Energy Conservation with Precast

Americans spend almost 90% of their time inside buildings. According to the U.S. Energy Information Administration, more than 2⁄3 of the electricity generated and more than 1⁄3 of the total energy (including fossil fuels and electricity) in the U.S. are used to heat, cool, and operate buildings. Significant energy could be saved if all buildings, including current building stock, were built to, or exceeded minimum national energy code standards. Saving energy will result in fewer power plants and natural resources being used to provide electricity and natural gas. It also means fewer emissions to the atmosphere. Emissions have been attributed to smog, acid rain, and global climate change.

Energy codes provide minimum building requirements that are intended to reduce energy consumption. The U.S. Energy Conservation and Production Act (ECPA) requires that each state certify that it has a commercial building code that meets or exceeds ANSI/ASHRAE/IES Standard 90.1.1 When subsequent versions of 90.1 are published, the Department of Energy determines whether these more-recent versions meet the requirements of ECPA. The most-recent version of the standard was published in 2013 and has been determined to meet the provisions of ECPA. The International Energy Conservation Code (IECC) allows Standard 90.1 as a compliance path and also generally complies with ECPA. The most recent version of the IECC is 2015. In this sense, “commercial” means all buildings that are not low-rise residential (three stories or less above grade). This includes office, industrial, warehouse, school, religious, dormitories, and high-rise residential buildings. Some states implement codes similar to ASHRAE Standard 90.1 and some have other codes or no codes. The status of energy codes by states is available from the Building Codes Assistance Project (BCAP). Building to minimum energy codes is a cost-effective method of saving energy. The designer is not constrained in aesthetic expression in applying the range of available high-performance building systems to meet the performance criteria of ASHRAE 90.1 or the IECC.

Sustainability or green building programs such as LEED™, 4 Green Globes, or EnergyStar encourage energy savings beyond minimum code requirements. The energy saved is a cost savings to the building owner through lower monthly utility bills and smaller, and thus less expensive, heating, ventilating, and air-conditioning (HVAC) equipment. Less energy use also means fewer emissions to the atmosphere from fossil fuel power plants. Some government programs offer tax incentives for energy-saving features. Other programs offer reduced mortgage rates. The EnergyStar program offers simple computer programs to determine the utility savings and lease upgrades associated with energy saving upgrades. Sustainable buildings often have features that have been shown to increase worker productivity, decrease absenteeism, and increase student test scores in schools.

The planned design of an energy-conserving or sustainable building requires the architect’s understanding of the effects of design decisions on energy performance. More than half of the true total costs incurred during the economic life of a building may be attributable to operating and energy costs. An integrated design approach considers how the walls interact with the building and its HVAC system. Using this approach early in the design phase helps optimize initial building costs and reduce long-term heating and cooling energy costs. This integrated design approach is recommended for cost-effective, energy efficient, sustainable buildings.

Precast concrete wall panels have many built-in advantages when it comes to saving energy and protecting the building from the environment. Their versatility leads to unique solutions for many energy conservation problems. The relative importance of particular design strategies for any given building depends to a large extent on its location and climate. For instance, buildings in northern, heating-season-dominated climates are designed differently than those in southern, cooling-season-dominated climates.

Several factors influence the actual energy performance of the building envelope. Some of these are recognized in energy codes and sustainability programs because they are relatively easy to quantify. Others are more complex and are left to the discretion of the designer.

Much of the information and design criteria that follow are taken from or derived from the ASHRAE Handbook: Fundamentals and the ANSI/ASHRAE/IES Standard 90.1. It is important to note that all design criteria are not given, and the criteria used may change from time to time as the ASHRAE Handbook and Standard are revised. It is therefore essential to consult the applicable codes and revised references for the specific values and procedures that govern in a particular area when designing the energy conservation systems of a particular structure.

~Information courtesy of PCI.

Benefits and Advantages of Architectural Precast Panels

Design considerations must balance a variety of needs, including aesthetics, function, and financing. Each plays a role in achieving success with the finished project. Architectural precast concrete not only can ensure these general goals are met, but it provides a myriad of lifecycle and ancillary benefits that are difficult to match with other materials.

