Ventilative cooling is the use of

natural Nature is an inherent character or constitution, particularly of the ecosphere or the universe as a whole. In this general sense nature refers to the laws, elements and phenomena of the physical world, including life. Although humans are part ...

mechanical ventilation Mechanical ventilation or assisted ventilation is the Medicine, medical term for using a ventilator, ventilator machine to fully or partially provide artificial ventilation. Mechanical ventilation helps move air into and out of the lungs, wit ...

to cool indoor spaces.P. Heiselberg, M. Kolokotroni.
Ventilative Cooling. State of the art review
. Department of Civil Engineering. Aalborg University, Denmark. 2015 The use of outside air reduces the cooling load and the

energy consumption Energy consumption is the amount of energy used. Biology In the body, energy consumption is part of energy homeostasis. It derived from food energy. Energy consumption in the body is a product of the basal metabolic rate and the physical acti ...

of these systems, while maintaining high quality indoor conditions; passive ventilative cooling may eliminate energy consumption. Ventilative cooling strategies are applied in a wide range of

buildings A building or edifice is an enclosed structure with a roof, walls and windows, usually standing permanently in one place, such as a house or factory. Buildings come in a variety of sizes, shapes, and functions, and have been adapted throughout ...

and may even be critical to realize renovated or new high efficient buildings and zero-energy buildings (ZEBs).

Ventilation Ventilation may refer to: * Ventilation (physiology), the movement of air between the environment and the lungs via inhalation and exhalation ** Mechanical ventilation, in medicine, using artificial methods to assist breathing *** Respirator, a ma ...

is present in buildings mainly for

air quality Air pollution is the presence of substances in the Atmosphere of Earth, air that are harmful to humans, other living beings or the environment. Pollutants can be Gas, gases like Ground-level ozone, ozone or nitrogen oxides or small particles li ...

reasons. It can be used additionally to remove both excess heat gains, as well as increase the velocity of the air and thereby widen the

thermal comfort Thermal comfort is the condition of mind that expresses subjective satisfaction with the thermal environment.ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupancy The human body can be viewed as a heat engine where ...

range. Ventilative cooling is assessed by long-term evaluation indices. Ventilative cooling is dependent on the availability of appropriate external conditions and on the thermal physical characteristics of the building.

Background

In the last years, overheating in buildings has been a challenge not only during the design stage but also during the operation. The reasons are: * High performance energy standards which reduce heating demand in heating dominated climates. Mainly refer to increase of the insulation levels and restriction on infiltration rates * The occurrence of higher outdoor temperatures during the cooling season, because of the

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

and the heat island effect not considered at the design phase * Internal heat gains and occupancy behavior were not calculated with accuracy during the design phase (gap in performance). In many post-occupancy comfort studies overheating is a frequently reported problem not only during the summer months but also during the transitions periods, also in temperate climates.

Potentials and limitations

The effectiveness of ventilative cooling has been investigated by many researchers and has been documented in many post occupancy assessments reports.F. Allard. “Natural Ventilation in Buildings: A Design Handbook”. Earthscan Publications Ltd. . 1998 The system cooling effectiveness (natural or mechanical ventilation) depends on the

air flow Airflow, or air flow, is the movement of air. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to those where the pressure is lower. Atmospheric air pressure is directly related to altitude, temperatu ...

rate that can be established, the thermal capacity of the construction and the

heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

of the elements. During cold periods the cooling power of outdoor air is large. The risk of draughts is also important. During summer and transition months outdoor air cooling power might not be enough to compensate overheating indoors during daytime and application of ventilative cooling will be limited only during the night period. The night ventilation may remove effectively accumulated heat gains (internal and solar) during daytime in the

building construction Construction are processes involved in delivering buildings, infrastructure, industrial facilities, and associated activities through to the end of their life. It typically starts with planning, financing, and design that continues until the a ...

s. For the assessment of the cooling potential of the location simplified methods have been developed. These methods use mainly building characteristics information, comfort range indices and local climate data. In most of the simplified methods the

thermal inertia Thermal inertia is a term commonly used to describe the observed delays in a body's temperature response during heat transfers. The phenomenon exists because of a body's ability to both store and transport heat relative to its environment. Sinc ...

is ignored. The critical limitations for ventilative cooling are: * Impact of

global warming Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...

* Impact of urban environment * Outdoor noise levels * Outdoor

air pollution Air pollution is the presence of substances in the Atmosphere of Earth, air that are harmful to humans, other living beings or the environment. Pollutants can be Gas, gases like Ground-level ozone, ozone or nitrogen oxides or small particles li ...

* Pets and insects * Security issues * Locale limitations

Existing regulations

Ventilative cooling requirements in regulations are complex. Energy performance calculations in many countries worldwide do not explicitly consider ventilative cooling. The available tools used for energy performance calculations are not suited to model the impact and effectiveness of ventilative cooling, especially through annual and monthly calculations.

Case studies

A large number of buildings using ventilative cooling strategies have already been built around the world. Ventilative cooling can be found not only in traditional, pre-air-condition architecture, but also in temporary European and international low energy buildings. For these buildings passive strategies are priority. When passive strategies are not enough to achieve comfort, active strategies are applied. In most cases for the summer period and the transition months, automatically controlled

natural ventilation Passive ventilation is the process of supplying air to and removing air from an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure differences arising from natural for ...

is used. During the heating season, mechanical ventilation with heat recovery is used for

indoor air quality Indoor air quality (IAQ) is the air quality within buildings and Nonbuilding structure, structures. Poor indoor air quality due to indoor air pollution is known to affect the health, comfort, and well-being of building occupants. It has also be ...

reasons. Most of the buildings present high

thermal mass In building design, thermal mass is a property of the matter of a building that requires a flow of heat in order for it to change temperature. Not all writers agree on what physical property of matter "thermal mass" describes. Most writers use ...

