Airflow - Revision history

Designing Buildings at 04:03, 20 September 2022

2022-09-20T04:03:44Z

Editor at 17:48, 19 September 2022

2022-09-19T17:48:13Z

← Older revision		Revision as of 17:48, 19 September 2022
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	* Controlled airflow - might be airflow that is designed into a building, forming part of its servicing strategy, to maintain comfort and performance. This type of controlled airflow normally either forms part of a passive or natural building design ventilation strategy or it is part of a mechanical ventilation strategy, or indeed a cross between the two.		* Controlled airflow - might be airflow that is designed into a building, forming part of its servicing strategy, to maintain comfort and performance. This type of controlled airflow normally either forms part of a passive or natural building design ventilation strategy or it is part of a mechanical ventilation strategy, or indeed a cross between the two.

−	How airflow moves outside or around a building form can also impact the above internal airflow strategies but is also concerned with external spaces in the built environment and increasingly the role air quality and pollution ~~has~~ on ~~this~~.	+	How airflow moves outside or around a building form can also impact the above internal airflow strategies but is also concerned with external and often public spaces in the built environment and increasingly the role air quality and pollution.
		+
		+	* Wind airflow loads on main structural elements of buildings (overall wind loads)
		+	* Wind airflow loads on facade, openings or roof elements.
		+	* Wind airflow loads on ancillary building items.
		+	* Wind and airflow effects on building design strategies such as natural ventilation.
		+	* Localised wind effects of buildings on external or public spaces.
		+	* Localised wind effects on air quality, particulates and pollution.
		+
		+	At the more holistic scale changes in global atmospheric circulation, impacts global weather patterns which can result in changes in localised weather patterns, wind speeds, driving rain and air quality which can directly impact how buildings buildings perform.

	= Thermodynamics =		= Thermodynamics =

Editor at 13:35, 19 September 2022

2022-09-19T13:35:17Z

← Older revision		Revision as of 13:35, 19 September 2022
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	= Types of airflow =		= Types of airflow =

−	As such the term can be used to describe air movement in relationship to moving objects, such as cars or aeroplanes as well as fixed objects such as the external form of buildings (see aerodynamics and wind tunnels). It also be used to describe how air moves within buildings and as part of design strategy (see ventilation and infiltration). Finally in broader sense airflow might also be referred to in describing how air circulates around the globe, forming wind and weather patterns (see ~~atmosphere~~ and coriolis effect).	+	As such the term can be used to describe air movement in relationship to moving objects, such as cars or aeroplanes as well as fixed objects such as the external form of buildings (see aerodynamics and wind tunnels). It also be used to describe how air moves within buildings and as part of design strategy (see ventilation and infiltration). Finally in broader sense airflow might also be referred to in describing how air circulates around the globe, forming wind and weather patterns (see global atmospheric circulation and coriolis effect).

	= Characteristics =		= Characteristics =
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	* Draughts in buildings		* Draughts in buildings
	* Fresh air		* Fresh air
		+	* Global atmospheric circulation.
	* Heat transfer in buildings		* Heat transfer in buildings
	* Indoor air velocity.		* Indoor air velocity.

Editor at 09:41, 16 September 2022

2022-09-16T09:41:48Z

← Older revision		Revision as of 09:41, 16 September 2022
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−	[[File:~~Airflow mix~~.jpg]]	+	[[File:Airflow_mix.jpg\|link=File:Airflow_mix.jpg]]

	Airflow in simple terms describes the movement of air from one place to another, within a space or around an object.		Airflow in simple terms describes the movement of air from one place to another, within a space or around an object.
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	* Air quality.		* Air quality.
	* Building services.		* Building services.
		+	* Domestic Ventilation Systems - a guide to measuring airflow rates (BG 46/2022)
	* Discharge coefficients, free, effective and equivalent areas		* Discharge coefficients, free, effective and equivalent areas
	* Domestic ventilation systems performance		* Domestic ventilation systems performance

Editor at 08:44, 16 September 2022

2022-09-16T08:44:49Z

← Older revision		Revision as of 08:44, 16 September 2022
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		+	[[File:Airflow mix.jpg]]
		+
	Airflow in simple terms describes the movement of air from one place to another, within a space or around an object.		Airflow in simple terms describes the movement of air from one place to another, within a space or around an object.

