The main objective of building services engineers and anyone involved in designing a built environment is to create a space conducive to the function of the building. Too often this gets lost in the plethora of other requirements; regulatory, economic and aesthetic. At BSRIA we see specifications in which the design parameters are not clearly defined and this frequently leads to gaps between expectation and performance and doubts about whether the completed building meets the client’s requirements. Some specifications indicate winter or summer temperatures, with no mention of tolerances or where the temperatures must be measured.
There are hundreds of useful standards, guides and codes of practice to every aspect of the built environment and of course, BSRIA contributes to this array of publications. But some buildings don’t warrant all the detail from these publications and a basic specification is better than no specification.
One new Standard aims to bring together the key requirements for Indoor Environmental Quality (IEQ).
BS ISO 177721 specifies requirements for indoor environmental parameters: temperature, indoor air quality, lighting and acoustics and specifies how to establish these parameters for environmental design. It was drafted to provide a common basis for energy performance calculations but it has wider application as a basic standard for IEQ.
This standard is applicable where the criteria for indoor environment are set for human occupancy and where the production or process does not have a major impact on indoor environment. It includes design criteria for the local thermal comfort factors, draught, radiant temperature asymmetry, vertical air temperature differences and floor surface temperature. It also specifies occupancy schedules to be used in standard energy calculations and how different categories of criteria for the indoor environment can be used.
The criteria in this standard can also be used in national energy calculation methods. It sets criteria for the indoor environment based on existing standards and reports.
It does not specify design methods, but gives input parameters to the design of building envelope, heating, cooling, ventilation and lighting.
The standard defines four levels of IEQ:
- IEQi High level of expectation and also recommended for spaces occupied by very sensitive and fragile persons with special requirements likesome disabilities, sick, very young children and elderly persons, to increase accessibility.
- IEQii Normal level of expectation.
- IEQiii An acceptable, moderate level of expectation.
- IEQiv Low level of expectation. This category should only be accepted for a limited part of the year.
The format of the standard is that the user should define the level of performance required for each parameter, to this end it provides forms to be completed by the user in Annexes A to F. However, in Annexes H to L it provides ‘default values’ for the parameters entered on the same forms and these are likely to be widely used.
Temperature is specified as the ‘Operative temperature’ effectively the mean of air temperature and radiant temperature at the building user’s location in most environments, where the air speed is under 0.2 m/s. Adaptive temperature, the user-acceptable temperature modified by the external temperature over the past seven days, is also recognised as relevant for spaces without mechanical cooling.
1 BS ISO 17772-1:2017, “Energy performance of buildings. Indoor environmental quality. Indoor environmental input parameters for the design and assessment of energy performance of buildings” is available to loan for members from the BSRIA Information Centre.