5 Sustainable Building Design Strategies to Make Your Next Project Greener

green, eco friendly mixed-use dual high-rise building with external hanging gardens

The built environment is changing.

Climate concerns, more stringent building codes and government regulations, and rising homeowner and building owner expectations are all contributing factors to how builders, architects, and all players in the industry are approaching new construction projects and retrofits.

The long-term goal of low carbon, low energy buildings and communities is certainly possible – we have everything we need already. We just have to commit to building in more sustainable, environmentally conscious ways.

The deadline for net-zero greenhouse gas emissions in both Canada and the United States will be here before you know it. That means the projects we’re building today will need to comply with the net-zero targets of the future.

With that in mind, we’ve compiled a short list of our five tried-and-true sustainable design strategies that will greatly benefit your clients and our planet.

1. Airtightness

2. Stormwater management and water efficiency

3. Improve indoor environmental quality (IEQ)

4. Building material selection

5. Retrofitting

1. Airtightness

An airtight building envelope is one of the most critical aspects of building sustainably. In fact, it’s unrealistic to design a high-performance enclosure without giving thought to airtightness. And with rising standards and stricter codes, designing an ‘average’ enclosure won’t even be a consideration on the table.

The adverse effects of a building envelope that is not airtight and therefore susceptible to air leakage are well documented:

  • Unwanted air migration, which leads to higher energy usage and costs
  • Reduced R-values due to moisture-laden insulation
  • More moisture intrusion through capillary action
  • The development of toxic mold, wood rot, and corrosion
  • Premature failure of building components

Air leakage makes the entire building less efficient, as heating, ventilation, and air conditioning ventilation systems (HVAC) will have to work harder to balance out the comfort of the interior. Higher levels of airtightness ensure the inside stays in, and the outside stays out.

This leads to the other important aspect of an airtight enclosure – the quality of the indoor environment. Indoor environmental quality (IEQ) depends greatly on the building envelope. When air leaks into or out of a building, the enclosure’s role as an environmental separator is compromised. That can lead to comfort complaints due to drafts, poor humidity control, dust, noise, and poor indoor air quality. And this all affects the sustainability (and durability) of the whole building.

Testing for airtightness

To test how airtight your enclosure truly is, we suggest conducting a blower door test.

The test involves, as you might have guessed, a blower door – essentially, a fan attached and sealed to a door – to measure the flow rate of air through any cracks in the building envelope. The idea here is to find the air changes per hour (ACH) by multiplying the volumetric flow rate from the outside (measured in cubic feet per minute) divided by the building volume.

So, what’s a good baseline test score?

Man on a laptop conducting a blower door test

The average blower door numbers to aim for will largely depend on factors such as insulation levels, the installation of windows and doors, and the size of the building. In terms of homebuilding, according to Barrier Sciences Group, a new home should test less than 3.5 ACH50. But in general, you are looking for the lowest possible ACH – the lower the number, the more airtight the building.

Achieving airtightness

Airtightness must be achieved in the design and building stages. Air leakage is not resolved with some caulking around windows, doors, and other penetrations, and calling it a day.

A high-performance air barrier will be a critical component you will specify in pursuing airtightness targets. Air barriers are the most reliable defenders against air and moisture infiltration, which are the primary culprits of some of the aforementioned issues such as poor IEQ and overtaxed HVAC systems.

The Air Barrier Association of America (ABAA) specifies that a quality, successful air barrier will:

  • Reduce required HVAC system size, while improving efficiency
  • Properly manage air pressure relationships
  • Allow water vapor to escape from wall cavities
  • Increase occupant comfort through reduced drafts
  • Enhance indoor air and environmental quality

When selecting an air barrier for your projects, be mindful of options that are specifically designed for energy efficiency. These materials should be manufactured sustainably and made from recycled materials or are recyclable at the end of their lifecycle. If it’s a LEED®-certified product, you have a winner on your hands.

