Practices

Parametric models for buildings and building clusters: Building features and boundaries

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Already today buildings can be realised in the nearly zero and plus energy standard. These buildings achieve extremely low energy demands and low CO2 emissions and can be operated economically. For this reason, the motivation in the CRAVEzero project is not only based on the energy characteristics of buildings, but also on their life-cycle costs. However, the broad market deployment of these buildings is progressing very slowly so far, as methods and processes for the cost-optimal integration of efficiency measures and renewable energies are not yet sufficiently described and therefore not yet common. As a consequence many poorly planned buildings are criticised for the fact that the actual energy consumption of highly efficient buildings is higher than the predicted demand and that high-efficiency standards are expensive and uneconomical. The influence of the user behaviour of such energy efficient buildings is another aspect, which has to be considered to evaluate the impact on the energy consumption of the building.

 

The identification of suitable methods for the energetic-economic optimisation of highly efficient buildings in all life-cycle phases is a prerequisite for the broad market implementation. In the energetic-economic optimisation of buildings, there are different interests of the actors and, derived from this, different perspectives, time expectancies and goals. There are the tenants/users, the real estate agents, building contractors, planner, property managers, investors, owners and also companies which are directly or indirectly involved within the building process. On the basis of the results, the statement is confirmed: nZEBs are economical. It can now be shown that the additional costs of efficiency measures are so low that highly efficient buildings have the lowest life-cycle costs. nZEB measures only have a small percentage influence on construc-tion costs, but can reduce CO2 emissions many times over. When considered over the service life, these measures are usually cost-neutral or even economical.

The following points can be summarised in detail:

 

-The energy standard has a small influence on the building and construction costs. Energy ef-ficiency is therefore not a major cost driver in construction.

 

-The additional construction costs of nZEBs are compensated in the life-cycle of most technologies even without subsidies.

 

-The cost optimum of primary energy demand and CO2 emissions is in the range of nearly zero and passive houses. Highly insulated enve-lopes and highly efficient windows are usually economical even without subsidies. This is also due to the long service life of these compo-nents in comparison to HVAC systems.

 

-The optimum cost curve in relation to CO2 emissions is very flat. Low emissions and en-ergy requirements can therefore be achieved with different energy concepts as long as the envelope is very efficient. This means architectural and conceptual freedom.

 

-It is shown that energy efficiency and economic efficiency are not contradictory strategies, but can complement each other very well.

 

-The parametric simulation results showed that the variance in the financing costs (20%) and the net present value (15%) is relatively low, whereas the primary energy demand (66%) and the CO2 (73%) emission vary in a broader range.

 

-It is possible to find a solution set with nearly equal financing cost and/or net present values, but with less primary energy consumption and/or CO2 emissions.

 

-The sensitivity analysis showed that the interest rate and the inflation of energy costs had the highest influence on the LCC costs. Further important factors were the maintenance cost, electricity costs and the cost of the structural elements with a medium influence on the LCC costs.

 

-The user behaviour had a major influence on the total energy consumption of a building. A highly efficient building can at least support the user to further reduce his energy consumption.