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Student Essay: Passive Design for Indoor Air Quality

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| 2019 May 03 |
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Student Essay: Passive Design for Indoor Air Quality

Student: Linnea Langford
University : British Columbia Institute of Technology

The City of Vancouver has a Greenest City 2020 target and in support of this goal, a bylaw passed for all new homes to be designed to meet Passive House Standards. This means the new homes will have optimum “occupant comfort and energy performance” (City of Vancouver). Passive Houses are internationally seen as “the strongest way to build for comfort, affordability and energy efficiency of residential, institutional and commercial buildings, through all stages of design, construction, and livability.” (Passive House Canada)

The city of Vancouver is allowing some flexibility by letting designers provide alternate solutions to avoid unconventional design solutions that would otherwise be difficult to comply with such demanding requirements for the efficiency that Passive Houses require. The key criteria Passive Houses need to meet fall under three categories, Space Heat Demand, Air Tightness, and Total Primary Energy Renewable.

Traditional homes typically use basement heaters, fireplaces, windows, or air conditioners to control the indoor air comfort in buildings. In 1991 Physicist Dr. Feist in Austria built the first Passive house, which changed the perspective on Energy Efficiency and Indoor Air Quality. Passive Houses work efficiently when there is proper insulation, no air leakages, no thermal bridges for warmth to escape to the outside, triple pane glass, and most importantly a HRV system for fresh air so there is no need for old forms of heaters or air conditioners. If done correctly, Passive Homes are overall less expensive and better for the environment. HRV stands for Heat Recovery Ventilator. This is an air exchanger that captures stale air in the home and uses the heat to warm up new fresh air. Passive houses have excellent indoor air quality because of these mechanical systems.

The HRV systems work to remove air quality pollutants, moisture and bad smells from the air. This high level of filtration benefits people who suffer from allergens and minor respiratory issues. The ideal Passive House will provide higher air quality levels, even temperatures throughout, and reduce costs. However, with strict air flow entering and leaving the home, does it really improve the air quality? With Passive House design it is important that the air moisture levels in the home are monitored. Extremely well insulated houses can also trap moisture which can promote mold growth. With careful attention, Passive homes can be built in all climates if done correctly.

So why isn’t every house built passively? Passive Houses require careful attention to detail from the start of construction. There is also no exact formula or plan for a passive house, as they all can vary from the materials they are built with, to the direction the windows face the sun.

Dangers that can come with building an incorrect Passive House, are high humidity levels mixed with incorrect ventilation. Mold can grow where there are high levels of humidity, and thermal bridges. An even temperature throughout and the removal of water vapor from daily use should be maintained. Not only does mold threaten the health of the inhabitants, it also can be damaging to the structure.

Designing the building envelope accordingly, directly effects the quality of air that the house will have on the inside. Other less intrusive ways to improve the Indoor Air Quality inside are ensuring the Kitchen and Bathroom Exhaust Fans are not obstructed and can be easily cleaned. High preforming Entry doors can help keep out excess moisture, and drying laundry in a well-ventilated space can prevent excess condensation. Preventative steps taken to minimize mold growth in a Passive Houses are essential to ensure the HRV is installed correctly with proper technical analysis of the building’s inhabitants. Mold in the location where thermal bridging occurs is due to poor construction or design, but it is up to the user of the building to control the ventilation in the space and to use the building as it was designed for.

During Renovations or new Construction, we should keep in mind how much impact the building industry has on the environment, and the health of the people indoors. The building can be manipulated to capture heat from existing sources such as the sun, internal heat (appliances, people, pets), and heat recovery, while creating a healthy indoor environment for its inhabitants, and using less energy in the process.

I am an interior design student in Vancouver BC and have grown up with asthma and other sensitivities. I value the fresh air I breathe between the ocean and mountains and wish for all air inside and out to be healthy to inhale. With this scholarship I plan on investing further into my education by completing the Building Envelope Course that my school BCIT currently offers. I understand respiratory problems, so it is important for me to be able to provide design solutions that will help homeowners feel safe and comfortable in their own space. The quality of air you breathe at home, asleep or awake should not be of concern.

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