Diagram of the DELTA VENT-SA air and moisture barrier

Taking all of those factors into consideration, a product like the DELTA®-VENT SA air barrier embodies all of those green qualities, and can help you achieve LEED® status (as it’s done for our partners in the past).

Learn more about the importance of airtightness and how it can be achieved in this Q&A session with RDH’s building scientist Dr. John Straube.

2. Stormwater management and water efficiency

Incorporating an efficient system that collects and reuses rainwater not only protects the long-term integrity of the structure from moisture, but also conserves one of our planet’s most important resources.

Stormwater management practices, such as garden rooftops, roadside plantings, and absorbent gardens are just a few building design strategies that effectively capture, filter, and reduce stormwater. In doing so, it cuts down on the amount of flooding and reduces the polluted runoff that reaches sewers, rivers, lakes, and oceans.

Garden roofs, also called living roofs, are everywhere in Europe, but we are seeing more of them in North America as a reliable rainwater management solution for large commercial buildings and low-rise apartments and condominiums. Besides adding more green space – always a welcome sight from an aesthetic perspective – garden roofs can:

  • Extend the life of the roof
  • Slow the transfer of thermal energy
  • Improve surrounding air quality
  • Reduce loads on storm sewer systems
  • Combat the ‘urban heat island’ (UHI) effect 
  • Reduce the amount of energy needed to moderate building temperatures


Isometric view of a city with several green roofs

But before building occupants and the environment can benefit from your garden roof, it needs to be correctly designed. At the highest level, effective living roof design works by draining and storing water by the substrate, and then taken up by plants, from which it is returned to the atmosphere via transpiration and evaporation.

The key word there is ‘draining.’ Above all else, a garden roof needs an effective drainage system to perform as intended. And here’s how you can properly design a garden roof.

Besides garden roofs, storm and rainwater can be managed in other sustainable ways:

Downspout disconnection

According to the Building America Solution Centre, just a few inches of rain falling on a house can lead to thousands of gallons of stormwater runoff. This water is often channeled into storm drains via gutters and downspouts, and it’s this runoff that greatly increases the risk of sewer system overflows.

Downspout disconnection is a building design strategy where rooftop runoff is redirected from storm drains to permeable surfaces, such as a lawn, or even rain barrels or cisterns.

Rain gardens

Rain gardens are highly flexible water management systems that utilize native vegetation planted in shallow basins. Their purpose is to trap and absorb rainwater from rooftops, sidewalks, and streets (like we said, they are highly versatile).

Because they are more absorbent than conventional lawns – up to as much as 30 per cent more efficient – rain gardens are an excellent choice to recharge underground aquifers, add curb appeal, provide a habitat for wildlife, and keep stormwater from reaching sewers and other waterways.


Bioswales are long, deep channels filled with plants, grass, and soil that typically run parallel to parking lots of roads. Suited for commercial properties, they can manage substantial volumes of water runoff from impervious surfaces.

Like the other stormwater management solutions, they primarily slow the release of water into sewers or surface waters, and help limit flooding. A well-designed bioswale can capture and filter out as much as 90 per cent of solids (i.e., sediments), and 80 per cent of trace metals, oils, and grease.

3. Improve indoor environmental quality (IEQ)

We briefly mention IEQ in the airtightness section, but it bears repeating and going into more detail. IEQ is more important than ever because we’re spending more time indoors (Americans, for example, on average spend approximately 90% of their lives indoors) as we shift to work-from-home schedules.

Poor indoor environments, or what the World Health Organization coined ‘sick building syndrome’ in the 1970’s, has led to a number of reported ailments from building occupants: coughs, headaches, nausea, skin problems, fatigue, and more.

Studies on the effects of indoor environments on human health have helped us find new ways to improve life indoors. There are many ways to go about it. But let’s start with indoor air quality, as it is the most well-known and studied of all the factors that affect IEQ.

