Transparent building envelope: characteristics, heat losses and information on the materials used for setting up large windows.
L'glazed building envelopecan help us make the most of solar radiation both for natural lighting and for the management of the building's thermal load. Based on what has just been said, thetransparent building envelopeit must be wellsized and follow a guideline in order to ensure good solar gains. Based on factors such asthickness, materials, air chambers, single glass or double glass, L'transparent building envelopeit can help maintain a good energy efficiency of the entire building by containing heat loss.
Transparent building envelope, energy efficiency and criticality
L'glazed building envelopehas several critical issues: while it is true that it offers natural lighting and solar radiation, on the other it forces the construction sector to develop strategies to protect the inhabitants from the high thermal load that the sun's radiation itself produces. Other critical issues are connected with glare and thermal bridges.
The solar radiation offered by thetransparent building envelopeit is positive in winter but negative in summer. For this reason it is necessary to develop control systems and solar shading (to learn more: solar shading, what they are) in the summer months so as not to burden the air conditioning. The glare problem is solved byanti-solar and anti-reflective shielding filmswhile to maximize irradiation in winter and minimize it in summer, there is no lack of automatic home automation systems capable of changing orientation based on the sun, temperature and preferences of the inhabitants (for further information: solar shields).
Other critical issues of no secondary importance are related to noise pollution: thestained glass windowit must insulate from cold in winter, from heat in summer but also from noise at any time of the year. In addition, the effect of solar radiation on interior furnishings should be considered: the sun tends to dilate the skin, paintings and other materials of particular value are sensitive to prolonged sun exposure.
To guarantee the maximumsoundproofing, L'transparent building envelopemust exploit the same measures used to ensure control of thermal transmission, namely:
- Frames and boxes with well built structures.
- Increased thickness.
- Increase in the number of glasses used.
- Air chambers or other gases interposed between the layers of glass to decrease thermal transmittance and increase soundproofing.
- Use of new transparent materials.
When it comes totransparent building envelope, the need for shielding systems and filters is mandatory by law. The regulatory reference for new buildings and in the case of renovation is Presidential Decree 192/2005, in particular Article 3, paragraph 2.
For thecalculation of thermal transmittanceofglazed building envelopeit refers toUNI EN ISO 10077-1. This principle applies both to windows (glass, plastic, with air or other gas cavities ...), to all types of frames and to closures according to their air permeability. On the contrary, the calculation of theUNI EN ISO 10077-1it should not be applied in case ofcontinuous transparent building envelope, i.e. curtain walls and glass structures not embedded in a frame (excluding skylights).
The materials to consider in case ofstained glass windowsThey are different. To name a few:
- Common glass
It is the classic transparent glass and forms the basis of special glass.
- Solar control glass and reflective glass
They intercept infrared radiation without hindering visible radiation. The glass absorbs infrared rays without letting them penetrate the home environment.
- Low-emissivity glasses
They reduce heat loss in winter.
- Selective glasses
They take advantage of the properties of low-emission glass and reflective glass.
- Diffuser glasses
Guy glass brick, these are frosted, satin or ornamental glass that let the light through but are not transparent.
- Absorbent glass or athermic glass
They are coated with natural films and control solar radiation by energy absorption, they have the defect of not guaranteeing maximum natural lighting in the environment.
- Photochromic glasses
Like photochromic lenses, they become dark in the presence of a lot of light and migrate towards transparency when the light intensity decreases.
- Safety glass and wired glass
These are high-thickness or two-layer glasses. They can have a fine metal mesh (wired glass). They work like a car windshield: in case of breakage, a film retains the glass fragments.
- Solar collapsing glass
It allows the transmission of sunlight but shields radiation of different wavelengths.
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