ARTIFICIAL THERMAL BRIDGE WITH A DEW POINT SWITCH. Martin Krus Fraunhofer-Institute of Building Physics, Holzkirchen

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1 ARTIFICIAL THERMAL BRIDGE WITH A DEW POINT SWITCH TO ENABLE A MAINTAINANCE-FREE ENERGY-SAVING VENTILATION-SYSTEM FOR THE PREVENTION OF MOULD GROWTH Martin Krus Fraunhofer-Institute of Building Physics, Holzkirchen

2 Mould Growth inside Buildings Background In colder regions increasing problems with inside mould growth (in spite of improved insulation) Reasons less infiltration due to tighter windows changed times of sojourn missing adaptation of the inhabitants to a correct airing behaviour 2

3 Influence of the tenant`s behaviour My houseowner said, in winter time I should ensure a good ventilation and put away the furniture from the wall conflict: tenant contra houseowner 3

4 Influence of the tenant`s behaviour conflict: tenant contra lessor 4

5 Model for Mould Prediction WUFI-Bio 5

6 Model for Mould Prediction WUFI-Bio 6

7 Whole Building Hygrothermal Model WUFI-Plus so far: hygrothermal behaviour inside building parts now: Modelling the hygrothermal behaviour inside the room coupling of heat and moisture 7

8 Example of Use Flat with 3 rooms and its corners humidification of each room according to ist usage different insulation standard Bad Bathroom 9 m² Schlafzimmer Bedroom 14 m² Kammer Cabinet 3 m² Flur Corridor 10 m² Küche 10 Kitchen m² Wohnzimmer Living room 20 m² Kinderzimmer Child`s room 16 m² Balkon Balcony 8

9 Proceeding Iterative determination of the necessary ventilation to prevent mould growth Climate Building part Humidification Ventilation Yes Evaluation Whole Building Model Biohygrothermal Model Mould? No 9

10 Results Iterative determination of the necessary ventilation to prevent mould growth modern building airing rate [h -1 ] moisture production [g/h] normal permanent ventilation intermittent ventilation infiltration bedroom cloth drying time [h] time [h] 10

11 Results Iterative determination of the necessary ventilation to prevent mould growth old building airing rate [h -1 ] normal permanent ventilation intermittent ventilation infiltration bedroom cloth drying old windows time [h] time [h] airing rate [h -1 ] permanent ventilation intermittent ventilation infiltration new tight windows time [h] time [h] 11

12 Results Iterative determination of the necessary ventilation to prevent mould growth old building air change [1/h] old building old windows intermittent ventilation cloth drying normal air change [1/h] old building new tight windows SR CR LR Bath Kit SR CR LR Bath Kit airing requirements are very complex people have no feeling for inside r.h. measure to minimize the risk of mould growth is necessary 12

13 Requirements appropriate ventilation system has to prevent surface conditions suited for mould complex central ventilation systems too expensive and not suitable for old buildings missing maintenance causes new health risks for energy saving purposes a permanent ventilation is no acceptable solution ventilation has to take place subjected to unsteady humidification processes measurement of surface temperature and humidity too expensive and needs permanent maintenance Idea for a new and simple system 13

14 Dew Point Switch artificial thermal bridge with a dew point switch design of the thermal bridge using Biohygrothermal Model dew water just when a critical moisture is reached at the most problematic area (mostly corner of outer wall) 14

15 Dew Point Switch artificial thermal bridge with a dew point switch design of the thermal bridge using Biohygrothermal Model dew water just when a critical moisture is reached at the most problematic area (mostly corner of outer wall) dew water is switching the ventilator 15

16 Field tests Test building with low insulation standard 16

17 Field tests Test building with low insulation standard 17

18 Field tests 18

19 Field tests Control of inner climate 19

20 Field tests First results 20

21 Dew Point Switch Advantages Ventilation only when necessary (minimisation of airing heat losses) no temperature or r.h. sensors required reliable prevention of mould growth minimal maintenance low-priced suited for existing buildings No replacement of the normal airing behaviour of the inhabitants it s just a security measure 21

22 Dew Point Switch No replacement of the normal airing behaviour of the inhabitants it s just a security measure 22