Effective ventilation in buildings - Revision history

Editor at 13:09, 5 January 2022

2022-01-05T13:09:05Z

← Older revision		Revision as of 13:09, 5 January 2022
Line 48:		Line 48:
	* Indoor air quality.		* Indoor air quality.
	* Indoor air velocity.		* Indoor air velocity.
		+	* Let us evolve our buildings from being passive structures to interactive and reactive systems.
	* Mechanical ventilation's role in improving indoor air quality.		* Mechanical ventilation's role in improving indoor air quality.
	* Timber and healthy interiors.		* Timber and healthy interiors.

Editor at 11:46, 4 November 2021

2021-11-04T11:46:52Z

← Older revision		Revision as of 11:46, 4 November 2021
Line 36:		Line 36:
	--[[User:BSRIA\|BSRIA]]		--[[User:BSRIA\|BSRIA]]

−	= Related articles on Designing Buildings ~~Wiki~~ =	+	= Related articles on Designing Buildings =

	* Air change rates.		* Air change rates.
Line 48:		Line 48:
	* Indoor air quality.		* Indoor air quality.
	* Indoor air velocity.		* Indoor air velocity.
		+	* Mechanical ventilation's role in improving indoor air quality.
	* Timber and healthy interiors.		* Timber and healthy interiors.
	* Ventilation.		* Ventilation.

Editor at 15:29, 17 November 2020

2020-11-17T15:29:02Z

← Older revision		Revision as of 15:29, 17 November 2020
Line 50:		Line 50:
	* Timber and healthy interiors.		* Timber and healthy interiors.
	* Ventilation.		* Ventilation.
		+	* Ventilation and control of COVID-19 transmission.

	= External resources =		= External resources =
Line 55:		Line 56:
	BSRIA, [https://www.bsria.com/uk/test-research/research/isolation-rooms/ Isolation rooms]		BSRIA, [https://www.bsria.com/uk/test-research/research/isolation-rooms/ Isolation rooms]

−	[[Category:~~Research_/_Innovation~~]] [[Category:DCN_Research,_Development_and_Innovation]] [[Category:Design]]	+	[[Category:DCN_Guidance]] [[Category:DCN_Research,_Development_and_Innovation]] [[Category:Research_/_Innovation]] [[Category:Design]]

Editor at 11:40, 7 August 2020

2020-08-07T11:40:57Z

← Older revision		Revision as of 11:40, 7 August 2020
Line 45:		Line 45:
	* Ensuring good indoor air quality in buildings.		* Ensuring good indoor air quality in buildings.
	* HVAC balancing.		* HVAC balancing.
		+	* HVAC industry defines post COVID-19 changes.
	* Indoor air quality.		* Indoor air quality.
	* Indoor air velocity.		* Indoor air velocity.
Line 54:		Line 55:
	BSRIA, [https://www.bsria.com/uk/test-research/research/isolation-rooms/ Isolation rooms]		BSRIA, [https://www.bsria.com/uk/test-research/research/isolation-rooms/ Isolation rooms]

−	[[Category:Research_/_Innovation]] [[Category:Design]]	+	[[Category:Research_/_Innovation]] [[Category:DCN_Research,_Development_and_Innovation]] [[Category:Design]]

Editor at 13:16, 24 July 2020

2020-07-24T13:16:40Z

← Older revision		Revision as of 13:16, 24 July 2020
Line 1:		Line 1:
−	[[File:~~Air con office~~.jpg]]	+	[[File:Air_con_office.jpg\|link=File:Air_con_office.jpg]]

	= Introduction =		= Introduction =
Line 42:		Line 42:
	* Air tightness in buildings.		* Air tightness in buildings.
	* At a glance - Indoor air quality.		* At a glance - Indoor air quality.
		+	* BSRIA articles on Designing Buildings Wiki.
	* Ensuring good indoor air quality in buildings.		* Ensuring good indoor air quality in buildings.
	* HVAC balancing.		* HVAC balancing.

Editor at 13:11, 24 July 2020

2020-07-24T13:11:37Z

← Older revision		Revision as of 13:11, 24 July 2020
Line 1:		Line 1:
		+	[[File:Air con office.jpg]]
		+
	= Introduction =		= Introduction =

Editor at 13:07, 24 July 2020

2020-07-24T13:07:22Z

← Older revision		Revision as of 13:07, 24 July 2020
Line 3:		Line 3:
	The World Health Organisation has published information about the airborne transmission of COVID-19. This information further emphasises the importance of having good, effective ventilation in a building.		The World Health Organisation has published information about the airborne transmission of COVID-19. This information further emphasises the importance of having good, effective ventilation in a building.