. User behavior is crucial element for successful performance of the method.

Building components and control strategies

Building components of ventilative cooling are applied on all three levels of climate-sensitive building design, i.e. site design, architectural design and technical interventions . A grouping of these components follows: * Airflow guiding ventilation components (

window A window is an opening in a wall, door, roof, or vehicle that allows the exchange of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent ma ...

s, rooflights,

doors A door is a hinged or otherwise movable barrier that allows ingress (entry) into and egress (exit) from an enclosure. The created opening in the wall is a ''doorway'' or ''portal''. A door's essential and primary purpose is to provide secu ...

, dampers and grills, fans, flaps, louvres, special effect vents) * Airflow enhancing ventilation building components ( chimneys, atria, venturi ventilators, wind catchers, wind towers and scoops, double facades, ventilated walls) * Passive cooling building components (convective components, evaporative components, phase change components) * Actuators (chain, linear, rotary) * Sensors (

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...

radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes: * ''electromagnetic radiation'' consisting of photons, such as radio waves, microwaves, infr ...

, , rain,

wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

) Control strategies in ventilative cooling solutions have to control the magnitude and the direction, of air flows in space and time. Effective control strategies ensure high indoor comfort levels and minimum

. Strategies in a lot of cases include temperature and monitoring.P. Heiselberg (ed.). �
Ventilative Cooling Design Guide
��. Aalborg University, Denmark. 2018 In many buildings in which occupants had learned how to operate the systems, energy use reduction was achieved. Main control parameters are operative (air and radiant) temperature (both peak, actual or average), occupancy, carbon dioxide concentration and humidity levels. Automation is more effective than personal control. Manual control or manual override of automatic control are very important as it affects user acceptance and appreciation of the indoor climate positively (also cost). The third option is that operation of facades is left to personal control of the inhabitants, but the building automation system gives active feedback and specific advises.

Existing methods and tools

Building design Building design, also called architectural design, refers to the broadly based architectural, engineering and technical applications to the design of buildings. All building projects require the services of a building designer, typically a licen ...

is characterized by different detailed design levels. In order to support the decision-making process towards ventilative cooling solutions, airflow models with different resolution are used. Depending on the detail resolution required, airflow models can be grouped into two categories: * Early stage modelling tools, which include empirical models, monozone model, bidimensional airflow network models;and * Detailed modelling tools, which include airflow network models, coupled BES-AFN models, zonal models, Computational Fluid Dynamic, coupled CFD-BES-AFN models. Existing literature includes reviews of available methods for airflow modelling.

IEA EBC Annex 62

Annex 62 'ventilative cooling' was a research project of the Energy in Buildings and Communities Programme (EBC) of the

International Energy Agency The International Energy Agency (IEA) is a Paris-based autonomous intergovernmental organization, established in 1974, that provides policy recommendations, analysis and data on the global energy sector. The 31 member countries and 13 associatio ...

(IEA), with a four-year working phase (2014–2018). The main goal was to make ventilative cooling an attractive and energy efficient cooling solution to avoid overheating of both new and renovated buildings. The results from the Annex facilitate better possibilities for prediction and estimation of heat removal and overheating risk – for both design purposes and for energy performance calculation. The documented performance of ventilative cooling systems through analysis of case studies aimed to promote the use of this technology in future high performance and conventional buildings.venticool, the international platform for ventilative cooling. �
About Annex 62
��. Retrieved June 2018 To fulfill the main goal the Annex had the following targets for the research and development work: * To develop and evaluate suitable design methods and tools for prediction of cooling need, ventilative cooling performance and risk of overheating in buildings. * To develop guidelines for an energy-efficient reduction of the risk of overheating by ventilative cooling solutions and for design and operation of ventilative cooling in both

residential A residential area is a land used in which houses, housing predominates, as opposed to industrial district, industrial and Commercial Area, commercial areas. Housing may vary significantly between, and through, residential areas. These include ...

and

commercial buildings Commercial property, also called commercial real estate, investment property or income property, is real estate (buildings or land) intended to generate a profit, either from capital gains or rental income. Commercial property includes office b ...

. * To develop guidelines for integration of ventilative cooling in energy performance calculation methods and regulations including specification and verification of key performance indicators. * To develop instructions for improvement of the ventilative cooling capacity of existing systems and for development of new ventilative cooling solutions including their control strategies. * To demonstrate the performance of ventilative cooling solutions through analysis and evaluation of well-documented case studies. The Annex 62 research work was divided in three subtasks. * Subtask A "Methods and Tools" analyses, developed and evaluated suitable design methods and tools for prediction of cooling need, ventilative cooling performance and risk of overheating in buildings. The subtask also gave guidelines for integration of ventilative cooling in energy performance calculation methods and regulation including specification and verification of key performance indicators. * Subtask B "Solutions" investigated the cooling performance of existing mechanical, natural and hybrid ventilation systems and technologies and typical comfort control solutions as a starting point for extending the boundaries for their use. Based upon these investigations the subtask also developed recommendations for new kinds of flexible and reliable ventilative cooling solutions that create comfort under a wide range of climatic conditions. * Subtask C "Case studies" demonstrated the performance of ventilative cooling through analysis and evaluation of well-documented case studies.

References

Low-energy building Heating, ventilation, and air conditioning Ventilation Energy conservation