A building’s energy performance depends on more than its heating and cooling equipment. Walls, roofs, windows, doors and framing systems determine how easily heat moves between indoor and outdoor environments.
When the building envelope performs poorly, HVAC systems must compensate for heat loss, solar heat gain and air leakage. During colder months, heat moves through poorly insulated surfaces, while conditioned air may escape through gaps around windows, doors and joints. In warmer conditions, direct sunlight and high outdoor temperatures can increase cooling demand.
High-performance glazing, effective seals and properly designed aluminum frames can limit these exchanges. Technologies such as insulating glass, Low-E coatings and thermally broken framing can improve indoor comfort while reducing the energy required to maintain stable temperatures.
What Is Energy Efficiency in a Building?
Building energy efficiency refers to the ability to maintain comfortable and functional indoor spaces without consuming more energy than necessary.
It depends on the interaction between several elements:
- Building design and orientation.
- Performance of walls, roofs and exterior openings.
- Heating, ventilation and air-conditioning systems.
- Air leakage around doors, windows and joints.
- Glass and framing specifications.
- Local climate and seasonal temperature changes.
Thermal performance is one part of energy efficiency. It describes how well the building envelope controls heat transfer between the interior and exterior.
A building with better thermal performance experiences fewer temperature fluctuations around its perimeter. This can reduce the workload placed on heating and cooling systems and improve comfort near windows, entrances and glazed walls.
How the Building Envelope Controls Heat Transfer
The building envelope separates conditioned interior areas from the outdoor environment. It includes roofs, walls, floors, windows, skylights, storefronts and exterior doors.
Heat commonly moves through the envelope in three ways:
- Conduction: Heat passes through materials such as glass, aluminum, concrete and framing components.
- Solar heat gain: Solar radiation enters through glazing and raises indoor temperatures.
- Air infiltration: Outdoor air passes through gaps, joints or poorly sealed openings.
A storefront, for example, may conduct heat through its aluminum frame while also allowing air to pass through worn seals or improperly finished perimeter joints.
Exterior openings require particular attention because several materials and connection points meet within a relatively small area. Glass, framing, gaskets, thresholds and surrounding construction must work together to control heat transfer and air leakage.
Exterior entrances
Commercial entrances are opened frequently and remain exposed to changing outdoor conditions. Gaps around door panels, thresholds and frames may allow unwanted airflow, particularly when seals are damaged or incorrectly fitted.
Glazed openings
Large glass areas provide daylight, visibility and an open architectural appearance. Their energy performance, however, depends on the glass composition, coatings, sealed airspace and framing system.
Aluminum frames
Aluminum offers strength, durability and narrow profiles, making it suitable for storefronts, entrances and other architectural systems. Because it conducts heat efficiently, exterior aluminum framing may require a thermal break to separate its indoor and outdoor surfaces.
Joints and transitions
Connections between glass, frames, walls and adjacent materials must be sealed correctly. Even a well-designed glazing system can underperform when installation gaps permit uncontrolled airflow.
How Windows and Doors Affect Building Performance
The performance of a window or door depends on the complete assembly rather than one material considered in isolation.
Important factors include:
- Number and type of glass panes.
- Width and condition of the sealed airspace.
- Low-E or reflective coatings.
- Thermal performance of the frame.
- Quality of gaskets and perimeter seals.
- Size and orientation of the opening.
- Direct solar exposure.
- Fabrication and installation quality.
A system designed for the building’s climate and orientation can limit heat loss during colder periods and reduce unwanted solar heat gain in warmer weather. It can also improve interior surface temperatures, reducing uncomfortable hot or cold zones near exterior openings.
A west-facing commercial storefront, for example, may require greater solar control than a shaded entrance. An opening in a colder climate may place more emphasis on insulating performance and interior surface temperature.
Energy-Efficient Glass Options
Glass selection affects thermal performance, daylight, glare, appearance and occupant comfort. The appropriate configuration depends on the location of the opening and the priorities of the project.
Insulating Glass Units
Insulating glass units, or IG units, consist of two or more panes separated by a sealed airspace.
