Unsplash/Erik Mclean

The building envelope is one of the most important parts of any structure, and knowing how to design a long-lasting one will increase the home's HVAC efficiency and decrease the likelihood of structural damage. Building envelope failure can take many forms, whether it’s excessive air leakage or water damage, but there are a few helpful steps you can take to protect your building and create an envelope that will stand the test of time as well as the elements.

1. Prioritize Moisture Management
Moisture management should be a top priority when designing and constructing a building envelope. An estimated 50% of envelope failures are due to moisture penetration. Moisture can wreak havoc on buildings; what might start as a small leak can become mold or mildew the longer moisture is allowed to build up.

The best way to prevent this is to keep moisture from invading the envelope to begin with. There are several strategies that can be used to accomplish this:

  • Vapor Retarders: This is an extra layer that is integrated into the insulation to contain any moisture that does seep in and stop it from spreading. Which side of the envelope the vapor retarder is applied to depends on climate. If the building is in a primarily heating climate, the vapor retarder should be on the interior-facing side. If the climate is primarily cooling, it should be on the exterior-facing side.
  • Air Pressure: Similar to vapor retarders, air pressure should be handled differently depending on what climate the building is in. Air pressure determines the direction of airflow to and from the building, so the outside climate is the controlling factor. A slight positive pressure is good for warm, humid climates. Cold, dry climates, however, require a slight negative pressure.
  • Monitoring Indoor Humidity: Not all buildings have humidity monitors, but they are a valuable asset if moisture management is a concern. This is especially important if the building is in a heating climate where humidity buildup is more likely, or if the building’s purpose requires a precisely controlled environment.
  • Airtight Construction: This is more common with buildings that use filtration systems to control the quality of air coming and going. It can be applied to any project, though. Where there is special concern over preventing moisture from getting in (as opposed to getting moisture out), airtight construction methods are a good idea. There are various methods of achieving airtight construction, and it can be challenging, but leads to decreased heat and energy leakage and a lower likelihood of moisture damage. It is often a matter of creating an envelope that is, to the best of the constructor’s ability, one continuous material. Consequently, strong, high-quality seals at joints are critical.

2. Use the Right Materials
High-quality building materials are important for structural integrity and aesthetics, but they affect envelope quality as well. Poor workmanship is a common cause of envelope failure, which can apply to how the building materials were made as well as how they were handled during construction.

When choosing materials for your project’s windows, doors, walls, roof, and insulation, take the time to carefully source and research them before buying. You may find that one company uses cheap wood in its doors, for example, or that a certain brand of window is especially resistant to leakage. Finding materials that are good value and high-quality will be well worth the extra time and effort and pay off in the long run by protecting your project better.

Additionally, make sure all of the materials you choose are compatible with one another. For example, the vapor retarder you select might not be a match with some of your insulation material. Depending on the environment your project is in, some materials may perform better than others or be more durable for the nature of your building. Every detail of each material used for the envelope should be taken into account during the design and construction process.

Along with the materials themselves, as mentioned above, the way they are put together during the construction process makes a difference as well. Hiring a team with good quality control procedures and a trustworthy record will make certain the building materials you purchase are utilized well and decrease the likelihood of accidents and design inaccuracies.

3. Increase Design Scope
When approaching building envelope design, a lot of details need to be accounted for, especially for more complex designs, such as those for airtight buildings. It is important to remember to keep a broad scope during the design process, though. The whole building should be taken into consideration, from the foundation to the air conditioning. Rather than focusing exclusively on the things immediately related to the building envelope, expand your view to include the HVAC system, as well.

Everything in the building is tied together, and creating an envelope that meshes well with the HVAC system will offer a few benefits, including more efficient air conditioning. This is absolutely necessary if you plan to make your project airtight. The HVAC system will be crucial for maintaining the high-quality air in the building.

You may also find that your HVAC system is efficient enough to save some money on the building envelope, or, conversely, that your building envelope will need more support in certain areas of the building design where the HVAC system may not be as effective.

A great way to save up to 65% on utility bills while significantly increasing efficiency is by using a geothermal heat pump in your project’s HVAC system. While this option can cost more than others, it is highly versatile and has a long lifespan in addition to good control of heating and cooling, which, as mentioned above, is critical for moisture management in the building envelope.

4. Hire a Trained Inspector
Neglecting to bring in a qualified building envelope inspector has been cited as one of the top causes for envelope failure. While everyone does their best to make sure their project is constructed to top-notch standards, mistakes can still happen. An inspector is there to make sure that nothing was accidentally overlooked and offer any recommendations for improvement.

Allowing the extra time and money in your project schedule for an inspector to look over your envelope will verify it is in good working order, as leak-proof as possible, and prepared for long-term use. A good inspector will go over the entirety of the building, from the flooring to the garage and even the plumbing and wiring.

Integrity and Longevity
The building envelope makes the difference between mere shelter and a home. Creating a comfortable environment inside, one that is inviting for visitors or residents and optimized for the unique needs of the building, depends on a good building envelope. Using these tips will make certain your project’s envelope does an outstanding job and remains strong, sealed, and stable for years to come.