VC

The framework of the research presented in the paper is a project oriented to promote the use of concrete solutions in buildings based on maximizing the benefits of its thermal inertia for cooling periods.

The constructive solution developed has one configuration for summer (cooling mode). This configuration is similar to a ventilated facade that is formed by a thermally insulated outer layer of concrete, an intermediate air layer and an inner layer of concrete. The inner layer is cooled at night by forced ventilation using an outdoor - outdoor scheme.

As the benefit of natural ventilation in reducing operational cost is well recognised, the concept of natural ventilation is becoming more received by residents and designers alike.

Nearly all retail locations use ventilation and cooling systems to ensure adequate air exchange for health reasons and indoor comfort temperatures. These systems can run for over 2,000 hours per year and we expect that average operating hours will continue to rise across Europe because of the continued trend towards longer opening hours and increased number of opening days. Shopping malls often enclose large open spaces and atria with high solar and internal gains that can drive ventilative cooling.

The Kindergarten Solhuset is built according to the Active House vision with an emphasize of good daylight conditions and fresh air. The house was completed in 2011, and detailed measurements of the indoor environment have been performed since the completion. The daylight performance is evaluated with daylight factor simulations. The main activity rooms have daylight factors of 7%, while the innermost rooms with only roof windows achieve a high daylight factor of 4%. Electrical light is used frequently in daytime during the winter, but much less frequently during summer.

The present paper addresses experiences with ventilation and thermal comfort in the Active House concept, based on the Active House Specification and realized Active Houses. The Active House Specification is based on a holistic view on buildings including Comfort, Energy and Environment. It uses functional requirements to indoor air quality and thermal comfort. Experiences from realised Active House projects show that better airtightness than nationally required has been achieved.

The thermal comfort of the residential buildings Sunlighthouse in Austria and LichtAktiv Haus in Germany are investigated with a particular focus on the summer situation and the role of solar shading and natural ventilation. The houses have generous daylight conditions, and are designed to be CO2 neutral with a good indoor environment. The thermal environment is evaluated according to the Active House specification (based on the adaptive method of EN 15251), and it is found that the houses achieve category 1 for the summer situation.

Increasing airtightness and isolation of residential buildings in today’s climates cause challenging situations for the summer indoor climate. In combination with ventilation for fresh air, it calls for intelligent control of passive cooling when available, and active cooling when needed.

The combination of heat recovery ventilation and an air-to-air heat pump cooling system is a solution to these challenging situations. With the exhaust air heat pump cooling system, heat is transferred from the supply air (which is getting colder) to the exhaust air (which is getting warmer).

The effect of a cooling jet from ceiling on thermal comfort, perception and subjective performance in warm office environment (29.5 °C) was studied. Altogether, 29 participants (13 male and 16 female) participated. All participants were tested in both thermal conditions and the order of the thermal conditions was counterbalanced between the participants. During the experiment, participants filled questionnaires and performed computerised tasks. Using the cooling jet significantly improved the whole body and local thermal comfort.

This position paper gives a brief overview of opportunities and challenges for ventilative cooling solutions both:

• To contribute to the 2020 objectives of the EU in the building sector with regard to energy savings and greenhouse gas emissions;
• To contain the overheating risk, which is an increasing concern in low-energy buildings.

venticool partners believe policy makers and standard bodies should take steps together with the implementation of the EPBD recast to accelerate the uptake of this technology.

Adopting natural ventilation as a retrofit strategy for cooling, due to the low impact nature of the installation, is attractive due to the cooling potential of untreated outdoor air for large periods of the extended cooling season, particularly in northern climates. In line with this it is important to characterise the performance of natural ventilation components in low energy buildings in successfully transferring the cooling potential of outdoor air to the occupied zone.