For nearly two centuries in the United States, there was no legislation enforcing energy efficiency in either residential or commercial construction. It wasn’t until 1977, following the national energy crisis, that the Department of Energy (DOE) was created to help reduce energy usage and investigate environmental conservation.
Since then, energy codes across the United States have grown increasingly strict, with long-term goals of an 80% reduction in greenhouse gasses from the national housing portfolio by 2050. Therefore, it should be no surprise that green building is becoming a topic of interest in the US and worldwide.
Let’s take a deeper look at the building industry’s impact on a global scale and how modern building solutions are helping combat the issue from the ground up.
Table of Contents
Why is building an energy-efficient house important?
We’ll break down the importance of sustainable building into two parts, emission control and the lifetime value of the structure.
To put it into perspective, the building sector accounts for nearly 40% of global CO2 emissions annually. 28% of which can be attributed to operational emissions, and the other 11% linked to building materials and construction.
Operational Emissions – Operational emissions are emissions associated with the mechanical systems within the structure, such as HVAC (heating, ventilation, air condition) and electrical.
Building Materials & Construction – A bit more straightforward, the building materials and construction emissions are associated with the sourcing and manufacturing of materials, as well as the assembly of the structure. The emissions are referred to as embodied carbon. Meaning that the carbon is solidified in the structure as it is built.
Both forms of CO2 emission are equally as impactful on the environment; it just so happens to be that operational emissions are easier to control. Modern energy codes require certain specifications from new construction that reduce overall energy consumption (operational emissions). On the other hand, Embodied carbon is much more challenging to reduce/control, considering that it is locked into the structure.
In order to build sustainably, as defined above, both forms of emission must be addressed throughout the entire construction process, continuing throughout the lifetime of the home. Sadly, that hasn’t always been the case and still isn’t the case in many locations.
Improved Lifetime Value of the Structure
When you choose to build an energy-efficient home, you’re investing in more than just the environment; you’re investing in the future.
How so? Well, there are several ways that building a sustainable home can help maximize the lifetime value of your investment.
Building Codes: The DOE’s energy codes are growing increasingly strict, with the latest updates to residential codes in 2021. Meanwhile, more states are moving forward with the adoption of the International Energy Conservation Code (IECC). Design, materials, and construction methods all exceed the IECC requirements when building a sustainable home. Therefore, you will not need to modify your home for code requirements in the chance of a remodel or addition in the future. The underlying infrastructure has already been set in place.
Reduce Energy & Save Big: Reducing energy usage is most certainly the primary benefit of building a sustainable home. When homeowners spend their money on sustainable building materials and design optimization, they regularly save upwards of 50% or more on heating and cooling expenses. Those savings add up substantially over the lifetime of the structure.
Going one step further, sustainable buildings also help isolate homeowners from future variations in energy prices.
Improved Home Valuation: Over the past decade, numerous studies have analyzed the market value of energy-efficient (US) homes that qualify for either the LEED (Leadership in Energy & Environmental Design) or Energy Star certification. The results show a clear correlation between valuation and efficiency in rental and resale markets. It does vary from location to location, but overall, the market value of a sustainable home ranges from 5%-35% more than a standard home with similar overall specifications.
Three-Pronged Approach to Green Building
- The Use of Sustainable and Energy Efficient Building Materials
- Sustainably Minded Architectural Design
- Streamlined Construction for Reduced Carbon Footprint
The Use of Sustainable and Energy Efficient Building Materials
It may seem simple, but the best way to address the impact of the carbon emissions throughout the structure’s lifetime is to build with the best materials. Not just the most “energy efficient” materials, because the harsh reality is that doesn’t always result in a reduced carbon footprint. So, let’s get into it.
Timber Frame Construction
Heavy timber framing has proven for centuries to be one of the most durable and long-lasting forms of construction that relies almost solely on the use of sustainable building materials. We’ll start from the seed to better understand just how sustainable timber framing is.
