The Passive House and Net Zero high-performance building concepts have gained a lot of attention over the past few years, as homeowners are becoming more environmentally aware. Both of these green design approaches prioritize energy efficiency, and minimal environmental impact while aiming to build homes that require minimal or zero energy, while delivering the highest level of comfort.
Sweeping initiatives across Canada are making owning a passive house/net zero home within reach for prospective homeowners. Home building trade groups, mortgage bankers, utility companies, manufacturers of appliances and sustainable housing materials, tech companies, designers and builders, and building performance consultants have been working collaboratively to make net zero living not only attainable but also more affordable.
High-performance homes must be more sustainable and energy-efficient, but also comfortable and healthy to live in. Central to the success of these high-performance home design approaches are advanced home ventilation systems, including heat recovery ventilation (HRV) and energy recovery ventilation (ERV) solutions.
In this article, we will explore these advanced ventilation systems, their role in passive house and net zero designs, and their benefit to the environment – and most importantly – to your family.
Passive house design
The Passive House (passivhaus) standard originated in 1988 in Darmstadt, Germany. It focuses on creating buildings that require minimal energy for heating and cooling, achieved primarily by optimizing airtightness and insulation and eliminating thermal bridging.
Superior insulation and airtightness: Installing a layer of continuous insulation on either the interior or exterior wall is the most effective way to stop thermal bridging. Thermal bridging occurs when materials like wood studs, joists and rafters, window and door frames, and gaps in insulation form a bridge between the inner and outer faces of the construction. Continuous insulation, with taped and sealed joints, restricts air movement through the walls, significantly reducing energy and heat loss.
A sealed building envelope and superior insulation deliver a moisture-resistant solution, protecting the thermal performance of your home. Having a nearly airtight building prevents condensation, moisture, mould growth, drafts, low air quality and heat loss.
High-performance windows and doors: Windows are typically ‘thermally broken’ with foam-filled frames, fully airtight, and triple glazed, with the gaps between glass panes filled with argon or krypton gas. Window units with a Uw-value of 0.14 BTU/hr.ft2.°F or less are suitable for a passive house (0.8 W/(m²K)).
Passive house doors resemble those on a vault, at least 10cm in thickness, with multiple gaskets and latches to ensure maximum sealing. They have a highly insulated body with at least R-10 insulation. If doors have glass panels, they will also be triple-glazed with argon or krypton gas-filled spaces between the glazing.
Ventilation: Excellent air quality is one of the most important objectives of passive house design. To achieve this, stale air is exchanged with fresh outdoor air at regular intervals with a mechanical ventilation system with heat recovery.
Net zero design
Where passive house design principles focus on energy efficiency, the Net Zero design concept aims to produce as much energy as your home consumes over a year. While some detractors have argued that all that’s required to make a house net zero is bolting enough solar panels onto the roof, a true net zero home balances energy-efficient features with renewable energy sources such as solar panels.
Energy efficiency: Net zero homes maximize energy efficiency by using advanced insulation, super-sealing the building envelope, installing insulated windows and doors, using Energy Star appliances, installing energy-efficient lighting and choosing an energy-efficient heating and cooling system and water heating solution.
Renewable energy: Solar panels and/or wind/micro-hydropower turbines generate energy on-site to cover your home’s energy consumption. According to Natural Resources Canada, about half of Canada’s electrical needs could be met by installing solar panels on residential buildings.
Grid-tied solar system: BC Hydro’s net metering is for homeowners who generate electricity for their own use but offers the flexibility of maintaining a connection to the power grid. These systems generate electricity from the sun, but rather than storing surplus energy in batteries for backup power, they feed it to the utility grid. Your home’s smart meter measures how much of the electricity supplied by BC Hydro you’ve used, and how much excess you’ve sent to the grid. The excess generation is credited to you on your next bill.
Advanced HVAC systems: High-efficiency HVAC and lighting technologies are important in meeting energy targets. HVAC system designers work with advanced controls, the most efficient compressors, fans and pumps to meet net zero energy targets. They develop strategies that address heating, cooling and air circulation to maximize your comfort. Today’s advanced equipment delivers capacity modulation, matching the required heating and cooling. By modulating air conditioning, for example, your system could offer improved humidity control and air quality.
The importance of superior ventilation in passive house and net zero design
Effective ventilation is crucial in any building, but it’s particularly important in energy-efficient structures like passive houses and net zero buildings. Airtight building envelopes minimize heat loss and reduce the need for traditional heating and cooling systems, but they can inadvertently lead to indoor air quality issues if they are not properly ventilated.
Heat recovery (HRV) systems
A heat recovery ventilation system brings a fresh supply of fresh clean air to every room of your home all year round while removing stale air, maintaining a healthier and more comfortable internal climate. An HRV pretreats the incoming air and removes stale air, but it does not transfer moisture from one airstream to the other; just heat or cooling.
What that means it that in winter an HRV tends to dry out the house, and in the summer it will bring in moisture. Most homes that have air conditioning will benefit from an ERV, rather than an HRV because it helps the air conditioner keep humidity in check.
Energy recovery ventilation (ERV) systems
An energy recovery ventilation system will bring fresh air into your building, diluting any stale air in the home. At the same time, the ERV removes some of the air from the home, balancing incoming air with exhaust air. On the way out, the static-plate core of the ERV separates airstreams, transferring both energy and humidity.
In the winter, that means the incoming air is preheated and humidified, and in the summer the incoming air is pre-cooled and dehumidified. This minimizes the energy impact of heating and cooling your house while maximizing your comfort.
Using an ERV with a heat pump
If your home employs a heat pump, it pushes heat or cold air in through ducts to all the rooms in your house. And your ERV mixes fresh air into the ducts, so all of the rooms will also receive some of the fresh air. This is particularly important for rooms where family members are spending a lot of time, such as the living room, theatre room and bedrooms. With an ERV, even a bedroom with a closed door will not become stuffy. And a living room full of guests will offer plenty of fresh air, even with all of the windows closed.
The ERV is also removing air from the home at the same time, taking indoor pollutants like C0_2, particulates and volatile organic compounds like ammonia (NH_3) with the stale air that is exiting via the exhaust stream. Your air indoors resembles the outdoor air, except it has been filtered and has been heated or cooled for your comfort.
Your home’s building performance consultant may measure and adjust the airflow, working with your installer to make sure your heat pump and ventilator are working together, setting up the controls for optimal performance in your building.
Integration with passive house and net zero designs
The best design for balanced ventilation in a high-performance home is based on continuous low-volume ventilation. Your system should, however, be able to increase the ventilation flow based on family activities such as taking a shower, cooking or entertaining guests.
The correct size ERV system allows you to comfortably boost to high speed when more ventilation is needed, and then return the controls back to low speed as conditions normalize.
For sizing purposes, a useful rule of thumb is about 50 cfm (cubic feet per minute). For large homes with large open areas, you will most likely require a system that delivers more air.
Ventilation system controls
With a balanced ventilation system, you must understand your system and learn how to operate it. With a continuous ventilation system, your ventilation air is riding along with the heating and cooling air, so that means your heat pump will also be circulating the air.
Most modern heat pumps and air handlers have a ventilation setting that moves just enough air to distribute the ventilation. So when you want more ventilation air, you’ll use the ventilator control to increase the speed. Most ventilation controls will return the ventilation system to normal speed automatically after a preset period.
It’s very important with a high-performance home with a sealed building envelope that you never turn off the ventilator or disable the continuous circulation of the heat pump.
Generate your own electricity
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The Ultimate List of Net Zero FAQs for BC Homeowners