Residential Living in the Age of Climate Change
by Stephen Colley, AIA, LEED AP,
I tend to agree with the vast majority of research indicating the climate is dramatically changing and that the massive release in greenhouse gases into the atmosphere due to human activity is a major cause. This blog is not an expansion or a repeat of what most recognize as the cause and effect of climate change. This is just an observation of one small corner of human activity in the climate change conversation - residential design and construction of homes.
But in fact, residential construction activity is not really a small corner at all. According to the National Association of Homebuilders (NAHB), residential housing, which includes both single-family and multi-family examples, accounts for between 15 and 18 percent of American Gross Domestic Product (GDP) (footnote 1). Additionally, the amount of construction waste in 2018 in America was almost 60 million tons. This does not include demolition waste which represents a much higher tonnage (footnote 2). Compare that to the total municipal solid waste generated that same year at over 292 million tons (footnote 3). By anyone’s standards, this is a considerable percentage of productive activity and waste.
Ignoring for just a second the housing stock that is out there for purchase or rent, what would the ideal properties of today’s housing be to respond to the challenges of climate change? First, housing should be durable. And this includes being resilient to the ravages of severe weather-related events such as flooding, wildfires, extended periods of high and low temperatures, and high winds. Housing needs to provide a healthy place to live. The conditions within a home or apartment must be comfortable for habitation and limit unhealthy concentrations of toxins while maximizing clean, fresh, healthy air quality. Ideally, housing should also not be a major contributor to the generation of greenhouse gases. People usually think of energy and water efficiency choices and methods, but many do not realize that housing construction itself contributes to the production of greenhouse gases. From the harvesting of raw materials to the processing of finished materials to the assembly of finished goods to the transport of the goods to the site and to the assembly of the thousands of pieces resulting in a finished structure, a lot of energy is consumed. A lot. The term for the energy required just to build a structure is “embodied energy” or “embodied carbon”. Globally, around eleven percent of all energy emissions is produced in just the act of building stuff (footnote 4). And on a building by building basis, the embodied energy represents about a quarter of the total energy lifecycle emissions of a building (footnote 5). Additional carbon emissions related to demolition or re-purposing a building is not included in this calculation and is beyond the focus of this article.
The Status Quo
Does the housing available today address these ideal conditions? How are today’s houses and apartments built? If you have ever seen the activity in the new housing developments, you are familiar with the concrete foundations and the wood light frame construction on top of it. The wood frame is eventually concealed by gypsum board on the interior frames and sheathing with some type of finish material on the exterior walls with a variety of finishes available for the roof surfaces. Wood light frame construction has changed little since the explosion of mass produced housing developments following the Second World War.
Builders seventy years ago weren’t considering durability or indoor air quality. They were not concerned with the energy efficiency of mechanical systems or whether the lawns were designed to match the climate and expected rainfall patterns. Builders were plentiful and their primary concern was what their competition was doing. They knew that if their homes cost as little as three hundred dollars more than their competition, they would lose potential sales. This resulted in builders providing housing as cheaply as they could while still adhering to the building codes currently in effect. I remember talking with one builder who gestured to a newly completed home and saying that if he had left just one nail out, it would not pass code. Imagine that, builders being proud to provide the bare minimum required. They had years of building with methods that started with a visibly flimsy structure held together with a series of skin layers and attachments. And to be fair, builders were not encouraged to engage in incremental changes in materials and methods to improve what they were building. Such improvements would certainly result in an increase in the “sticker price” and leave the builder vulnerable to the other builder down the street who, if they were also making changes, might have made adjustments to make their houses cost even less. Only a few bold builders had the courage to move the needle in the right way toward durability or energy efficiency. They had to educate their customers that additional money invested up front could lead to long term savings. This was a route that few volume builders chose.
But with over 99 percent of housing in America based on wood light frame construction, is it any surprise that the 900+ page International Residential Code includes structural chapters almost exclusively devoted to the method? Codes have changed over the years. The current cycle of code changes is three years and the more recent incremental changes have indeed given a certain amount of attention to requiring better energy efficiency. These changes have mostly been confined to the building “envelope”, the foundation, walls, roof, doors, and windows. And changes have mostly addressed improvements in wall insulation, air barriers, and following (and driving) the latest improvements in energy efficiency added to mass produced windows and doors. Envelope changes are not unlike thinking about icing on the cake. Yes, there have been breakthroughs in the icing, but when it comes down to it, the problem of housing’s response to climate change can not be found exclusively with the icing. The problem is with the cake!
As outlined above, the core of almost all housing in America is wood light frame construction. On the bright side, wood is a renewable resource. But lumber is at the mercy of fire, high winds, mold, rot, and pests. Therefore, it’s not a material that one would consider as durable. Wood framing totally depends on that “icing” for protection. Careful attention to materials and detail during construction is absolutely essential to protect the wood from damage or failure. Consider too, that the cross section of an exterior wall or roof reveals a half-dozen or more different materials and cavities between the interior surface and the exterior finish. With differing reactions to changes in temperature and humidity, wind-driven rain, and different rates of expansion caused by temperature fluctuation or soils expansion below the foundation, breaks in the continuity of the different skin materials is not only likely, it should be expected. Slight interruptions in the skin integrity can result in a loss of conditioned air further leading to increased air conditioning or heating costs. It can also lead to opportunities for moisture to condense on materials that can result in mold or rot. Don’t forget the insect and rodent pests too who are looking for food indoors or just a cozy place in a wall cavity to set up a home within your home. When considering high winds or seismic forces, the building code clearly describes the various requirements to keep a structure anchored in place. These methods include hurricane clips, anchors, wind bracing panels, and fastener patterns. Careful inspection is critical to know what is needed to conform with code and recognize any shortcomings before framing is concealed by sheathing and gypsum board. But this is also where the individual sub-contractors charged with adhering to the sometimes complicated code requirements may make errors. They could be cutting corners out of a constant push from superintendents to finish construction quickly, or simply not knowing what to do. And often, the third-party inspectors might also be rushed to conduct inspections and not be afforded the time to check connection details before the errors are concealed beneath finishes.
