Energy Efficiency and Building Science News
Gains in lighting and space heating efficiency have decreased energy intensity in commercial buildings, but demand in other areas is driving increased commercial energy use overall.
Energy efficiency is many things to many people, encompassing a wide range of technologies and approaches, from building insulation or LED lightbulbs to vehicle fuel economy or manufacturing practices. Its diverse and ubiquitous nature explains why it’s often difficult to characterize efficiency’s full impact, and why there hasn’t been a single resource that summarizes energy efficiency’s full range of benefits.
With that in mind, the Alliance to Save Energy joined with the American Council for an Energy-Efficient Economy (ACEEE) and the Business Council for Sustainable Energy (BCSE) in December to release the Energy Efficiency Impact Report (EE Impact Report)—a first-of-its-kind publication that uses reams of data and intuitive graphics to tell the comprehensive story of energy efficiency’s impact on the U.S. economy, environment, and society. While there’s no shortage of technical reports that discuss the benefits of energy efficiency in specific sectors, the EE Impact Report instead tells a broader story of this incredible resource by characterizing 54 indicators that highlight the breadth, depth and diversity of the energy efficiency market and explore how policies and programs have incentivized energy efficiency in a variety of sectors.
One of the main characters in the energy efficiency story is buildings: residential and commercial energy consumption primarily occurs indoors. In fact, energy consumption in homes and other residential buildings is responsible for approximately 20 percent of total primary energy use in the U.S. But even though the average U.S. resident lives in larger, better-acclimated homes with significantly more devices, the EE Impact Report shows that residential energy use per household has fallen by roughly 16 percent from 2001 to 2018.
How can we have bigger homes and plug more devices in them and still use less energy per household? Energy efficiency.
Decades of experience have taught us that energy efficiency isn’t a rabbit pulled out of a hat. Rather, it requires strong policies and proactive support from a diverse set of stakeholders. In addition to summarizing efficiency’s impact, the EE Impact Report highlights the urgent need to do more in the buildings, utility, transportation and industrial sectors. Readers can use the Index to navigate by topic, download data and PowerPoint slides from the Resources page, or skim the footnotes in each section for even more resources.
Here are some of the most effective policies that the EE Impact Report identifies for energy efficiency in buildings.
Building Energy Codes
Building energy codes set minimum efficiency requirements for renovated or new buildings. Because the average building lasts about 100 years, stringent building energy codes lock in savings throughout a building’s lifespan. These codes have reduced covered energy use in buildings by more than 40 percent over four decades. Model building energy codes are expected to save $126 billion in energy costs and 13 quads of primary energy between 2010-2040. Moreover, a home built to the specifications of the International Energy Conservation Code of 2018 would use 40 percent less code-covered energy than if it had been built using standard practices in 1975.
Commercial Building Energy Performance Benchmarking
Benchmarking is a mechanism to gauge a building’s energy performance, helping facility managers set reasonable energy efficiency goals and assess the effectiveness of their energy savings programs. The U.S. Environmental Protection Agency (EPA) found that buildings that were consistently benchmarked reduced energy use by an average of 2.4 percent per year. Many states and municipalities have set benchmarking requirements using the EPA’s ENERGY STAR Portfolio Manager. Benchmarking through Portfolio Manager has grown to represent close to 25 percent of U.S. commercial floorspace.
Residential Home Energy Use Rating and Certification Tools
Ratings and certifications bring greater transparency to energy use. They can help homeowners better understand their utility bills and recognize opportunities for savings. There are several rating and certification tools available to help residential homeowners, builders, and property developers improve energy performance, including the Home Energy Rating System (also known as HERS ratings) and the Home Energy Score (HES rating). More than four million energy performance ratings and certifications have been performed since 2012.
Commercial Building Certifications
Building certifications help guide, demonstrate, and document efforts to construct or retrofit highly efficient buildings. Two of the most common commercial building certifications are ENERGY STAR and Leadership in Energy and Environmental Design (LEED), which have increased by nearly three- and six-fold since 2010. An ENERGY STAR certified building must perform better than at least 75 percent of similar buildings nationwide, while LEED requires the modeled design for its certified buildings to be better than a baseline building’s performance by 5 percent for new construction and 3 percent for major renovations. The first generation of certification programs often took a prescriptive approach. Now, certification programs are increasingly performance-based, which allows for flexibility in choosing strategies to meet whole-building energy performance requirements.
