Ventilative cooling is the use of

natural Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans ar ...

mechanical ventilation Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV), is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move a ...

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 Cooling is removal of heat, usually resulting in a lower temperature and/or phase change. Temperature lowering achieved by any other means may also be called cooling.ASHRAE Terminology, https://www.ashrae.org/technical-resources/free-resources/as ...

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 activit ...

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 and walls standing more or less permanently in one place, such as a house or factory (although there's also portable buildings). Buildings come in a variety of sizes, shapes, and func ...

and may even be critical to realize renovated or new high efficient buildings and

zero-energy building A Zero Energy Building (ZEB), also known as a Net Zero Energy (NZE) building, is a building with net zero energy consumption, meaning the total amount of energy used by the building on an annual basis is equal to the amount of renewable energy ...

s ( 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 *** Ventilator, a m ...

is present in buildings mainly for

air quality Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different types ...

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 satisfaction with the thermal environment and is assessed by subjective evaluation ( ANSI/ASHRAE Standard 55).ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupan ...

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 Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (me ...

rates * The occurrence of higher outdoor temperatures during the cooling season, because of the

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

and the

heat island effect An urban heat island (UHI) is an urban or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparent ...

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 (

) depends on the

air flow Airflow, or air flow, is the movement of air. The primary cause of airflow is the existence 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 a ...

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 conducti ...

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 is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and com ...

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 In thermodynamics, a material's thermal effusivity, thermal inertia or thermal responsivity is a measure of its ability to exchange thermal energy with its surroundings. It is defined as the square root of the product of the material's thermal ...

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

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

* Impact of urban environment * Outdoor noise levels * Outdoor

air pollution Air pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. There are many different type ...

* 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 force ...

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 and around buildings and structures. IAQ is known to affect the health, comfort, and well-being of building occupants. Poor indoor air quality has been linked to sick building syndrome, reduce ...

reasons. Most of the buildings present high

thermal mass In building design, thermal mass is a property of the mass of a building that enables it to store heat and provide inertia against temperature fluctuations. It is sometimes known as the thermal flywheel effect. The thermal mass of heavy structura ...

. 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 mat ...

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 security by ...

, dampers and grills, fans, flaps, louvres, special effect vents) * Airflow enhancing ventilation building components (

chimneys A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typ ...

, 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 expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

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, dew, or fog to be present. Humidity dep ...

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

, , rain,

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ...

) 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 {{CO2 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 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 licensed architect. Smaller, less complica ...

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 organisation, established in 1974, that provides policy recommendations, analysis and data on the entire global energy sector, with a recent focus on curbing car ...

(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 housing predominates, as opposed to industrial and commercial areas. Housing may vary significantly between, and through, residential areas. These include single-family housing, multi-family resi ...

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 ...

. * 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