The stilt houses on Chiloé Island, Chile, traditionally built in local timber, are currently in poor conditions and lack of maintenance that contributes on a very poor thermal performance.To carry out interventions and inform decision making to intervene on such unique pieces of cultural heritage in fragile conditions, a computerized dynamic thermal simulation tool (software DesignBuilder®) is used to understand and assess the energy performance of these typology of houses, identifying their annual energy losses, and determining their current annual heating demand of ten case studies.The current annual heating demand of the stilt houses is high, due to the thermal transmittance values of the building envelopes. They exceed in five times the value recommended by Chilean Building Code for the climatic zone under study. Especially critical are heat losses through the ventilated floor (external floor under DesignBuilder® template) and air infiltration, which on average contributed to 30.5% and 28.85% of all energy loss, respectively. According to simulations for ventilated floor, walls, and roofs, the obtained performance could be improved to 65% with thermal reconditioning and measures to enhance airtightness, although the feasibility of such interventions without damaging the heritage houses needs to be carefully considered.