The above-mentioned policies and programs are just a snapshot of the array of tools available to improve energy efficiency in buildings. Despite monumental progress, there is still tremendous potential for improving energy efficiency in buildings. An influx of innovative technologies—such as smart meters, advanced controls and automation—along with greater integration of building systems are poised to drive even deeper energy savings in buildings.
The upshot of the EE Impact Report is that energy efficiency is a process, not a destination. It will continue to change along with our evolving energy system and technology landscape, creating countless new opportunities. While buildings are meant to last 100 years, their operations must continue to change and improve to optimize energy use.
DAP’s newest wall & floor sealant, the Sound Block E90, is designed specifically to reduce sound transmission through penetrations in wall and floor systems, as well as improve STC ratings in sound-rated applications.
The sealant is recommended for use with openings around electrical boxes, pipes, duct systems, cut-outs, and other types of penetrating utility equipment, as well as abutting surfaces, corner joints, and other perimeter edges. It is tested to meet ASTM E90, C919 and E84/UL723, and also serves to reduce smoke and draft penetration.
“Sound Block E90 offers general contractors, builders and drywall installers an easy to use acoustical sealant for sealing top and bottom runners, cut-outs and perimeter joints that passes all industry standards for sound transmission while also reducing smoke migration and drafts,” says Justin Lingenfelser, product manager at DAP. “It is designed to gun easily and tool smoothly in all temperatures, not slump or sag, and maintain excellent adhesion on a variety of substrates.”
The Sound Block E90 is sold in 28 fl. oz. plastic cartridges designed for easy gun application. The formula is paintable within two hours, cleans up easily with water, and provides strong multi-material adhesion and strong cold weather performance. It will be available at lumberyards and building material distributors starting in June 2020.
Huntsman Corporation today announced that it has branded its world leading spray polyurethane foam (SPF) Business as Huntsman Building Solutions (HBS). HBS is a global platform within Huntsman’s Polyurethanes division.
The SPF Business was formed when Huntsman acquired leading North American SPF company Icynene-Lapolla in February and combined it with Demilec, which Huntsman acquired in 2018. HBS is now one of the world’s leading SPF providers and the fifth largest insulation manufacturer. Simon Baker, previously president of Demilec, and Doug Kramer, formerly president of Icynene-Lapolla, jointly lead HBS. Baker is responsible for Canada and international business and Kramer for U.S. business.
Commenting on the new name, Tony Hankins, President of Huntsman’s Polyurethanes division, said: “Integration of the two legacy companies is progressing well and the selection of the new name is an important milestone for the Business. I’m excited about the opportunities that lie ahead, notwithstanding the current challenges caused by the Covid-19 pandemic. SPF is a highly attractive growth business; we have a product offering which is second to none and our products provide significant environmental benefits – not just in terms of energy savings, as they are the most effective thermal insulants in the market; but also in terms of the upcycling of PET bottles and scrap, which are used in our TEROL® polyols, a key ingredient in the production of SPF. HBS will consume significant volumes of our low er margin polymeric MDI – the other key ingredient in SPF formulations – to produce higher margin specialized SPF systems.”
A renewed need for medium-density housing within and surrounding East Coast cities, and economic pressures following the recent recession, have led to an increased use of economical wood-framed construction in large, multi-story residential buildings. The preferred aesthetic of these buildings in the mid-Atlantic region includes brick masonry facades. The technical aspects of brick cladding in wood-framed low-rise residential structures are well understood by practitioners, but the desirable look of brick masonry combined with the bargain of wood framing can be problematic in multi-story construction.
Fig. 1- Photo of window damage due to differential movement.
