Green Construction with AAC Prefab Products
AAC technology has developed over the last years and brings green and durable living closer to all of us. Energy-saving buildings are now more than a trend across many countries. Institutional Directive issued by EU in 2010 sets the target to achieve publicly constructed. Owned buildings are nearly zero-energy buildings since 2018 and all buildings by end of 2020 are to be nearly zero-energy. The New Energy Efficiency Directive of 2012 complements the EU Directive of 2010 by setting a goal for the decrease in energy consumption of EU member countries.
What does zero carbon, zero energy or energy neutral building mean?
A zero carbon building, or carbon neutral building, is one that causes no increase in CO2 (carbon dioxide) emissions. It means that energy consumption against energy delivered by its site should be in balance, or neutral. To achieve this objective an obvious step is to reduce energy consumption of buildings which has a direct impact on building products as well as construction processes. Worldwide supported governmental objectives for green housing (GHG) set firm requirements to building methods and materials produced by the local building industries. Today, in most Western European countries the required Rc (thermal resistance) values of > 6 m2 K/W for flooring, walls and roofing are a standard. For instance, Passive Houses in the Netherlands can obtain Rc values of up to 10 m2 K/W.
Finished construction of a energy neutral house with a local farm look from the Netherlands
The role of low-density AAC prefab products towards energy efficiency
For AAC producers, this global trend of strict energy efficiency offers more opportunities than threats. The key aspect in successfully adapting to new regulations offers building solutions supported by the products that have a combination of excellent thermal and mechanical properties. The main AAC properties provide the foundation for durable and energy-efficient construction.
High-quality AAC products used in durable and energy-efficient construction takes the main AAC properties as the fundament
The thermal conductivity has to come down considerably to comply with the EU regulations. AAC production technologies have also accommodated the production of low density (300kg/m3) blocks and panels with a λ value of 0,07-0,08 W/mK. Density is directly linked with the compressive strength and achieving a good combination of the two while reducing the thermal conductivity is a real challenge. Only by having the right quality of raw materials, precise formula design with additives and state-of-the-art production technology, low-density AAC elements can be made with precise dimensions and Super Smooth surfaces at the above-described values.
Typical AAC characteristics
Green building standards force the AAC industry to focus also on ultra-low density products. AAC blocks at densities of 110 – 130 kg/m3 with thermal conductivity of λ=0,044 W/mK are not an exception anymore. Products up to 200 thickness address the target of reducing energy consumption considerably. Due to the limited mechanical properties (compressive strength), ultra-light AAC products are non-load bearing and are mainly used for insulation purposes.
Preventing air leakage in energy neutral buildings
Importantly, in order to use less energy to constantly heat up and cool the building, appropriate airtightness has to be attained according to EU regulations EN-13829, in other words, poor sealing that might result in drafts must be eliminated. Air infiltration and exfiltration rate fall within the competency of design decisions (e.g. multiple layer windows/doors), the ways of building as well as characteristics of adopted materials. Tight tolerances of AAC prefab products and the application of thin-bed adhesive improve the chances of highly air-tight building. Ventilation of housings with fresh air is secured by heat exchangers in the installation phase.
The risk of building with AAC blocks comes with the large number of joints that need to be manually glued during assembly. Building with AAC panels minimizes the number of joints that need to be skimmed, thus making the construction less prone to air release. It is crucial to note that, even though the walls can be subsequently plastered, improper gluing during AAC block laying results in the decreased airtightness levels. Therefore, for high performance of energy neutral buildings, large format AAC panels are preferred over blocks when it comes to energy-saving and fast construction. A shift towards greener buildings marks an end to thick mortar bricklaying. Achieving a perfect carbon-neutral housing also implies abandoning of hand grips in AAC blocks and profiles in AAC wall panels as all sides of the building product in energy efficient construction shall be covered with a thin layer of adhesive in order to minimize air leakage.
The future of energy efficient buildings
The construction sector plays an important role in the delivery of the EU’s goals for sustainable, energy efficient buildings. It has a direct impact on construction products including the application with AAC prefab products. Large developers and contractors for both the public and private sector are strongly committed to finding solutions to meet the close‐by future regulations. Building material producers and suppliers are now asked to provide integrated solutions, rather than a stand‐alone product. They can develop, create, and install the elements that are needed now and in the near future. These integrated material systems, offered by the new suppliers, generate value to the end-user and meet the new way of green and efficient building for the world of tomorrow.
Several reinforced panel application elements used in the modular AAC building system (Source: Willem van Boggelen)
AAC as a material has many valuable and powerful properties to be used as a key element for building systems of the future. In combination with steel frame, reinforcement, wood, and CFS (Frame‐Crete), one can build rapidly a shell or a building envelope according to the customer’s requirements. AAC prefab products are light and can be transported easily to building sites, realizing short delivery times. Installers can easily install up to 50 m2 per day. BIM will play an even greater role to reduce costs upfront and increase efficiency in modular construction.
Download your free AAC Installation Manual:
The purpose of this manual is to serve as a reference to builders, contractors and those seeking experience in how to build with AAC prefab products and the Aircrete Building System. This step-by-step guide includes tools, materials, mortar types, installation time, finishing works and samples after installation. Click here to download your free copy of the AAC Installation Manual.
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