, fresh air has a harder time getting through a tight shell, which often results in poor indoor air quality. Loosely constructed buildings allow more air to enter and escape, which means that fresh air is always passing into the space. At the same time, conditioned air is able to freely exit, which results in poor energy efficiency and higher utility bills.

To balance this problem, homeowners can take steps to tighten up a loose building, or add mechanical ventilation systems to a tight building. To tighten up a building shell, one may add insulation, caulk cracks or openings in exterior walls, and add weatherstripping around windows and doors. Homeowners may also invest in energy efficient doors and windows, which can greatly reduce thermal transfer through these surfaces. Simple ventilation systems consisting of fans and intake grilles can help to bring fresh air into a tightly constructed building shell.

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Discussion Comments
By OeKc05 — On Jul 11, 2012

I think that building locations probably have something to do with the way the shell is designed. My husband used to live in New York, and he said that many of the older homes there were built to thoroughly shut out the cold air, because they had vicious winter snowstorms and biting temperatures.

However, we now live down South, and just about every home I've been in here has a looser shell. Air circulation is important, because in the summer, it can get stifling hot quickly. Even the winters are mild, so it isn't the end of the world if you have some gaps in your home's shell.

We are living in an old house right now, and the windows don't even shut properly. I can feel the air coming in around them. So, I keep thick curtains hung in front of them to control the air temperature.

By Perdido — On Jul 11, 2012

@lighth0se33 – I envy you! I am currently renting a home that was built in the 1960s, and its shell is just full of entryways for a variety of critters. There are too many for me to caulk up on my own, and the landlord doesn't want to remodel, so I'm stuck with them.

Even mice get into the building using the large gap in the bathroom closet around a pipe. I can actually see through to the ground by looking in it.

All I can do is stuff a towel there, but since mice like to chew on things, that won't keep them out for long. Also, I have seen everything from crickets to wasps in here, due to the many gaps around the windows.

By lighth0se33 — On Jul 10, 2012

I'm glad I live in a home that was built just a few years ago. I couldn't bear to live in an older home with all those loose areas for bugs to get into!

My house is tight, and I hope it stays that way. There are no cracks around the windows and doors, and even the trim around the walls is very well sealed.

If I ever do start to see bugs in here, I will be calling a professional to come and seal whatever cracks in the shell of the building that they're using. I get chills when I think about bugs walking over me in my sleep, and I'm extraordinarily freaked out by them, so I will do whatever it takes to keep my house a safe haven from insects.

By kylee07drg — On Jul 09, 2012

It's always interesting to pass by future building locations and see the shells being constructed. You always see the shell up before the rest of the building, and all the windows and doors are just empty frames at that stage.

I like seeing a building go from being just a shell to a fully developed piece of architecture. I get to see several on my way to work each day, because I have a thirty-mile commute.

I am fascinated by how quickly some structures are developed around their shells. It seems that once the basic framework has been laid, the hardest part has been completed.

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