Performance Criteria

Health and comfort

The rationale for the definition of essential requirements for health, and therefore for indoor environmental quality, include parameters that are related to IAQ, thermal, lighting and acoustics

A standardised definition of IAQ is not available. Based on the definitions of WHO[10], [11] for the purpose of this project indoor environment can be defined as healthy when the complex of its physical, chemical and biological properties are such that :

• they do not to cause or aggravate any illnesses in the building occupants;
• they secure a high level of comfort to the building occupants in the performance of the designated activities for which the building has been intended and designed.

Health and comfort performance criteria for buildings have been defined taking into consideration a set of measurable parameters related to indoor air pollutants and to physical characteristics of the indoor environment (Maroni et al. 2003). Compliance with these criteria is expected to assure, with a high degree of confidence, the provision of acceptable performance of buildings and zones within them.

Target values of the selected pollutants have been set taking as reference the WHO air quality guidelines, when available, or exposure limits adopted by other Agencies or suggested in the literature. For each parameter or pollutant, two levels of target have been defined: BASIC and OPTIMAL. The BASIC target is intended to define the minimum acceptable condition, i.e., at least 80% of the population satisfied for comfort parameters and no effect level value for health risk factors. The OPTIMAL target instead represents a condition of excellent quality, in the context of current building design, operation and management, i.e., > 80% of the population satisfied for comfort parameters and a further reduced value for health risk factors to account for uncertainty and human inter-individual variation.

Setting target values is questionable for some health risk factors such as radon, benzene and asbestos, that are carcinogenic substances. Although the ALARA-principle (As Low As Reasonably Achievable) is recommended for carcinogens (WHO, 2001), we have adopted a pragmatic approach by identifying "reasonable" levels endorsed by international agencies or determined by the outdoor air context of the building.

The building symptom index (BSI) for perceived health is the mean number of acute health symptoms experienced by occupants that were believed to be building-related, and is a well-established metric. Symptoms included in the questionnaire are: . dry eyes, . itching or watering eyes, . blocked or stuffy nose, . runny nose, . dry throat, . headache, . tiredness or lethargy, . flu-like symptoms, . difficulty breathing, . chest tightness.

The health and comfort hazards assessed through the checklist have been classified into three classes, based on the severity of their expected/possible health outcome:

• Class 1 - Hazards that increase the risk of causing death or an illness with a high probability of being fatal (e.g. lung cancer). This class includes: asbestos, radon, carcinogenic volatile organic compounds (VOCs), Environmental Tobacco Smoke (ETS) and high carbon monoxide concentrations.
• Class 2 - Hazards that increase the risk of causing systemic illness (principally respiratory illnesses). This class includes: ozone, nitrogen oxide, particulate matter, infectious agents (from the building or from occupants), house dust mites (only for residential buildings), fungi, other allergens, non-carcinogenic VOCs, CO at low concentrations.
• Class 3 - Hazards that increase the risk of minor diseases or causing discomfort. This class includes: noise, lighting, too hot, to cold.

Building classification as to health and comfort. Combining the results of the building health hazards assessment and the results of the questionnaire, three categories have been identified to classify buildings: healthy building, uncertain healthy building and unhealthy building:

CATEGORY 1- HEALTHY BUILDING
A building or an area within it is considered healthy if it complies with all the performance parameters, i.e. no health hazards are present nor significant complaints about the air quality and the environment are detected. Category 1 implies that no further diagnostics is needed to assure that healthy and comfortable environmental conditions are being provided.

CATEGORY 2 - UNCERTAINLY HEALTHY BUILDING
A building or an area within it is considered uncertainly healthy if further diagnostics should be considered before assuring that health hazards do not exceed the target values, while no excessive frequency of complaints about the air quality and the environment is detected.

CATEGORY 3 - UNHEALTHY BUILDING
A building or an area within it is considered unhealthy if health risk factors are definitely present or an excessive frequency of complaints about the air quality and the environment is detected. Category 3 implies that further diagnostics is recommended to confirm the extent of the problems, to determine their causes, and to identify interventions to eliminate or mitigate them.

Energy efficiency can be defined in various ways. The physical one is the ratio of the useful energy to the used energy. This defines the efficiency of the system transforming the final energy (e.g., oil, electricity, gas) into useful energy (e.g., heat, light, etc.). This definition may lead to wrong conclusions when looking to buildings. For example, a very poor building equipped with a very efficient boiler or heat pump may show a good system efficiency, but still host dissatisfied inhabitants. It is therefore very important to distinguish between building energy efficiency and system efficiency. One objective of design, building and operating a building is to minimize the energy consumed without compromising the occupant exposure. Also, the building as a system should operate to achieve minimum life-cycle costs, including the cost of salaries. This criterion adds occupant performance and system productivity to the life-cycle cost models that otherwise tend to minimise for energy consumption. An effective way to assess the energy efficiency of a building is by comparison with other buildings on a local scale as well as on a global scale. This means that the energy values related to the specific building being analysed are compared and ranked with the local best energy usage (e.g., best 10% of the buildings with the lowest energy index) achieved in similar buildings locally (i.e., regional/national scale). Further, these values could be assessed in relation to usages achieved in other regional contexts.

If building of various sizes should be compared, it is useful to use an index, relating the energy use to some building dimension. This dimension could be its volume, its envelope area, its population, or its heated floor area. It is proposed to use the latter one, because it is already of wide use and is easier to assess from the blueprints or on site as any other one. An energy index is then defined as:

The gross heated area, Ah, is defined as the area of all heated floors, including walls (i.e. measured with the external dimensions of the building) but excluding unheated zones such as garages, cellars or unoccupied attics. Correction factors can be applied for partially heated zones or large floor-to-ceiling heights.

This allows to determine the total energy index, I t, , the heating index, I h, and the electricity index, I e