Abstract
In the City of Prague centre, an investor had the intention to convert the unused attic space of a historical palace into office and exhibition floor. It was necessary to design such a solution that would not worsen the humidity conditions and would not jeopardize the original Renaissance roof truss. The requirements of the heritage protection agency and the architect predetermined the use of very efficient thermal insulation above the rafters. The paper introduces and assesses several design solutions for: (1) new roofing layers and (2) the critical detail near the eaves, including variants with active heating elements. The assessment was based on results of 2D steady-state hygrothermal modelling using two criteria: (1) the interior surface temperature under winter design boundary conditions and (2) the relative humidity in the area of the timber elements under average January boundary conditions. The results showed hygrothermal implications of different design measures and helped to identify acceptable solutions for further project phases.
Highlights
In the City of Prague centre, an investor had the intention to convert an unused attic space of a historical palace under heritage protection into an office and exhibition floor
The calculations show that the relative humidity on the upper surface of the rafters is lower than the relative humidity of the external air, i.e. lower than in the current state
The computational assessment of the current state did not identify any significant risk for the timber elements within the assessed detail at the eaves in terms of water vapour diffusion
Summary
In the City of Prague centre, an investor had the intention to convert an unused attic space of a historical palace under heritage protection into an office and exhibition floor. The roofing was made of ceramic tiles (traditional mission style), stacked on battens and counterbattens, without protective waterproofing. The paper presents design and hygrothermal assessment of several refurbishment options that would ensure new, energy-acceptable, economical, and moisture safe use of the attic space. A special attention was paid to the area at the eaves where several moisture sensitive timber elements are in direct contact with masonry
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