Editor at 08:32, 16 September 2022

2022-09-16T08:32:54Z

← Older revision		Revision as of 08:32, 16 September 2022
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	= Types of airflow =		= Types of airflow =

−	As such the term can be used to describe air movement in relationship to moving objects, such as cars or aeroplanes as well as fixed objects such as the external form of buildings (see aerodynamics and wind tunnels). It also be used to describe how air moves within buildings and as part of design strategy (see ventilation and infiltration). Finally in broader sense airflow might also be referred to in describing how air circulates around the globe, forming wind and ~~weaher~~ patterns (see atmosphere and coriolis effect).	+	As such the term can be used to describe air movement in relationship to moving objects, such as cars or aeroplanes as well as fixed objects such as the external form of buildings (see aerodynamics and wind tunnels). It also be used to describe how air moves within buildings and as part of design strategy (see ventilation and infiltration). Finally in broader sense airflow might also be referred to in describing how air circulates around the globe, forming wind and weather patterns (see atmosphere and coriolis effect).

	= Characteristics =		= Characteristics =
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	Airflow both externally (wind speed) and internally is measured using anemometers, of which there are many different types, each focussing on different characteristics of airflow such as air velocity, differential pressure, temperature, humidity or volumetric flow. Other types of measuring devices also use ultrasound to measure energy transfer with passing particles and are capable of calculating air flow along with wet bulb temperature, dew point, and also turbulence.		Airflow both externally (wind speed) and internally is measured using anemometers, of which there are many different types, each focussing on different characteristics of airflow such as air velocity, differential pressure, temperature, humidity or volumetric flow. Other types of measuring devices also use ultrasound to measure energy transfer with passing particles and are capable of calculating air flow along with wet bulb temperature, dew point, and also turbulence.

−	A more general representation of airflow commonly used within buildings is the rate of air changes per hour (ACH), this measures how often the air in a space is replaced every hour with fresh air. It is calculated by multiplying the volume of air being delivered by one hour (60 minutes) and dividing by the volume of the space. Measures of ACH in houses can vary from 0.2 to 1, whilst passivhaus require less that 0.6 ACH at 50 pascals.	+	A more general representation of airflow commonly used within buildings is the rate of air changes per hour (ACH), this measures how often the air in a space is replaced every hour with fresh air. It is calculated by multiplying the volume of air being delivered by one hour (60 minutes) and dividing by the volume of the space. Measures of ACH in houses can vary from 0.2 to 1, whilst passivhaus require less that 0.6 ACH at a certain pressure level ( in this case 50 pascals).

	Airflow more specifically, for the purpose of mechanical systems is measured by velocity and volume, such as litres per second (l/s), metres cubed per hour (m3/h) or similarly in cubic feet (ft3/min or ft3/h). Occasionally it may also be measured by the mass of air such as kilograms per second (Kg/s)		Airflow more specifically, for the purpose of mechanical systems is measured by velocity and volume, such as litres per second (l/s), metres cubed per hour (m3/h) or similarly in cubic feet (ft3/min or ft3/h). Occasionally it may also be measured by the mass of air such as kilograms per second (Kg/s)

Editor at 08:30, 16 September 2022

2022-09-16T08:30:56Z

← Older revision		Revision as of 08:30, 16 September 2022
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	As such the term can be used to describe air movement in relationship to moving objects, such as cars or aeroplanes as well as fixed objects such as the external form of buildings (see aerodynamics and wind tunnels). It also be used to describe how air moves within buildings and as part of design strategy (see ventilation and infiltration). Finally in broader sense airflow might also be referred to in describing how air circulates around the globe, forming wind and weaher patterns (see atmosphere and coriolis effect).		As such the term can be used to describe air movement in relationship to moving objects, such as cars or aeroplanes as well as fixed objects such as the external form of buildings (see aerodynamics and wind tunnels). It also be used to describe how air moves within buildings and as part of design strategy (see ventilation and infiltration). Finally in broader sense airflow might also be referred to in describing how air circulates around the globe, forming wind and weaher patterns (see atmosphere and coriolis effect).