In multi-story wood-framed buildings brick masonry is typically supported at the foundation level or at a concrete podium level, and brick masonry heights often exceed prescriptive code limits. The brick masonry and the wood framing will both undergo volume changes (expansion for the brick and contraction for the wood) that are not only opposite but irreversible. The significant and additive differential movements of these two materials are proportional to height and therefore more impactful on taller buildings. Without relieving angles or another form of intermediate support for the brick cladding, the wall assembly cannot incorporate horizontal brick masonry expansion joints customarily used in multi-story brick construction. Building elements that bridge from the wood-framed structure across the brick masonry, such as windows, dryer vents, etc., require special detailing to accommodate this differential movement. If the wall system is not detailed to accommodate this movement, damage can occur at these restrained elements that project into the plane of the brick masonry but are anchored to the building frame. (Figure 1).Code requirements
Section 1405.6 through 1405.9 of The International Building Code (IBC) recognizes the potential problems generated by differential movement between brick masonry and wood-framed supporting structures by referencing Section 6.1 of TMS 402/ACI 530/ASCE 5.
ACI 530 includes several requirements for anchored masonry veneer, which originate from the master requirement set forth in Section 6.1.2 “Design of Anchored Veneer,” which states:
Anchored veneer shall meet the requirements of Section 6.1.6 and shall be designed rationally by Section 6.2.1 or detailed by the prescriptive requirements of Section 6.2.2.
Section 6.1.6 “General Design Requirements,” includes a requirement to “Design and detail the veneer to accommodate differential movement.” This requirement is a catch-all that puts the burden on designers to determine the amount of anticipated differential movement through analysis, and to detail the veneer accordingly, regardless of whether designed by rational analysis or using the prescriptive approach.
Section 6.2.2 “Prescriptive Requirements of Anchored Masonry Veneer” of ACI 530 includes requirements for the anchoring of brick veneer and, most relevant to the subject of differential movement, Section 188.8.131.52 “Vertical Support of Anchored Masonry Veneer” requires that the height of anchored veneer with a backing of wood framing not exceed the height above the noncombustible foundation of either 30 feet at a plate or 38 ft. at a gable. This limit sets the maximum height allowed using prescriptive detailing without conducting a rational analysis. Assuming a floor-to-floor height of 10 to 12 ft., the code practically limits the vertical height of brick masonry to only three stories without further analysis.
Fig. 2. Example of Type III-A construction.
Many wood-framed structures are Type III-A construction that extend four or five stories above the foundation or podium base. These buildings require a rational design for the support of the brick masonry following requirements of Section 6.2.1 “Alternative Design of Anchored Masonry Veneer.” These larger wall heights also require accommodation of proportionally larger differential movement between the anchored veneer and wood-framed backup. A rational analysis should examine the potential magnitude of movement and include exterior wall details that can handle the anticipated movement. The remaining sections of this article can assist designers whether designing rationally or detailing exterior walls using prescriptive requirements.Methods to quantify differential movement
To properly detail portions of the wall that bridge between the brick masonry and backup structure (e.g., masonry veneer anchors, windows, mechanical penetrations) to accommodate movement, designers must first quantify the anticipated differential movement.
In order to understand how much movement can occur between the brick masonry and back-up wood-framed structure, designers must examine the design of the structure, calculate estimated wood shortening, and add the effects of brick masonry growth to that of the estimated shortening of the wood framing to determine the total differential movement.
Total differential movement between the brick masonry and wood-framed backup structure can be estimated using the following simple equation:
(Δbrick moisture + Δbrick temp) + (Δwood drying shrinkage + Δwood creep) =Δdifferential
In this equation, the left parenthetical represents the contribution of brick growth and the right parenthetical represents the contribution of wood shortening.
The total estimated brick growth includes Δbrick moisture for the irreversible growth of brick over time with increase in moisture content and Δbrick temp for growth of brick with increase in temperature. Total estimated shortening of the wood framing includes Δwood drying shrinkage for shortening of the wood due to drying from the moisture content at installation to the equilibrium moisture content and Δwood creep for shortening of the wood framing due to time dependent strain under sustained long-term load. The temperature range experienced by the brickwork is the difference between low and high mean temperatures of the brickwork after construction and is based on the low and high temperatures of the exterior ambient air.