Softwood lumber used in residential and commercial construction is one of the only structural and renewable resources available to builders. Concrete, Steel, and other materials are mined, heavily processed, and by no means renewable. Lumber starts from the seed, often planted in a sustainably managed forest with strict environmental oversight. It then helps remove CO2 from the atmosphere over its 20-50+ year lifespan through photosynthesis.
Once the timber is cut, the carbon is embodied within the wood itself, acting as a carbon sink. It can then be milled into dimensional sizes for residential construction. All of the scrap produced at the mill is recycled, biodegraded, or burned as biofuel, resulting in virtually 0 waste or carbon emissions. Then, it’s off to construction.
Timber frame structures use less wood overall than a conventionally framed alternative. The heavy timbers provide structural support for the building, allowing alternative framing systems to be used in the walls and roof. Panelized systems such as structurally insulated panels (SIPs) do not require 2×4″ or 2×6″ studs which dramatically reduces the amount of lumber in the structure.
The final aspect of timber frame construction regarding sustainability is all about durability. With proper engineering, a timber frame home can withstand just about any adverse weather conditions for hundreds of years after it was first erected! The hundred-plus-year lifespan of a timber frame building helps prolong the storage of the embodied carbon for an extended period. Then, once ready for deconstruction, the timbers can be dismantled, reclaimed, and reused for future projects.
Panelized Wall & Roof Systems
Panelized wall and roof systems have been around for over 50 years, but they are just now gaining mass popularity with the movement towards a more sustainable and energy-efficient US housing portfolio. The panelized system is the most sustainable wall and roof framing option for several reasons: Insulation Value, Recyclability, Off-Gassing, & Assembly. For the purpose of this article, we will focus on structural insulated panels (SIPs).
Insulation Value: SIP Wall & Roof panels provide continuous foam core insulation, which reduces thermal bridging resulting in a more air and energy-tight home. Closed-cell foam insulation offers a superior R-Value (24 @ 6″) than blanket style or open-cell foam insulation commonly installed in a conventionally framed structure. The foam is installed in a factory-controlled environment which also helps reduce the mess and cost associated with insulating on the job site.
Recyclability: The expanded polystyrene (EPS) foam core used in a SIP wall and roof system is among the world’s most recyclable insulating materials. EPS can be ground and recycled into numerous different consumer goods such as food packaging. In the SIPs manufacturing process, the EPS cut from the panel during prefabrication is ground up and reused to fabricate the next panel.
Off-Gassing: You may have heard of the term off-gassing in reference to some building materials, but more likely, finish materials such as carpeting, flooring, or paint. The term refers to the emission of CO2 or other Volatile Organic Compounds (VOCs). EPS foam used in the core of a SIP is naturally free from harmful chemicals and therefore emits no VOCs. The OSB used in SIPs is weather-treated with Zinc Borate rather than any toxic chemicals such as formaldehyde. The two components come together to form a wall & roof system free of VOC off-gassing.
Assembly: Framing a structure with a SIP wall system saves builders considerable time in the field, which translates to a reduction in carbon emissions. The more trips the builder has to make to and from the job site to complete the structure, the greater the emissions. The longer machinery runs on the job site, the greater the emissions. The more men and women required on the job site, the list compounds. All variables can be thwarted by using a SIP wall & Roof system.
SIPs are such an efficient wall and roof system that the Leadership in Energy & Environmental Design (LEED) has them certified for the following qualifications:
- Energy Efficiency
- Recycled Content
- Localized Distribution
- Indoor Air Quality
- Sustainable Job Sites
If you’d like to learn more about SIPs and how they are used in residential construction, check out our previous article SIPs 101, for an in-depth breakdown of the panels and step-by-step installation instructions (video).
High-Efficiency Windows and Doors
The final component of the exterior building envelope that we will discuss is windows and doors, specifically glass doors, and how they impact the overall energy consumption and sustainability of new construction.