Durability
Architectural precast concrete offers the building owner peace of mind that results from the certain knowledge that the building’s walls have long-term durability and require little or no maintenance to preserve their original look. This requires high cement contents and low water-cement ratios. Combined with good compaction and curing in a controlled factory environment, these factors ensure a dense, highly durable concrete. A low water-cement ratio has been proven to increase resistance to weathering and corrosion. Entrained air may be used to improve freeze-thaw resistance in particularly severe environments.

Aesthetics
Architectural precast concrete panels provide the designer with an unlimited architectural vocabulary of expression. Whether the project’s aesthetic intent is traditional or contemporary, precast concrete can be shaped in a cost-effective manner. The material is incredibly responsive to the designer’s needs. The only limits are imagination and creativity.

Visual interest in the building’s façade can be enhanced with architectural devices such as ribs, bullnoses, reveals, chamfers, or casting against various types of form liners. Precast may be designed with a combination of concave, convex and flat sectional shapes.

Taking advantage of precast’s initial plasticity can economically create these shapes, adding considerable aesthetic appeal to a project. Design flexibility is possible in both color and texture by varying aggregate and matrix colors, size of aggregates, finishing processes and depth of exposure.

Combining different finishes using the same or different concrete mixes within a single precast concrete unit can provide additional flexibility. A highly articulated pattern of color and texture develops a richness of architectural expression.

Commitment to Quality
Architectural precast concrete units produced by PCI-certified plants are produced under strict, factory-controlled conditions to ensure a high quality façade in the desired shapes, colors and textures along with close tolerances. Every PCI member must undergo two stringent unannounced inspections each year by independent auditors to maintain PCI certification. The inspections focus on the process by which the unit is produced, as well as the plant’s general operation.

Certification pays off for owners and designers because it produces fewer worries about onsite discovery of units out of tolerance, connection details that aren’t cast precisely or finishes that aren’t matched from panel to panel. It also minimizes the need for continuous inspections.

Life Cycle Cost
When comparing the cost of alternative façade systems, the cost throughout the design life of the building needs to be evaluated. A precast façade can be designed to match the intended life of a building with minimal maintenance, providing substantial long-term savings. Precast concrete panels present a durable aesthetically pleasing exterior surface that is virtually air and watertight and does not require painting. This helps the building remain in first class condition long after the mortgage is repaid, ensuring its desirability to future tenants or owners. It also means attractive refinancing can be accomplished more advantageously, too.

Initial Cost
Precast’s speed of erection and its ability to be cast and erected in all kinds of weather aid the entire construction team. Since the casting process does not rely on other critical-path activities to begin, units can be produced as soon as drawings are approved, ensuring units are ready for erection as soon as foundation work and other site preparation is completed. These advantages allow the building’s shell, whether load-bearing or cladding, to be enclosed quickly. This, in turn, lets interior trades begin work earlier and reduces overall construction time.

Faster completion reduces interim financing costs, results in earlier cash flows, and produces other economic benefits. This ultimately lowers the building’s long-term overall cost and can make the use of precast concrete more economical than other façade materials.

Load-bearing panels can reduce framing costs by providing a column-free perimeter. Depending on the floor plan, there also is potential for reducing the number and/or size of interior columns, adding layout flexibility. This results in a more efficient and less costly construction. Cost savings are greatest for low -to mid-rise structures of three to 1 0 stories with a large ratio of wall-to-floor area.

Energy Efficiency
Precast concrete panels can be designed to provide a high degree of energy efficiency for the buildings they enclose. Recessed window walls, vertical fins and various other sculptured shapes facilitate the design of many types of shading devices for window areas to reduce glare and solar gain. This provides economies in the cost of the air-conditioning system by reducing thermal load. Specific wall thermal characteristics can be designed for each face of the structure to suit its sun orientation.

To obtain a range of R-values, precast concrete walls may have insulation applied to the back, or the insulation may be incorporated into a sandwich wall panel to reduce heating and cooling costs. The thermal mass inertia of concrete, which is recognized in ASHRAE standards, also reduces peak heating and cooling loads, thus saving energy year-round by reducing large daily temperature swings.

Other Inherent Benefits
Architectural precast concrete is non-combustible with inherent fire-resistant capability, creating a safe envelope that helps protect personnel, equipment, and the building itself. That in turn reduces insurance rates. It also eliminates the need and cost of additional fireproofing measures, except on structural-steel frames.

