Construction of a Single-Family House – Cost Justification of Thermal Insulation Guidelines in Building

Building construction is a long-term and knowledge-intensive process that can only be successfully carried out with the collaboration of the right personnel. The author of the diploma thesis first set out to produce a building plan, which served as a guide for preparing the elaborates. Regarding the choice of thicknesses, the author drew the basis from low-energy house suppliers, who already have certain assemblies and thicknesses of insulation and other layers prepared, and the results can be continuously compared and adjusted using the URSA 4.0 programme, so that by entering all parameters and thicknesses, final results were obtained. For all three cases, the author could start from one basis; it was only necessary to adjust the construction assemblies.

Problem

Building construction is a long-term and knowledge-intensive process that can only be successfully carried out with the collaboration of the right personnel.

Solution and Method

The author of the diploma thesis first set out to produce a building plan, which served as a guide for preparing the elaborates. A plan was prepared for a building with external dimensions of 9.85 × 7.85 m and a height of 7.35 m, and the building itself is designed according to the low-energy building method, meaning that transparent parts are appropriately oriented and appropriately sized according to orientation. The author also opted for a timber-frame house suitable for low-energy building, into which sufficient thickness of thermal insulation can be installed, in this case mineral wool.

It is necessary to select the right solutions for thermal bridges and to choose appropriate windows or glazing with a suitable thermal insulation factor. The author of the diploma thesis focused on the thickness of thermal insulation of the entire external envelope. All construction assemblies were entered into the programme, and the areas of facades, glazing and rooms were calculated.

Results

Regarding the choice of thicknesses, the author drew the basis from low-energy house suppliers, who already have certain assemblies and thicknesses of insulation and other layers prepared, and the results can be continuously compared and adjusted using the URSA 4.0 programme, so that by entering all parameters and thicknesses, final results were obtained. For all three cases, the author could start from one basis; it was only necessary to adjust the construction assemblies. Based on the programme calculations, a document on the energy performance certificate of the building was exported, which was attached for all three cases, and for the purposes of more detailed work, an elaborate for the field of efficient use of energy in buildings was also exported, from which precise data for both cases were obtained and from which the tables of construction assemblies also originate.

All parameters that were needed were combined in Excel, which served as the basis for calculations and tables. The first model is a well-insulated building with a consumption of 22.71 kWh/m²a, which placed it in class B2. If mechanical ventilation with heat recovery had been used in this model, at least 50% lower consumption would have been expected.

The second case was selected on the basis of the PURES guideline and consumes 68.09 kWh/m²a, which placed it in class D of energy efficiency. The last case achieved a much worse result, namely 112.18 kWh/m²a, which places it in class E – wasteful buildings. Data were obtained from official price lists, with which actual prices for the thermal insulation thicknesses used were calculated.

For more accurate data, only the change in price for thermal insulation was considered, as it can be assumed that all other construction assemblies are mandatory and do not change. This also yielded more transparent data. From the prices, based on the areas of the assemblies, actual costs were calculated, and from this, the differences that arise when increasing the thickness of insulation were obtained.

It was calculated that the difference (higher investment) for this building with good thermal insulation is €12,417.26 and for a building according to PURES guidelines €2,212.34. It was previously assumed that the payback period would vary depending on the choice of energy source for heating. Six of the most common energy sources were selected, their current market prices were evaluated, and the efficiencies of the systems that use that energy source were determined.

From the data on the annual consumption of the building, actual heating costs were obtained according to different energy sources. From this, actual savings could be calculated and finally a final estimate, which is the average of all energy sources. Based on the calculations and comparisons, it was established that the theses were set in the right direction and that the assumptions were confirmed.

It is established that low-energy building definitely pays off in the long term. The low-energy building itself pays back on average in 24 years, which is much less than the actual expected lifespan of the building. A building constructed according to PURES guidelines pays back on average in 9 years.

It is considered that the investment is justified in both cases, but special attention is certainly required in all aspects of execution, so that the building does not need comprehensive energy renovation before the payback period expires. Finally, a calculation of heating savings over the entire expected lifespan of the building, 80 years, was prepared. It was calculated that with a well-insulated building, on average €35,092.56 would be saved, which amounts to €486.66 annually and clearly shows that the investment pays off in full.

For a building according to PURES guidelines, €10,994.00 would be saved, which amounts to €137.42 annually and is also economically justified. It is established that all assumptions were confirmed and the economic viability of low-energy building was proven.