−	= Characteristics ~~and categories~~ =	+	= Characteristics =

	In physics airflow will be determined either by the natural characteristics of that air in relation to heat, pressure, and density, including pressure from an external force, such as winds or a fan. In relation to buildings, airflow can impact all aspects of a building from its form in design, its fabric in construction, to it occupation and operation. Airflow will often be discussed along with heat flow and moisture flow due to the interrelationship of all three, alongside, in some cases pollution.		In physics airflow will be determined either by the natural characteristics of that air in relation to heat, pressure, and density, including pressure from an external force, such as winds or a fan. In relation to buildings, airflow can impact all aspects of a building from its form in design, its fabric in construction, to it occupation and operation. Airflow will often be discussed along with heat flow and moisture flow due to the interrelationship of all three, alongside, in some cases pollution.

−	Inside a building airflow might be simply categorised ~~in to~~ just two types:	+	= Categories =
		+
		+	Inside a building airflow might be simply categorised into just two types:

	* Uncontrolled airflow - which is often unwanted airflow that passes through gaps in the building fabric which can impact overall performance in terms of comfort, energy use and detailing. This type of airflow might be described as infiltration, draughts, leaks, breezes, wafts or chills.		* Uncontrolled airflow - which is often unwanted airflow that passes through gaps in the building fabric which can impact overall performance in terms of comfort, energy use and detailing. This type of airflow might be described as infiltration, draughts, leaks, breezes, wafts or chills.
−	* Controlled airflow - might be airflow that is ~~design~~ into a building, ~~form~~ part of its servicing strategy to maintain comfort and performance. This type of controlled airflow normally either forms part of a passive or natural building design ventilation strategy or it is part of a mechanical ventilation strategy, or indeed a cross between the two.	+	* Controlled airflow - might be airflow that is designed into a building, forming part of its servicing strategy, to maintain comfort and performance. This type of controlled airflow normally either forms part of a passive or natural building design ventilation strategy or it is part of a mechanical ventilation strategy, or indeed a cross between the two.

	How airflow moves outside or around a building form can also impact the above internal airflow strategies but is also concerned with external spaces in the built environment and increasingly the role air quality and pollution has on this.		How airflow moves outside or around a building form can also impact the above internal airflow strategies but is also concerned with external spaces in the built environment and increasingly the role air quality and pollution has on this.
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	In weather patterns when hot air meets cold air, it spreads it out, eventually taking over, and is called a warm front. When cold air pushes into warm air, a cold front is created, this pushes the warm air ahead and often creates storm clouds.		In weather patterns when hot air meets cold air, it spreads it out, eventually taking over, and is called a warm front. When cold air pushes into warm air, a cold front is created, this pushes the warm air ahead and often creates storm clouds.

−	In turn when moist air is warmed so too are the water molecules, so warm air filled with ~~highly-energized~~ water molecules, contains more water molecules than cool air. Moist air is lighter than dry air if both are at the same temperature and pressure, because by adding water molecules, the heavier molecules are replaced with lighter molecules.	+	In turn when moist air is warmed so too are the water molecules, so warm air filled with these energised water molecules, contains more water molecules than cool air. Moist air is lighter than dry air if both are at the same temperature and pressure, because by adding water molecules, the heavier molecules are replaced with lighter molecules.

	When the kinetic energy is lost, and air cools, air molecules contract, compress, and lay in closer proximity to each other with a heavier density. Cooler air, which is filled with water molecules can more easily condense and become water.		When the kinetic energy is lost, and air cools, air molecules contract, compress, and lay in closer proximity to each other with a heavier density. Cooler air, which is filled with water molecules can more easily condense and become water.
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	In buildings the same principle applies, where, for example warm moist internal air meets a cold surface, as it cools rapidly the water molecules condense and become water. In buildings where this occurs within a wall build up it might be known as interstitial condensation and can be problematic ofr the fabric of a building.		In buildings the same principle applies, where, for example warm moist internal air meets a cold surface, as it cools rapidly the water molecules condense and become water. In buildings where this occurs within a wall build up it might be known as interstitial condensation and can be problematic ofr the fabric of a building.

