Passive construction? Is it a trend that is likely to develop in Poland? Practice shows that yes. Those who focus on energy saving, on ecology, build in at least energy-saving standard, and increasingly often just passive. What does a passive house mean ? How to choose windows for such buildings?
The most important thing that must characterize a passive building, i.e. one with advanced energy-saving technologies, is very low energy demand for space heating.
Energy demand
The annual energy demand of a passive house must not exceed 15 kWh/(m²*year). This is very little, considering that, for example, for an energy-efficient house it is a maximum of 40 kWh/(m²*year), while in traditional construction it reaches up to 180 kWh/(m²*year).
Such high requirements entail the need to use the highest quality building materials, including very warm modern windows. It is the windows that have quite a challenge here, because a passive building must make the most effective use of the natural energy source, which is solar radiation. So the role of windows is very important here, hence the need to install passive windows, with large glazing, installed on the appropriate side of the house, which will allow heating the interior with the heat energy of the sun.
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Heat transfer coefficient of passive windows
Uw, or the heat transfer coefficient for the entire window, is one of the most important parameters for passive windows. A good window for a passive house must meet the standards required by the Passive Building Institute in Darmstadt. The heat transfer coefficient for the entire window Uw must not be higher than 0.8 W/m²K!
Solar radiation transmittance g
Windows in the passive standard must also have a certain solar transmittance called g. The g-factor indicates what proportion of the energy of solar radiation that falls on the glass is let into the room - g is expressed as a percentage. The higher the g-factor, the more radiation reaches the interior. In passive windows, g ≥ 50%.
Air permeability
The tightness of windows depends on this parameter. The lower the air permeability, the better the tightness of the windows. Air permeability is the amount of air flow through a closed window, caused by the difference in pressure on the outside and inside of the building. The parameter is expressed in m³/h. Good windows should have air permeability in classes 3 or 4. This is a classification of air permeability in relation to the length of the contact line at a pressure of 100 Pa and maximum test pressure:
- class 3 - air permeability of 2.25 m³/(h-m) and maximum test pressure of 600 Pa,
- Class 4 - air permeability of 0.75 m³/(h-m) and maximum test pressure of 600 Pa.
Passive windows should have a class 4 rating.
Temperature coefficient fRsi
Windows are also subject to requirements relating to surface condensation. This parameter is called the temperature coefficient fRsi. The coefficient is used to assess the possibility of condensation, and thus the danger of mold formation on the surface of building partitions. The value of fRsi is the difference between the surface temperature and the outdoor air temperature (θsi - θe) divided by the difference between the indoor and outdoor air temperatures (θi - θe). Standards allow a minimum value of fRsi = 0.72. Partitions (including windows) should have at least this fRsi value.
Layout of windows in a passive house
The more glazing on the southern (sunniest) side, the better. The larger the glazing dimensions are designed on this side of the building, the greater the energy gains from solar radiation will be.
NOTE: Large glazings should have as few divisions as possible, since any division worsens the window's Uw coefficient and causes heat loss.
Installation of passive windows
To reduce heat loss as much as possible, you need to take care of proper window installation. Here not only the technique and materials used for this, but also the experience of the installation team are important. The most important thing is to achieve excellent insulation of walls with window openings, and this forces the location of the window in the thermal insulation layer. Such an installation is not typical, as it is necessary to extend the windows into the thermal insulation, which is troublesome. Therefore, it is recommended to use system solutions that allow windows to be installed in the plane of thermal insulation (these include reinforced anchors or special profiles mounted to the wall, helping to keep the windows in the plane of insulation). Passive window installation should also use special sealing tapes that insulate both the prepared window opening and the frames. Professional installation and proper insulation of the windows are aimed at eliminating thermal bridges, which is insanely important in passive construction.
Passive window covers
On sunny days, large glazings acquire energy. However, when it is very hot outside, even hot, effective window guards may be necessary. Therefore, when ordering windows right away, you should think about blinds (including external), roller blinds, awnings... On the other hand, when it's a cloudy day, large windows can cause heat loss. Then these covers will reduce the escape of heat to the outside.
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The perfect window for a passive house
AdamS is the first certified manufacturer of passive windows. It has obtained a certificate confirming the production of PASSIV-LINE ULTRA windows from certified passive building components, which have been tested by the Passive House Institute in Darmstadt. The certificate was issued by the Polish Günter Schlagowski Institute for Passive Building and Renewable Energy.
Choosing these PASSIV-LINE ULTRA windows, we are assured of their high quality and compliance with the requirements and standards for passive houses:
- Very good heat transfer coefficientUw=0,66 (W/m2K)
- The profiles of these windows have thermoplastic inserts reinforced with fiberglass and chambers filled with polyurethane foam.
- Warm triple-glazed, double-chambered package withUg=0.5 (W/m2K).
- Used ECLAZ glazing, which allows 10% more light Lt to pass into the room and solar energy g to extract energy from radiation.
- The SWISSPACER ULTIMATE warm frame eliminates thermal bridges at the interface between the frame and the glass. The frame is recognized by the Darmstadt Institute as necessary to meet the requirements for passive windows.
- They have a high airtightness Q100 = 0.06m3/(hm), which is one of the necessary parameters for passive windows.
More about the PASSIV-LINE ULTRA window: here