Dust and dirt coming through a ventilation grill

According to the Whole Building Design Guide, there are a few ways to improve the quality of air in your buildings:

  • Prevent airborne bacteria, mold, and other fungi, as well as radon, through building envelope design that properly manages moisture sources from outside and inside the building, and with heating, ventilating, air-conditioning (HVAC) system designs that are effective at controlling indoor humidity;
  • Use materials that do not emit pollutants, or are at least low-emitting; and
  • Supply an adequate quantity and quality of ventilation and intake of outside air to ensure acceptable indoor air quality.

So, how can this be achieved?

For the first point, you will want to carefully consider your building envelope design, and how to prevent moisture infiltration. This is what creates harmful bacteria, mold, and fungi. As we mentioned before, a high-performance barrier that controls vapor and air infiltration will be critical here. You can learn more about air and moisture control in buildings in this blog.

Selecting materials that do not emit pollutants is relatively straightforward. Be sure to examine product specifications to ensure they meet your standards for sustainability and recyclability.

Ventilation must be approached carefully, as outdoor air, while beneficial in improving air quality, can also contain outdoor pollutants such as smoke or refuse. Outdoor air can enter a home or building by:

  • Natural ventilation, such as through windows and doors
  • Mechanical means, such as through outdoor air intakes associated with the heating, ventilation, and air conditioning (HVAC) systems
  • Infiltration, a process by which outdoor air flows into the house through openings, joints and cracks in walls, floors and ceilings, and around windows and doors.

With that said, keep in mind that ventilation affects moisture and air flow through the building envelope, and may lead to moisture problems that degrade the structure. Ventilation changes the pressure differences throughout the building and can cause or prevent the infiltration of pollutants from adjacent spaces.

DELTA VENT SA air barrier wrapped around a commercial building envelope

Once again, a vapor-permeable air and moisture barrier can help manage this, as it will provide airtightness qualities to keep the envelope efficient, while allowing any moisture within the building to escape.

If you’d like to learn more about improving indoor air quality, read this guide from ASHRAE.

As for other sustainable building design practices that can elevate IEQ, they include improving:


Indoor lighting can be improved by providing daylighting for ambient lighting purposes where possible, choosing high-performance glazing systems for windows, installing active or passive skylights designed for heat gain and loss, avoiding dark wall colors, implementing more dimmable fixtures, and supplementing natural lighting with high-performance ballasts, lamps, and controls.

Acoustical comfort

Designing for better acoustical comfort can be tricky. Traffic and noise bylaws are equally important in managing acoustics, but those are out of our control. However, what we can do for new builds or retrofits is integrate noise-reducing technologies like laminated core gypsum boards, acoustic insulation, or noise-dampening windows. If wholesale changes aren’t realistic, even simple modifications such as carpets or heavy curtains can also add to acoustic comfort.


Ergonomics is how we interact within our environments, and encompasses everything including cognition, physical properties, and organization. In other words, it’s all about designing a building that considers our satisfaction with the environment.

Because it involves our interactions at physical and cognitive levels, sustainable building design for ergonomics can be approached in many ways. This can include design elements you may not give a second thought to, like the optimal height of kitchen countertops, or if areas are optimally lit for safety.

4. Building material selection

Efforts towards sustainable building design can be wasted if you’re not using the right materials for the job.

When selecting materials for green construction, they should contribute to thermal mass, airtightness, and continuous insulation, as they are all factors in moderating indoor temperatures, energy usage, and health. When it comes to their effects on the planet, sustainable materials go a long way in minimizing environmental impacts such as global warming and natural resource depletion.

So, what makes a building product sustainable? These are seven characteristics you’ll want to look for:

  • Energy efficiency. These materials should contribute to lowering energy costs and usage of HVAC systems.
  • Recyclable, or made from recycled materials. Materials that are recyclable or are comprised of recycled materials can save energy, and reduce waste. Recyclable materials are great because they can be used again and again. Products made from recycled materials can be reused to make new materials, extending their value lifecycle.
  • Nontoxic. Sustainable materials do not emit odors, irritants, or hazardous substances. One example of a toxic substance is formaldehyde, a colorless volatile organic compound (VOC) with a strong odor that is relatively common in traditional building materials.
  • Durable. Materials that are durable need less repairs, preserving resources and energy. The fact they last longer means less replacements as well, meaning less manufacturing of products, once again saving energy and resources.
  • Locally-sourced or manufactured. Transporting products across far distances eats up a lot of energy. Purchasing locally is easier on the planet (and the shorter delivery times don’t hurt, either).
  • The Declare Red List Free label. Declare is essentially a nutrition label for building products. It tells specifiers exactly what the product is made of, allowing them to quickly identify if it will meet their project requirements. You can learn more about the Declare program on their website.

