             ! " # $ % This paper deals with the issue of seismic retrofit and energy sanation of existing older buildings. A possibility for solving both problems at once by applying a new outer shell made of cross laminated timber (crosslam or XL) plates and effective aerogel insulation is presented. A seismic strengthening case study is presented on a 3 story reinforced concrete frame building. Thermal insulation properties of the insulated panels are presented. &’% timber, seismic retrofit, energy   $( A majority of the buildings on seismically active areas built before the nineteen sixties or seventies have two major problems – first they are seismically unsafe because of the lack of seismic design codes at the time they were built. And second, they have a high energy consumption because of lack of insulation, proper details etc. The proposed retrofit system deals with both problems at once; a new outer cross laminated timber wall stabilises a building against horizontal shear forces that are caused by earthquakes – on one hand the timber panels have a low mass and therefore don’t contribute much to seismic forces, but are very stiff on the other hand [1] and provide high shear resistance. In addition the new outer wall – if combined with an effective insulation – provides a very good thermal insulation of the building – a combination of a 95 mm cross laminated timber plate and 60 mm thermal Aerogel Spaceloft insulation gives a U factor of 0,19 W/m2K [2]. Timber panels also store CO2. A 170 mm outer shell (including a facade) could therefore provide sufficient building thermal insulation and strengthen a reasonably sized building against earthquakes. The new outer shell could be integrated with windows, doors and a facade already in the manufacturing plant. Than the panels could be transported to sight and rapidly attached to the building (with proper detailing, subjected to earthquake demands). The system is still in development but so far seems to be most suitable for buildings up to 4 or 5 floors, even floor plans, structures with stiff floor 1 Iztok Sustersic, CBD d.o.o. , Lopata 19G, 3000 Celje, Slovenia. e=mail: iztok.sustersic@cbd.si 1 dr. Bruno Dujič, CBD d.o.o. , Lopata 19G, 3000 Celje, Slovenia. e=mail: bruno.dujic@cbd.si membranes and access to all outer walls. Another positive aspect of the outer shell is that there are no harsh interventions to a building and that people don’t have to move out during the construction phase (unlike when using most of conventional methods for seismic retrofit). All together it makes a unique system that solves two major problems in older buildings on seismically active areas and therefore prolongs the lifespan of constructions, contributing to sustainability. In the following chapters the system is presented more in detail. Crosslam timber panels [1, 3, 4] are presented as well as the Aerogel Spaceloft material [2]l. The background of seismic analysis and the performance based design N2 method [5] used for the evaluation of the seismic resistance of the case structure are discussed. Thermal properties of the outer crosslam shell combined with Spaceloft are presented as well as a comparison with conventional insulation. $   $)     Crosslam timber panels have been developed in Austria in the late 1990s. The panels are glued together from several (min. 3 and up to 9 layers for standard setups) layers of spruce boards where each layer (Fig 1) runs perpendicular to the neighbouring two (or occasionally the most outer two layers run parallel to achieve greater strength and stiffness in one direction). Due to the high stiffness, strength and in=plane stability, crosslam quickly gained popularity among architects due to the possibilities the system offered in construction design.