HEAT INSULATION OF OUTER BUILDING WALLS
One of the main measures to curb energy losses and reduce greenhouse gas emissions in the municipal sector involves the activities implemented at heat-user end, namely, improving the heat insulation of the shell works of residential and public buildings.
Outer walls have the largest surface area within building enclosure, therefore, their impact on building heat losses is the greatest, alongside heat losses via windows.
Approximate Distribution of Building Heat Losses
The main regulatory requirements to heat-insulating performance of building enclosures are presented in the National Building Code DBN V.2.6-31:2006 "Heat Insulation of Buildings" as amended of 1 July 2013, which came into effect in 2014.
The heat insulation performance of outer walls specified in the National Building Code (DBN) for the Ukrainian regions located in the temperature zone one (the majority of oblasts in Ukraine) can be achieved by applying on outer walls the heat insulating materials (polystyrene foam or mineral wool with the heat conductivity factor of about 0.05W/m gram) approximately 120 mm thick.
The activities of improving the thermal resistance of outer walls can be carried out using such heat insulating materials as: mineral/glass wool boards; rock/basalt wool; polystyrene foam and extruded polystyrene foam; polyurethane foam; urea formaldehyde foam insulation; green fiber; foam glass; and other materials (see below). The materials properties are listed in Appendix L to the abovementioned DBN.
Technologies Used for Strengthening the Thermal Resistance of Structures
1. The method of attached heat insulation consists in securing insulation boards to the wall using special adhesive and special concrete nails, protecting their surface with polymer cement composites, reinforced fiberglass mesh, and applying a coat of decorative plaster. The boards shall be installed virtually without gaps, so that they make up a continuous and uniform heat envelope without cold bridges.
|1. Shell works (wall)
2. Board adhesive compound
3. Thermal insulation (100mm thick)
4. Concrete nail
5. Adhesive mixture
6. Reinforced fiberglass mesh
8. Decorative coat
9. Plinth course
Installing an Attached Thermal Insulation System
The total cost of works and materials varies from UAH 500 to UAH 1000 per 1m2, however, it could differ significantly depending on actual market situation.
2. Using a ventilated façade method allows making a more durable structure. With this method of lining the building façade, a ventilated air gap is left between the external envelope and building wall. In general, the ventilated façade is made up of a structure for attaching the protective decorative lining (steel or aluminum), thermal insulation, house wrap, house wrap façade lining, and façade lining.
The system operational principle is based on that the technological gap left between the thermal insulation and the lining provides for a free flow of air. This keeps the wall dry at all times, thus preventing the formation of condensed water vapor and moisture. The ventilated façade installation schematic diagram is shown in Fig. 2.3.
Ventilated Façade Method Heat Insulation
А – Schematic Diagram
2 – Insulating board;
3 – House wrap;
4 – Metal substructure;
5 – Anchor clamping of heat insulation;
6 – Air gap;
7 – Protective decorative lining.
B – Overall view of the heat insulated façade with fiber-reinforced cement paneling
The total cost of ventilated façade works is UAH 1000 to UAH 2000 per 1m2 of wall surface and it varies significantly depending on the type of facing materials used. The most commonly used are aluminum composite panels, ceramic granite, fiber-reinforced cement panels, metal siding, and vinyl façade siding.
Materials Used for Thermal Insulation:
The activities of improving the thermal resistance of outer walls can be implemented using such heat insulating materials as: mineral/glass wool boards; rock/basalt wool boards; polystyrene foam and extruded polystyrene foam; polyurethane foam; urea formaldehyde foam insulation; green fiber; foam glass; and other materials. Properties of those materials are listed in Appendix L to DBN V.2.6-31:2006 "Heat Insulation of Buildings" as amended of 1 July 2013. The abovementioned heat insulating materials have similar heat insulating performance; however, mineral wool has certain properties, which put it at an advantage compared to other heat insulating materials.
