The Built Environment
When addressing carbon in the built environment we can break it down into two categories, operational carbon, and embodied carbon. Both can be equally impactful, but each requires a different approach to help limit the footprint of your project. Here we will explore what exactly these terms mean, and how we can take action to reduce our impact and ensure we can feel good about our built environment.
Operational Carbon is just what it sounds like, it is the carbon emitted during the operation of a building. It is a byproduct of the use of fuel to heat, cool, ventilate, light, and power our homes. This is the focus of current building regulations being implemented by provincial and federal governments, and as such, if you are going to undergo a building project you will need to ensure that your designs adhere to these regulations. The first thing that usually comes to mind when people think about reducing operational carbon is photovoltaic power, or solar panels. This is certainly one part of it, but there are many more pieces to the puzzle, and with careful planning and attention to detail most can be accomplished with minimal expense. The following is a brief overview of some of the areas that we focus on while designing your project, and why they are important.
Controlling the movement of air in and out of a building can be one of the most important factors when increasing a homes efficiency and reducing operational carbon. Fortunately, it has also been identified as the most cost-effective way to achieve these goals. Uncontrolled air movement allows unconditioned air to enter the building and subsequently increases the energy demand required for your HVAC system to keep interior conditions comfortable. A well sealed house with marginal insulation is actually more efficient than a well insulated house with poor air sealing. Creating a building envelope that is conducive of a continuous air barrier is top of mind when completing our designs, as well as providing in depth detail drawings for openings and connections to ensure the system comes together as planned. Material selection is completed at an early stage of the design process to ensure compatibility with adjacent systems and materials so once the construction process gets underway there are no issues with functionality or process delays to deal with.
Making a building efficient and comfortable will of course largely depend on the thermal barrier system. All major assemblies should be tied into each other to form a continuous thermal barrier that will reduce heat transfer through the building envelope and lower the energy demand of the HVAC system. One of the most common and costly mistakes in this area of design is the lack of attention to detail when it comes to eliminating thermal bridges. Thermal bridges are localized areas in the building envelope where heat transfer is higher than the surrounding area. For example, a wood stud in a conventional stick frame, cavity insulated wall will contact both exterior and interior faces with no insulative barrier. Because of this, the overall thermal resistance of the assembly will be significantly reduced due to the higher conductivity of the stud. With this in mind we custom design foundation, floor, roof, and wall assemblies for each home we create and digitally analyze the building envelope as a whole to ensure that the house will perform as expected, without having to compensate for unnecessary losses.
Wall Assembly with Thermal Bridging
This is an example of thermal imaging performed on a conventional stick framed, cavity insulated wall. Not only is heat transfer gradual throughout, but the dew point in the wall is within the cavity, allowing for potential condensation and resulting issues.
Wall Assembly with Thermal Break
This is an example of thermal imaging performed on a wall assembly designed with a thermal break. Heat transfer is minimized and controlled evenly throughout. The dew point in the assembly is moved to the exterior face, creating an effective and healthy wall.
Passive Design Strategies
One of the best ways to minimize the need for a mechanical system to control your conditioned space is to implement passive design strategies. Passive design strategies are areas of design that will utilize or divert ambient energy sources to optimize interior conditions without the use of mechanical systems. Our largest source of ambient energy is of course the sun, so the first thing we try to utilize is referred to as solar responsive design. This includes elements like site location, building orientation, material colours, exterior shading, window orientation / size, and glazing type. Implementing these strategies will help to passively control heat transfer and reduce loads on the HVAC system.
Windows and Shading
Solar radiation can cause significant changes to interior temperatures, which can be beneficial or detrimental to maintaining comfortable interior conditions. In the summer, when the sun is higher in the sky, an exposed window can allow solar radiation to enter the building and drive temperatures up. By calculating site specific solar geometry values, properly sized horizonal shades or overhangs can be used to block radiation in the warmer months, but allow it to penetrate the opening when the solar angle lowers as outside temperatures drop, helping to utilize passive heating while lowering mechanical demand. Additionally, the distribution of openings on each given elevation can have significant impact on passive heating. While south facing windows can be controlled using overhangs, east and west facing windows are more difficult to control due to low solar angles at sunset and sunrise. Avoiding using large areas of glazing on these elevations is usually the best option to ensure solar heating is adequately controlled. Another solution is to use properly specified windows for each opening. Proper use of SHGC (Solar Heat-Gain Coefficient) in each window can significantly improve your homes ability to minimize or maximize solar heat gains, and remain comfortable and efficient all year long.
