2. Simple Calculation Method
Project Overview
WP1: State of the Art
WP2:
Non-techno-logical Barriers
WP3:
Benchmarks and Certification
WP4:
Simple Calculation Method
WP4:
Simple Calculation Method
WP5:
Best Practice Guidelines
WP6: Dissemination

3. Why a Simple Calculation Method for Double Skin Facades?
Present situation:
assessment of thermal behaviour and energy efficiency of naturally ventilated DSF is only possible by using complex simulation tools
interconnections between fluid dynamics, energy balances, and optical mechanisms
-> iterations are necessary
impossible to have reliable predictions on energy efficiency and impact on comfort in the early planning stage
BESTFACADE is developing an assessment method that can be integrated in the national calculation methods of the EPBD with sufficient accuracy of thermal behaviour and the energy performance

4. Analysed (Standard) Approaches
prEN/ISO Energy performance of buildings
ISO/FDIS – Thermal performance of buildings
DIN V – German standard for EPBD calculations
Platzer approach – modified prEN/ISO 13790
WIS approach – EU project WinDat
EN – Curtain walling
prEN – Thermal performance of curtain walling with ventilated and unventilated air spaces
ISO – Thermal performance of windows....
ISO Energy performance of fenestration systems - Calculation procedure
does not yet foresee the calculation of DSF
no consideration of solar radiation
similar to wintergarden in prEN/ISO 13790, solar radiation model includes weaknesses
( )
stationary calculation, requires a computer tool and various input data
only definitions, no calculation procedures
only calculates the reduced transmission losses (buffer effect), no influences on solar gains
only thermal characteristics, no energy, no coupling to building ( )
facade rating, can be used for DSF

5. The Application of DSF in the DIN V 18599
DIN V follows the philosophy of the prEN/ISO 13790: holistic calculation
DSF constructions are a subsystem of unheated glazed annexes
The solar heat gains in the building zone are calculated as:
QS,tr = FF,iu * Aiu * geff,iu * FF,ue * e,ue * IS * t
The heat flow through the glazed annex or conservatory must be calculated in order to determine the temperature in that space.
The solar radiation entering the annex or conservatory must be calculated using equation
 S,u = FF,ue * Aue * geff,ue * IS
DIN V demands to use an air change rate nue = 10 h-1

6. Further Development of the Simplified DIN V 18599 Approach within BESTFACADE
more detailed approximation of the ventilation rate in the air gap
air flow rate will take into account the facade geometry and the temperature difference
based on measured data from:
- BiSoP Baden (IWT)
- VERU Holzkirchen (Fraunhofer-IBP)
- Postcheque building, Vliet test building, Aula Magna building (BBRI)
Validation: use of different models like WIS, Energy Plus and Parasol

7. Characteristic values based on measurements: BiSoP

8. Characteristic values based on measurements: VERU

9. Characteristic values based on measurements: VERU

10. Characteristic values based on measurements: VERU

11. Characteristic values based on measurements: VERU

12. Default ventilation rates
Façade control strategy
(Default) air change rate [h-1]
Summer (April–Oct.)
Winter (Nov.–March)
Open at all times 25
Adjustable flaps 4

13. Application of the Method in an internet-based Information Tool
DSF information tool for the first planning stage
use of an existing environment developed at Fraunhofer-IBP
further development is a cooperation between different partners in BESTFACADE
will allow the energy performance assessment for heating, cooling, ventilation and lighting of a standard room behind a DSF
lighting: prEN with DIN V (facade performance)

23. Available on the BESTFACADE website: www.bestfacade.com