−	= ~~Calculating air~~ change rates =	+	= Air change rates =

	Ensuring correct air change rates in an occupied space has always been an important design consideration - one perhaps perceived as only being critical in healthcare settings. Given our ‘new normal’, the emphasis on correct air change rates across all occupied settings is becoming crucial.		Ensuring correct air change rates in an occupied space has always been an important design consideration - one perhaps perceived as only being critical in healthcare settings. Given our ‘new normal’, the emphasis on correct air change rates across all occupied settings is becoming crucial.
Line 10:		Line 10:

	Ventilation is paramount to dilute the concentration of airborne contaminants and it is important to understand how contaminants are diluted, in order to establish procedures, i.e. time that has to pass between patients entering a room in a hospital.		Ventilation is paramount to dilute the concentration of airborne contaminants and it is important to understand how contaminants are diluted, in order to establish procedures, i.e. time that has to pass between patients entering a room in a hospital.
		+
		+	= Making calculations =

	By means of visualising the air change rate in a room, if we have an empty glass simulating our room - which is sitting under a tap acting as our ventilation system - and the tap is turned on the equivalent air change rate is a count of how many times the glass can be filled with water in a certain period of time. If some or all of the water misses the glass and goes directly down the drain, the air change rate is effectively reduced. As in the case of a ventilation system, consideration would also need to be given as to what the consequences may be if the tap water were contaminated.		By means of visualising the air change rate in a room, if we have an empty glass simulating our room - which is sitting under a tap acting as our ventilation system - and the tap is turned on the equivalent air change rate is a count of how many times the glass can be filled with water in a certain period of time. If some or all of the water misses the glass and goes directly down the drain, the air change rate is effectively reduced. As in the case of a ventilation system, consideration would also need to be given as to what the consequences may be if the tap water were contaminated.
Line 32:		Line 34:
	--[[User:BSRIA\|BSRIA]]		--[[User:BSRIA\|BSRIA]]

−	= Related articles on ~~Desiging~~ Buildings Wiki =	+	= Related articles on Designing Buildings Wiki =
		+
		+	* Air change rates.
		+	* Air filtration and clean Indoor air quality standards.
		+	* Air tightness in buildings.
		+	* At a glance - Indoor air quality.
		+	* Ensuring good indoor air quality in buildings.
		+	* HVAC balancing.
		+	* Indoor air quality.
		+	* Indoor air velocity.
		+	* Timber and healthy interiors.
		+	* Ventilation.

	= External resources =		= External resources =

Editor at 13:03, 24 July 2020

2020-07-24T13:03:37Z

← Older revision		Revision as of 13:03, 24 July 2020
Line 17:		Line 17:
	The decay of the concentration can be expressed by the equation:		The decay of the concentration can be expressed by the equation:

−	[[File:WHO.Figure1.jpg]]	+	[[File:WHO.Figure1.jpg\|link=File:WHO.Figure1.jpg]][Please click on the image to see the equation.]

	We do have to take into account the fact that the air supplied must be fresh, i.e. not recirculated and that the ventilation must be effective; fresh air must not be short circuited into the extract and it must reach everywhere in the room, to avoid areas of high contaminant concentration (stagnation).		We do have to take into account the fact that the air supplied must be fresh, i.e. not recirculated and that the ventilation must be effective; fresh air must not be short circuited into the extract and it must reach everywhere in the room, to avoid areas of high contaminant concentration (stagnation).

−	[[File:WHO.Figure2.jpg]]	+	[[File:WHO.Figure2.jpg\|link=File:WHO.Figure2.jpg]][Please click on the image to see the equation.]

	This means that it will take longer to purge the contaminant from the room i.e. If the ACR of an isolation room is 10 ACH, for a k value of 0.6, the effective ventilation rate would be 6 ACH.		This means that it will take longer to purge the contaminant from the room i.e. If the ACR of an isolation room is 10 ACH, for a k value of 0.6, the effective ventilation rate would be 6 ACH.
Line 37:		Line 37:

	BSRIA, [https://www.bsria.com/uk/test-research/research/isolation-rooms/ Isolation rooms]		BSRIA, [https://www.bsria.com/uk/test-research/research/isolation-rooms/ Isolation rooms]
		+
		+	[[Category:Research_/_Innovation]] [[Category:Design]]

Editor at 12:58, 24 July 2020

2020-07-24T12:58:49Z

← Older revision		Revision as of 12:58, 24 July 2020
Line 1:		Line 1:
−	The World Health Organisation has recently published information about the airborne transmission of COVID-19. This new information further emphasises the importance of having good, effective ventilation in a building.	+	= Introduction =

−	~~Ensuring correct air change rates in an occupied space~~ has ~~always been an important design consideration and perhaps perceived as only being critical in healthcare settings~~. ~~Given our ‘new normal’,~~ the ~~emphasis on correct air change rates across all occupied settings is becoming crucial~~.	+	The World Health Organisation has published information about the airborne transmission of COVID-19. This information further emphasises the importance of having good, effective ventilation in a building.

