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Assessing the Ventilation Effectiveness and Indoor Air Quality of a Net-Zero Pilot House for Northern… Crosby, Sarah; Rogak, Steven 2017-11-27

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INTRODUCTIONCONCLUSIONSRESULTSMETHODOLOGYSarah	Crosby,	Steven	RogakDepartment	of	Mechanical	Engineering,	The	University	of	British	Columbia• In cold countries like Canada, inhabitants spend more than 50% ofthe time in their homes. In certain population groups, this proportionis even exceeding 90%. Maintaining indoor air quality, thermalcomfort and adequate ventilation is essential for a healthy andefficient building. Therefore, the ventilation effectiveness is a criticalissue that needs to be assessed to avoid unhealthy living conditions.• In this work, an experimental system is designed and constructed toassess the ventilation adequacy, thermal comfort, envelopeinfiltration and indoor air quality inside a net-zero pilot house.• Aiming to achieve a net zero design and an air tight passive house,this house is intended to address the needs for the Northerncommunities, where indoor humidity has produced famouslyunhealthy conditions. Hence, ventilation effectiveness is a criticalissue that needs to be assessed.• The house aims to provide a cost-effective design while maintaininghigh levels of livability and sustainability. It intends to provide thiscost effectiveness by using a good building envelope (R30), efficientheat pump, exhaust air energy recovery and smart controls.• Mathematical	Model:The air change rate 𝜆, is determined experimentally through thetracer gas technique .This technique consists of introducing a certainquantity of a known gas in the space where the air exchange rate is tobe measured—the tracer gas—and measuring the tracerconcentration along time. Once the tracer concentration evolutionwith time is known, using appropriate evaluation algorithms,𝜆 can becalculated from the data obtained:	ln(𝐶'( 𝑡 − C,-.) = −λt + ln 𝐶'(4 − 𝐶567Following ASTM E-741, and using theregression concentration method dataanalysis for the concentration decaytechnique, the air change rate of asingle-zone is evaluated.Performing a regression of 𝑙𝑛(𝐶'( 𝑡 − C,-.)	to find the constants	𝑎and	𝑏 in the relationship: 𝑌 = 𝑎𝑥 + 𝑏	.	In this case λ corresponds toa, ln 𝐶'(4 − 𝐶567 corresponds to b, ln (𝐶'( 𝑡 − C,-.)correspondsto Y, and t corresponds to X. Thus, with the best curve fitting, the airchange can be then calculated.• The tracer gas:The gas used in this work is CO2. The advantages of using CO2 astracer gas are that; It is cheap, it is easily available, it is easilydetectable and it has relatively high PEL ( 5000 ppm)• Results show that the house has high ACH, higher than ASHRAE standardsrecommendations, which means that the ventilation is adequate withoutthe need of opening any external windows or doors.• By comparing the ventilation with and without the bathroom vent, resultsshow that the ventilation is better when the bathroom vent is ON. Thus, itis recommended to always open both bathroom vents in the top andground floors.• Air tightness test results give very slow decay of the tracer gasconcentration i.e. very low air change rate, which proves that the buildingenvelope is air tight.• 3D contours of temperature show that there are no major cold or hotspots in the living areas.• There are also no swings in temperature with time and temperaturefluctuations band is within the thermal comfort band in living areasrecommended by ASHRAE.• Results show that there is no spatial changes in temperature alongdifferent rooms which means adequate mixing of supply air with theroom air.Assessing	the	Ventilation	Effectiveness	and	Indoor	Air	Quality	of	a	Net-Zero	Pilot	House	for	Northern	CommunitiesEXPERIMENTAL	SETUP Special	designed	ventilated	internal	doors	which	allow	the	ventilation	while	suppressing	the	noise	which	avoid	the	need	of	using	undercut	doors.	Tracer	gas	tests	experimental	setup	at	the	AYO	house• The sublimated dry ice is placed in the return air duct, this ensureswell mixing of the tracer gas with the supply air and evendistribution into all zones.The	sensor	package	components• The tracer gas concentration is logged using multiple CO2 sensors Thetemperature and relative humidity are recorded over time for thethermal comforts assessment using T and RH sensors.• For the ease of DAQ, sensor packages are built to combine all thesensors in an Arduino UNO board coupled with Arduino data loggingshield for DAQ .• Ground and top floors are divided into 8 different zonesC-Thermal Comfort Tests:Three thermal comforts tests are designed: First test: T and RH are logged over time and the results are comparedwith ASHRAE standards for thermal comfort zones. Second test : The temperature is recorded with time and alongdifferent heights. Third test: The spatial variation of temperature is logged with time in different zones.A-Tracer	gas	tests:9	different	tracer	gas	tests	are	designed	with	different	internal	doors,	HVAC	and	bathroom	vent	arrangements.Schematic	of	ground	floor	zones	and	sensors	locationsLiving	Room KitchenBedroom	2Bathroom	(Ground)Bathroom	(Top)Bathroom	Vent	ON 0.6134 0.5824 0.6432 0.7244 0.7131Bathroom	Vent	OFF 0.4254 0.4352 0.389 0.4948 0.4754ASHRAE	Standards	:	ACH	for	living	areas=0.353D	contours	of	temperature	variation	with	time	and	heightThermal	Comfort	Zone	in	a	Psychrometric	Chart-ASHRAE	Handbook	showing	the	house	data	as	the	shaded	area.Concentration	decay	curve- living	room	for	the	air	tightness	testComparison	between	concentration	decay	curves	in	bathroomComparison	between	ACH	in	bedroom	2	with	vent	ON	and	OFFB-Air	tightness	tests:HVAC	system	is	turned	off		and	all	doors	and	windows	are	closed.ACKNOWLEDGMENTThis research project is funded by the NSERC Engage Grant. We would like tothank the AYO Smart Home company for their support and for generouslyproviding full access to the pilot house during the experiments.Spatial	variation	of	temperature	along	different	zones	in	AYO	House


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