Airtightness is often spoken about when it comes to building eco-homes. There are many benefits to airtight buildings such as reduced heat loss, savings on energy, improved comfort and protection of the building fabric. Builders can achieve airtightness by sealing a structure to reduce infiltration and leakages, this is sometimes called uncontrolled ventilation.
Airtightness is measured by monitoring the amount of air that escapes or enters a building at a pressure of 50 Pascals. Airtightness for Passivhaus buildings is measured in air changes per hour (ACH) – the number of times an hour that the air in the building changes when it is pressurised – negatively or positively.[1]
Through careful planning at the design and construction phases, buildings can achieve high levels of airtightness. However, it is important to consider ventilation. If a building is not ventilated properly, airtight structures can have poor indoor air quality. Therefore, controlled mechanical ventilation with heat recovery (MVHR) is required in Passive House buildings. This involves extracting hot air from wet rooms and supplying fresh air to living and bedrooms. This is heated through a heat exchanger. In very cold climate, the fresh air can be heated through ground or air heat pumps.
When it comes to specifying materials for an airtight structure in offsite construction, it is important to choose robust products that can withstand transport and site conditions. There are a number of factors to consider, such as, are they durable, long lasting, and do they meet the code requirements. To help achieve airtightness in a building, MEDITE SMARTPLY’s engineered wood panels can help.
Working with SMARTPLY
MEDITE SMARTPLY has two airtight products, which can be used together to form an airtight envelope in a structure: SMARTPLY PROPASSIV and SMARTPLY SURE STEP. SMARTPLY PROPASSIV can be used for the walls and ceilings, while SMARTPLY SURE STEP can be used for floors and roofs, forming an opaque envelope in buildings. Due to it being only 12.5mm thick, SMARPTLY PROPASSIV cannot be used in flooring.
SMARTPLY PROPASSIV is a structural OSB/3 panel with integrated air barrier and vapour control properties. The panel is airtight and is designed for use as internal structural sheathing on the warm side of the insulation in timber frame construction systems.
Its green coating offers consistent vapour resistance over the entire surface and eliminates the need for additional Air and Vapour Control Layout (AVCL) membranes. The vapour control layer aims to prevent moisture movement – ‘vapour diffusion’. This refers to the transfer of vapour through materials by humidity or temperature differences. SMARTPLY PROPASSIV is certified as an airtight component by the Passive House Institute and therefore contributes to comply with the air permeability requirements set out by the Passive House Institute.
As an example of how engineered wood panels can dramatically reduce embodied carbon outcomes, ‘live’ assessments were carried out using SMARTPLY PROPASSIV. The panels’ airtight performance was found to reduce heat loss by up to 90% in a typical building and up to 60% in a property constructed to current building standards.[2]
SMARTPLY SURE STEP is an airtight, tongue and groove OSB/3 panel with a high-performance and durable coating. Using SURE STEP as an air tight layer for flooring or decking can contribute to sustainable building practices as well as reduce the energy consumption for heating. Its unique coating also brings improved durability during the construction phase and slip resistance to the panel in all site conditions.
SMARTPLY SURE STEP is certified airtight by the Passive House Institute and is ideal for flooring or roofing applications, providing a robust solution to end users. It was certified by the Passive House Institute in Germany as an airtight panel.
A sustainable solution for offsite construction
Timber can be one of the most sustainable construction materials if it’s properly managed and SMARTPLY OSB is made from FSC® certified timber from sustainable, fast-growing pine and spruce, which includes the tops that are not used to make any other wood-based product. Additionally, SMARTPLY OSB is made of wood strands from a whole tree, therefore nothing is wasted.
As a business, MEDITE SMARTPLY is committed to move towards carbon neutrality by 2030, through scopes 1 & 2, with the ultimate aim of being a net zero manufacturing company by 2050. MEDITE SMARTPLY is committed to manufacturing environmentally conscious products that add value throughout the supply chain. Carbon is stored in its products and remains locked inside throughout the lifespan of the product.
In short, airtightness is a key principle in low energy construction, and achieving this requires careful planning and the use of appropriate materials. Through their efficiency, performance, and environmental consciousness, MEDITE SMARTPLY’s wood panels underscore the vital role of airtightness in advancing eco-homes and sustainable offsite construction.
Discover more about SMARTPLY OSB: https://mdfosb.com/en/products/smartply-osb.
