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The Building Envelope
Energy Efficiency, Comfort, and Health | Components | Thermal Insulation | Air Sealing and Weatherization | Radiant Barrier | Vapor Barrier | High Performing Double Pane WindowsQuick Facts
- Isolates the interior of a home from the exterior environment, keeping a home warm in winter, cool in summer, and preventing infiltration of exterior pollutants into the living space, when defined correctly
- A network of functional subsystems which work together to protect the home from different types of infiltration and conduction
- Ideally should be addressed and properly defined as a first step in the home energy retrofitting process, prior to heating and cooling systems or renewable energy production
- A properly designed and installed building envelope can substantially reduce active cooling and heating needs and indoor air pollution
Energy Efficiency, Comfort, and Health
The building envelope is what separates your home from the outside world. It can be thought of simply as the walls, windows, doors, roof, and floor but in fact it can be much more. A properly designed and installed building envelope can reduce the load on your heating and cooling systems by isolating interior temperatures from exterior influences. The goal is to cost effectively increase the comfort of your home while simultaneously making it more energy efficient. In addition, a properly sealed building envelope will stop the flow of pollutants from unconditioned regions of the home such as the attic and the crawlspace, making the living space a much cleaner, healthier living environment.
Components
Thermal Insulation | Air Sealing and Weatherization | Radiant Barrier | Vapor Barrier | High-Performing Double-Pane Windows
All systems are made up of functional components. Like any system, the value of the whole is worth much more than the sum of the parts. The components cannot be considered independently of the others.
Thermal Insulation
This is the most familiar and well known component of the building envelope. In any climate it is vital that a home be properly insulated or conditioned air (heated or chilled) will be wasted. Insulation works by capturing air in millions of tiny pockets in order to impede the conductive transfer of heat between regions which are different temperatures. However, like a warm sweater on a windy day, it will not function properly if air is allowed to flow through it. The effectiveness of insulation is measured in R-value, which is severely compromised by convective air flow. The solution is stopping that air flow with a proper air barrier and thorough air sealing . [+] MORE
Air Sealing and Weatherization
A home’s building envelope should be sealed even before it is insulated. Much like a water pitcher full of cracks will not hold water, a house full of leaks and cracks will not retain the conditioned air, nor a comfortable interior temperature. Conditioned air will be expelled out of even the tiniest of air leaks; insulation will not be able to do its job and energy used to heat or cool the air will be wasted. Sealing a home with simple tools such as caulk and foam is the most cost effective way of improving your home’s performance and of assuring the other systems can work properly and efficiently. Leaks add up and they are often difficult or nearly impossible to detect by the untrained homeowner, and only a home performance expert will have the tools and technology to fully seal your home. [+] MORE
Radiant Barrier
In many climates, the positive effects of insulation and air sealing can be further extended by the application of a radiant barrier; particularly if your heating or cooling systems are in the attic. Comprised of reflective material, a radiant barrier is the first line of defense against radiant heat transfer along the building envelope by reflecting heat out in the summer and inside in the winter. [+] MORE
Vapor Barrier
In humid climates, moisture can severely compromise the health and comfort a home if is allowed to infiltrate the building envelope. In this case the installation of a non-permeable surface can greatly improve the functioning or the home’s other systems (such as air conditioning and air filtering) by reducing loads and the risk for a moldy or overly dry living space. A vapor barrier must be planned in conjunction with the home’s ventilation system in order to fine tune optimal humidity levels and breathability. [+] MORE
High-Performing Double-Pane Windows
While windows may not be the first thing that comes to mind when people think of insulation, high performance windows, when installed correctly, can have a dramatic effect on the insulation of the building envelope since almost a third of the heat in a home can be lost through low performing windows (including basic double pane windows as well as single pane windows). While replacing windows with high performing ones may not provide cost effective air sealing and insulation in all regions (they will be more cost effective in areas with more extreme weather—hot or cold), it is certainly an important step for attaining the most significant improvements. [+] MORE