When it comes to building construction and design, one would think that the most important parts of it are the shape, design, engineering choice of site, the layout plan of the building, etc. These components tend to overshadow an important aspect when erecting a building which is called Building Envelope. This factor is crucial to the heating and cooling service demands as well as comfort, indoor environmental quality and safety. These days, buildings are constructed with the sole aim of producing neutral energy emissions, not only to support greenery but to maintain energy impact on the world and building envelope performances can provide that pleasure. Compared to other solutions in buildings, the selection of envelope structure and materials is particularly important, considering the lifecycle of buildings and the associated cost of the envelope. This article would emphasize more on this aspect of a building project and a subject that should not be overlooked.

What is building envelope? Just like an envelope, the inside and its contents are protected from the outside by a seal. It is similar to the context. A building envelope is a physical barrier that separates the inside conditioned space from the outside unconditioned environment. It is the part of the building structure that separates the outdoor environment from the indoor environment, and that also includes the doors and windows, roofs, walls and foundation.

A standard, high performance building envelope comprises of every element of a building’s exterior that aids the control of different variables within the building structure such as the air, temperature, noise, humidity, and several other factors that operate within the building.

Building envelope is more than just regulating energy consumption, it is sensitive and responsible to its environment to make your home healthy, comfortable and efficient. It protects the interior energy from the exterior damages or hazards. Most construction projects today continue to ignore the importance of this factor in a building and it had led to unsatisfied occupants and high-cost maintenance. A high performance building envelope is responsible for as much as the comfort of the inhabitants of that building. It regulates the temperature within the structure, and determines how conducive it is for its inhabitants.

Building envelope is dependent on the climate, culture and the available resources. There are a number of environmental considerations that should be taken into account when dealing with building envelopes for building construction and design:

Climate control:

One of the most essential functions of designing a building envelope is to enable climate control. Buildings are not just simply barriers but building systems that offer the opportunity to activate buildings against climate changes, by changing the energy balance of the building through convection flow by using vapor barriers effective in vapor control; radiation using high thermal resistant materials in the building's veneer; energy storage by having efficient window and door seals, and effective air flow control to minimize infiltration of outdoor air. There are different types of climates such as tropical, cold, dry or mixed climates. And the building envelope should be characterized by the climate influenced on it. For example, in tropical climates, the weather is not so stable; it could be hot today and cold tomorrow, dry for a time and wet throughout the year. For this sort of climate, a thermal insulation can be applied, like during the dry season, the windows are glazed in a dark texture that would limit the sunlight entering the building, and the air ventilation through the roof would hold the air from escaping to the outside or the air from outside to flow inside.

Support

A building envelope keeps a building structurally sound. This mainly affects the exterior of the building. Regardless of the site or soil, the foundation of a building must be held firmly upright with the load bearing walls to keep the building safe. There are rules and regulations that building construction must comply to. And these codes provide basic safety nets and account for concerns like hurricanes, landslides, earthquakes, etc, especially in the performance of a building envelope.

Aesthetic value

When you see a building, the first thing you notice is the shape, size, texture, scale, just the culture of the building speaks heavily of it. Basically, the design of a building, its exterior to be precise, plays a significant role to maintain a certain appeal, and a building envelope provides that: an attractive appeal while maintaining the internal condition of the building.

To understand how to apply this system to construction, there are two major forms called tight and loose building envelopes.

Tight envelopes deal with well ventilated vents and air conditioners of fresh air, which is almost completely protected from the outside. The air is regulated out of the building through the vents, which forces the air in and out. The air is contained in a seal or it is insulated along the exterior walls, roofs, and floors. Damp air in a home in a cold or humid climate can encourage the growth of moss and fungi which is unhealthy to the house or institution. Also, in a tight envelope, since air is trapped, there is no more and no less energy consumption. Even the building's conditions are strictly controlled to reduce decay, corrosion, etc, and the buildings last longer with less maintenance costs.

Loose building envelopes is obviously the opposite of the aforementioned. It encompasses a higher risk of air exposure with large air gaps and spaces between the layers of the building. Fungi and moss is highly expectant and while this form guarantees a great, natural air transfer, it can create unwanted cold or hot spots in the building.

There is the possibility of the both forms of the building envelope, for example, insulation methods for climate control yet there are still air gaps to be uncovered. Or there is a ventilated system but it cannot provide good air quality.

When creating and maintaining building envelope performance, several components are involved; the materials, the structure itself, and the systems that support the building. These components include the walls, foundation, roofs, doors, windows etc. For the walls, you can't build a house without it, no matter what shape or form they are, whether glass, metal, concrete and so on. The main challenge to a good wall assembly is the penetration of water through it. There are different types of wall systems to protect a wall: barrier, damage and sealed-surface systems.

Drainage systems let any water that may leak into the wall to drain out. It may also be ventilated to help with the drying.

Barrier walls allow water to be absorbed but not penetrate through the wall, for example; weather-proofing barriers protect basements from groundwater with the moisture barrier under the basement floor. This prevents intrusion, smells, or mold especially during wet seasons. Even air barriers are good for air movement, wind-washing or cold air passing through insulation and convective loops. Air control is vital to safeguard high air quality, control energy consumption, avoid condensation, and provide comfort.

Sealed-surfaced barriers don't let the water to penetrate the outside of the sliding materials of the building. This system is rarely used but some family or residential homes prefer this method of wall protection.

Another significant part to verify or improve the importance of a building envelope are the varieties of materials mixed and matched in many ways to create a unique style to the building structure. There is the use of insulating boards for roofs and walls, even for the basement, to prevent moisture from entering the space. There is also spray foam. This method is used for the exterior part of a building and it is the most effective solution for a complete seal in a property. It can be injected or sprayed into all relevant cavities - under the floor, directly into a roof structure or into wall spaces themselves. It expands when it meets the air, filling every nook and cranny that needs sealing off. But it doesn't mean that there is lack of ventilation in a property sealed with a spray foam insulation.

Even common materials like concrete, steel, metal, and so forth can make a great building envelope if applied correctly.

While the installation of this building envelope system appears to be productive in every way, it is not always guaranteed to be that way. Poor infrastructure or bad building envelopes can cause a lot more damage than one can imagine. For a building to function as designed, it must be properly constructed and maintained or the building envelope will fail, and more or less of what should be expected will be lacking. To know whether a home or institution building is poorly insulated, consider the following:

Check your energy bill history. Your bill dashboard or record book can help to track your energy consumption overtime and compare it to your previous seasons to know whether you are losing or maintaining the energy inside.

Check the temperature of any room available. If the rooms are not corresponding to the supposed air movement, it means there is an air ventilation problem.

Cracks and crevices in the walls, windows, roofs, floors could lead to energy loss. Spray foam system is a solution to covering up these cracks.

The aura of the building is also another factor of building failure. When a home is meant to be warm and dry yet it feels damp or cold, know that the house is poorly insulated. Also, the exterior should be cold because the warm air is inside the house.

Water leaks around the windows or roofs or the basement indicates poor building envelopes that can attract mould or fungi.

There are other ways to detect building envelope failure. Yet for some buildings, not every part of the structure is covered by a building envelope. Although it might compromise the regulation of temperature on the building, it can also be a part of visual appeal, giving a unique insight into the structure from various viewpoints.

A Building envelope is a practical system that offers the possibility for an energy efficient home, and ensures safety and protection for your home. With the progress in the improvement of the envelope performance and air conditioning equipment, it is particularly needed due to its growing demands.

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