Revealed: Building Material Breathability Experiment (surprising result)
Skill Builder
8 min, 0 sec
A detailed experiment was conducted to assess the breathability of various building materials, highlighting the vapor permeability of traditional and modern mixes.
Summary
- An experiment was conducted to determine the breathability of common building materials, particularly focusing on lime versus other materials.
- Materials tested included sand and cement mixes at different ratios, natural hydraulic lime (NHL) of different strengths, and Dry Zone renovation plaster.
- Petri dishes were filled with materials, sealed, and water evaporation was measured over 12 months at 16°C to simulate vapor permeability.
- Results showed sand and cement mixes had varying degrees of breathability, with a 6:1 sand to cement to lime mix being the most vapor permeable.
- NHL at a 3.5 strength was almost as breathable as a 6:1 mix but NHL at 5.1 strength was less so; Dry Zone High Lime had similar permeability to NHL mixes.
Chapter 1
The experiment was introduced to determine the breathability of common building materials with an emphasis on lime.
- The team set out to explore which building materials allow a house to 'breathe' by conducting a long-term experiment.
- Lime was a material of interest due to its reputation for breathability in construction.
Chapter 2
The experiment was meticulously set up using Petri dishes filled with various materials and water to simulate vapor permeability.
- Petri dishes were filled with materials like sand, NHL lime, and cement in various ratios to represent different mortar mixes.
- Water was placed in cups with the material samples sealed on top to ensure only vapor could pass through the material.
Chapter 3
The experiment was conducted under natural conditions without acceleration to faithfully simulate building drying times.
- The experiment was designed to be long-term, mimicking the slow drying process of buildings, with water left to evaporate at room temperature.
- Evaporation was not influenced by external pressures or heat to ensure the results reflected only the material's breathability.
Chapter 4
The experiment yielded surprising results, revealing the effectiveness of various material mixes in allowing vapor to pass through.
- Sand and cement mix at a 3:1 ratio and rapid set plaster were the least breathable.
- Increasing the sand ratio and adding hydrated lime improved vapor permeability.
- NHL lime showed varied results based on strength, with 3.5 being nearly as permeable as a 6:1 sand to cement to lime mix.
- Dry Zone High Lime had comparable breathability to NHL limes.
Chapter 5
Conclusions were drawn about the ideal material mixes for breathability and the self-healing properties of lime.
- A 6:1 sand to cement to lime mix is preferred for repointing due to its vapor permeability and the self-healing properties of lime.
- Hydrated lime is recommended over hydraulic lime for most cases as it is more readily available and effective.
Chapter 6
Anticipating skepticism, the presenter defended the experiment's methodology and suggested future studies to address more myths.
- Anticipating criticism, the presenter affirms the consistency of the water levels and the integrity of the experimental conditions.
- The presenter invites suggestions for future experiments to debunk other construction myths.