−	Likewise when warm air heated in the building is lost through openings in the fabric the energy used to to heat the air is also lost, systems such as Mechanical Ventilation Heat Recovery (MVHR) aim to remove the heat from the air being expelled and use this to preheat the incoming fresh air, thus retaining invested heat energy.	+	Likewise when warm air heated in the building is lost through openings in the fabric the energy used to to heat the air is also lost, systems such as Mechanical Ventilation Heat Recovery (MVHR) aim to remove the heat from the air being expelled and use this to preheat the incoming fresh air, thus retaining invested heat energy as well as removing some pollutants.
		+
		+	Heating, Ventilation, and Air Conditioning (HVAC) systems also make use of various technologies to control the temperature, humidity, and quality of air, using fans to bring fresh air in, exchanging the heat or coolth from the expelled air, as well as heating or cooling the air as required and pumping it to the required location in a building. Both systems above rely on airflow to function, the airflow is mechanically driven by fans and pressure or naturally driven of used as a mixed mode system, which includes the opening of windows or vents.
		+
		+	= Measurement =

−	~~Heating~~, ~~ventilation~~, ~~and~~ air ~~conditioning (HVAC) systems~~ also use ~~of various technologies~~ to ~~control the temperature, humidity,~~ and ~~quality~~ of air, ~~using fans to bring fresh air in~~, ~~exchange with heat or coolth from expelled air, as well as heating or cooling as required~~ and ~~pumping it to the required location in a building~~.	+	Airflow both externally (wind speed) and internally is measured using anemometers, of which there are many different types, each focussing on different characteristics of airflow such as air velocity, differential pressure, temperature, humidity or volumetric flow. Other types of measuring devices also use ultrasound to measure energy transfer with passing particles and are capable of calculating air flow along with wet bulb temperature, dew point, and also turbulence.

−	~~Both systems above rely on~~ airflow ~~to function~~, the ~~airflow~~ is ~~mechanically driven by fans and pressure. This type of~~ air ~~flow~~ is ~~measured~~ by the volume of air ~~passing through the system and the velocity~~ (~~or speed~~) of that ~~air~~.	+	A more general representation of airflow commonly used within buildings is the rate of air changes per hour (ACH), this measures how often the air in a space is replaced every hour with fresh air. It is calculated by multiplying the volume of air being delivered by one hour (60 minutes) and dividing by the volume of the space. Measures of ACH in houses can vary from 0.2 to 1, whilst passivhaus require less that 0.6 ACH at 50 pascals.

−	A more ~~general representation of airflow within a building might be taken as~~ the ~~rate~~ of ~~air changes~~ per ~~hour~~ (~~ACH~~), ~~this measures how often the air in a space is replaced every~~ hour ~~with fresh air~~.	+	Airflow more specifically, for the purpose of mechanical systems is measured by velocity and volume, such as litres per second (l/s), metres cubed per hour (m3/h) or similarly in cubic feet (ft3/min or ft3/h). Occasionally it may also be measured by the mass of air such as kilograms per second (Kg/s)

	= Related articles on Designing Buildings =		= Related articles on Designing Buildings =

Editor at 06:54, 16 September 2022

2022-09-16T06:54:30Z

← Older revision		Revision as of 06:54, 16 September 2022
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	= Types of airflow =		= Types of airflow =

−	As such the term can be used to describe air movement in relationship to ~~fixed or~~ moving objects, such as cars or aeroplanes as well as the external form of buildings (see aerodynamics and wind tunnels) ~~but can it~~ also be used to describe how air moves within buildings (see ventilation and infiltration) ~~as well as~~ in ~~the~~ broader sense ~~as airflows~~ around the globe (see atmosphere and coriolis effect).	+	As such the term can be used to describe air movement in relationship to moving objects, such as cars or aeroplanes as well as fixed objects such as the external form of buildings (see aerodynamics and wind tunnels). It also be used to describe how air moves within buildings and as part of design strategy (see ventilation and infiltration). Finally in broader sense airflow might also be referred to in describing how air circulates around the globe, forming wind and weaher patterns (see atmosphere and coriolis effect).

