Energy Efficiency Starts with Airtightness
Building for sustainability, safety, and comfort requires the combined effort of engineers, architects, sub-contractors, and builders who understand how to design and specify an energy-efficient building envelope. This begins with the design concept and carries through to pricing, design review, construction, and building envelope commissioning.
The preferred method for significant reduction in energy use and greenhouse gas emissions involves an integrated approach since a variety of interacting building components have an impact on overall energy consumption.
However, some elements have a stronger influence on energy consumption and deserve deeper consideration.
The Building Envelope:
The building envelope functions as a thermal barrier regulating interior temperatures and thus affects the amount of energy needed to maintain thermal comfort. Curtailing energy transfer through the envelope is key to reducing requirements for heating and cooling.
The building envelope design influences how much lighting, heating, and cooling a building will need, with local climate playing a large part in how design features that reduce energy use are specified. These might include passive solar heating with south-facing windows, or summer shading in hot climates to lessen reliance on mechanical or electrical equipment.
Strategically adding insulation to the building’s envelope to prevent enegy flow will increase building efficiency as long as leaks and cracks are properly sealed against air flow. There are various methods for insulating such as: insulating concrete forms, fiberglass, spray or rigid foam, and rockwool.
Although insulation improves thermal performance, the envelope design must also manage air and water infiltration with appropriate air and water-resistive barrier products. Water-resistive membranes (WRB) tend to be overshadowed by other considerations such as aesthetics, and their importance needs to be highlighted. Air barrier membranes allow for moisture that is trapped within building to escape with high permeability, while controlling convection and air leakage through air-tightness.
Water-Resistive Air Barrier Membrane:
Although insulation keeps the temperature regulated, an air barrier membrane is what really keeps a building airtight. If we think of insulation as a down jacket, the down keeps you warm until high winds hit and the air blows right through the feathers. An air barrier membrane is the windbreaker. It keeps the structure air-tight and prevents drafts, making the building more energy efficient.
Before water-resistive air barrier membrane’s, buildings had drafts running through them, allowing moisture that did enter the building to dry. Now, because the building is airtight, there is no draft to dry up moisture. This is why water-resistive air barrier membranes need to be not only airtight, but waterproof. WRBs keep water out, by channeling water from wind-driven rain and snow to the outside of the structure. Their high vapor permeability allows moisture that accumulates from within the building to escape. The airtightness is what really helps make the building energy-efficient and with airtightness comes moisture prevention.
How engineers design walls and the materials they specify for construction determines the amount of energy retention or loss through the walls. The building’s energy storage ability partly depends on material selection. Buildings high in thermal mass absorb energy slower and hold it longer, which minimizes indoor temperature fluctuations and brings down heating and cooling costs. For thermal mass, engineers build with conventional products like stone and adobe or use more recent innovations incorporating phase-change materials.
Roof material and design influence heat loss and gain. Increasing reflection of solar heat and reducing absorption lessens the need for air conditioning. Attic and building cavity insulation impedes heat transfer. Incorporating roof gardens cuts down on absorption of heat and conserves rainfall. Roofs can also house or integrate on-site photovoltaic systems.
Using energy-efficient windows with glazing specifications can lower energy use 10-50% in residential construction and saves 10-40% on HVAC and lighting costs in commercial buildings. Fenestration design and material determines both energy transmission through skylights, windows and doors and air leakage around them.
Watch Dr. John Straube dive into the importance of airtightness and how it’s critical for maintaining a building’s performance in his latest webinar.
Dörken delivers innovative, high-performance air and moisture barriers for commercial and residential construction sold under the DELTA® brand name. A North American manufacturer based out of Beamsville, Ontario, Dörken Systems, Inc. is a subsidiary of Ewald Dörken AG, a leading European developer and manufacturer of waterproofing and drainage products sold worldwide. Dörken is known for delivering premium products while providing educational programs and full technical support. For more information, call 1-888-4DELTA4 (433-5824) or visit https://www.dorken.com/en/