Under certain conditions, migration of small amounts of moisture in the envelope of buildings can cause heat flow through permeable thermal insulation materials due to the conversion of latent heat when moisture evaporates from a warm surface, diffuses through the insulation, and condenses on a colder surface. In these cases, the magnitude of the latent heat flux can be of the same order as the heat transfer by conduction. The latent heat transfer may result in a heat gain which coincides with other gains of an occupied building, and thus can cause an extra requirement for cooling. The paper reviews and quantifies the importance of heat flow processes in moist insulation systems. It then employs modeling to analyze the effect of extra heat gain caused by latent heat transfer in the envelope on the thermal load on an office building chosen as an example. An extra cooling requirement of 6-7 % is found.

• coupled heat and moisture calculations : latent heat on light wieght roofs
• roof : latent heat on light wieght roofs

1. eds. Annex 41 Final Report, Volume 1: Modelling Principles and Common Exercises
2. Empirical validation of a transient computer model for combined heat and moisture transfer
3. Experimental investigation of the hygrothermal performance of insulation materials
4. Full-scale testing of indoor humidity and moisture buffering in building materials
5. Global building physics
6. International building physics toolbox, general report
7. Investigation of Microclimate by CFD Modeling of Moisture Interactions between Air and Constructions
8. Model and experiments for hygrothermal conditions of the envelope and indoor air of buildings
9. Moisture buffer value of building materials
10. Moisture Buffer Value of Materials in Buildings
11. Moisture buffering of building materials
12. Moisture conditions of non-ventilated, wood-based, membrane-roof components
13. Moisture: its effects on the thermal performance of a low-slope roof system
14. Non-isothermal water vapour transmission through porous insulation. Part 1: The climate chamber
15. Organic insulation materials: effect on indoor humidity and necessity of a vapor barrier
16. Test cell measurements of moisture buffer effects
17. The importance of moisture buffering for indoor climate and energy conditions of buildings
18. The International Building Physics Toolbox in Simulink
19. The self-drying concept for flat roofs
20. Tools for performance simulation of heat, air and moisture conditions of whole buildings
21. Whole-building Hygrothermal Simulation Model  

1. Assessing the service life of building envelope constructions service life of building envelopes
2. Methods for designing building envelope components prepared for repair and maintenance