	= Characteristics and categories =		= Characteristics and categories =

−	In physics airflow will be determined either by the natural characteristics of that air in relation to heat, pressure, and density ~~or as a result of~~ an external force ~~or pressure~~ such as a fan. In relation to buildings, airflow can impact all aspects of a building from design ~~and~~ construction, to ~~operation~~ and will often be discussed along with heat flow and moisture flow due to the interrelationship of all three.	+	In physics airflow will be determined either by the natural characteristics of that air in relation to heat, pressure, and density, including pressure from an external force, such as winds or a fan. In relation to buildings, airflow can impact all aspects of a building from its form in design, its fabric in construction, to it occupation and operation. Airflow will often be discussed along with heat flow and moisture flow due to the interrelationship of all three, alongside, in some cases pollution.

−	~~In particular~~ airflow ~~in buildings~~ might be categorised in to just two types:	+	Inside a building airflow might be simply categorised in to just two types:

−	* ~~uncontrolled~~ airflow - which is often unwanted airflow through gaps in building fabric ~~causing~~ draughts, leaks, breezes, wafts or chills~~, infiltration.~~.	+	* Uncontrolled airflow - which is often unwanted airflow that passes through gaps in the building fabric which can impact overall performance in terms of comfort, energy use and detailing. This type of airflow might be described as infiltration, draughts, leaks, breezes, wafts or chills.
−	* ~~controlled~~ airflow - ~~which~~ might be ~~required~~ to maintain comfort ~~levels, such as in~~ natural or mechanical ventilation.	+	* Controlled airflow - might be airflow that is design into a building, form part of its servicing strategy to maintain comfort and performance. This type of controlled airflow normally either forms part of a passive or natural building design ventilation strategy or it is part of a mechanical ventilation strategy, or indeed a cross between the two.
		+
		+	How airflow moves outside or around a building form can also impact the above internal airflow strategies but is also concerned with external spaces in the built environment and increasingly the role air quality and pollution has on this.

	= Thermodynamics =		= Thermodynamics =

Editor at 13:14, 14 September 2022

2022-09-14T13:14:09Z

← Older revision		Revision as of 13:14, 14 September 2022
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	* Re-circulation air.		* Re-circulation air.
	* Ventilation.		* Ventilation.
−	*

	[[Category:DCN_Commentary]] [[Category:DCN_Definition]] [[Category:DCN_Research,_Development_and_Innovation]] [[Category:Definitions]] [[Category:Theory]] [[Category:Health_and_safety_/_CDM]] [[Category:Standards_/_measurements]] [[Category:Design]] [[Category:Operations]] [[Category:Products_/_components]]		[[Category:DCN_Commentary]] [[Category:DCN_Definition]] [[Category:DCN_Research,_Development_and_Innovation]] [[Category:Definitions]] [[Category:Theory]] [[Category:Health_and_safety_/_CDM]] [[Category:Standards_/_measurements]] [[Category:Design]] [[Category:Operations]] [[Category:Products_/_components]]

Editor at 13:13, 14 September 2022

2022-09-14T13:13:50Z

← Older revision		Revision as of 13:13, 14 September 2022
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	As such the term can be used to describe air movement in relationship to fixed or moving objects, such as cars or aeroplanes as well as the external form of buildings (see aerodynamics and wind tunnels) but can it also be used to describe how air moves within buildings (see ventilation and infiltration) as well as in the broader sense as airflows around the globe (see atmosphere and coriolis effect).		As such the term can be used to describe air movement in relationship to fixed or moving objects, such as cars or aeroplanes as well as the external form of buildings (see aerodynamics and wind tunnels) but can it also be used to describe how air moves within buildings (see ventilation and infiltration) as well as in the broader sense as airflows around the globe (see atmosphere and coriolis effect).

−	Characteristics and categories	+	= Characteristics and categories =

	In physics airflow will be determined either by the natural characteristics of that air in relation to heat, pressure, and density or as a result of an external force or pressure such as a fan. In relation to buildings, airflow can impact all aspects of a building from design and construction, to operation and will often be discussed along with heat flow and moisture flow due to the interrelationship of all three.		In physics airflow will be determined either by the natural characteristics of that air in relation to heat, pressure, and density or as a result of an external force or pressure such as a fan. In relation to buildings, airflow can impact all aspects of a building from design and construction, to operation and will often be discussed along with heat flow and moisture flow due to the interrelationship of all three.