According to the Department of Energy, glass windows and doors are responsible for 25-30% of residential heating & cooling expenses. We’ll break down how inefficient windows are wasting your energy:
1: Air Infiltration – The exchange of air from inside the home out, and vice versa. Infiltration typically occurs along gaps in the exterior shell of the structure.
If you’ve ever been standing by a closed window or door and still felt a draft, that is a perfect example of air infiltration. The exchange of either warm or cold air from outside the structure can dramatically impact the energy consumption required for proper climate control.
When discussing windows and doors, air infiltration typically occurs where the sash meets the frame and where the frame meets the wall. Poor installation is to blame in this situation rather than the window itself.
Kit home manufacturers have helped eliminate the issue of air infiltration by utilizing panelized wall systems with window and door openings precision-cut to 1/16″. When lumber is cut on the field, there are much greater margins of error, leading to air infiltration issues over the structure’s lifetime.
2: Radiant Energy – For this article, we will discuss radiant energy as the energy produced by the sun and focus specifically on Infrared and UV waves.
Infrared Waves are what we associate with the heat produced by the sun. On the other hand, ultraviolet (UV) waves are what we associate with sunburn, fading furniture, and even fading paint.
Infrared waves directly impact the energy consumption of your home or structure, especially during the summer months. The warming effect of the waves can directly penetrate inefficient windows and glass doors, causing unnecessary heating.
UV waves don’t necessarily impact the efficiency of your home, but they do affect the overall finish quality requiring more regular maintenance. The UV waves cause molecules in paints, dyes, and resins to break apart. The reaction results in a faded coloration of furniture, drapes, and sometimes artwork. With hardwood flooring, the UV can eat at the resin, causing chipping and flaking, posing a threat to children and pets.
Companies such as Pella have engineered windows and glass doors to help thwart the impact of radiant energy. A very subtle silver coating is applied to the glass, which acts as a mirror. The LowE (Low Emissivity) glass reflects radiant energy toward the source while still allowing for the passage of visible light into the structure.
3: Conduction – The transmission of energy through a material. In this case, we will be discussing thermal energy.
An excellent example of thermal conduction is found in the freezer aisle at your local grocery store. Put your hand on the glass. The exterior pane of glass is cold because of thermal conduction and the transfer of cold energy through the glass. Now go to the deli. Put your hand on the hot case (just a second). The heat you feel is produced through thermal conduction.
There are two separate ways that conduction impacts the efficiency of windows and glass doors. The first is rather obvious. Depending on the season, hot or cold air is transferred directly through the glass pane.
The second factor to consider with windows and doors is thermal bridging throughout the frame. A thermal bridge is an area or component of an object with a higher thermal conductivity than the surrounding objects, creating a path of least resistance for heat transfer.
First, let’s focus on the glass. Single pane glass is the least efficient option, as it provides a continuous surface for thermal conduction to take place. Double pane glass is slightly more efficient because it allows for a buffer of air, slowing the conduction process. Filling the space between the glass panes with either Argon or Krypton gas is where dramatic efficiency improvements are made. Both gasses are far denser than air and therefore slow the movement of air between the panes, dramatically reducing thermal conduction.
Thermal bridging directly applies to the framing of windows and glass doors. Thermal energy is transferred throughout the continuous aluminum or wooden window framing material. Sustainable window options provide a thermal break, which reduces conduction. The thermal break involves using two different but well-insulated framing materials: fiberglass, vinyl, wood, aluminum, or composite.
It is essential to work with a reputable window manufacturer that values sustainability. Pella windows do not only produce Energy Star-rated windows and doors in every state/region. They take sustainability one step further by either reusing or recycling their waste through work with local (Pella, IA) partners.
How do you know if you have sustainable, energy-efficient windows?
Leadership in Energy & Environmental Design – Performance standards for LEED Homes V4 (Windows)
Energy Star – Window Qualifications
Cool Roof – Finish Roofing Material
Around 90% of the homes in the US have a dark-colored roof. Traditional roofing materials such as laminate or vinyl shingles in dark colors have virtually no reflective properties. Therefore, radiant energy from the sun can heat the roof substantially (100 F over ambient air temp) throughout the day. The heat absorbed in the roofing material eventually makes its way inside the structure through conduction.
