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What Is the Building Envelope?
The building envelope is defined as the exterior shell of a house that repels the elements. The envelope is an under-appreciated engineering system that combines structural integrity, moisture control, temperature control, and air pressure boundaries into a single design strategy. "Loose" building envelopes do allow for natural ventilation in the home. However, they also become drafty, uncomfortable and make your HVAC equipment work harder to maintain your home at a comfortable indoor temperature. Almost half of the US's total household energy use is dedicated to heating and cooling our homes. So, sealing the building envelope is widely seen as one of the best ways to reduce our households' energy use and carbon footprint
Why Is the Building Envelope So Important?
The relationship between building envelopes and the energy efficiency of our homes is easy to imagine. The cracks, gaps, and fissures around our home allow the conditioned air inside our houses to escape. At the same time, they allow the unconditioned, outside air into our homes. Even if you have chosen the best, high-performance insulation and have gone above and beyond the recommended R-values for your region, a leaky building envelope essentially renders that insulation ineffective. When temperatures are below zero or above 100 degrees Fahrenheit outside, even a small gap in your building envelope can lead to drastic changes in your home's interior temperature.
There are dozens of different kinds of high-performance building tape, including options that have been specifically designed for use on:
- Rigid fiberglass duct board and flexible air duct: These tapes are usually made from aluminum foil material.
- Metal and Sheet Metal applications: Several types of building adhesive tapes are designed to cover junctions on ductwork and other areas where metal or sheet metal join or overlap.
- Sheathing: There are different types of building tape for specific use around wood and plywood sheathing.
- House Wrapping: Double-sided adhesive tape is most often used for overlaps on moisture barrier house wrap. This characteristic ensures that water and moisture can't get through.
- With Vapor Barriers in Crawl Spaces: Again, double-sided adhesive building tape is a good option for connecting vapor barriers to cement walls in crawl spaces. This feature helps to reduce moisture infiltration in basements and crawlspaces.
- Insulation: High-performance building tapes are also being increasingly used to ensure that batt-type insulation sticks to the walls where it is installed.
- Outdoor Component Layers: Specific building tapes such as the Wigluv tape by SIGA offer diffusible and rainproof properties for permanent wind-tight bonding of exterior component layers.
- Window and Door Frames: Building tapes can also be used to seal window and door frames permanently. This strategy improves your building envelope's airtightness even as wood or metal frames shrink or warp over time.
How Much Energy Can You Save with High-Performance Building Tape?
According to some experts, energy losses due to air leaks in a home's building envelope can range from 10 to 50 percent of total heat loss. A house with a significant amount of air leaks around door and window frames, exterior sheathing, and foundation connections is most likely spending a lot of money on its heating and cooling bills. Even with high-quality insulation that goes above and beyond the recommended R-values for your region, major air leaks will essentially render that insulation ineffective.
It is nearly impossible to put a number on potential savings associated with improving your building envelope's airtightness. However, several examples of passive homes with an utterly airtight building envelope spend $0 on their monthly energy bills. For example, this Denver townhouse combines an airtight envelope with other net-zero construction aspects. They save significant money on their monthly energy bills, even during the harsh Rocky Mountain winters. Using high-performance building tape to reduce air leaks will undoubtedly help reduce your monthly energy bills.
How to Install High-Performance Building Tape
Each type of high-performance building tape will have further instructions for proper installation and use. You apply most of these tapes by hand in the specific joints and overlaps where you need to cover. Double-sided adhesive building tapes will have a protective liner on one side. It will help if you peel this off before adhering, such as in the case with connecting overlaps of moisture barriers. Some products also come with a hand tape applicator that can efficiently and accurately apply your high-performance building tape for the specific use you need.
Benefits and Drawbacks of High-Performance Building Tape
High-performance building tape offers a cost-effective way to improve the airtightness of your building envelope drastically. SIGA, 3M, Lamatek, and others provide a wide range of products that can replace mechanical fasteners like rivets, screws, spot welds, and (potentially stinky) liquid adhesives on a variety of surfaces. More airtight building envelopes can quickly drive down your energy bills and help avoid moisture damage that can lead to issues for your home's insulation, framing, or other structural components. The only real downside associated with high-performance building tapes is that, in most applications, they are best used during the initial construction phase or significant renovations.
Tobias Roberts
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.