Compared with single-pane glass, this construction reduces heat transfer through the glazed area. IG units may also incorporate tempered, laminated, tinted or coated glass, depending on the application.
Their performance is influenced by:
- Glass composition.
- Airspace width.
- Spacer system.
- Perimeter seal.
- Low-E coatings.
- Framing system.
Insulating glass is widely used in exterior windows, entrances, storefronts and other applications where thermal performance is a design priority.
Low-E Glass
Low-emissivity glass includes a thin coating that controls the movement of infrared energy through the glazing.
Depending on the coating and its placement within the glass assembly, Low-E glass can reduce heat loss, limit solar heat gain or balance both requirements. It allows projects to improve thermal performance without eliminating natural light or exterior visibility.
Low-E coatings are commonly incorporated into insulating glass units to improve the performance of the complete assembly.
Reflective Glass
Reflective glass is designed to reflect part of the solar energy reaching the building. It can reduce glare and solar heat gain while creating a distinct exterior appearance.
This option is often considered for commercial facades and large glazed openings exposed to strong sunlight. Its use should account for building orientation, desired visible light levels and the appearance of the surrounding facade.
Why Thermally Broken Aluminum Systems Matter
Aluminum is frequently used in storefronts and exterior entrances because it combines structural performance, durability and clean architectural lines. Its conductivity, however, can allow exterior temperatures to move through the frame.
A thermally broken system separates the interior and exterior aluminum sections with a less conductive material. This interruption limits direct heat transfer through the frame.
Depending on the complete system and project conditions, thermal breaks can provide:
- Better frame thermal performance.
- More stable interior surface temperatures.
- Improved compatibility with insulating glass.
- Greater comfort near exterior openings.
- Better condensation control under appropriate indoor and outdoor conditions.
Using high-performance glass with a conventional conductive frame may limit the improvement achieved by the glazing. For this reason, the glass and aluminum system should be specified together.
- Benefits Beyond Lower Energy Use: Improved thermal performance can affect more than utility consumption.
- Greater comfort near exterior openings: Better-performing glass and frames reduce extreme interior surface temperatures. This can limit hot and cold zones near windows, storefronts and entrances.
- Lower heating and cooling loads: When the envelope limits heat transfer and air leakage, HVAC equipment has fewer temperature changes to compensate for. The actual reduction in energy use depends on the climate, building design, existing equipment and installation quality.
- Improved condensation control: Higher interior surface temperatures can reduce the likelihood of condensation in colder conditions. Indoor humidity, ventilation and exterior temperature must also be considered.
- Acoustic improvement: Insulating glass may contribute to better sound control, particularly when combined with laminated glass, different glass thicknesses or asymmetric configurations. Acoustic performance should be evaluated separately from thermal performance because the best solution for one objective is not always the best for the other.
What to Consider Before Selecting a System
The appropriate glass and aluminum configuration changes with the building, climate and intended application. Before specifying an exterior system, project teams should evaluate:
- Local climate and seasonal temperature ranges.
- Orientation and solar exposure.
- Size and location of glazed openings.
- Applicable building and energy codes.
- Required U-factor and solar heat gain performance.
- Safety, security and impact requirements.
- Desired daylight and exterior appearance.
- Interior humidity and potential condensation.
- Compatibility between glazing, framing, seals and hardware.
- Fabrication and installation requirements.
These factors help determine whether the project requires insulating glass, a Low-E or reflective coating, thermally broken framing or a combination of several technologies.
Energy-Efficient Glass and Aluminum Solutions from PRL
PRL Glass & Aluminum fabricates coordinated glass and aluminum systems for residential, commercial and industrial projects.
Available options include insulating glass units, Low-E and reflective coated glass, as well as thermally broken aluminum systems for storefronts, entrances and bifold doors. Glass configurations can be selected according to the thermal, safety and architectural requirements of the application.
PRL can also provide complete pre-glazed systems with specified hardware and materials. Coordinating the glass and aluminum within the same fabrication process can reduce compatibility issues and simplify installation at the project site.
For buildings that require improved thermal performance, PRL can help architects, contractors and property owners evaluate glass and framing options based on the opening, climate and intended use.