−	The air change rate (ACR) in a room is a function of the ventilation supply or extract flowrate (in l/s or m3/h) and a function of the volume of the room (m3). The resultant air change rate, normally expressed as air changes per hour (ACH) (h-1), gives us an indication of how many times per hour the ventilation system provides the room with new fresh air.	+	= Calculating air change rates =
		+
		+	Ensuring correct air change rates in an occupied space has always been an important design consideration - one perhaps perceived as only being critical in healthcare settings. Given our ‘new normal’, the emphasis on correct air change rates across all occupied settings is becoming crucial.
		+
		+	The air change rate (ACR) in a room is a function of the ventilation supply or extract flowrate (in l/s or m³/h) and a function of the volume of the room (m³). The resultant air change rate, normally expressed as air changes per hour (ACH) (h-1), gives us an indication of how many times per hour the ventilation system provides the room with new fresh air.

	Ventilation is paramount to dilute the concentration of airborne contaminants and it is important to understand how contaminants are diluted, in order to establish procedures, i.e. time that has to pass between patients entering a room in a hospital.		Ventilation is paramount to dilute the concentration of airborne contaminants and it is important to understand how contaminants are diluted, in order to establish procedures, i.e. time that has to pass between patients entering a room in a hospital.

−	By means of visualising the air change rate in a room, if we have an empty glass simulating our room, which is sitting under a tap acting as our ventilation system and the tap is turned on the equivalent air change rate is a count of how many times the glass can be filled with water in a certain period of time. If some or all of the water misses the glass and goes directly down the drain, the air change rate is effectively reduced. As in the case of a ventilation system, consideration would also need to be given as to what the consequences may be if the tap water were contaminated.	+	By means of visualising the air change rate in a room, if we have an empty glass simulating our room - which is sitting under a tap acting as our ventilation system - and the tap is turned on the equivalent air change rate is a count of how many times the glass can be filled with water in a certain period of time. If some or all of the water misses the glass and goes directly down the drain, the air change rate is effectively reduced. As in the case of a ventilation system, consideration would also need to be given as to what the consequences may be if the tap water were contaminated.

	If the source of contaminants is still in the room, the ventilation system will eventually provide a steady state concentration of contaminants, which is diluted if compared to the source. If there are (airborne) contaminants in the room, but the source has left (e.g. the patient has left the surgery) the ventilation system will purge the contaminants with every air change.		If the source of contaminants is still in the room, the ventilation system will eventually provide a steady state concentration of contaminants, which is diluted if compared to the source. If there are (airborne) contaminants in the room, but the source has left (e.g. the patient has left the surgery) the ventilation system will purge the contaminants with every air change.
Line 13:		Line 17:
	The decay of the concentration can be expressed by the equation:		The decay of the concentration can be expressed by the equation:

−	~~C = Cmax~~ . ~~(e -t/)~~	+	[[File:WHO.Figure1.jpg]]

−	~~C = [Cmax~~, ~~0] as t = [0~~, ∞)	+	We do have to take into account the fact that the air supplied must be fresh, i.e. not recirculated and that the ventilation must be effective; fresh air must not be short circuited into the extract and it must reach everywhere in the room, to avoid areas of high contaminant concentration (stagnation).

−	~~Where~~:	+	[[File:WHO.Figure2.jpg]]

−	* t is the ~~time~~ from the ~~start~~ of ~~the rise or decay (s)~~	+	This means that it will take longer to purge the contaminant from the room i.e. If the ACR of an isolation room is 10 ACH, for a k value of 0.6, the effective ventilation rate would be 6 ACH.
−	* τ is known as the “half-life” or air change (s)	+
−	* C is the concentration at time t (ppm)	+
−	* Cmax is the ~~maximum concentration during rise or decay (ppm)~~	+

−	~~τ is~~ calculated ~~by:~~	+	BSRIA has studied several hospital isolation rooms with dedicated ventilation. The k factor in those rooms, which were considered well-mixed, was k= 0.8, calculated using gas tracer methodologies.

−	~~= V~~/Q	+	-----
		+	This article originally appeared on the BSRIA website under the title, "[https://www.bsria.com/uk/news/article/new_world_health_organisation_information_emphasises_effective_ventilation_in_buildings/ New World Health Organisation information emphasises effective ventilation in buildings]." It was published July 2020.

