Background
Residential housing, built in 1960-1995 can be featured by poor thermal properties. New requirements assigned for energy efficiency of buildings called for insulation. Heat losses are primarily specified by thermal properties of building envelopes depending on what humidity conditions construction materials are exposed to. High humidity of exterior walls can result in diminution of thermal properties and increase in heat losses. A structure for external walls insulation based on heat insulating slabs made of rock wool has been taken as a study. A required thickness of an insulation material has been determined, and an analysis of humidity conditions for insulated and non-insulated exterior walls has been performed.
The study of Mr. Viktor Pukhkal has been my inspiration to continue on the same foot steps of thermal insulation that are used as layers of humidity absorption in the inner surface of the vertical members. his study is more related to Saint-Petersburg. A major issue for the city’s economy of Saint-Petersburg is its energy consumption. More than 50% of all the fuel and energy city resources are consumed to supply heat. Residential housing in Saint-Petersburg built-up in 1960- 1995 can be featured by poor thermal properties. Heat losses are primarily specified by thermal properties of building envelopes.
His study states on various materials such as Brick, large-panel and block constructions are widely-spread; living floor area of brick buildings amounts to 55 132 K sq. m2 (46.1%), panel and block-panel buildings is light-weight aggregate concrete (density 900-1200 kg/m3) and autoclaved aerated concrete (600-700 kg/m3). Estimated values of the resistance to heat transfer in regard to main series of panel buildings in Saint-Petersburg do not exceed 1 m2 /kW, that is three times less than it is required according to up-to-date heat protection standards [32], and actual values are 0,7-0,85 m2 /kW. It can be explained by high humidity of building envelopes. With moisture content increase in buildings envelopes thermal conductivity coefficients of building materials increase as well, and this causes extra heat losses. For example, heat losses through brick walls under high-humidity conditions exceed normal standards for apartments located at corner of a building by 36%, and for apartments Saint-Petersburg can be distinguished by frequent climatic changes. Annual dynamics of external air temperature Moistening of building constructions under climatic conditions of Saint-Petersburg may result in deterioration of buildings. Ice crystals formation on the surfaces of cracks, cavities and porous spaces in construction structures can cause deformations due to temperature and humidity changes and may lead to deterioration of buildings fig:1
2. Insulation in mass residential housing
When it comes to reconstruction and repair works with the aim to insulate buildings facades outside location of insulation layers (Fig. 2, 3) are preferred. If materials are located on exterior walls surfaces there are more advantages as compared with location on interior surfaces:
3. Inspection of humidity conditions for an exterior wall in the case of outside insulation using a protective decorative coating made of thin plaster
The following method has been applied to test the structure for condensation inside the exterior wall with insulation and without one the resistance to vapour permeability of the wall is determined (we do not consider the resistance moisture exchange in the area of external and internal surfaces) (1)
Where G i is the thickness of a layer ‘i’ of an envelope to material’s layer ‘i’ of an envelope,
the partial pressure of water vapour insidea wall is computed is a relative humidity of external and internal air, respectively, saturated water vapour, Pa, at the internal temperature and external temperature
When it comes to reconstruction and repair works with the aim to insulate buildings facades outside location of insulation layers (Fig. 2, 3) are preferred. If materials are located on exterior walls surfaces there are more advantages as compared with location on interior surfaces:
- x there are no ‘thermal bridges’ after insulation has been done;
- x there is no need in insulation vapour barrier;
- x location of a material with high heat accumulation performance at positive temperature, and this increases heat inertia of envelopes and contributes to improvement of thermal properties when there is unsteady heat transfer;
- x a major material of a wall (brick or panel) is protected against alternate freezing and melting and other atmospheric effects;
- x there is no decrease in housing area, there is no need to open floors and dissemble heating system, exterior look of a building may be improved.
3. Inspection of humidity conditions for an exterior wall in the case of outside insulation using a protective decorative coating made of thin plaster
The following method has been applied to test the structure for condensation inside the exterior wall with insulation and without one the resistance to vapour permeability of the wall is determined (we do not consider the resistance moisture exchange in the area of external and internal surfaces) (1)
Where G i is the thickness of a layer ‘i’ of an envelope to material’s layer ‘i’ of an envelope,
the partial pressure of water vapour insidea wall is computed is a relative humidity of external and internal air, respectively, saturated water vapour, Pa, at the internal temperature and external temperature
Sources
1. Pukhkal, V., Vatin, N., Murgul, V. Centralized natural exhaust ventilation systems use in multi-story residential buildings (2014) Applied Mechanics and Materials, Vol. 680, pp. 529-533.
2. Viktor Pukhkal.test/humidity-conditions-for-exterior-walls-insulation-case-study-of-residential-housing-development-in-saint-petersburg
3.Murgul, V. Solar energy systems in the reconstruction of heritage historical buildings of the northern towns (for example Sankt-Petersburg) (2014) Journal of Applied Engineering Science, Vol. 12 (2), pp. 121-128
4.Gabriyel, I., Ladener, Kh. Rekonstruktsiya zdaniy po standartam energoeffektivnogo doma [Reconstruction of buildings for energy efficiency standards at home] (2011) St. Petersburg: BKhV-Peterburg, 325 p. [38] SP 23-101-2004. Thermal performance design of buildings (2007) 320 p.
2. Viktor Pukhkal.test/humidity-conditions-for-exterior-walls-insulation-case-study-of-residential-housing-development-in-saint-petersburg
3.Murgul, V. Solar energy systems in the reconstruction of heritage historical buildings of the northern towns (for example Sankt-Petersburg) (2014) Journal of Applied Engineering Science, Vol. 12 (2), pp. 121-128
4.Gabriyel, I., Ladener, Kh. Rekonstruktsiya zdaniy po standartam energoeffektivnogo doma [Reconstruction of buildings for energy efficiency standards at home] (2011) St. Petersburg: BKhV-Peterburg, 325 p. [38] SP 23-101-2004. Thermal performance design of buildings (2007) 320 p.