How are High-Performance Buildings Achieved?

Many think that adding insulation and installing energy-efficient equipment is all you need to create a high-performance building, but there are numerous factors and they are all interrelated. The following are important elements and systems that one needs to pay attention to while designing a high-performance building:

• Solar Control (relating to Solar Heat Gain): Project location and climate should direct the design of the enclosure. In colder climate zones you want to design for maximum heat gain, while in warmer climates you want to limit heat gain. In temperate climates you need to design to gain and retain heat in the winter while limiting heat gain in the summer. Walls built into the earth, mass walls, sunshades, solar shelves, rainscreens and overhangs are design strategies that can be actively or passively used.
• Glazing: This is key to controlling daylighting which can cause solar heat gain and glare inside interior spaces. Glazing is also a weak link in the continuous insulation of a building, because it has an R-value lower (or higher U-factor) than the rest of the enclosure. Air leaks and water penetration are additional concerns. One needs to analyze the entire glazing unit assembly for its U-factor, coatings and reflectivity. Glazing selection is integral to how the building mass and light shelfs are designed to help with solar control.
• Continuous Insulation: High-performance buildings should have continuous insulation that exceeds standard code compliance for R-value. Alone it is not effective enough to create a high-performance building, and there is a diminished rate-of-return value for the heat flow to R-value ratio. Continuous insulation should be coupled with a continuous air and vapor barrier.
• Continuous Air and Vapor Barriers: Even the smallest crack will allow moisture and humidity into the building. This will affect dew points within the wall system and can lead to operational and maintenance issues in the future. Potentially, this could lead to mold growth or material deterioration. Continuous air and vapor barriers placed in the correct location will prevent dew points from occurring in the wall assembly where it could be harmful to the system or to the inhabitants.
• Duct Sealant and Insulation: Often overlooked, these are vital when heating and cooling a building. Properly installed, they limit the temperature change of the conditioned air traveling throughout the building and help keep the building comfortable. If inadequate or installed poorly, more heating or air-conditioning will be necessary to achieve the desired temperature. Also, sealing ducts will prevent “back drafting” of gases like carbon monoxide from escaping back into spaces instead of being exhausted outdoors. If fumes from items such as equipment are not exhausted, they could affect occupants with allergies or asthma.
• Reduced Plug Loads: Plug loads can account for almost 50 percent of energy use in a building (Higgins & Harris, 2013). Specifying the right energy-efficient equipment at the proper size will reduce plug loads. The higher the plug load the more heat is generated, which will lead to more energy needed to cool a space. Plug loads from lights, computers, monitors, etc. add up quickly to heat up a space. One can look at three areas to reduce plug loads:
• Software – Use software to a lower power mode or to turn off computers and equipment when not in use over extended periods of time.
• Hardware – Replace old, inefficient equipment with new high-efficient equipment and use systems such as advanced power strips and timers that automatically control loads after business hours and on weekends.
• People – Engaging building occupants is critical to any effort to impact the energy use of plug loads.
• Building Controls and Enhanced Commissioning: A high-performance building will not meet expectations if you do not verify that its systems are properly sized, controlled and functioning. Would you buy a car from a manufacturer that doesn’t test to see if it runs properly or provide a maintenance/operational manual?

Image courtesy of Albert Kahn Associates Inc.

Sunshades, solar shelves, and overhangs on the building’s exterior, as well as their effective system controls are some of the ways to achieve a high-performance building.

How Can a High-Performance Building Fail?

Think of a high-performance building like the ecosystem of an animal’s habitat. Everything has a purpose and must function in harmony with each other to maintain the life-cycle and keep it properly balanced. Even a simple change can have a profound affect. This is also true with a high-performance building; the smallest error could lead to a large impact on the overall building. The entire enclosure, including the walls and underground slab, plays an important role in the building’s effectiveness. Temperature transference, lack of humidity control, air and vapor transmittance, solar heat gain, and lack of daylighting can all have negative impacts on the occupant’s comfort, as well as making the building energy inefficient. For example, there are completed LEED-certified projects that do not function as efficiently as modeled during design. One such building was LEED Platinum, however it was not properly commissioned and was operating with an Energy Use Intensity (EUI) rating of 78 instead of 37. It’s very important to have proper and adequate metering and controls in place to accurately monitor the systems’ function and verify they are performing as modeled.

In addition to shortcomings in the controls and commissioning of the building, there are several other ways high-performance building design can fail and waste energy or make the space uncomfortable for the occupants:

• Insulation, vapor and air barriers not designed or installed correctly will require the mechanical systems to work extra hard and use more energy.
• Ductwork not sealed or insulated properly will leak and waste conditioned air.
• Operation deviations from the original specifications can lead to poor system performance. In order to function as designed, equipment must be properly commissioned and the owner’s maintenance staff must be properly trained and given access to the operating manuals. Failure to perform proper maintenance on the mechanical systems can lead to inefficiencies over time. Always plan for periodic recommissioning.
• Unaccounted/unplanned plug loads can easily be missed during design and not included in the energy models. The importance of accurate and forward-thinking planning for this aspect of the design must be made clear to the owner, for often they will provide inaccurate numbers from user groups who incorrectly estimate their equipment needs.