The Impact of Emissions from Building Materials on Energy

Minimum ventilation rates for buildings are specified in building codes that typically reference ANSI/ASHRAE Standard 62.1 [17]. A portion, estimated to be around 40%, of the minimum ventilation rate is based upon the emissions from building materials and products into the indoor air. When emissions are reduced, indoor concentrations of contaminants are reduced, and human health, productivity, and performance are improved. Therefore, when emissions are reduced, outdoor air ventilation rates may be decreased with potentially significant energy savings. Since energy is required to move, heat, cool, and dehumidify the outdoor air that is used to ventilate buildings, a substantial amount of the total energy used nationally could be saved if low emission materials and products were adopted into building design and use.

The following is an overview on the relationship between building ventilation and the emissions from building materials. Standard 62.1 provides two procedures for determining outdoor air intake rates, described as follows:

Ventilation Rate Procedure. "This is a prescriptive procedure in which outdoor air intake rates are determined based on space type/application, occupancy level, and floor area. Note: The Ventilation Rate Procedure minimum rates are based on contaminant sources and source strengths that are typical for the listed space types" (Sect. 7.6.1.1).

IAQ Procedure. "This is a design procedure in which outdoor air intake rates and other system design parameters are based on an analysis of contaminant sources, contaminant concentration targets, and perceived acceptability targets. The IAQ Procedure allows credit to be taken for controls that remove contaminants (for example, air cleaning devices) or for other design techniques (for example, selection of materials with lower source strengths) that can be reliably demonstrated to result in indoor contaminant concentrations equal to or lower than those achieved using the Ventilation Rate Procedure..." (Sect. 7.6.1.2).

Outdoor air intake rates for new commercial buildings are usually determined using the Ventilation Rate Procedure. Outdoor air rates based on people-related pollutant sources and area-related sources are listed in ANSI/ASHRAE Standard 62.1. Outdoor air intake rates for area-related sources (the building and its materials) are converted to units of cubic feet per minute (cfm)/person using default occupant density values from the Standard. "People" and "area" outdoor air rates are added to determine the total outdoor air intake rate. The Ventilation Rate Procedure is a relatively simple method for determining outdoor air intake rates based on assumed pollutant emissions from people and materials in buildings, and is the chosen procedure for nearly 100% of building covered by the standard.

Outdoor air intake rates can be reduced through the use of the IAQ Procedure with the selection of building materials with lower emissions (contaminant source strengths), and energy savings can result. Potential nationwide energy savings are difficult to quantify due to a lack of data. Research is needed to quantify the potential savings, because limited existing data indicate that energy savings may be substantial. In applications where gas-phase filtering is an option, such as in typical offices or school classrooms, ventilation can typically be reduced from 20 cfm/ person to 5 cfm/person or 5% of supply air (whichever is greater). A case study [15] of a multiplex movie theater showed that the ventilation rate could be reduced from 20 cfm/person to 5 cfm/person through application of the IAQ Procedure by cleaning and recirculating air. Low-emission building materials could have a similar impact by removing indoor air pollutant sources. McDowell et al. [18] conducted a modeling study to estimate energy usage of 25 buildings representing the U.S. core office building stock. Decreasing ventilation from 20 cfm/person to 5 cfm/person decreased heating load by 17% and decreased cooling load by 6%. Decreasing ventilation from 20 cfm/person to 10 cfm/person decreased heating load by 9% and decreased cooling load by 4.5%. For all energy used in commercial buildings, space heating accounts for approximately 34% and cooling accounts for about 15% [6]. Assuming that, for commercial buildings, the average outdoor air intake rate could be reduced from 20 cfm/person to 5 cfm/person through low-emission building materials, total commercial building energy savings is calculated as follows

Commercial buildings consume approximately 18% of all U.S. energy, so savings of total U.S. energy could be as much as 1.2%, although there is much uncertainty in this estimate. Turnover time of the building stock is relatively long, so it would take many years to realize the full potential savings, but the average time for renovation of buildings is relatively short, so potential savings can start immediately.

Most residential buildings in the U.S. are ventilated with air that leaks through the building shell by design. However, new residential construction practices, especially in colder climates, are changing to provide tighter building shells and, in some cases, controlled mechanical ventilation. As new residential buildings become more like commercial buildings with controlled ventilation, low-emission building materials can provide potential long-term energy savings similar to the projected savings for commercial buildings.

In addition to building materials, human activities and many products used inside buildings affect indoor air quality. Human activities include cleaning, cooking, personal care, hobbies, crafts, etc. Products include cleaners, personal care chemicals, office equipment, solvents, adhesives, coatings, etc. When indoor air contamination is reduced by use of lower emitting products, less ventilation air is required, and energy savings results.

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