Those properties include high heat and acoustic insulation capacity, fire resistance, and non-flammability. Mineral wool boards are easily attached to uneven surfaces. The material has high permeability, which facilitates quick evacuation of moisture and drying of the structure. However, it has considerable weight (for insulating facades using the technology of attached heat insulation, use shall be made of the boards with densities of not less than 145 or 160 kg/m3). The cost of 1m3 of mineral wool for façade insulation is UAH 150 to UAH 200.
Insulation systems based on polystyrene foam boards of the П25…П-35 grades are those most commonly used for heat insulation of individual apartments in multistory buildings and of one-family houses. This results from financial considerations. Polystyrene foam is almost 2.5 times cheaper than mineral boards. One square meter of polystyrene board 100mm thick costs about UAH 70-100. Therefore, the total cost of insulation work is about UAH 300 to UAH 500 per 1m2 of outer walling.
Polystyrene foam is very light, with 1m2 of system using polystyrene foam boards 100mm thick weighing not more than 10 to 15kg, which makes the performance of works at great heights easier. However, this material has low vapor-permeability and acoustic isolation factors; it is categorized as flammable material (groups Г1, Г2). Therefore, its use in the buildings of preschool and educational institutions, as well as healthcare institutions, and multistory buildings (taller than 26.5m if non-flammable plaster is used, and taller than 15m when using flammable plaster) is prohibited (as required by DBN V.2.6-33:2008 "Constructions of Buildings and Structures. Constructions of Outer Walls with Façade Thermal Insulation. Requirements to Design, Installation, and Operation").
Use of polystyrene foam in multistory buildings should be accompanied by lining the window and door openings with mineral wool or other non-flammable material, and installing uninterrupted belts made of non-flammable heat insulating materials every three floor levels.
When using polystyrene foam in one-family low-rise buildings, the roof framing should be made of non-flammable materials (as a rule, it is made of wood) or the wall cornice area should be lined with non-flammable heat insulating material. Replacing the grade П25-П35 polystyrene with the П-15 packing grade polystyrene is not permissible. Use of polystyrene foam in systems with ventilated facades is not allowed.
Extruded polystyrene foam is a variety of polystyrene. Boards made of this materials are more resistant to physical stress, they are light and have low flammability (class Г-1), which sets them apart from type ПСБ-С polystyrene foam boards, which are categorized as class Г-3 or Г-4 (elevated or medium flammability).
In terms of its flammability, the extruded polystyrene foam falls in the class of moderately flammable materials (B-2), which do not cause inflammations (class РП-1). Closed material cells of 0.1-0.2mm diameter ensure low water absorbency and high thermal insulating performance, the material is decay-resistant and nontoxic. It is frost-proof, durable, chemical-resistant (except organic solvents). It is used in high-humidity environments. For walling insulation, use is made of special boards with rough or honeycomb textured external surfaces to facilitate subsequent plastering or application of other facing materials. The price per 1m2 is UAH 100 to UAH 150.
How to Choose Materials for Heat Insulation:
For weatherization of various parts of the building select the insulation material, which is the best suited for specific operating conditions. For instance, extruded polystyrene foam is better suited for insulating foundations, flat roofs, basement walls, and floors. The homogeneous structure of this material's tightly sealed cells ensures its nearly zero water absorption, resistance to repeated freezing/thawing cycles, low vapor permeability, and absence of capillarity. This material also provides excellent results for insulation of outer walling.
Mineral wool has an important advantage compared to other organic insulation materials in that it is a non-flammable material with high vapor permeability. Mineral wool boards should be chosen for thermal modernization of multistory buildings, educational and healthcare institutions.
The cost efficiency of outer walling weatherization activities is measured by the amount of reduction in heat losses via walls before and after completion of the activities, as well as by heat energy tariffs.
An activity of improving the heat insulating performance of shell works could have any significant impact on overall consumption of thermal energy for heating only if a comprehensive thermal modernization of the whole building is implemented, including upgrade of the heat insulation to the standard requirements of DBN В.2.6-31: 2006 "Heat Insulation of Buildings" of not just walls, but also insulating the roofing (built-up or garret roofs), basement floors or ground floors, replacing transparent enclosures, reconstructing the building entrance, and inlet heating unit, as well as reducing infiltration heat losses for building ventilation.