−	~~Where~~:	+	--[[User:BSRIA\|BSRIA]]

−	* V is the volume of the room (m3)	+	= Related articles on Desiging Buildings Wiki =
−	* Q is the ventilation rate (m3/s)	+

−	~~The initial concentration before the decay, is the maximum concentration Cmax. When t~~=~~τ (half-life or 1 air change), then the concentration in the room has reduced to 0.37Cmax. and when t~~=3τ, then the concentration C= 0.05.Cmax. This means that after 3 half-lives, the concentration in the room has been reduced by 95%. Therefore in practice, 3 τ is considered to be the time to achieve steady state conditions, for a rise, or the time to clear the room, for a decay.	+	= External resources =
−		+
−	We do have to take into account the fact that the air supplied must be fresh, i.e. not recirculated and that the ventilation must be effective; fresh air must not be short circuited into the extract and it must reach everywhere in the room, to avoid areas of high contaminant concentration (stagnation).	+

−	~~The mechanical air change rate provided by the ventilation system is not often the same as the effective air change rate. The concept of a “mixing factor~~, ~~k” can be used to describe the quality or effectiveness of the mixing process in a space~~. ~~Mathematically, Q'=kQ where k = 1 for ideal mixing and k = 0~~.~~5 for poor mixing. The effect on decay levels is shown in the following equation:~~	+	BSRIA, [https://www.bsria.com/uk/test-research/research/isolation-rooms/ Isolation rooms]

Editor: Created page with "The World Health Organisation has recently published information about the airborne transmission of COVID-19. This new information further emphasises the importance of having goo..."

2020-07-22T11:25:36Z

Created page with "The World Health Organisation has recently published information about the airborne transmission of COVID-19. This new information further emphasises the importance of having goo..."

New page

The World Health Organisation has recently published information about the airborne transmission of COVID-19. This new information further emphasises the importance of having good, effective ventilation in a building.

Ensuring correct air change rates in an occupied space has always been an important design consideration and perhaps perceived as only being critical in healthcare settings. Given our ‘new normal’, the emphasis on correct air change rates across all occupied settings is becoming crucial.

The air change rate (ACR) in a room is a function of the ventilation supply or extract flowrate (in l/s or m3/h) and a function of the volume of the room (m3). The resultant air change rate, normally expressed as air changes per hour (ACH) (h-1), gives us an indication of how many times per hour the ventilation system provides the room with new fresh air.

Ventilation is paramount to dilute the concentration of airborne contaminants and it is important to understand how contaminants are diluted, in order to establish procedures, i.e. time that has to pass between patients entering a room in a hospital.

By means of visualising the air change rate in a room, if we have an empty glass simulating our room, which is sitting under a tap acting as our ventilation system and the tap is turned on the equivalent air change rate is a count of how many times the glass can be filled with water in a certain period of time. If some or all of the water misses the glass and goes directly down the drain, the air change rate is effectively reduced. As in the case of a ventilation system, consideration would also need to be given as to what the consequences may be if the tap water were contaminated.

If the source of contaminants is still in the room, the ventilation system will eventually provide a steady state concentration of contaminants, which is diluted if compared to the source. If there are (airborne) contaminants in the room, but the source has left (e.g. the patient has left the surgery) the ventilation system will purge the contaminants with every air change.

The decay of the concentration can be expressed by the equation:

C = Cmax . (e -t/)

C = [Cmax, 0] as t = [0, ∞)

Where:

* t is the time from the start of the rise or decay (s)
* τ is known as the “half-life” or air change (s)
* C is the concentration at time t (ppm)
* Cmax is the maximum concentration during rise or decay (ppm)

τ is calculated by:

= V/Q

Where:

* V is the volume of the room (m3)
* Q is the ventilation rate (m3/s)

The initial concentration before the decay, is the maximum concentration Cmax. When t=τ (half-life or 1 air change), then the concentration in the room has reduced to 0.37Cmax. and when t=3τ, then the concentration C= 0.05.Cmax. This means that after 3 half-lives, the concentration in the room has been reduced by 95%. Therefore in practice, 3 τ is considered to be the time to achieve steady state conditions, for a rise, or the time to clear the room, for a decay.

We do have to take into account the fact that the air supplied must be fresh, i.e. not recirculated and that the ventilation must be effective; fresh air must not be short circuited into the extract and it must reach everywhere in the room, to avoid areas of high contaminant concentration (stagnation).

The mechanical air change rate provided by the ventilation system is not often the same as the effective air change rate. The concept of a “mixing factor, k” can be used to describe the quality or effectiveness of the mixing process in a space. Mathematically, Q'=kQ where k = 1 for ideal mixing and k = 0.5 for poor mixing. The effect on decay levels is shown in the following equation: