Water vapor diffusion resistance
The water vapor diffusion resistance (also vapor barrier value ) expresses how much a building material hinders the diffusion (lat. Diffundere, `` spread '', here: migration of water vapor molecules) of water vapor and is expressed in the form of the water vapor diffusion resistance factor (also water vapor diffusion resistance factor , symbol µ ).
The water vapor diffusion resistance of a building material is a dimensionless material parameter that indicates the factor by which the material in question is denser than a layer of static air of the same thickness. The larger the µ number, the more vapor-tight the building material is. The water vapor diffusion resistance factor cannot assume values less than 1 (μ air = 1), but it can increase to infinity. The following applies: 1 ≤ μ ≤ ꝏ.
The µ-numbers for the most common building materials are numbered in DIN EN ISO 10456 and DIN 4108-4.
If the water vapor diffusion resistance factor is multiplied by the thickness of the component layer , the air layer thickness ( sd value ) equivalent to water vapor diffusion is obtained .
A component usually consists of several layers, so that the Sd values of the respective layers must be added to calculate the diffusion resistance of the entire component.
In heated buildings, there is a temperature gradient from the inside to the outside in winter . Warm air can hold more water in vapor form than cold air. As a rule, this leads to a vapor pressure gradient in the same direction as the temperature gradient . The water vapor tries to diffuse outwards in the direction of the vapor pressure gradient. This results in a vapor diffusion flow that is limited by the diffusion resistance of the component and, in particular, the vapor barrier contained in the component .
Precise knowledge of the water vapor diffusion resistance values of individual building materials in a component is important to avoid condensation and mold formation.
In contrast to the water vapor diffusion resistance, the water vapor transmission resistance also takes into account the vapor transmission through materials due to an air flow ( convection flow ). This is important when assessing the breathability of textiles , wound dressings and food packaging .
Fabric examples
The resistance numbers are divided into wet and dry. This is due to various test procedures in which the relative humidity is varied in each case. In the dry area, the humidity is between 0 and 50% and the water vapor is mainly transported by vapor diffusion. In wet areas, the humidity levels range from 50 to 93%. The pores are enriched with water in liquid form, which increases the flow of liquid. Smaller water vapor diffusion resistance numbers are measured.
Water vapor diffusion resistance number of some substances according to DIN EN ISO 10456:
| material | Gross density kg / m³ |
µ | |
|---|---|---|---|
| dry | wet | ||
| air | 1.23 | 1 | 1 |
| plaster | 600-1,500 | 10 | 4th |
| Plasterboard | 700-900 | 10 | 4th |
| Concrete , medium bulk density | 1,800 | 100 | 60 |
| Concrete, high density | 2,400 | 130 | 80 |
| Glass, metals | - | ∞ | ∞ |
| Thermal insulation materials | |||
| Expanded polystyrene - foam (EPS, polystyrene) |
10-50 | 60 | 60 |
| Extruded polystyrene rigid foam (XPS) |
20-65 | 150 | 150 |
| Rigid polyurethane foam | 28-55 | 60 | 60 |
| Mineral wool | 10-200 | 1 | 1 |
| Foam glass | 100-150 | ∞ | ∞ |
| Perlite plates | 140-240 | 5 | 5 |
| Wood fiber insulation panels | 150-250 | 10 | 5 |
| Masonry materials | |||
| Solid brick (fired clay) | 1,000-2,400 | 16 | 10 |
| Sand-lime brick | 900-2,200 | 20th | 15th |
| Aerated concrete | 300-1,000 | 10 | 6th |
| Wall mortar , plastering mortar | 250-2,000 | 20th | 10 |
| Wood, wood-based materials | |||
| Construction timber | 500 | 50 | 20th |
| Construction timber | 700 | 200 | 50 |
