The two enemies of durable, comfortable, and efficient housing in residential construction are poor heat and moisture management. To address these issues, we must first start with a solid understanding of good building science. Today, we take an excerpt from Essential Building Science: Understanding Energy and Moisture in High Performance House Design by Jacob Deva Racusin, where he unpacks why we need building science.
Excerpt from Essential Building Science
Why do we need building science? We’ve been building shelter just fine, all around the world and throughout time, without quantifying the physics of heat and moisture movement. Safe shelter is a birthright to all, and the potential to design, to build, to create, exists within each of us. Doesn’t all this complicated building science just get between us and the work, complicate things and distract us from our intuition?
So, why do we need building science? Because our buildings have grown increasingly complex, and we expect very high levels of comfort from them. Many of the biggest problems we have with our homes arise from problems with how our buildings manage heat and moisture. Much of the housing stock in North America is plagued by significant moisture problems (rot and mold), poor indoor air quality, and exorbitant energy loads, leading to great expense — for both the climate and for owners. We ask a lot of our buildings in terms of interior climate control, comfort, healthy space, and good durability, and in pursuit of these goals we burn a lot of carbon and use a lot of toxic materials. We need the tools and understanding afforded to us by the practice of applied building science to understand these problems better, so we can choose solutions that will create buildings that meet our needs without enacting such a heavy toll on the planet’s well-being.
Some of these solutions are old. We have been building with low-impact materials such as wood, stone, earth, lime, and straw for thousands of years. After nearly a century of building with whatever (possibly toxic) materials manufacturers were offering, many people now demand healthy homes built with low-toxic materials that provide high levels of efficiency with low carbon footprints. Those time-tested natural materials we built with for all those pre-Industrial Revolution years are more relevant than ever. To adapt them into this new context, we need to apply building science principles to ensure we use these natural materials effectively to create durable, high-performance homes.
Some of these solutions are new. So, we need to be able to predict how a building might perform before taking risks and trying new things. We can never really know, of course, until a building has been up for a few decades — but we need to know enough to manage risk and innovate appropriately. We need to have some benchmarks and goals to know if the new things we try are indeed working. Most of all, we need building science because we need to elevate the bar of quality for our built environment, not just incrementally, but significantly and quickly, to address the critical issues of climate destabilization, unsafe and insecure housing, “sick” buildings, and housing that costs too much to operate. We can use what we have learned through observation and experimentation with heat, moisture, and materials, and by referencing patterns that have surfaced in thousands of buildings over the last few hundred years to dramatically improve the durability, safety, comfort, cost, and impact of our buildings. While it is far from the only discipline involved in creating the built environment, building science has to play a critical role if we want to achieve the lofty goals we have set for ourselves.
Building Science: A Very Brief History
Humans are innate scientists — or at least, there are a few in every crowd. A true survey of the applied practice of building science, across cultures and throughout the ages, would make for a fascinating read. Here in North America, we have been building wood-framed and masonry (earth, brick, stone) homes for the last few hundred years. Most have been lost to the ravages of time, but many have endured. Homes built of solid wood (i.e., logs, planks) and earth were very durable and quite comfortable. As structural engineering advanced, and we began building lighter structures out of smaller things (wood studs, steel, glass), our houses became less comfortable as we lost the thermal properties and tightness of those solid earth and wood walls. Around the 1920s and 1930s, we decided as an industry that insulation in our buildings was a good idea and worthy of bringing to market.
It took only a short decade or two before we began to see the first signs of moisture damage — paint began to peel from the siding. The prevailing hypothesis: vapor was moving through the walls from the inside, pushing through the wood siding, and driving the oil-based paint off the wood. The proposal, codified in building codes for decades to come: a vapor barrier to be installed on the inside of the building, stopping the vapor before it could move into the wall. The result: the continuation of vapor-related damage on both exterior and interior wall surfaces. The diagnosis was correct, but as we will learn, simply putting up a vapor barrier does not take into account the full cycle of vapor movement in our buildings; therefore, it is not in and of itself a suitable cure to the problem. A systems-level solution is needed for a systems-level problem.
In the 1970s, the United States and Canada experienced dramatic increases in fuel prices, resulting in energy improvement measures across all sectors of the economy, including buildings. We developed diagnostic technology, like the blower door, to be able to understand how air leaks occur in our buildings, and we dramatically increased the amount of insulation in our walls and roofs. New materials were employed; new innovations were brought to the market.
Again, we began to see moisture damage: rotting roofs, sheathing, siding, and framing. Over the decades to follow, we have steadily been learning what we can and cannot get away with in our buildings — as the invisible worlds of heat and vapor are made visible through the observations of how our buildings hold up, and what patterns of failure emerge.
When we add more insulation, walls get colder and stay wet longer. Some materials seem to hold up when they get wet, and others fail quickly. For those of you new to the high-performance building world, it is worth noting that few of the strategies we will present are new — we have been building super-insulated, airtight, low-load, passive solar-heated buildings successfully (and not so successfully) for over 40 years. It is on the shoulders of the giants who raised these buildings that we stand, and the presentation of the information in this book is possible only because of the curiosity, leadership, fearlessness, and innovation of the designers, builders, engineers, and owners before us who were committed to learning what they could in pursuit of building better buildings.