What are the structural features of wooden houses?What are the advantages of a construction with a wooden structure compared to traditional structural materials such as masonry, reinforced concrete and steel?What are the most popular technologies?How does using wood as a structural material for architecture favor the absorption of carbon dioxide from the atmosphere?In this article we will answer these and other questions.To do this as accurately as possible, we contacted the engineer Fernando Pizzarelli, Marlegno technical area, to whom we asked specific questions, which would remove any doubts in terms of structural resistance of wooden houses.In fact, we asked Fernando about the structures of wooden houses with regard to their characteristics of resistance, their technological characteristics and their innate sustainability.Antonia: Let's start by debunking the myth of the wooden house imagined as less resistant than an equivalent in brick, reinforced concrete or steel, is that right?Fernando: Absolutely not!Wood is a material regulated and regulated by the Technical Regulations for Construction (NTC 2018) just like other building materials!The Technical Standards for Constructions contain all regulations that the structural designer must respect when carrying out the calculations for the structure of any building, be it masonry, reinforced concrete, steel or wood.This means that performance levels are guaranteed regardless of the material used for the construction.A wooden house is just as safe as a house built of other materials.Transport to the construction site of a prefabricated wooden wall complete with systems and finishesAntonia: With the same structural strength, what are the advantages of a wooden house?Fernando: The advantages of a wooden frame house are essentially three:Let's start with lightness.Compared to other building materials, wood has a very advantageous strength / weight ratio.To achieve the same performance, concrete or steel structures can weigh 5 times (concrete) or 16 times (steel) more than wooden ones.With the same type of construction, this makes a wooden structure extremely lighter than one made of masonry, concrete or steel.To understand, a given level of performance is obtained from a wooden structure with a lighter building.Lightness has two great advantages.The first is related to anti-seismic.The effects of earthquakes on a given building are greater the greater its weight.In the event of an earthquake, light buildings, such as those made of wood, experience less stress.Another advantage of the lightness of wood is related to the cost.Wooden residential buildings have reinforced concrete foundations (and basements).Lightweight buildings load the soil less and require smaller, therefore cheaper, foundations.Along with lightness, another great advantage of wooden structures is prefabrication.Unlike brick or reinforced concrete houses, entirely built on site, wooden structures are prefabricated in the factory and only assembled on site.Even prefabrication, like lightness, brings with it further advantages: the quality of the finished product, speed of execution, site safety and reduced costs.The installation of prefabricated wallsHaving to build the structure in the factory, all the construction details, the most complex knots and the technical devices are examined in detail and studied at the table during the design phase, guaranteeing a high quality of the final product.While the work on site is subject to unforeseen circumstances, the production in the factory is much less: the controls are systematic, the precision with which each element is made is greater.Thanks to prefabrication, the construction site is a safer place and the building can be completed in less time.Antonia: Lightness and prefabrication, together with all the advantages they bring, are convincing in themselves, but you mentioned the sustainability of using wood for architecture and I would like you to make clear to our readers the mechanism for which to pick up a tree from the forest and using it for structural uses saves CO2.How can this be explained?Fernando: Let's start from the beginning ... during its life, a tree growing in a forest captures CO2 from the environment and stores it inside, acting as a natural reservoir of carbon dioxide.In an uncultivated forest, when the tree ends its life cycle it decomposes, and the carbon dioxide it absorbed during its life is released into the environment.In sustainably cultivated forests, trees are not allowed to decompose but are harvested earlier.In this way they continue to retain all the CO2 inside them.Furthermore, in sustainably managed forests, the removal of a tree corresponds to the planting of a new tree: a new potential CO2 reservoir.Therefore, using wood for construction prolongs the tree's ability to store CO2 and favors the creation of new carbon dioxide "reservoirs".To get an idea of ​​the quantities, each cubic meter of wooden structure is capable of retaining approximately one ton of CO2.For the structure of a single-family wooden house, about 40 cubic meters of material are needed, equivalent to 40 tons of CO2 taken from the environment!Despite the carbon dioxide emitted during the collection, processing and construction of a wooden structure, the one absorbed is such that the overall balance remains largely positive.Antonia: The wooden structures therefore have a positive balance: masonry, reinforced concrete and steel only cause CO2 emissions, no withdrawal from the environment!So tell me some practical aspects: what technological systems are adopted?Fernando: If we restrict the field to residential buildings, there are two construction systems:Schematic representation of the two construction systems with which it is possible to build a wooden house and relative stratigraphy: the light frame structural system on the left and X-LAM on the rightThe light frame system, also called platform frame, provides load-bearing walls consisting of a series of vertical uprights arranged at a constant center distance (approximately 62cm), connected to an upper and a lower beam.All these elements are connected to each other (in technical jargon "packaged") by an internal and external panel that give rigidity to the structure, among which the thermal acoustic insulation, the systems etc. are placed.The X-LAM system, also called CLT, acronym for the English “cross laminated timber”, provides walls made of solid wood panels, typically 10 cm thick for a two-storey building.As the English name suggests, which translates as "cross-layered wood panels", these panels are formed by joining 5 layers of 2cm thick boards glued together so that the wood fibers have an alternating orientation.The frame system is lighter and is suitable for 2-3 storey buildings.The X-LAM is recommended for structures higher than 3 floors.It is also perfectly suitable for lower buildings but by providing for the use of more material, with the same two-storey structure, it is more expensive.Thanks, Fernando!The structures of the wooden houses are no longer a mystery!