INTERNATIONAL. STANDARD. ISO. First edition. Thermal performance of windows, doors and shading devices — Detailed calculations. 5 Jan ET ISO Thermal performance of windows, doors and shading devices [ archiveorg width= height= The standard is identical with ISO Thermal performance of windows, doors and shading devices — Detailed calculations published by International.

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They have mainly an effect on the temperature and radiation conditions outside the window. An appropriate value is to be determined iso 15099 the basis of experiments or calculations [computational fluid dynamic CFD modelling].

Once iso 15099 beam transmitting through or reflecting iiso a solar shading device is split into a direct and a diffuse part, the diffuse part continues its route through the system.

It is necessary to determine the portion of incident solar radiation, at a given wavelength, that is absorbed at each of the glazing layers. Use the following criteria to determine if it is kso to apply the above procedure.

The direction of heat flow shall be determined from the temperature difference between vertical and horizontal surfaces of the equivalent cavity. The optical properties for radiation from the inside are needed isoo iso 15099 multiple reflections at the successive layers in the transparent system. In the heat balance equations for the isl, the heat extracted from or supplied to the gap by ventilation is added to this air gap node. Also, it is important to inspect the direction iso 15099 heat flow after the initial run, because if the direction of the bulk of heat flow 1099 different than iso 15099 specified, it will need to be corrected for the next run.

Since those factors are highly variable, an exact mathematical analysis of the iso 15099 surface convective heat transfer is not possible at this time due to the difficulty in defining the external surface and the highly variable wind conditions. In each case the following spectra shall be used. iso 15099

## ET ISO 15099: Thermal performance of windows, doors and shading devices — Detailed calculations

If neither of these sources is used, the thermal conductivity values are to be determined in accordance with ISO guarded hot plate or ISO heat flow meter at a mean temperature appropriate to national standards. Second, use Equation A. The equivalent conductivity is twice that of an unventilated air cavity of the same size in accordance with 6.

Using the bulk model, the optical indices of the material can iso 15099 be calculated and used to derive the hemispherical properties. For undated references, the latest edition of the referenced document including any amendments applies. In that case the equations given above remain valid, if “air” is replaced by “gas-mix”, with the corresponding gas-mix properties.

It is often assumed that internal fenestration surfaces are irradiated only by the internal room surfaces, which are treated as a large enclosure existing at the internal air temperature.

For these cavities, the following procedure shall be used to determine which surfaces iso 15099 to vertical iso 15099 horizontal surfaces of equivalent rectangular cavity see also Figure The effect of three-dimensional heat transfer in frames and glazing units is not considered. A, 16 5 Vision area properties 5.

The emissivity of the internal surface is reduced by the factor iso 15099 in Equation Iso 15099 jamb frame sections, frame cavities are oriented vertically and therefore the height of the cavity is in the direction normal to the plane of the cross section. The governing equation shall be discretized using a iso 15099 formulation i.

The heat exchange by ventilation between the shading and the next layer pane can be described on the basis of an appropriate value for the air flow or velocity. Finally, the desired portions of incident radiation at each of the iso 15099 layers are given by: It is assumed that external longwave irradiance depends on the clearness of the sky factor, f iso 15099.

The temperature profile in the spaces is represented by the thermal equivalent temperature [Equation ].

### ISO – Thermal performance of windows, doors and shading devices — Detailed calculations

Frames iso 15099 be made from a variety of materials, but most common materials are wood, iso 15099, aluminium and combinations of those iso 15099.

The cloudy portion of the sky is treated as large enclosure surfaces existing at the external air temperature. Consequently the following solar properties of the solar shading device are required or transmittance, for beam radiation, for each angle of incidence: For a glazing assembly in which a shading device is involved, the amendments to the equations of 5. The radiosity of surface j, Jj, is given by: Nu is calculated using correlations based on experimental measurements of heat transfer across inclined air layers.

Where this is iso 15099 the case the values listed in ISO may be used, but only if they directly match the materials used in the window construction.

Due to the air flow through the space, iso 15099 air temperature in the space varies with height iso 15099 Figure NOTE For more information on the norm or root mean square values of the temperature vector, see [30]. The following equation shall be used to calculate the total thermal transmittance: Adjustments to the dimensions of the geometric model are allowed only if they have no significant influence on the calculation see ISO Because the layer iso 15099 of shading device is modelled as a iso 15099 layer similar to a pane or film, the two- or three-dimensional characteristics shall be translated into one-dimensional numbers.

For conservative design calculations, the izo for the equivalent air permeability of the surface, A hocan be set to extreme low and extreme high values, thereby giving two extremes for the total solar energy transmittance.

Also, for more information on the cross-string rule, see [26]. Intermediate values iso 15099 E X W shall be found by linear interpolation of the tabulated values. Internal irradiance then becomes: In the case where there are exterior and interior open frame profile cavities ventilated cavities and groves the procedure described in 6.

For an unventilated, irregularly shaped frame cavity, the isl shall iso 15099 converted into the equivalent of a rectangular cavity in accordance with the procedure in ISO see also Iso 15099 For field conditions, external irradiance can be defined ido the use of external mean radiant temperature, T m iso 15099 NOTE Depending on future modifications of ISOspecific additions may be added to this International Standard covering 1509 effects of optical properties of products shading devices, diffusing panes, etc.

For these systems, individual fenestration surfaces iso 15099. For slat type shadings, equations to calculate these properties are given in 7.