Other factors contribute to differential movement, but can be considered negligible compared to these mechanisms. For example, brick creeps under sustained load, but the amount of shortening due to brick creep is small. After framing reaches its equilibrium moisture content, thermal expansion of moist wood (moisture content greater than 5 percent) tends to be negated by drying shrinkage due to additional moisture loss. Framing also shortens from settlement of construction gaps. Articles by Alfred Cummins and Dominic Matteri estimate this settlement of the wood framed construction to be as much as 1/8-inch per floor. However, this value is difficult to predict and some gaps may disappear as the building is loaded during construction, and prior to brick installation, reducing its effect on differential movement.
Exterior sheathing and interior finishes tend to restrain and therefore reduce the amount of wood shortening, but this restraint depends on type and arrangement of these components and should not be fully relied upon. Example estimated quantities of brick growth and wood shortening for balloon and platform framing are provided below without consideration of restraints from sheathing and finishes. Note that while the calculations assume design values for both brick growth and wood shrinkage based on applicable guidelines, these design values can increase or decrease depending on actual project circumstances.Brick growth
Movement of brick masonry is expected in new construction. The values in Table 1-1 reflect the movement of unrestrained brick masonry due to changes in temperature and moisture in the summer months, when brick expansion due to temperature change is the greatest.
Table 1-1 – Brick Expansion
Note: The calculations above assume a story height of 10 ft.
The calculations tabulated above consider the temperature range experienced by brickwork to be 100°F and a coefficient of moisture expansion of 5×10-4 in./in. as recommended by Brick Industry Association Technical Note 18.
The calculations tabulated above also consider coefficient of thermal expansion of 4×10-6 in./in./°F as recommended by ACI 530. These and other resources such as Masonry Designers’ Guide provide designers alternative coefficients for expansion based on industry recommendations.Wood shortening
Fig. 3 – Platform framing.
To quantify wood shrinkage due to moisture content change, Δwood drying shrinkage, designers can consult the Wood Handbook published by the United States Department of Agriculture, which describes shrinkage of common wood species based on change in moisture content and dimensional change coefficients dependent on species and orientation of grain. Mid-rise residential and mixed-use buildings usually include wood framing oriented in a balloon configuration similar to traditional balloon-framing. Low-rise residential structures are frequently constructed using platform framing (Figure 3).
Approximate values of per-floor shortening due to change in moisture content and creep for typical assemblies are tabulated below. The shrinkage strain for members loaded across the wood grain such as plates and joists is significantly higher than that of studs which are loaded parallel to the wood grain. The balloon framing calculations assume two head plates and one sill plate at each floor while platform framing calculations assume two head plates, one sill plate, and 2×10 floor joists at each floor.
Table 1-2 Wood Shortening
Note: The calculations tabulated above assume a story height of 10 ft.
The calculations above also consider southern pine in the mid-Atlantic region with moisture content at installation of 19 percent and an equilibrium moisture content of 12 percent. The designer should use the appropriate values and properties for the environmental conditions for their location. The values in Table 1-2 above do not include an allowance for settlement of construction gaps in the wood framing.
During the summer months the average temperature of the brick will be at its highest value for the year. The accumulation of moisture expansion of brick, wood drying shrinkage, and wood creep increases with time. The cumulative expansion of the brick masonry and shortening of the wood framing over time and considered during the summer results in a total maximum differential design movement between the brick and wood backup systems as follows:
Table 1-3 – Total Differential Movement (Considering Balloon Framing)
Note: Values in the table above represent theoretical and probably upper-bound anticipated movement for balloon-framed structures, using the assumptions noted above for the masonry and wood. The theoretical movements for platform framing are higher than these. In our experience actual movements will be less than the computed movements. This difference is due, in part, to restraint of wood shrinkage and creep by attached interior finishes.Effects of differential movement on penetration detailing
Differential movement between cladding and backup is straightforward to address in blank masonry walls. The brick veneer must be attached with wire type brick veneer anchors that engage a backup plate and allow vertical movement of the anchor with respect to the backup plate without compromising the anchor’s load capacity. These anchors can provide several inches of vertical adjustability that is primarily intended to facilitate brick veneer installation, but, if the anchors are deliberately installed with appropriate clearance, they can allow the wire anchor to slide upward with the brick masonry veneer, while remaining engaged in the backup plate.