Environmental Impact
In addition, the inherent sound attenuation properties due to precast concrete’s mass provide an economical acoustical barrier to exterior or interior noise penetration. These attributes enhance the cost effectiveness of precast panels. The life-safety and tenant benefits provide a potent marketing asset when attracting long-term occupants. Precast concrete is an environmentally sound material. It is produced from natural materials. No toxic substances are produced in its production or use. Also, the production energy consumption of the concrete is quite small. The thermal mass of concrete saves energy year-round by reducing temperature swings.

Concrete’s high albedo (or ratio of light reflected) has the added quality of reflecting heat as well as light, thus reducing the “heat island” effect and higher temperatures endemic to urban areas. The resulting lower overall temperatures can make a difference in the amount of electricity consumed in air conditioning and can reduce smog formation, potentially improving air quality in urban areas. Precast wall panels can be reused when buildings are expanded. Non-loadbearing panels on the end simply are disconnected from the framing and additional panels and framing are added on each side. With the new addition in place, the end panels can be replaced. Concrete measures up well in regard to sustainability. It strikes a perfect balance between meeting today’s needs and natural resources for tomorrow.

Single-Source Provider
As a single unit, precast panels provide one source for supplying the entire exterior wall system. When load-bearing precast structural floors along with panels are specified, it concentrates the complete shell with one certified and reliable producer. This approach ensures complete responsibility and accuracy for meeting design specifications rests with only one supplier. The precaster is responsible for all manufacturing and constructability issues. This reduces the number of subcontractors and minimizes trade coordination. Also, the producer’s competent staff of plant engineers is available to assist the design team.

Supplier Assistance
PCI member precasters can offer detailed expertise that allows the development of design techniques, engineering innovations and scheduling improvements that save time and money from conceptual design to project completion. To maximize these benefits, the design team should interact with the precaster early in the project’s development stage. This ensures each element is as cost effective as possible and will take full advantage of precast’s inherent performance characteristics. The result will be a functionally efficient, aesthetically pleasing structure produced on time and on budget that meets all programmatic needs.

~ Information provided courtesy of PCI.

The Building Envelope

Due to its density, concrete has the capacity to absorb and store large quantities of heat, contributing to a high-performance building envelope. Its thermal mass allows concrete to react very slowly to changes in outside temperature to reduce peak heating and cooling loads and delay the time at which these loads occur. The resulting savings can be significant—up to 25% of heating and cooling costs.

Thermal mass and energy savings

ASHRAE Standard 90.1 acknowledges the thermal mass benefits of concrete walls in specifying lower minimum insulation R-value and higher maximum wall U-factors for mass (concrete) wall construction.

Research conducted by Oak Ridge National Laboratory compared the dynamic thermal performance of insulated concrete walls with that of a traditional wood frame.  Research shows that insulated concrete sandwich walls constructed with composite connector technology utilize the thermal mass effect of concrete to create an “equivalent wall performance R-value” several times greater than a traditional material R-value calculation.

Energy-saving benefits of thermal mass are most pronounced when the outside temperature fluctuates above and below the balance temperature of the building, causing a reversal of heat flow within the wall.  The balance point is generally between 50 and 70°F.

These ideal conditions for thermal mass exist on a daily basis at all locations in the United States.

Another factor affecting the behavior of thermal mass is internal heat gain.  This includes heat generated inside the building by lights, equipment, appliances, and people; and heat from the sun entering through windows.  Generally, during the heating season, benefits of thermal mass increase with the availability of internal heat gains.  During the cooling season, thermal mass exposed to the building's occupied spaces will absorb internal gains, shifting peak cooling periods.  Concrete exposed to the interior, not covered by insulation and gypsum wallboard, works best to absorb internal gains, saving cooling energy.

Thermal mass also works well when daily temperatures have large variations between the daytime high and nighttime low and when outdoor air can be used for nighttime ventilation.  Designs employing thermal mass for energy conservation should be given a high priority.

Color

Color (albedo) of precast concrete panels can be used to improve the energy-conserving features of the walls.  Panels with high albedo (generally lighter in color) can help reduce the urban heat-island effect.  Albedo is the ratio of the amount of solar radiation reflected from a material surface to the amount that shines on the surface.