DELTA-MS wrapped around a home's concrete foundation, with the Red List label in front

Two examples of building products that incorporate all of these qualities are a pair of our own: DELTA®-MS (a Declare Red List Free product made from 60% recycled HDPE) and DELTA®-VENT SA (Red List Free for LEED® v4 credits).

Other examples of green materials can include LED lighting, bamboo flooring, solar panels, high efficiency glazed windows, low VOC paint, and precast concrete slabs.

5. Retrofitting

Aging, energy-inefficient buildings aren’t a lost cause in contributing to a green built environment. In fact, existing buildings must be a part of the net-zero equation: According to the UN, over half the buildings that will still be in use in 2050 – the United States’ deadline for net-zero GHG – have already been built.

Because buildings last so long and have such a profound impact on people and the environment, retrofitting existing ones is critical to limit energy consumption and carbon emissions.

old museum building being retrofit

But before choosing this sustainable design strategy before the others, there are a few considerations to be mindful of first:

  • Determine if existing systems are operating at optimal efficiency before completely replacing old equipment.
  • For metered buildings, review your utility bills over the couple of years. Gauge if consumption – not cost – has increased.
  • Determine airtightness of the building enclosure. We suggested a blower door test earlier, but you will also want to look for leaky windows, gaps around vents, pipe penetrations, and any moisture intrusion. HVAC upgrades will do very little in making the building more efficient and sustainable if the envelope is not properly sealed. Methods to use include ASTM E1827 and ASTM E779.

Once you have the information and conclude retrofitting is the most beneficial approach to your building’s sustainability, here are just a few ways to create a more energy-efficient building envelope:

  1. Avoid thermal bridging. Thermal bridging occurs when structural elements conduct heat through the insulation.
  2. Ensure airtightness. An airtight enclosure maintains interior temperatures for optimal occupant comfort. A continuous air barrier, like we’ve said, will be key here.
  3. Implement a variable frequency drive in your HVAC system. Systems should be sized for maximum loads, otherwise it will consume more energy than what is needed. This can affect almost 30 per cent of a building’s total electricity usage. A variable frequency drive can help manage this.
  4. Invest in smart control lighting. Similar to the HVAC system, you don’t want lights on in areas where they are not required. Smart control lighting can affect 25 per cent of a building’s electrical consumption.
  5. Link occupancy sensors with thermostats. Having temperatures automatically rising or lowering with preset hours is very inefficient – occupants don’t always use every room in a building at the same hours each day. Linking occupancy sensors with your thermostats will help save on energy.
  6. Daylighting. According to the U.S. Department of Energy, 80 per cent of lighting-related energy costs can be reduced by daylighting. This can be achieved by designing high-efficiency skylights into your building envelope.
  7. South-facing windows. If it’s a new build, consider designing your building envelope with south-facing windows. This will take advantage of the facing sun during the winter, as the windows will passively absorb heat.
  8. Consider load curtailment programs. While not directly benefiting the building itself, this supports green communities beyond your building’s property.

Whether you’re new to sustainable building design practices or have been at the forefront of green building for years, we’re dedicated to helping our building community and planet thrive. Keep our DELTA® Academy bookmarked for the latest in net-zero building, new scientific research, and the latest in sustainable building practices.

In the meantime, find inspiration for your next sustainability building project with our case study on the Edelweiss House project, which we helped earn the first LEED® v4 Certification in Canada.