Fig. 4 – Window head.
Fig. 5- Window jamb.
Windows and doors, balconies, and mechanical penetrations such as dryer vents and PTAC unit sleeves that will bridge the backup and brick veneer are more challenging to deal with than anchoring penetration-free walls. Strategies to accommodate movement include allowing the penetrants to flex between the structure and brick cladding, or to allow the brick cladding to slide around them. After determining the required clearance between the penetrant and the brick veneer based on the expected total cumulative differential movement, the brick veneer must be installed with this clearance around each penetration or fenestration. The resulting gaps must be covered to protect vulnerable backup construction, including the building’s water-resistive barrier and window perimeter flashing, and to be aesthetically pleasing, all the while accommodating vertical movement. The large movement demand prevents the installation of reasonably-sized sealant joints, so the gaps must be filled with overlapping flashing or trim components that can slide over each other and are detailed to keep out bulk water and insects. The following arrangements cover some typical cases. These examples are not attempting to address water and air penetration resistance of these details – these are important considerations for all enclosure detailing, but beyond the scope of this article.
Window head: At window heads, the upward movement of the brick veneer will tend to open up a gap between the underside of the steel loose-lintel and the window frame. After the window is integrated into the wall water-resistive barrier, a trim piece that is fabricated from durable sheet metal flashing or synthetic wood board to match the appearance of the window frame can be installed over the window head. As the steel lintel moves upward over time, an increasing portion of this trim is exposed.
Fig. 6- Window sill.
Window jamb: Along the window jamb, the upward movement of the brick veneer results in a shearing motion between the brick and the window. This movement can be managed with an L-shaped metal trim cavity closure piece that is attached to the backup along the jamb. The brick masonry is finished to the closure.
Window sill: The required gap between the window sill and brick masonry results in a skyfacing opening that has to be covered with a piece of metal cap flashing trim that keeps out bulk water, and must
Fig. 7 – Mechanical penetration.
be integrated with the window jamb trim. The large downturned leg of the trim piece represents a significant aesthetic compromise over stone sills or brick masonry rowlock sills that are traditionally used for this detail.
Mechanical penetrations: These typically extend beyond the face of the masonry and the required gaps at the perimeter of the penetration sleeve can be covered with a flashing collar that extends over the brick masonry.Summary
The past years have seen an increase in wood-framed buildings that are covered with multi-story brick veneer cladding without intermediate gravity load supports. This configuration can result in substantial differential vertical movement between veneer and backup. Designers should calculate anticipated differential movement on a project-by-project basis. The building enclosure details must consider the organization of the structure to successfully accommodate movement. To avoid damage to façade components that straddle the backup and the veneer, the enclosure design for these buildings must include effective provisions to accommodate this movement.
In an earlier article we explained how the code defines cavity and continuous insulation. Cavity insulation goes between (and is interrupted by) framing whereas continuous insulation is continuous and not interrupted by framing other than fasteners or service openings. In general, there are three ways of using cavity and continuous insulation materials, to varying degrees, to provide thermal control for light-frame exterior walls (see Figure 1):
- cavity insulation alone,
- cavity and continuous insulation together (i.e., a ‘hybrid’ wall) or
- continuous insulation alone (the so-called ‘perfect’ wall).
Figure 1. Three Insulation Approaches for Thermal Control of Light-Frame Exterior Walls
NOTE: Click on the above source for access to design recommendations in Tables 2(A) and 2(B) referenced in the above figure.
The insulation strategy selected – where to locate insulation in the wall to comply with the energy code – is in many ways a foundational decision because it affects other decisions related to matters of building code compliance. For example, the insulation strategy and properties of those materials should affect decisions regarding the specification of vapor retarders (vapor control layer) and even the water-resistive barrier (water control layer) depending on the properties of those layers and the climate. Cladding specification and installation details also may be affected, such as fastening methods and provision for drainage or back-ventilation to control moisture. For commercial Type I, II, III, or IV buildings, it can also affect wall assembly details and material specifications to achieve code compliant fire safety. These are not difficult decisions or hard to achieve. It is simply a matter of knowing that these inter-relationships exist and executing them effectively.
