The Vapour Permeability of Building boards

 

Measuring the water (or other) vapour permeability of building boards.

Building boards and vapour permeability

Building regulations impose strict regulations on the flow of water vapour through buildings.

This permeability, or breathability, is a material's ability to let water vapour diffuse through the material of a structure, it is frequently confused with keeping liquid water out. But it is not the same thing at all, and a material that is excellent as a barrier to liquid water can be almost usless when it comes to water vapour (which is a gas). In fact material such as silicone, cellulose, EVOH and PVOH are so permeable to water vapour that they might as well not be there at all!

Numerous regulations and standards govern the area, including Building Regulations' Part L, yet vapour permeability testing has traditionally been hard and longwinded.  Versaperm equipment can overcome this and test the permeability of materials, components and entire structures, including walls, bricks, plaster, plastics, DPCs, coatings, felts, sarking board, mastics, laminates and a wide range of commonly used products. 

 

Versaperm equipment is unusual as it can measure very thick samples such as laminated building boards, even including those with foil or plastic vapour barriers.

Even with the standard flat sample chamber it can measure samples up to 50mm thick, which is sufficient for most building boards and items used by the building industry.

However, we also have a number of non-standard chamber configurations for measuring almost any thickness of building material.  Our specialist equipment is designed to measure the leakage rate of adhesives, mastics and other sealing products.

We developed our own range of permeability measurment equipment from top to bottom, so that it can produce accurate and reliable results that are accurate in the parts per million – sometimes in the parts per hundreds of million, range.  With some materials this can be achieved in as little as 30 minutes, but even with hard to measure foils, results can normally be turned around in a day. 

Versaperm equipment can be also configured to measure the permeability of many gases including Oxygen, Carbon Dioxide, water vapour  and hydrocarbons.  Additionally, the company offers a laboratory testing service for companies that test too few samples to make the purchase of equipment viable.

Diurnal and seasonal cycles vapour permeability testing

Recently, the latest Versaperm VI system has not only made it much faster, less costly and more accurate when meauring vapour permeability, but it can also control temperature and other conditions.  This means you can not only simulate the diurnal cycle but you can measure it during winter's freezing sub-zero temperatures or summer's most blazingly hot days – and beyond to desert or Arctic conditions as well! 

Materials and structures as diverse as building boards, walls, screeds, laminates, roofing felts, vapour barriers and special coatings are all part of the vapour/ moisture control of a building. The permeability of these changes with conditions throughout the day and night and with the year's seasons. The only effective way to ensure that they meet your regulatory and performance requirements is to test them, especially as structures rely on multiple and sometimes competing components and assemblies.

Versaperm's permeability equipment range can measure the permeability of anything from a single vapour barrier through to a complete wall structure, including adhesives, mastics and other sealing or structural materials. Results are typically accurate in the parts per million range and the equipment can optionally measure it not just for water vapour but also for CO2, hydrocarbons, oxygen and virtually any other gas or vapour.

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