Styronit insulation and protection

WHAT IS THE MOST EFFECTIVE THICKNESS OF THERMAL INSULATION MATERIAL FOR WALL SURFACES IN BUILDING INSULATION?

What should be the effective application cross-sectional thickness of the thermal insulation material used for wall surfaces in the building to provide minimum specific heat loss for the building, is the first matter in question or the most attractive subject in the building insulation projects. In the theoretical calculations related to thermal insulation in construction projects showed that the thickness of the thermal insulation material applied onto wall would be of high thickness values, that is 7-9 cm. To which extent the insulaton material could provide heat energy savings for the building when very thick insulation material is used, should need to be analyzed, as well as this situation causes disadvantage in practice for most of the undertakers.

According to construction components and technical specifications described by the master sample building (Figure 1) enclosed in the standard decleration, TS 825/April 1998 with heading "Thermal Insulation Standard for Buildings" issued on Turkish Official Gazette dated June 14, 1999 and numbered 23725, the heat energy savings provided by the thickness of the applied thermal insulation material have been analyzed to give an opinion relavant to this matter.

Technical data used in thermal insulation analysis of the master sample building are as follows:
Building width                                                    : 9 m
Building length                                                   : 10 m
Building height                                                   : 5.5 m
Average monthly internal temperature           : 10 oC
Specific internal heat gain                                : 5 W/m2
Number of replacement of space air           : 1
Flat height                                                          : 2.5 m
Total area of windows area on North side     : 2 m2
Total area of windows on South side             : 10 m2
Total area of windows on east side                : 4 m2
Total area of windows on West side             : 4 m2
Shadowing factors:
(ri) month                                                      : 0.60
(gi) month                                                     : 0.60

Construction elements and technical data in the analysis of the master sample building:
Wall surfaces :
2 cm           Internal plaster                                                                      (l = 0.87 W/mK)
19 cm         Horizontal hollow brick                                                        (l = 0.45 W/mK)
6 cm           Thermal insulation material                                                 (l = 0.04 W/mK)
0.5 cm        External siding                                                                     (l = 0.87 W/mK)
Ground/Floor components :
3 cm           Grout                                                                                (l = 1.40 W/mK)
8 cm           Thermal insulation material                                              (l = 0.04 W/mK)
2 cm           Leveling grout                                                                 (l = 1.40 W/mK)
10 cm         Light concrete                                                                    (l = 1.10 W/mK)
15 cm         Blokage (without reinforcement)                                      (l = 1.74 W/mK)
Ceiling Components :
2 cm           Internal plaster                                                              (l = 0.87 W/mK)
15 cm         Reinforced concrete                                                        (l = 1.30 W/mK)
12 cm         Thermal insulation material                                              (l = 0.04 W/mK)

It is possible to make the following assessment analysis to define to which extent the insulation material applied onto the exterior wall surfaces could be effective on heat savings when the thickness of the material is of concern, when master sample building and its constructional components presented as numerical analysis sample in the calculation algorithm prescribed in Turkish Standard TS 825, is taken into consideration:

In this analysis, the situation is such that there isn't any insulation material applied to the exterior wall surfaces of this master sample building, that is "naked wall", has been preferentially assumed and total specific heat loss, according to the algorithm prescribed in TS 825 has been calculated as 532.29 W/K. But, when the walls are insulated with different material thicknesses to reduce the the heat dissipation from exterior wall surfaces and consequently ensure energy savings of the building, the parametric values shown at Table 1 were obtained.

Table 1. Calculated heat loss values of the master sample building.

Thickness of Thermal Insulation Material Applied onto Wall Surface (cm)	Heat Dissipation from wall surface(W/K)	Total Conductional Heat Loss due to Construction Components(W/K)	Specific Heat loss of Building(W/K)
0	304.37	401.61	532.29
1	217.00	314.24	454.92
2	168.61	265.84	396.52
3	137.86	235.10	365.78
4	116.6	213.83	344.51
5	101.02	198.25	328.93
6	89.11	186.35	317.03
7	79.71	176.95	307.63
8	72.11	169.35	300.03

As shown at Table 1, when application thickness of the thermal insulation material used on the wall surface increases, the conductional heat loss through both of the wall surfaces and construction components of the building shows a decreasing tendency of certain proportion and the loss is prevented. But there is a remarkable point, such that; the decrease in the quantity of total heat loss of the building is not linearly proportional to the increase in the quantity of the thermal insulation material thickness. In this situation, the values of heat savings provided by the different thicknesses of the thermal insulation material applied onto the wall surface have been defined at the Table.2, in percentages relative to the value of the wall without any insulation material. Besides that, the percentage of the heat gain for the wall surfaces and building have been also calculated for each increment of insulation layer thickness.

