14 Ventilation

Communal ventilation system - KBCN1388

A communal ventilation system is acceptable as long as it meets the requirements in the HQM manual. In terms of maintenance, if it is not possible for the home occupants to carry out system maintenance themselves due to the type of system installed we would need a statement from the professional designing the system stating this. Instead, any specified ventilation system requiring maintenance must be designed to allow building services engineers to easily complete the work in a safe manner in accordance with manufacturer’s instructions and any other safety regulations, to prevent systems becoming redundant or being unable to function to their designed intention.

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Ventilation air intakes CIBSE TM21 compliance - KBCN0669

As TM21 largely contains general guidance, rather that strict rules, it is expected that the designer or services engineer would be familiar with the requirements within TM21 and be able to determine which sections are relevant for the development in question. The main areas to consider in relation to TM21 are: • Provision of filtration • Positioning inlets to minimise impacts of traffic pollution • Positioning inlets to minimise impacts of other local sources of pollution • Positioning inlets to minimise recirculation from ventilation exhausts Confirmation is required that each of these items (and anything else the designer/engineer deems relevant) has been considered in determining the location of air intakes. Suitable evidence may for example be in the form of a short report with diagrams indicating the proposed location of intakes, with respect to sources of pollution and with reference to the relevant parts of TM21.

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Ventilation controls - KBCN0932

To meet the requirements of crit 9, CO₂ levels (monitored via sensors in bed and living rooms) can be used as a proxy for occupancy levels within a home. The increase in ventilation rates above the minimum set out in Approved Document F should be proportional to the rise in occupancy above that set out in Approved Document F. Relative humidity sensors can be used to trigger a 'boost' mode in wet rooms.  

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Ventilation rates criteria for MVHR - KBCN0924

The ventilation rates provided  in Approved Document F 2010 are explicitly stated as being the ‘minimum’. 25% as a boost should be factored in as a matter of good design. If systems are so critically sized that an increase of 25% requires larger MVHRs, and larger ducts then this suggests there was no flexibility in the original design/sizing and AD-F was deemed to be the target ventilation rate. Correct sizing of systems is  especially critical for flats where we have the worst problems of under ventilation and where making changes retrospectively may be costly. MVHRs should not be operating above 50% fan speed in background mode, so the ability to achieve boost should always be present, regardless of dwelling type.

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