Policy Brief: Net Zero Energy Design Strategies

August 6, 2026

By University of Waterloo x Lark Scientific

Who is this aimed at

Policy makers and municipal leaders.
Architects, engineers, and infrastructure designers.
Environmental planners and sustainability advisors.
Community stakeholders, funders, and industry advocates.

Key messages

Halton region has committed to net-zero emissions by 2045, this requires quantifiable and measurable actions. Emergency services facilities offer a high-visibility opportunity to demonstrate tangible climate action. The proposed paramedic headquarters in Oakville is aiming for net-zero, making it a good opportunity to explore innovative design strategies.
Solar walls, green façades, and biosolar roofs are passive and nature-based design strategies that are highly effective yet underutilized in public buildings.
These technologies are low-maintenance, cost-effective, and synergistic, helping reduce operational emissions while enhancing air quality, urban resilience, and visual aesthetic.

Policy options

1. Innovative approach:

Install a south-facing solar wall integrated with an exterior green façade to reduce summer heat absorption.
Add a living wall on the interior side of the solar wall to improve indoor air quality and thermal regulation.
Implement a biosolar roof system that combines rooftop vegetation with solar panels to enhance panel efficiency and stormwater management.
Incorporate a rainwater harvesting system to support irrigation needs of green infrastructure and reduce reliance on potable water.

2. Feasible approach:

Adopt a south-facing solar wall paired with an exterior green façade, complemented by a rooftop solar panel system, to generate renewable energy while mitigating excess heat gain during summer months.

Executive Summary

Despite regional and national climate commitments, municipal infrastructure in Ontario continues to fall short of net-zero performance standards. This policy brief addresses a critical challenge: the lack of tangible integration of passive and nature-based technologies in high-performance building design. The proposed Net-Zero Paramedic Headquarters in Oakville (South Hub), while ambitious, risks missing its full environmental and social potential without the adoption of solar walls, biosolar roofs, and green façades - proven strategies currently underutilized in public infrastructure.

Existing policies and energy codes focus heavily on mechanical and operational efficiencies but neglect building-integrated renewables, biodiversity-friendly design, and urban cooling solutions, especially in emergency service infrastructure. This disconnect has resulted in missed opportunities for energy savings, climate adaptation, and public engagement.

We propose a bold but feasible shift: incorporate solar walls to reduce heating loads, biosolar roofs to merge energy generation with ecosystem services, and green façades to deliver passive cooling and air purification. These technologies offer a holistic approach to net-zero by enhancing performance, aesthetics, and community value. Let Oakville’s Paramedic HQ become a living model of net-zero success - where clean energy meets green design, and sustainability is visible, measurable, and inspiring.

Background & Context

In 2019, Halton Region became the first in Canada to declare a climate emergency, acknowledging the growing risks of climate change and the need for decisive local action. This commitment was formalized through the Halton Corporate Climate Action Plan, which set a target of net-zero corporate greenhouse gas emissions by 2045. Since then, the Region has built a strong foundation: introducing climate governance frameworks, aligning policy lenses with sustainability principles, and beginning the work of climate-conscious decision-making across departments.

Yet, as the conversation around net-zero evolves, there remains a need for visible, built examples that showcase how policy commitments translate into public infrastructure. Emergency services facilities are particularly well-positioned to lead this shift. Not only do they operate year-round with demanding energy loads, they also represent high-profile, community-trusted sites where innovation can be both functional and symbolic.

The Paramedic Headquarters in Oakville presents a timely and practical opportunity to bridge Halton Region’s climate commitments with measurable design outcomes. With a net-zero trajectory already shaping its foundational plans, integrating strategies such as solar walls, green façades, and a biosolar roof becomes less a leap, and more a logical progression. These interventions align with the building’s operational needs and climate goals, offering a clear signal that Halton is not only envisioning net-zero, but actively constructing it, one decision at a time.

This facility has the potential to serve as a demonstration project, showcasing how sustainability, performance, and aesthetics can align to meet both regional and national climate goals. It represents a natural next step for Halton Region: transitioning from strategic vision to tangible construction, and positioning civic infrastructure as a catalyst for climate-aligned design. With the proposal still in its early design phase, this is a pivotal moment to embed solutions that reflect long-term values, choices that not only serve this facility, but shape the future standard for public buildings across the region. It is a chance to set precedent through action, and to ensure that Halton’s net-zero ambitions begin with a build that exemplifies them.

Policy Options & Research Overview

Solar walls

Solar walls (SW) are an effective method of passive internal temperature regulation. There are many types of solar walls, however the Trombe Wall (TW) stands out as the most reliable and low maintenance passive energy solution for pre-heating ventilation air. Trombe walls are a proven passive solar strategy for pre-heating ventilation air and can cut winter heating loads by up to 36 percent in climates similar to southern Ontario.

