Achieving good indoor air quality without excessive energy use
July 18th 2006

The new Building Regulations 2006 enforceventilation (Part F) and conservation offuel and power (Part L). The ApprovedDocuments that support theseregulations are:Approved Document F: Means of VentilationApproved Document L1A: Conservation of fuel andpower in new dwellingsApproved Document L1B: Conservation of fuel andpower in existing dwellingsApproved Document L2A: Conservation of fuel andpower in new buildings other than dwellingsApproved Document L2B: Conservation of fuel andpower in existing buildings other than dwelling.

These can be purchased from RIBA publications(www.ribabookshops.com) or downloaded for freefrom the ODPM website (www.odpm.gov.uk).

The main thinking behind these changes is to reducethe energy consumption of buildings while ensuringsufficient ventilation is provided. Approved DocumentF is all about ensuring healthy indoor environments byreducing the levels of pollutants and mould growth,whereas the Part L Approved Documents are all aboutreducing energy consumption. An overview of thesetwo documents follows.

Approved Document F

For dwellings and offices, Approved Document F 2006gives three ways of complying with the newregulations:

1. Specified Ventilation Rates This is a performancebasedmethod based on specified supply and extractrates for different rooms. A fresh air supply rate of10L/s/person to office areas is specified. The 2002Approved Document specified a rate of 8L/s/person,but many designers have been specifying higher freshair ventilation rates for some time.

2. System Guidance This is a prescriptive method thatgives guidance for natural and mechanical ventilationsystems. Either way, similar ventilation rates apply as forthe performance-based method outlined above. Someof this guidance is contained within the ApprovedDocument, for example on controls and locations ofventilators. Second tier documents are relied on forfurther guidance, including:

• CIBSE AM13: Mixed Mode Ventilation
• CIBSE AM10: Natural Ventilation
• CIBSE Guides A and B2

3. Performance Criteria This is also a performancebasedmethod. It details limits for pollutants such asNitrogen dioxide, Carbon monoxide and VolatileOrganic Compounds. There is little guidance on howthese criteria can be met but all of them can bemeasured in some way. The measured levels of thepollutants listed above can be compared against theWorkplace Exposure Limits (WEL) detailed in EH40 2005produced by the HSE. These parameters are all keyindicators of air quality.

Approved Documents L1A, L1B, L2A and L2B

A brief overview of the changes to the Part L ApprovedDocuments is as follows:

• Annual CO2 emissions must be predicted usingapproved calculation methods. These calculationstake into account the measured airtightness, andmust be carried out by registered competentpersons,
• Predicted emissions must meet a target, which is 20to 28% better than the emissions for a building thatpassed the 2002 regulations.
• Dedicated Approved Documents have beenproduced for work in existing buildings, outliningreasonable provision for a variety of situations.
• When extension to large non-domestic buildings arebuilt, improvements have to be made to the energyefficiency of the existing building.

Airtightness

As airtightness testing will no longer be optional, allenvelope elements must be designed for airtightness,and construction quality must match the designer'sspecification (visit www.bsria.co.uk/airtightness formore information).

Achieving good Indoor Air Quality (IAQ) is an importantissue. Office IAQ is particularly important as theworkforce is a company's biggest asset and keepingthem comfortable in their work environment isbeneficial to all concerned. Improved airtightnessmeans that designers can no longer rely on "accidentalventilation" to achieve good IAQ. Building ventilationrates can only be accurately predicted if the airtightnessof the building envelope is known.

Leaky buildings lose more conditioned air due toinfiltration and so require more energy to maintain theinternal environment. Improved airtightness shouldresult in reduced CO2 emissions from buildings.

Multidisciplinary Teams

The design of all building services systems and also thebuilding envelope has an impact on CO2 emissions, soeverybody involved in the design needs to bedesigning with energy efficiency in mind. Thetightened targets give the message that energyefficiency can no longer be an afterthought, and needsto be considered at every step. A multidisciplinary teamneeds to be assembled at an early stage in the designprocess and CO2 emissions calculations also need to becarried out from the outset.

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