Rehva guidebook

7Thermal Comfort and Energy-Efficient Cooling

3. 
   guarantee enhanced visual, acoustic, and thermal comfort and therefore provide a high-quality workplace environment, which improves the occupant’s productivity and reduces the impact of the built environment on the occupant’s health.
   
4. 
   harness the building’s architecture and physics in order to considerably reduce the annual heating and cooling demand (building envelope, day lighting concept, natural ventilation, passive heating and cooling technologies).
   
5. 
   put emphasis on a highly energy-efficient heating and cooling plant with a significantly reduced auxiliary energy use for the generation, distribution and delivery of heating and cooling energy. The applied components and technologies are soundly orchestrated by optimized operation and control strategies.
   
6. 
   use less-valuable primary energy, e.g., renewable energy from environmental heat sources and sinks, solar power, biomass, etc.
   

Figure 6 illustrates an individual building signature correlating useful or cooling energy use [kWh_therm/(m²_neta)], the building’s total primary energy use for heating, cooling, ventilation, and lighting [kWh_prim/m²a] and thermal and humidity comfort classification according to EN 15251:2007-08. The green triangle represents the target objective for these three parameters and the arrows indicate the direction of the optimum.

Figure 6 Building signature. This building signatures show results from the Finish monitoring campaign and its evaluation according to the guidelines given in this Guidebook. The thermal indoor environment meet the requirements of class II. The useful cooling energy meets the building-physical requirements on summer heat protection. Only the primary energy demand of the building is higher than the target value and does not meet the requirements.

Occupant thermal comfort assessments of the buildings in summer are evaluated according to the European guideline EN 15251:2007-08. The building signatures present the time during occupancy at the required comfort class. Thermal comfort is evaluated by the proposed methodology according to the

1. 
   adaptive comfort approach for building concepts with passive cooling and
   
2. 
   PMV comfort approach for building concepts with water-based mechanical cooling and mixed-mode cooling.
   

Measurements of useful cooling energy are derived from the long-term monitoring campaigns –carried out by the particular ThermCo partners. If measurements are not available, simulation results or calculations are presented. Cooling energy use depends on the building’s architecture, the user behavior, the climate, and the potential of the heat sink employed. Therefore, the cooling load [W/m²] increases from North to South mainly due to higher temperatures and to a lesser extent due to higher solar heat gains. Consequently, the target objectives for the cooling energy use vary due to the climate and the building concepts. For the building assessment, objective cooling energy values are taken from the simulation study in Chapter 6, representing a typical low-energy non-residential building.

The primary energy consumption of the buildings considers the heating and cooling plant, as well as ventilation and lighting –and was limited to a value of 100 kWh_prim/(m²_neta). If not stated otherwise, plug loads are not included. The primary energy approach allows to compare concepts that use different energy sources such as fossil fuels, electricity, environmental energy, district heat, waste heat, and biomass. The primary energy factors are 2.5 MWh_prim/MWh_fin for electricity and 1.0 MWh_prim/MWh_fin for fossil fuels.

In conclusion, a well designed and operated building provides thermal and humidity comfort in compliance with the required comfort class of EN 15251:2007-08, with a reduced cooling energy demand (below values derived from the simulation study) and an overall efficient HVAC and lighting concept which results in a limited primary energy use of 100 kWhprim/m²a.