Key design parameters

Orientation & tilt
- True-south façade, tilted 10°–15° upward to boost low-sun winter gains.
Wall construction
- 200–300 mm thick high-mass wall (concrete or masonry), painted dark.
- 20–30 mm glazed air gap with top and bottom vents.
Siting
- Best installed in a south-facing, full-height bay (e.g., ambulance garage) where glazing is omitted, and emergency heating backup is critical.

Energy performance

Annual solar heat yield
- 40–80 kWh/m²·yr (3.7–7.4 kWh/ft²·yr) of usable heat delivered through the natural thermocirculation mode during winter.
Heating energy reduction
- Displaces 20 percent of electric-resistance heating or up to 36 percent under optimal mass-floor integration and climate conditions.

Cost, payback, and maintenance

Installation cost
- Approximately $140–170 per ft² for an 8″ concrete assembly, including glazing and vents.
Payback period
- ~8 years when offsetting electric heating; up to ~18 years when replacing natural-gas heating, based on current North American energy prices and typical installation costs.
Maintenance
- Annual inspection of seals, vents, and glazing - typically under $300/year (industry estimate).

Summer operation

Vents closed during peak daytime sun to suppress unwanted heat gains.
Optional night venting to purge residual heat and improve overnight comfort.

By delivering a 20–36 percent cut in annual heating energy at moderate lifecycle cost - and by operating passively during power outages - south-facing Trombe walls provide a cost-effective step toward net-zero performance in critical service bays.

Biosolar Roof

Biosolar roofs are a practical strategy for enhancing building energy performance through the integration of photovoltaic (PV) panels and extensive green roofs. In southern Ontario, where PV systems generate an average of 1100 to 1200 kWh/kWp annually, solar energy is a viable and strategic investment. However, panel efficiency declines when temperatures exceed 25 °C, which presents a significant challenge during warmer months. Biosolar systems help mitigate this issue, with vegetation reducing panel surface temperatures by up to 9.63 °C and roof temperatures by 6.93 °C. This cooling effect can increase solar output by 21% to 107%, depending on the season. For a net-zero energy building, integrating a biosolar roof can significantly lower operational energy demand while contributing to broader sustainability goals. Compared to standalone green roofs or PV systems, biosolar roofs offer shorter energy and carbon payback times, making them a low-risk, high-impact nature-based solution for municipal buildings.

Key design parameters

Orientation & tilt
- Solar panels should be oriented 18° east of south and tilted at a 30° angle
Structural strength
- Support the combined weight green roof and solar panels

Energy performance

Due to the cooling effect from the green roof, solar panels' efficiency is increased by 4%
In Toronto, green roofs have demonstrated direct annual energy savings of 4.15 kWh per square meter
Also in Toronto, for a 250 by 250 meter green roof, the overall energy consumption was reduced by 73%, 29% and 18% for the top and next floors under.

Cost, payback, and maintenance for a 10kW solar panel system

Average solar panel system installation cost in Ontario
- $1,000 - $1,500 per kW
Average solar panel cost in Ontario
- $2.42 - $3.05 per watt
Solar battery storage
- ~$10,000 for 10kWh Lithium-ion battery
Extensive green roof installation and plant cost
- $16 - $22 per square foot
Payback period
- ~13 years (same as solar panel system payback period)

Maintenance

Regular inspection of green roof vegetation, irrigation, drainage
Regular solar panel cleaning and electrical system checks

Table 1 - Comparison of Solar Roof Systems

Green Walls

Green walls are an effective form of passive design that support internal temperature regulation and reduce a building’s energy demand. Green walls come in two primary types: green façades and living walls. Both contribute to improved air quality, noise reduction, carbon sequestration, and enhanced biodiversity. Green wall systems are especially effective in mitigating the urban heat island effect and improving building energy performance. They can reduce exterior surface temperatures by an average of 0.6 °C per month, lowering cooling energy needs during warmer periods. In dense urban areas like those in southern Ontario, green walls offer a low-maintenance, space-efficient strategy to enhance thermal comfort and move buildings closer to net-zero energy goals.

Key design parameters

Structural system
- Needs to be capable of supporting the weight of the plants

Orientation

Maximize protection from winds by placing living walls east
Protective south and west orientation are still effective

Energy performance

Overall, green walls reduce energy consumption for HVAC systems
40 - 80% of incoming solar radiation is prevented from passing to the building’s interior
Green façades can reduce heating energy demand in buildings by up to 30%

Cost and maintenance

Installation cost
- Green façade: $45 - $70 per square foot
- Living wall: $80-200 per square foot
Maintenance
- Green façade: annual pruning and training, access to moisture, supplemental irrigation
- Living wall: consistent irrigation and fertilization, plant inspection

Table 2 - Comparison of Green façade and Living wall

Rainwater Harvesting

Rainwater harvesting is a sustainable approach to urban water management. By capturing and storing rainwater for non-potable uses such as irrigation and toilet flushing, rainwater harvesting systems provide an alternative high-quality water supply while significantly reducing demand on municipal infrastructure. In regions like southern Ontario, rainwater harvesting supports net-zero goals by lowering water-related energy use and utility costs, all while enhancing building resilience during periods of water stress.

