Solar shading in nearly Zero Energy Buildings · It reduces the heat losses of the window A solar protection device extended in front of a window introduces an additional air space

REHVA Annual Conference – May 19th and 20th 2011

Solar shading in nearly Zero Energy Buildings

Solar shading in nearlyZero Energy Buildings

Hervé LamyTallinn – May 19th 2011



► What are the Solar Shading products ?

Roller shutters

Pictures : Warema and France Fermetures




Roller shutters

Hinged shutters





Roller shutters

Hinged shutters

Concertina shutters





Roller shutters

Hinged shutters

Concertina shutters

External roller blinds





Roller shutters

Hinged shutters

Concertina shutters


Internal roller blinds





Roller shutters

Hinged shutters

Concertina shutters



Drop arm awnings





Roller shutters

Hinged shutters

Concertina shutters



Drop arm awnings

Folding arm awnings





Roller shutters

Hinged shutters

Concertina shutters



Drop arm awnings

Folding arm awnings

External venetian blinds





Roller shutters

Hinged shutters

Concertina shutters



Drop arm awnings

Folding arm awnings

Internal venetian blinds






Roller shutters

Hinged shutters

Concertina shutters



Drop arm awnings

Folding arm awnings



Conservatory awnings





Roller shutters

Hinged shutters

Concertina shutters



Drop arm awnings

Folding arm awnings




Façade awnings





Roller shutters

Hinged shutters

Concertina shutters



Drop arm awnings

Folding arm awnings




Façade awnings

And much more ...




All these products can be operated:

Manually (crank handle, …)

Motorised with an individual command

Motorised with a centralised command

Automated with a command depending on :

the time (clock)

the climatic conditions (incident radiation)

the connection to the Building Management System




The choice of a product and of a type of command will directly influence

• The thermal and visual properties of the windows and therefore the performance of the building

• Some parameters related to other functions of the products

Roller shuttersExternal venetian blinds



► What is the role of Solar Shading in nZEB ?

Role of the glazed envelope in nEZB :

1. To optimise the solar gains during the heating season

► Reduction of the heating needs

2. To minimise the solar gains during the cooling season

► Summer comfort or reduction of the cooling needs

3. To minimise the thermal losses

► Reduction of the heating and cooling needs

4. To insure the maximum of daylight all over the year

► Reduction of the lighting needs

5. To insure the visual comfort of the occupants

► Glare control

The properties of the glazed envelope shall vary depending on the

season, the period of the day, the wishes of the occupant, etc.

Thermal

Visual




Solar shading is the thermal and visual variator of the glazed envelope:

R1

1

U

U

w

ws

► It reduces the heat losses of the window

A solar protection device extended in front of awindow introduces an additional air spacecharacterised by an additional thermalresistance designated by R (in m².K/W). R iscalculated according to EN 13125.

The U value of a window associated to a solarprotection device is given by :






Some examples

Double glazing Uw = 1,8 W/m².K



R (m².K/W) 0,15 0,25 0,15 0,25 0,15 0,25

Uws (W/m².K) 1,42 1,24 1,29 1,14 1,16 1,04

Reduction of Uw -21,3% -31,0 % -19,3% -28,6 -17,4% -25,9%






► It controls the solar gains of the window

Solar shading varies the solar factor of the window:

• when retracted, the maximum flux is entering the room (heating period)

• when extended, it reduces the flux entering the room (summer comfort or cooling period)







The solar factor gtot is calculated for the association of the solarprotection device and the glazing according to :

• EN 13363-1 (simplified method), or

• EN 13363-2 (detailed method)

Example of the calculation according to EN 13363-1 (external blind)







EN 13363-2 considers the “real” behaviour the solar radiation througheach layer. It considers:

• The direct solar transmission t (short wavelength)

blind glass 1 glass 2









• The heat transfer (long wavelength) gth and the convection gc

glass 1 glass 2









• The heat transfer (long wavelength) gth and the convection gc

• The ventilation effect gv (in case of internal blinds)







Solar factor in the extended position

Solar factor with anexternal blind

Solar factor with aninternal blind







Example of detailed and simplified calculation for an external blind

Although it is detailed, EN 13363-2 shall consider some simplifiedhypothesis: the incident radiation is normal to the surface, forvenetian blind, there is no direct transmission, the radiation isperpendicular to the slat, etc.

EN 13363-1 EN 13363-2 (detailed)

gtot tv gtot te gth+gc tv tv,n-diff

White pearl 0,12 0,09 0,09 0,06 0,03 0,09 0,07

White grey 0,10 0,06 0,07 0,04 0,03 0,06 0,03

Grey 0,10 0,02 0,05 0,015 0,035 0,02 0,01







► It controls the visual transmittance of the window

Solar shading varies the light transmittance of the window:

• when retracted, the maximum flux is entering the room

• when extended, it protects the occupants from glare while allowing adiffuse light transmittance







► It controls the visual transmittance of the window

Light transmittance in the extended position

Light transmittance with aninternal blind





► Synthesis

A rather good description of a glazed envelope requires at least thefollowing values:

Glazed part with the solar shading

in the retracted position in the extended position

Thermal transmittance Uw Uws

Solar factor g

te

gtot

te

gth + gc gth + gc

gv = 0 gv

Light transmittancetv tv

tv,n-diff





► Synthesis

The consequence on the values:

Uw Uws

g

te

gtot

te

gth + gc gth + gc

gv = 0 gv

tv tv

tv,n-diff

Minimum valuesrequired

Maximum valuerequired in winter

Minimum valuerequired in summer

Maximum valuerequired alongthe year

Variable depending on the user needs

Holistic approach needed for the whole glazed part



► Some examples in residential premises

► Impact of the surface, the orientation and Uw of windows on the energy

needs

► The more there are glazed surfaces, the less are the energy needs

► A proper repartition of the glazed surfaces may even more reduce

the energy needs

Study carried out by Cardonnel Ingénierie (France)




► Impact of the surface, the orientation and Uw of windows on the energy

needs

► With the current technology there

is a limit of the U value reduction

► Solar gains are becoming the

relevant criteria, but then ...

Study carried out by Cardonnel Ingénierie (France)

What about the summer comfort ?




► But, then what about the summer comfort ?

Calculation made with Thermi’Baie® according to the Th-BCE rules (French RT2012)




► But, then what about the summer comfort ?

► Installation of a Solar Shading drastically reduces the overheating

period

► Summer comfort is optimised by using the proper scenario of

command



► Some examples in office premises



► Some examples in office premises

► In cooled premises, installation of Solar Shading drastically reduces the

cooling needs

► Cooling needs are even reduced by using the proper scenario of

command



► Conclusion

► Nearly Zero Energy Buildings will require to consider the glazed

system as a whole

► There is no definitive answer to choose the right products. A

holistic approach shall be considered to define the optimised properties of the components of the glazed system

► Solar shading will play a key role as being the variator of such

properties

► The number of criteria to be considered is so high that specific

tools shall be developed



► Thank you for your attention

Solar shading in nearly Zero Energy Buildings · It reduces the heat losses of the window A solar protection device extended in front of a window introduces an additional air space

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