Solar orientation helps to maximize the potential for passive heating by aligning the building's principle glazing areas with the southern exposure.
A - Poor solar orientation with the building's short axis facing south
B- Ideal solar orientation with the building's long axis facing south
C & D - Can still be optimized for good solar responsive design as the building's long axis is facing equal to or less than 30° of south
Mechanical systems are usually the fist thing people think of when they are considering strategies to reduce operational carbon, but they really should be closer to last. Installing an elaborate mechanical system in a poorly designed house could lead to overworked equipment and underwhelming results. Adapting building design to promote proper heat retention, rejection, and avoidance can significantly reduce the need for mechanical input, making the efficiency of the mechanical systems less impactful. That is of course not to say that this is not an important aspect of building. Recent advancements in heat pump technology have made it possible for our homes to get off of gas and remain equally as functional. Here in BC we are extremely fortunate to generate the majority of our electricity from what are considered to be renewable sources, and that should be taken advantage of when selecting mechanical systems. Furthermore, the cost and efficiency of photovoltaic systems (solar panels) are both trending in the right direction to make generating your own power much more attainable than it has been in the past. When designing your new home these additions could be the answer to pushing you over the top in achieving your operational carbon or energy consumption goals.
A heat pump is essentially just an air conditioning unit with a reverse switch. By no means is this new technology, but only recently have advancements made them a viable option for those of us living in colder climates. The biggest advantage heat pumps have over a conventional furnace is that they are not reliant on gas to operate. Not only does this eliminate the direct operational carbon emissions, it also makes for a safer, more comfortable living space by reducing temperature fluctuations and eliminating potential for carbon monoxide leaks. When paired with a renewable energy source, this is an extremely clean and reliable way to heat and cool your home.
Photovoltaic (PV) Panels, better known as solar panels, convert energy from the sun into electrical energy we can use to power our homes, cars, and anything else you can plug in. While this technology has been around for quite some time now, levels of efficiency and cost have now hit a point where it can be a viable solution to operating your home without complete reliance on municipal supply systems. Planning to install a PV system while in the design phase is key to ensuring you get the most bang for your buck. While completing the design, we can evaluate the approximate annual energy consumption of the building, and use that number, along with simulated solar exposure values and site orientation to plot out a roof layout that will accommodate a PV array suitable for your needs, while maximizing the system's efficiency. This will help to keep initial costs down while still generating enough power to achieve your goals.
Embodied carbon refers to the greenhouse gas emissions associated with the lifecycle of the materials being used in your construction project. This includes emissions related to the manufacturing process, transportation, installation, maintenance, and disposal of the product. Despite being equally as impactful as operational carbon, in Canada there are currently no building codes or regulations in place to control this aspect of construction. Unfortunately, that means that this part of the design process is overlooked in the majority of construction projects. One of the biggest issues here is that in order to meet operational carbon regulations, often times we are seeing high embodied carbon materials being used because they are effective in reducing a building's operational carbon emissions. However, this is simply front loading the carbon emissions associated with the structure, and not necessarily reducing its environmental impact, despite the reduced operational carbon. Not only is this increase in embodied carbon avoidable, it is actually possible in some cases to substitute materials that have biogenic storage, or carbon capture abilities, so as to reduce the overall impact of the building and turn it into a functional carbon sink. If we were able to do this on a large scale we could transform the building industry, from an environmental liability into an environmental asset. An LCA (Life Cycle Analysis) is completed on each of our designs to asses the impact of the building, giving us an opportunity to reassess material selections and ensure we have done our best to reduce the environmental impact of your home.