Key design parameters

Catchment area and storage capacity
- Directly impacts the potential volume of rainwater that can be collected and stored
Conveyance system
- To move the rainwater to its storage tank
Filtration system
- Needed if the water will be used for human usage
Distribution system
- To use the rainwater for its intended purpose, like irrigation or toilet flushing

Energy performance

Reduce energy consumption by lessening the amount of water needed to be pumped

Cost, payback, and maintenance

Cost of rainwater harvesting system
- Varies on size and complexity. Ranges from $2,000 to $15,000
Payback period
- Initial costs determine if payback is reached.
Maintenance
- Inspection of equipment and removing any debris biannually

Evaluation of Policy Options

The following criteria, presented in Table # below, were used to evaluate our policy options and shaped our recommendations.

Table 3 - Policy Options’ Evaluation Criteria

To advance net-zero energy performance, we recommend two possible strategies that integrate passive design, renewable generation, and sustainable water management.

Final Recommendations

Innovative Approach

Solar Trombe Wall
- Installed on the southern face of the building, facing true south at a 10° tilt
- Replaces the standard sidewall of the ambulance bay; the garage doors of the ambulance bay will ideally face true west, directly onto Bronte Road
Green façade
- Installed on the eastern and southern exterior façades of the building
- Provides shade for the solar trombe wall during the summer
Living Wall
- A limited implementation on the interior side of the trombe wall, to better regulate internal climate of the ambulance bay
Biosolar Roof
- Solar panels with a green roof that connects to the green façade and rainwater harvesting system
Rainwater harvesting system
- Runoff from the biosolar roof will be stored to be used as greywater as well as to water vegetation for the green façade and living wall

A green façade over a solar trombe wall enhances insulation, temperature control, and air quality. Inside, a limited living wall on the inner surface of the trombe wall aids thermal regulation and adds visual appeal. A biosolar roof boosts panel efficiency, manages stormwater, and mitigates urban heat. Rainwater harvesting sustains vegetation across systems. Combined, these strategies reduce energy and water use, generate renewable power, and strengthen climate resilience.

Feasible Approach

Solar Trombe Wall
- Installed on the southern face of the building, facing true south at a 10° tilt
- Replaces the standard sidewall of the ambulance bay; the garage doors of the ambulance bay will ideally face true west, directly onto Bronte Road
Green façade
- Installed on the eastern and southern exterior façades of the building
- Provides shade for the solar trombe wall during the summer
Traditional Solar Roof

A solar roof, green façade, and solar wall offer passive energy savings through low-maintenance tech. Solar panels generate reliable on-site power, while the green façade cools in summer and insulates in winter. The solar wall ensures steady indoor heat without moving parts. Together, they boost energy efficiency, reduce emissions, and support net-zero goals with minimal integration.

Conclusion

Whether through the fully integrated innovative approach or the more streamlined feasible pathway, each recommendation in this brief advances Halton’s net-zero ambitions in visible, measurable, and replicable ways. As the building moves from concept to construction, this is the moment to align policy with practice - to ensure the South Hub becomes more than energy-efficient: it becomes exemplary. Let this facility be a model of how municipalities can turn climate declarations into climate-ready infrastructure, setting a clear precedent for public buildings across Ontario and beyond.

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Appendix Letter A

Technical Description on Components of Biosolar Roofs

As a tool for sustainability, green roofs are key nature-based solutions in combating climate change. Also known as living roofs, they consist of live vegetation covering the roof system of a building. The addition of a green roof to a building supports biodiversity, reduces air pollution, provides noise mitigation, decreases rainwater runoff, mitigates the urban heat island effect, and a reduction in overall energy consumption for the building’s HVAC services.

There are two primary types of green roofs: extensive and intensive. Extensive green roofs are lightweight, shallow, and low-maintenance. They typically feature small, drought-resistant vegetation and do not require irrigation, making them ideal for areas with minimal foot traffic. In contrast, intensive green roofs are deeper and heavier, require more maintenance, and can support a wider variety of plant life, including trees and shrubs. These systems often include irrigation and are better suited for accessible green spaces.

Photovoltaic systems, like solar panels, convert sunlight into electricity and serve as a clean, renewable alternative to fossil fuels.

Figure 1. Biosolar Roof at GRIT Lab in Toronto

Appendix Letter B

Technical Description on Green Walls

As another tool for sustainability, green walls consist of a vertical structure that is partially or completely planted with vegetation. Green walls come in two main forms: green façades and living walls. Green façades use climbing plants that grow directly on a building’s surface or along a supporting framework. In contrast, living walls integrate vegetation directly into the wall system, using built-in growing mediums and irrigation systems to support plant life.

Figure 2. Living Wall at the University of Waterloo