.BuildSysPro.Building.BuildingEnvelope.HeatTransfer.DoubleGlazingWindow

Information

Double glazing model based on the Window model but with simplified settings including the characterization of glazing properties according to the three following parameters:

• U (thermal conductivity of the glazing)
• (energy transmission of solar energy)
• g (solar factor)

Hypothesis and equation

As for the generic glass model:

• SW (short wavelength) radiations for solar irradiance on the outer face are separated into diffuse and direct. They are obtained by separate calculations after consideration of the glazing tilt and azimuth.
• LW (long wavelength) radiations with the external environment can be taken into account by connecting this model to a sky temperature (boolean GLOext=True in advanced parameters) and by specifying the surface tilt.

Regarding the rolling shutters, the assumptions are:

• No solar flux transmitted by the part obscured by the shutters
• Absorbed flux unchanged (PVC absorbency similar to that of glass)
• If the shutter is not completely closed (Coeff_Fermeture <95%), unchanged thermal resistance
• If the shutter is fully closed, increased thermal resistance of an additional thermal resistance, evaluated at 0.2 m²K / W (PVC thickness of 12 mm approx.)

When the window is open, there is "broke" of the conductance through the glass, and instead of that a debit of air renewal by natural ventilation is computed (refer to WindowNaturalVentilation).

Reduction coefficients of direct and diffuse fluxes may also be considered (if useReduction=True), based on:

• Type of window / French window (the % of frame is deduced from that)
• Coefficient representing the decrease in fluxes through net curtains
• Coefficient representing the decrease in fluxes due to window position (inner or outer)
• Coefficient representing the decrease in fluxes through curtains
• Coefficient representing the decrease in fluxes due to shadows (NB: there is also a model that can calculate precisely the surface fluxes on a vertical wall in case of eaves: FLUXsurfMask)

In addition, it is assumed that:

• The glazing coefficient U is given by the manufacturer for heEN673 = 25 W / m²K and hi = 7.7 W / m²K (standard EN673)
• The absorption and transmission coefficients are calculated for heEN410 = 23 W/m².K et hi = 7,7 W/m².K (standard EN673)
• Outer glass properties are considered to be identical to inner glass ones (, et )
• The glass absorption and reflection coefficients are considered independent of the direction
• The coefficients for the diffuse radiation are derived from Cadiergues formulas
• The glazing direct transmissivity is calculated based on the angle of incidence according to the French building regulation (RT) formulas

The Window model needs to know the surface transmission coefficient k of the glazing and coefficients of transmission and direct and diffuse absorption (TRDIR, TrDif, AbsDir and AbsDif).

k is defined directly depending on U according to the standard EN673: where he = 25 and hi = 7.7 W/m².K

Then, knowing that , where qi is the factor of thermal retransmission towards the inside of the glazing.

And that where he = 23 and hi =7.7 W/m².K (standard EN410). The direct absorption coefficient of the solar energy outside of the glass is considered identical to the one inside.

The glass absorption coefficient is:

Coefficients of absorption and transmission by double glazing ( et ) of the direct radiation at normal incidence are then determined considering the laws of reflection and transmission in a double glazing with , and glass properties

Knowing and , is deduced after resolution of the above equations system.

The coefficient of direct radiation is deduced:

Note: these coefficients are then the ones used in the block DirectTrans that uses a correlation to determine these coefficients as a function of the angle of incidence. Then the weighting used is the one specified in the RT (French building regulation).

Then Cadiergues relations are used for the diffuse radiation

Concerning the calculation of natural lighting, global and diffuse light transmission factors that must be filled correspond to TLW, TLw_dif, TLsw and TLsw_dif which are calculated precisely in the EN 410 standard. However, it is possible to find tabulated values in the document Valeurs tabulées des caractéristiques des parois vitrées et des correctifs associés aux baies (Tabulated values of glass walls features and patches associated with windows) from CSTB. Thus, by default:

• For double glazing without sunscreen: TLW = 0.5, TLW dif = 0
• For double glazing with opaque and dark sunscreen on the outside: TLsw = 0, TLsw_dif = 0
• For double glazing with non-opaque and clear sunscreen on the outside: TLsw = 0.09, TLsw_dif = 0.03

