Up-scaling and mainstreaming sustainable building practices in western China
Up-scaling and mainstreaming sustainable building practices in western China 

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

In Europe have been developed a variety of future-oriented sustainable building materials and components. These include insulation materials, windows and glazing systems, Phase Change Materials (PCMs), and Advanced Building Integrated PV (BIPV) systems. This blog post will describe the performance, properties and application examples of advanced windows and glazing systems. For further details on insulation materials, Phase Change Materials (PCMs), and Advanced Building Integrated PV (BIPV) systems, please access the other parts of the blog posts on Future-oriented sustainable building materials/components in Europe.

 

      Part A: Insulation materials

     Part C: Phase Changing Materials (PCMs)

     Part D: Advanced Building Integrated PV (BPIV)

 

           Windows represent a very important part of the building envelope and are at the same time the least insulating elements of the        building shell. However, optimum designs for windows exist, which attempt to provide a balance between energy flows. 

 

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.

Example of a smart glass technology.

Left: more transparent, Right: less transparent 

(Albright, p.17)

For more information, please read our training handbook.

Albright, B. Switch Materials Inc. - Smart Window Technology (Presentation)