Another problem with conventional construction is the preponderance of unhealthy air quality inside buildings. Over the years, as building codes were requiring “tighter” homes that reduce air infiltration (and exfiltration), one result was the trapping of the outgassing of toxic materials inside the house along with the excess of carbon dioxide inside the house. Much of this is solved by the code requirement of ventilation, requiring circulation of fresh air along with the exhaust of stale air. But care must also be given in the choices of materials one makes regarding paint, flooring, cabinetry, and other finishes. Finally, is conventional residential construction resistant to wildfire? In a word, no. Search: “Paradise California fire.”
With so many opportunities for things to go wrong, claiming that conventional residential construction methods are appropriate for the challenges of climate change is a nearly impossible argument to make. Fiddling around the edges, making small improvements with the icing on the cake, is not going to be responsible if we are serious about minimizing the effects of climate change. Making things worse is the realization that continuing to build housing with wood light frame construction with regard to embodied energy and construction waste actually adds to the problem. Is there an alternative? Because you are reading this article on the ECI website, you already know where I’m going with this.
The Argument for Earthen Construction
It’s easy to make the argument that earthen construction is durable. It isn’t difficult to find, on five continents, examples of earthen construction still in use decades if not hundreds of years since they were built. The Taos Pueblo in northern New Mexico for example, has been continuously inhabited for well over 900 years. To be fair, I will not make the point that conventionally built residences lasting nearly that long do not exist. That is simply because current residential building stock, in order to be mass produced, depends wholly on dimensional lumber, plywood (or oriented strand board), and plentiful cheap fasteners like the nails, screws and clips that tie all the materials together on a modern home. The machinery to produce all these materials on such a large scale simply did not exist before the industrial revolution. Most of the construction materials machinery was developed since 1950. Additionally, don’t forget the miracles of chemistry in the glues, sealants, and insulation too. In short, conventional construction as we know it today could not have existed much more than eighty to a hundred years ago. So when I suggest to someone that maybe we should seriously consider earthen construction, I just have to chuckle when the response is that they don’t want to “try something new.”
Building with earth doesn’t mean building endless versions of small huts with thick walls and flat roofs. If you are so inclined, search for the many innovative modern examples of earthen structures around the world. And even close to home, the entire campus of Northern New Mexico College is earthen, even the auditorium. Earthen materials work quite well with twenty-first century technology, building science, and machinery.
Will earthen structures hold up to wildfires? Soil does not burn. That being said, earthen homes are not immune from wildfires; primarily because the weak points prone to fire damage are the windows, roof (if the roof is conventionally framed), and other architectural elements at risk during wildfires. Extreme care must be taken at ventilation penetrations, soffits (if present), and any location where glowing embers may ignite flammable material. The most obvious difference between earthen and conventional construction is the nature of the exterior walls. Earthen walls are solid and monolithic unlike walls of conventional construction which are made from many different materials and cavities. The solid nature of earthen construction provides not only the advantages of thermal massing, but the absence of wood, glues, and other flammable sources.
There remains the question whether earthen construction addresses the question of providing a structure linked to low embodied carbon. It’s difficult to add all carbon linked activities to ANY construction method. People are not in agreement where to draw the line regarding materials involved in construction. For wood light frame construction, a listing would have to be made of all the materials, their quantity, and then taking the calculations of energy required to harvest materials, process them, ship them to the construction site and then add the carbon expended to put the thousands of materials together to make a completed structure. Performing this carbon expenditure exercise on an earthen structure may be somewhat less complicated due to the shorter list of differing materials, but one still needs to keep in mind how far away the soil is from the building site. With that in mind, it’s presumptuous to make any blanket statement that earthen construction always has a lower carbon impact per square foot than conventional construction, but the suggestion that earthen construction embodied energy has a smaller embodied energy profile is compelling.
I’m not suggesting that wood light frame construction should be banned - at least not yet. But I am suggesting that architects, engineers, builders, planners, lenders, materials suppliers, building permit officials, insurance underwriters, and everyone connected to the massive machinery of homebuilding take a fresh look at this relatively new way of building: wood light frame construction. Maybe it’s not the best methodology as we face the challenges of climate change. Maybe taking a look at tried and true construction materials and methods that are hundreds of years old is worth another look.
1. “Housing’s Contribution to Gross Domestic Product” - National Association of Homebuilders www.nahb.org/News-and-Economics/Housing-Economics/
2. “Sustainable Management of Construction and Demolition Materials” - Environmental Protection Agency www.epa.gov/smm
3. “National Overview: Facts and Figures on Materials, Waste, and Recycling” - Environmental Protection Agency www.epa.gov
4. “Why the Building Sector?” - Architecture 2030 www.architecture2030.org
5. “How do Buildings Contribute to Climate Change?” - Curbed (VoxMedia) www.archive.curbed.com