When the graphic of the heat gain values and gain percentages related to sectional thickness of the insulation material used for energy saving at Table.2 are examined, to which degree the applied thermal insulation material to decrease heat loss of the wall could be effective on heat saving, can be easily seen.

Figure 1. Relation between the thickness of insulation material applied onto wall surface and heat gain.

Figure 2. Effects of the increase in thermal insulation material thickness on heat gained by the wall component.

Figure 3. Relation between the thickness of insulation material applied onto wall surface and heat gained by the building.

Figure 4. Effects of the increase in thermal insulation material thickness on heat gained by the construction components of the building.

When the graphical analyses given above are examined, it is possible to reach such general assessment: In order to attain heat savings, the application thickness only up to the certain extent for the materials which will be used for insulation on the exterior wall surfaces of the building can provide advantages. In other words, each 1 cm-increase in the application thickness of thermal insulation material could not bring us the same proportional amount of heat gain back. As shown in the example here, while the heat gain of the building is %14.54 when 1cm-thick thermal insulation material is applied onto any naked wall surface, the heat gain of the same building changes to % 25.51, when thickness of the insulation material is increased to 2 cm by adding further 1 cm-thick thermal insulation material onto the previous coat. In other words, if you add another 1 cm-thick thermal insulation material layer onto the existing 1 cm-thick layer, %10.97 of additional gain is obtained for the total heat gain of the building. Total heat gain of the building per unit of insulation thickness is parabolically decreasing as the application thickness of the insulation material is increasing. This shows, the application thickness only up to the certain extent for any thermal insulation material can provide reasonable advantages when the heat gained by thermal insulation material for the building is taken into consideration. The application on the wall surfaces which has thicker thermal insulation material than the required (optimum) application thickness will not provide the expected heat gain for the building. For the sample building handled here, the optimum thickness of the thermal insulation layer applicable onto wall surface has been determined as 3.2 cm. The application thickness which is greater than this optimum value will provide minor heat gain, if the effect of the thickness on specific heat loss of the building is taken into account. Furthermore, to make a thermal insulation application with the thickness greater than optimum thickness should be considered as non-effective application. Today, when the investment on thermal insulation of the building considering the prices of different types of materials used for thermal insulation of the buildings is examined, pretty high unit costs come into view. Therefore, to apply very thick thermal insulation material onto the surfaces of the building walls is not only uneconomical, but also increases the final wall thickness proportionally and unnecessarily {5cm increase in the thickness for a 100m long exterior wall means 5 m2 space loss (an area of one bathroom)}. This point is pretty remarkable from the applications of thermal insulation point of view. From the other side, considering that Turkey is a dependent country on these types of thermal insulation raw materials, thermal insulation applications exceeding the optimum value mean also investing unnecessarily more than required. This is important for national economy.

The important point in the thermal insulation; the heat losses for each of the construction components contained in the building project should be separately defined according to the algorithm of the thermal insulation calculation in TS 825 standard and specific heat loss of the building must be determined. In this calculation, the most optimum application thickness value for the cross-sectional thickness of the thermal insulation material applied onto the wall surface should be determied in terms of heat energy gain percentage. In the thermal insulation calculation, the heat loss values of the ground/floor or ceiling components in the contents of the building should be corrected with necessary thermal insulation to minimize the other heat losses excluding the heat losses corresponding to this value.

In most of the building projects today, thermal insulation for the building in the project covers the application of thermal insulation layers only for the walls without taking any thermal insulation application to ground/floor and ceiling components into consideration. But, in these types of applications, as a result of thermal insulation calculation carried out, the application thicknesses of the thermal insulation material applied onto the wall surfaces become extremely high. This, as it was already mentioned above, brings up the non-effective and unnecessary applications in terms of heat energy savings. Moreover, it could be observed that due to the increase in the unit weight value on the surface, especially in multi-storey buildings, sometimes the shell which is made of very thick applied insulation layer is cleared off the wall.
Consequently, it is required to determine the most ideal application thickness for the thermal insulation material which will be applied onto the wall surface according to the percentage of heat energy gain for the building in terms of the components for the thermal insulation of the building prescribed in the project. In addition to this, it is necessary to plan alternative thermal insulation solutions to minimize heat losses not from the exterior wall components but from ground/floor or ceiling components for the heat gain required for the building. As a general rule, according to the calculations done and detailed technical studies, the most ideal thermal insulation thickness on the wall surface should be between 3 cm and 3.5 cm.