Future-oriented sustainable building materials/components in Europe - Part B: Advanced windows and glazing systems

Double or triple glazing systems with low e-coating

Technical details

• The use of multiple glazing layers, low-conductivity gases (argon in particular) the layers, low-emissivity coatings on one or more glazing surfaces and the use of framing materials with much lower conductivity have improved the thermal conductivity of windows.

Application

• Their application is more prominent as part of the building envelope.

Performance

• These systems have only 25-35% of the heat loss of standard non-coated double-glazed and 15-20% of single-glazed windows.
• In recent years the performance of glazing design has been improved from single glazing with U-value=5.6 W/m²K (undesirable), to triple or even quadruple glazing with special treatment, achieving U-values=0.4 W/m²K (desirable).

Advantages/Disadvantages

• +Offer cooling or heating energy savings in the range of 3 % to 10% compared to typical single glazing systems.
• -The overall window U-value depends on the window frame and thermal bridging and thus reduces the glazing U-value by a marginal factor in highly insulated frames and by considerable factor in poorly insulated metal or wooden frames.

Smart and dynamic windows - Passive systems

Technical details

• Passive systems react to the natural light or heat stimuli in the immediate surroundings.
• There are two key passive technologies: Photocromatic glazing and Thermochromic glazing

Application

• The application of photochromatic glazing is more prominent in optical and car industry.
• The application of thermochromic glazing is more prevalent compared to photochromatic glazing.

Advantages/Disadvantages

• +They are easy to install and to maintain compared to the active systems;
• -They lack the user controllability

Photocromatic glazing:

• -High costs, uniform distribution of photochromatic substances and the loss of reversibility over time are major obstacles to their application in buildings.

Thermocromatic glazing:

• +Their application is more prevalent compared to phtochromatic glazing.
• -Key drawbacks of this technology include disability to eliminate glare in specific situations of low temperature and high solar radiation.

Smart and dynamic windows - Active systems

Technical details

• Are similar to passive systems in terms of modulating the optical properties, but can be directly controlled by the users or controlled automatically by the integration of a building automating or management system.
• They can be adjusted using minuscule energy, based on a variety of factors such as internal and external temperature, external radiation, natural lighting levels and user needs etc.
• Key active systems: Electrochromic devices (EC), Suspended particle devices (SPD), Polymer Dispersed Liquid Crystal Device (PDLC).

Application

• Large range of potential uses: building envelope, car industry and optical industry.

Performance

• EC - Light transmission lays between 1% and 60%. Energy required for the transition 1-2.5 W/m² , energy required to maintain the desired tinted state 0.4W/m²
• SPD – Block up to 99.4% of visible radiation, visual light transmission  0.5-65%. Energy required for the transition 5W/m², energy required to maintain the desired tinted state - 0.55 W/m²
• PLDC - Light transmission lays between 50-70%. Energy required to maintain the desired tinted state -  5-10 W/m² of energy to maintain the desired state.

Advantages/Disadvantages

• +Can be directly controlled by the user.