| Plywood according to DIN, light | 300 | 150 | 50 |
| Plywood according to DIN, heavy | 1,000 | 250 | 110 |
| Plywood, medium density 1) | 700 | 200 | 70 |
| Chipboard | 300 | 50 | 10 |
| Chipboard | 900 | 50 | 20th |
| OSB panel 2) | 650 | 50 | 30th |
| Wood fiber board | 250 | 5 | 3 |
| Wood fiber board, MDF 3) | 400 | 10 | 5 |
| Wood fiber board, MDF 4) | 600 | 20th | 12 |
| Wood fiber board, MDF 5) | 800 | 30th | 20th |
| Solid plastics | |||
| Acrylic plastics | 1,050 | 10,000 | 10,000 |
| Polycarbonates | 1,200 | 5,000 | 5,000 |
| Polytetrafluoroethylene (PTFE) | 2,200 | 10,000 | 10,000 |
| Polyvinyl chloride (PVC) | 1,390 | 50,000 | 50,000 |
| Polymethyl methacrylate (PMMA) | 1,180 | 50,000 | 50,000 |
| Polyacetate plastics 6) | 1,410 | 100,000 | 100,000 |
| Polyamide (nylon) | 1,150 | 50,000 | 50,000 |
| Polyethylene | 920-980 | 100,000 | 100,000 |
| Polystyrene | 1,050 | 100,000 | 100,000 |
| Polypropylene | 910 | 10,000 | 10,000 |
| Polyurethane (PU) | 1,200 | 6,000 | 6,000 |
| Epoxy resin | 1,200 | 10,000 | 10,000 |
| Phenolic resin | 1,300 | 100,000 | 100,000 |
| Polyester resin | 1,400 | 10,000 | 10,000 |
| rubber | |||
| Natural rubber | 910 | 10,000 | 10,000 |
| Chloroprene rubber | 1,240 | 10,000 | 10,000 |
| Butyl rubber | 1,200 | 200,000 | 200,000 |
| Foam rubber | 60-80 | 7,000 | 7,000 |
| rock | |||
| Crystalline natural stone | 2,800 | 10,000 | 10,000 |
| Sediment natural stone | 2,600 | 250 | 200 |
| Light sediment natural stone | 1,500 | 30th | 20th |
| Porous rock, e.g. B. Lava | 1,600 | 20th | 15th |
See also
literature
- Wolfgang M. Willems, Kai Schild, Simone Dinter: Vieweg Handbook Building Physics Part 1. Heat and moisture protection, comfort, ventilation. 1st edition. Friedr. Vieweg & Sohn Verlag, Wiesbaden 2006, ISBN 978-3-528-03982-2 .
- Lutz, Jenisch, Klopfer, Freymuth, Krampf, Petzold: Textbook of building physics. Sound - heat - humidity - light - fire - climate. 5th edition. Teubner publishing house, Stuttgart / Leipzig / Wiesbaden 2002, ISBN 3-519-45014-3 .
- DIN 4108-3: 2017. Thermal insulation and energy saving in buildings - Part 3: Climate-related moisture protection - Requirements, calculation methods and instructions for planning and implementation. Draft. Beuth Verlag, Berlin 2017.
Web links
Individual evidence
- ↑ DIN EN ISO 10456: 2010 . Building materials and building products - Thermal and moisture-related properties - Tabulated rated values and methods for determining the thermal insulation nominal and rated values (ISO 10456: 2007 + Cor. 1: 2009); German version EN ISO 10456: 2007 + AC: 2009 . Pp. 15-23.
- ↑ Ecological building material information system of the Federal Ministry of Transport, Building and Urban Development (BMVBS) WECOBIS ( Memento of the original from January 18, 2013 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (accessed January 2013)
- ↑ holz-kogler.de ( Memento of the original from February 28, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ see data sheet ( Memento of the original from March 12, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , P. 2, at Dataholz.com
- ↑ Information on ÖNORM EN 13986 and the research report "Testing of building physical characteristics of wood and wood-based materials", MA 39-VFA (2002) in the MDF data sheet ( Memento of the original from March 12, 2017 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , P. 2, as of 2012, at Dataholz.com
- ↑ see "Technical" tab on the high-density and medium-density fiberboard page at Wecobis.de
- ↑ Information on ÖNORM EN 13986 and the research report "Testing of building physical characteristics of wood and wood-based materials", MA 39-VFA (2002) in the MDF data sheet ( Memento of the original from March 12, 2017 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , P. 2, as of 2012, at Dataholz.com
