coldstores
Objectives of cold store floor insulation:
Creating a predictable and constant climate (constant physical contact with floors)
Preventing energy loss (environmental requirements)
Preventing frost heave
Enhancing economics
More than 20% of the total costs of a cold store building are consumed by the floor construction. From an investment point of view it is ranked like other means of production (e.g. machines, technical equipment). Repairs on cold store flooring are almost impossible; the importance of a well-functioning, safe industrial floor cannot be ranked high enough.
Floor insulation is the only application which requires the combination of two contradictory properties: thermal performance and mechanical strength. Thermal insulation is, from a mechanical point of view, the most sensitive layer in a floor construction.
Requirements
Mechanical:
Compressive strength - short-term and long-term
High modulus of elasticity - high foundation modulus
Thermal:
Low lambda
Hygroscopic Performance:
Resistance to water - liquid, vapour, ice
Workability:
Quick and easy to handle, cut and install
Edge design - thermal bridges
Design methods
In traditional low-level cold stores, where loads were relatively light, calculations to ascertain the ultimate loading on the floor insulation were based on a 45° load spread. Today's high-bay stores with their increasingly severe leg loads, demand more definitive design methods based on the Elastic Plate Theory. This theory is a method of determining and quantifying the structural behaviour of an insulated, loaded floor system by treating the floor construction as a series of interacting elastic layers. The combined behaviour of the layers, under a dynamic or static load, can be modeled and the load on each individual layer calculated.
Using Elastic Plate Theory calculations, the structural engineer can design the cold store floor systems in such a way that the mechanical properties of each layer are fully utilised. The ultimate load for the thermal insulation layer is the long-term compressive stress at a maximum of 2% compression, which is distributed onto the insulation by the top slab. To ensure a safe floor design, a safety margin for static and dynamic loads should be built in.
Installation
In coldstores, the Styrofoam boards should be installed on top of a suitable vapour barrier. The installation of the Styrofoam boards should be done in two layers, with the joints suitably staggered to prevent the formation of any cold bridging. It is recommended that a slip sheet is used between the insulation layer and wearing slab. This slip sheet should be loose laid onto the Styrofoam boards prior to pouring the concrete slab.
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