Indoor environmental quality assessment models: A literature review and a proposed weighting and classification scheme

Highlights

• Literature concerning indoor environmental quality (IEQ) models is reviewed.

• Tools and methods for IEQ physical measurements are reviewed.

• IEQ categories are discussed.

• An IEQ weighting and classification scheme is proposed.

Abstract

This paper explores the existing literature on indoor environmental quality (IEQ) evaluation models and proposes a new weighting and classification scheme. Studies that attempt to provide IEQ assessment of commercial buildings through a scoring system are reviewed and critiqued. Objective and subjective evaluation methods and correlations are discussed. The use of assessment categories (classes) in IEQ models is critiqued and an argument is proposed against their adoption. IEQ weighting schemes are summarized and compared against a newly developed scheme based on 52,980 occupant responses in office buildings. A binary assessment classification scheme is proposed in alignment with the ASHRAE/CIBSE/USGBC Performance Measurement Protocols for Commercial Buildings.

Introduction

The indoor environmental quality (IEQ) performance of buildings affects the health, productivity and well-being of building occupants, as well as lifecycle costs, and energy consumption. Poor indoor air quality (IAQ) is related to sick-building-syndrome (SBS) [1], [2], [3], and high IEQ is associated with company and employee productivity gains and employee retention though this area of research is contentious and in need of additional studies [1], [4], [5], [6], [7]. In commercial buildings, green building advocates and indoor environmental quality researchers argue that occupants represent the largest share of the operational costs of a building, which suggests that high IEQ could have economic benefits [8], [9], [10], [11]. IEQ parameters have a strong influence over energy consumption, both through design related decisions and in the operation of the building [12], [13]. Therefore it is important to evaluate IEQ performance at a whole-building level in order to ensure high IEQ as efficiency measures are ratcheted up in the face of more stringent energy regulations. According to ASHRAE TC 1.6 (Terminology) Indoor Environmental Quality is a perceived indoor experience about the building indoor environment that includes aspects of design, analysis, and operation of energy efficient, healthy, and comfortable buildings. Fields of specialization include architecture, HVAC design, thermal comfort, indoor air quality (IAQ), lighting, acoustics, and control systems.

We found eight studies that have proposed methods for evaluating indoor environmental quality in commercial buildings using a scoring/rating system [14], [15], [16], [17], [18], [19], [20], [21], [22]. The method used for selecting these papers is discussed in Section 2. While many of the methods presented in these studies overlap, there are important differences that highlight multiple issues with such scoring systems. While Frontczak and Wargocki [23] discussed the comfort-related conclusions of many of these studies, there has not been a literature review conducted on the specifics of these IEQ model scoring systems. The literature on this subject uses many different terms to describe a similar goal, including IEQ model, IEQ index, rating system, and scoring system. While there are subtle differences in these terms that will be discussed in this paper, the most general term “IEQ model” is used here to refer to any system that takes IEQ performance data and produces an evaluative numerical summary of the data.

IEQ models require aggregating data to provide a summary picture of how well a space or building is performing. These summary evaluations may be completed using objective physical measurements (e.g., measurement of noise level, air temperature, illuminance, etc.), subjective occupant surveys (e.g., how satisfied are you with the noise level in your workstation?) or both. The purpose of an IEQ model is to distill the data contained in these objective and subjective measurements into a rating or score. The accuracy, relevance and applicability of such scoring systems depend heavily on the quality of the objective and subjective assessment data that is collected. Therefore, before diving into IEQ models that use this data, this paper will briefly review the current state of subjective and objective measurement methods.

The aim of this paper is to provide: (1) an overview of subjective and objective IEQ evaluation methods and tools, (2) a literature review of IEQ models, (3) a discussion of the weaknesses of IEQ models and assessment class schemes, and (4) a proposal for a new weighting and assessment class scheme.