Bibliography

Normes EN410 et EN673

R. Cadiergues, 1978, L'absorption du rayonnement par les vitrages et son calcul. 1-Les vitrages non réfléchissants, Promoclim E, Etudes Thermique et Aérauliques, Tome 9 E, n°1

R. Cadiergues, 1978, Un mode simple de calcul des flux à travers les vitrages. 1-Les vitrages non traités, Promoclim E, Etudes Thermique et Aérauliques, Tome 9 E, n°1

Eclairement naturel : Règles Th-L - Caractérisation du facteur de transmission lumineuse des parois du bâtiment - CSTB Mars 2012, Valeurs tabulées des parois vitrées - CSTB Mars 2012

Instructions for use

The thermal ports T_ext and T_int must be connected to temperature nodes (connect T_ext to T_dry of Meteofile).

The external incident flows FLUX can come from the BoundaryConditions.Solar models which are the link between walls and weather readers.

The internal incident flows FluxAbsInt can come from occupants, heating systems but also from the redistribution of solar flux within a room (models from BoundaryConditions.Radiation).

Known limits / Use precautions

The following precautions should be considered:

• Internal and external convection coefficients can be different from those used for the standard for thermal calculations
• should not be confused with the coefficient TL which is light transmission often given by manufacturers

For the calculation of illuminance, it is needed to clarify whether there are upstream masks because then the consideration of shadows caused by the architecture is done in the mask model.

Validations

Model validated by verifying that the coefficients of absorption and transmission of direct and diffuse radiation as well as the input conductivities of Window model were well consistent with those determined via an Excel sheet based on the formulas of the standards used.

Validated model - Aurélie Kaemmerlen 05/2011

--------------------------------------------------------------
Licensed by EDF under a 3-clause BSD-license
Copyright © EDF 2009 - 2023
BuildSysPro version 3.6.0
Author : Aurélie KAEMMERLEN, EDF (2011)
--------------------------------------------------------------

Revisions

Gilles Plessis 06/2011 :

• Introduction coefficient normatif EN 410 et 673 pour he (respectivement 23 et 25 W/m²/K) et hi à 7.7W/m²/K
• k (conductance thermique du vitrage) est alors déterminé par he et hi de EN 673 au lieu de hs_ext et hs_int qui sont utilisées dans les calculs thermiques

Aurélie Kaemmerlen 10/2011 : Ajout des échanges avec l'environnement (ciel et sol)

• Un nouveau booléen a été ajouté pour permettre de considérer ou non ces deux échanges
• L'inclinaison et l'émissivité en GLO du vitrage ont ainsi été ajoutées pour caractériser ces échanges
• La transmittivité directe est calculée par la formule de la RT

Amy Lindsay 03/2014 : - ajout de la possibilité de commander un volet (fermeture_volet qui varie entre 0 et 1 - 1 quand le volet est fermé, 0 quand le volet est ouvert), avec la résistance thermique supplémentaire que cela engendre.

- ajout de la possibilité d'ouvrir la fenêtre (true quand la fenêtre est ouverte, false quand elle est fermée) avec le débit de ventilation naturelle que cela engendre

- ajout des coefficients de réduction des flux diffus/direct en fonction du type de fenêtre / porte fenêtre, de la présence de voilages, rideaux etc. issus des stages de Raphaelle Mrejen (2012) et Alexandre Hautefeuille (2013)

- changement des FluxSolInput en RealInput pour les flux absorbés intérieur pour éviter les confusions (ces flux absorbés en GLO ou en CLO peuvent non seulement provenir du soleil, mais aussi d'autres sources radiative)

Laura Sudries, Vincent Magnaudeix 05/2015 : Prise en compte des flux lumineux incidents sur la baie pour calculer les flux lumineux transmis à travers la baie considérée (direct, diffus, réfléchi par le sol) et l'éclairement total incident sur la baie. Equations issues de la RT2012.

Gilles Plessis 07/2015 : Homogénéisation des paramètres avec ceux du modèle Window.