Generally, materials that appear to be light colored have high albedo and those that appear dark colored have low albedo.  On exterior surfaces, high albedo decreases solar heat gain; low albedo increases solar heat gain.  A low albedo north wall and high albedo east and west walls and roof form the most energy-conserving arrangement in a northern hemisphere climate that uses both heating and cooling.  High albedo surfaces are especially important where cooling dominates the energy requirements. It should be noted, however, that the color of the exterior walls has less effect on energy consumption when the walls have high R-values and thermal mass.

Heat-island effect

Light-colored exterior surfaces also help reduce urban heat-islands.  Urban areas are up to 7°F warmer than the surrounding areas.  This difference is attributed to more buildings and pavements that have taken the place of vegetation.  Where buildings and paved surfaces are required, using materials with higher albedos will reduce the heat-island effect, save energy by reducing the demand for air conditioning, and improve air quality.

Air infiltration

Air infiltration has significant effects on the amount of energy required to heat and cool a building.  Large precast concrete panels have minimal joints, reducing uncontrolled air infiltration.

~ Information provided courtesy of PCI.

New Year, New Beginnings, New Goals

There is nothing quite like ripping the plastic wrapping off of a brand-new calendar.

Once that calendar is open, you can flip through the pages and start filling in all the things you have to look forward to in the coming year: birthdays, anniversaries, vacations, weddings, concerts, sporting events.  It's amazing how many wonderful things we have to anticipate each year... and then there is the anticipation of not yet knowing what might fill up the rest of your calendar for the year.  Will you receive an unexpected wedding invitation?  Maybe your sister will announce a pregnancy and you'll have a due date to add to your calendar?  What if your husband sets up a weekend getaway?  I'd want to add that to my calendar for sure (hint, hint, wink, wink my dear husband).

And what about resolutions?  Are New Year's resolutions something you make?  There are arguments on both sides of the fence for whether resolutions should or shouldn't be made.  For what it's worth, here are my two cents... My overall goal in life is to be better every day than I was the day before.  If setting a goal at the start of a new year can help someone become better than they were previously, I'm all for it!

So, what resolutions will you make this year?

It's a new year.  It's time for new beginnings and new goals.

Merry Christmas and Happy Holidays

There's something special about this time of year.

While it is cold outside, it's not the "I'm so cold I may never feel warm again" cold that we get later into the winter.  The snow - if we have gotten any - is still pretty. Houses are decked out for the holidays, with lights and garland decorating the outside, and the family Christmas tree glistening in the window.  The music is cheerful, and kids excitedly await the arrival of Santa.  People are getting dressed up for holiday parties, selecting the perfect presents for everyone on their list, wrapping pretty packages, planning holiday meals, baking cookies, and eagerly awaiting time with family and friends.

This is my favorite time of year.  I generally have 'Nsync's Home for Christmas album on repeat, make sure I have watched It's a Wonderful Life, Miracle on 34th Street, Elf and The Santa Clause at least once.  I bake hundreds of Christmas cookies and wrap presents in the prettiest paper I can find.  In fact, I like wrapping Christmas presents so much, I often spend at least a day with my parents, helping them get all of their wrapping done.  Despite the fact that their four children are grown, with three married with families of our own, my parents still treat Christmas as though we were kids and go just a little (read: A LOT) over the top on gift giving.  It turns out they love Christmas, too.  My husband and I always make an effort to get out to Christkindlmarket, take a drive around town to check out the holiday lights and generally enjoy spending time together, shopping for the holidays and decorating.

People are friendlier this time of year, wishing each other a Merry Christmas, Happy Holidays, and spreading messages of peace, joy, and good cheer.

And I just love spending time with my family, not just on the holiday, but all the time we spend together leading up to the holiday.  We still get the extended family together on Christmas day, bringing together four generations to spend a day together, enjoying the company of each other.  Of course, there is always some good-natured ribbing, too.  My family is close and for that, I am grateful.

So, what are your Christmas traditions?  What is your favorite part about this time of the year?  Enjoy a video from my very favorite Christmas album!

https://youtu.be/wKj92352UAE