Cool Roofing material is very similar to the energy-efficient glass discussed earlier. The concept refers to a finished roofing material that can reflect infrared waves rather than absorb them. A Cool Roofing material allows homeowners to achieve the desired aesthetic of a dark roof without compromising efficiency.
Sustainable Appliances, HVAC, Lighting, & Water Heating
Stepping inside the home, several systems still need to be optimized to be as efficient as possible. The Department of Energy (DOE) has put together a Whole-House Systems Approach that provides information on saving money and energy with energy-efficient mechanical, lighting, and plumbing systems.
Sustainably Minded Architectural Design
Constructing a home with sustainably sourced and energy-efficient building materials is a good step in the right direction. However, there is still plenty of room for inefficiencies without thoughtful planning and quality construction.
The construction of a sustainable home starts with the floor plan. Open floor plans provide the most efficiency and long-term flexibility and are a great starting point for most.
An open or open concept floorplan makes use of large open spaces throughout the home’s interior and minimizes the redundancy of many small, privatized enclosed rooms. The large open rooms allow for improved air circulation and the optimization of natural lighting, which ultimately helps you save energy and money.
According to the World Green Building Council, some essential elements in building a Green Home are building for both flexibility and resiliency. Open concept floor plans provide many dynamic spaces throughout the home, which can shift over time to accommodate change. Not only is that a benefit for the homeowner, but also the structure’s longevity, as there is more flexibility for the future homeowner, decreasing the chances of demolition & new construction.
Going one step further, the layout of rooms within the floorplan can also impact the structure’s efficiency. Our general recommendations are as follows:
- South Facing = Primary Living Spaces (Most Sun)
- East Facing = Kitchen and Bedrooms (Morning Sun)
- North Facing = Garage, Storage, Utility Room (Least Sun)
Another preliminary design that is often not associated with efficiency is site planning. When designing a site plan for a structure, it is crucial to factor in space for trees, shrubs, and other natural vegetation. The natural vegetation will provide shade in the summer months and help block the wind. Both wind reduction & shade will help reduce the overall energy consumption of the structure.
When designing a site map, the specific natural elements don’t need to be decided upon upfront, but it is crucial to factor in the space required for future landscaping.
Streamlined Construction for Reduced Carbon Footprint
Once you have sustainable plans designed and energy-efficient building materials secured, all that’s left is assembly. Assembly is one of the most energy-intensive steps, with roughly 10% of global carbon emissions attributed to construction site activity.
That number is primarily due to inefficiencies in how construction is performed at a mass scale. Most residential structures are still 100% site-built, meaning that materials arrive raw on the job site and must be measured and cut to size before assembly. On-site fabrication can nearly double the timeline of a project.
Now consider that we are still a handful of years away from using heavy electrical machinery (backhoe, lift, etc.). Therefore, every piece of machinery on the job site is running on fossil fuels and contributing to the structure’s carbon footprint. Reducing the timeline of any construction project will, in return, reduce the fossil fuel consumption on site.
Prefabricating the materials needed for site-built construction can dramatically reduce the project timeline and the required workforce. Both are factors that contribute toward a more efficient home or structure.
Sustainability of Kit Homes
We’ve touched on a lot of the negative environmental impacts of construction throughout the article, hoping to provide the best possible options for mitigation. You may have noticed that many of the solutions share similarities. That’s because the best way to mitigate the environmental impacts of new construction is to build better, faster, and more robust.
Panelized kit homes constructed from environmentally sourced materials are the solution. CNC (Computer Numerical Control) fabrication provides a level of precision that cannot be replicated in the field, allowing builders to build better than ever before. Building materials prefabricated and labeled per plans help builders in the field to work faster than ever before. Last but certainly not least, timber framing provides a structurally sound home that will maintain its integrity for hundreds of years, allowing builders to build more robust structures.