You see, we are dealing with a highly integrated system of several individual, and sometimes multi-functional, components. Consequently, these component parts of an exterior wall system have important interactions or inter-dependencies with other components in the system. These must be properly managed or coordinated to capitalize on strengths and avoid weaknesses. When done well, the whole is better than the sum of the parts. When not done well, the whole is no better than the worst of the parts.
We can no longer get away with treating the design and construction of walls as a series of independent component specification decisions. We need to get this system thing right in codes and in practice. Why? The answer is simple and we need not look any further than the intent of the building code:
“R101.3 Intent. The purpose of this code is to establish minimum requirements to safeguard the public safety, health and general welfare through affordability, structural strength, … energy conservation and safety to life and property from fire and other hazards attributed to the built environment…”
The issue here is not so much that the code is aimed at minimum requirements, but that the code and practice must also facilitate how those minimum requirements are implemented from a system-based design standpoint with inter-relationships between various minimum requirements properly coordinated so as to achieve the full intent of the code. It also is not so much a change in cost of construction as it is a more cost-effective approach to construction planning and specification. To the extent that this goal is achieved, more benefits are leveraged in the execution of a minimum code at little to no additional cost. These benefits include qualities such as durability and resiliency. It also helps to ensure that the flexibility to competitively use a variety of alternative solutions to specific energy and building code requirements remain available while avoiding inadvertent or unexpected outcomes.
In general, building codes do strive to effectively address matters of integrated system-based design (e.g., see “Fire Safety and Foam Sheathing Use” as a positive example of coordinating an energy code insulation choice with fire safety requirements of the building code). In other cases, such as matters related to moisture control and its effect on durability, these inter-relationships may not be completely accounted for. Fortunately, codes are continually improving and this is exhibited by a major step forward in the 2021 editions of the IBC and IRC to more completely address the inter-relationships between insulation strategy and water-vapor retarder strategy. Please refer to a separate article published on this topic.
In next month’s EEBS we will broaden this article’s discussion on thermal control layer strategies to include all of the key control layers together: water control, air control, thermal control, and water vapor control. These are key components of the building envelope system that protect the building structure and its occupants over the life of the building.
A new “open file” research report has just been completed to assess the role of building science and healthy buildings in relation to controlling the risk of health threats such as the COVID-19 pandemic.
The research report is titled Healthy Buildings & the COVID-19 Pandemic: Building Science for HVAC Systems and Building Envelope Best Practices.
Source: ASHRAE as reported in https://www.eeba.org/the-health-window.
Science has been building a case, and leading us for the past 100 years, to better understand the importance of the indoor environment for human health. It has better defined appropriate target conditions for the indoor environment (e.g., temperature, humidity, and air quality) for human health, comfort, and productivity. Furthermore, these advancements in science have pointed to various “building science” opportunities to engineer and construct building systems to better control optimal indoor conditions for a healthy indoor living environment.
This topic has been taken more seriously for health care facilities (for obvious reasons) than other buildings such as homes, offices, shops, schools, restaurants, and enclosed spaces where people may be more routinely exposed to the risk of disease transmission.
The report asks the reader to:
“Think of the building envelope as the protective skin or PPE of the building and the HVAC system as the internal lymphatic system to maintain internal health and help suppress pathogen propagation and survival within the building’s body.”
The research report recognizes that a healthy indoor environment requires an integrated approach. To be able to effectively control indoor environmental conditions (temperature, humidity, and ventilation) at any time of the year and in any climate, and not expend excessive cost and energy doing so, one must have a good building envelope as a foundation so that good HVAC design can then do its job effectively and efficiently.
COVID-19 is not the only reason to consider that it may be time to apply this “healthy building” knowledge to a broader array of buildings, but perhaps it is the crisis that may finally cause appropriate action to be more broadly considered, accepted, and implemented.