Hi all

This one crops up from time to time when dealing with planning applications.  

Imagine an existing building in commercial use within the boundary of an AQMA, and as it is 1.5m from the kerbside levels of NO2 are known to be above the objective at the facade.  An application is submitted to convert the commercial use to residential (in my example a 12 bed HMO), thereby introducing new receptors into the AQMA.

As we know the thrust of planning policy os to (wherever possible) approve and condition rather than refuse;

The applicant submitted an Air Quality Impact Assessment (AQIA) together with a Noise Impact Assessment (NIA).

Unsurprisingly the AQIA recommends mitigation in the form of whole house ventilation with intake air taken from the rear or the roof of the premises (thereby providing "clean" air to the occupants.  The NIA (again unsurprisingly) recommends upgraded acoustic glazing on the facade facing the road, together with whole house ventilation.

The question is, do I allow opening windows, or required sealed glazing on the facade facing the road?

In my scenario (and many other small-scale multi-apartment conversions) the floor layout means that if the glazing is sealed on those facades, there would be no openable windows in those rooms (living rooms and bedrooms).

I am minded to allow openable glazing (well fitted with no gaps etc) with the following thinking, and I wondered if there were any other views/experiences out there?

- The ventilation system will include "boost", so occupants would only open windows by choice, or for purge/summer cooling, as such the times when windows need to be open is reduced ergo exposure to NO2 is reduced?

- This is Manchester, and the times when Summer cooling is required equates to hours per year!!

- Opening windows at night in bedrooms (when traffic levels are significantly reduced) would be unlikely to expose residents to levels of NO2 above the objective.

- Draft guidelines from the ANC (Acoustics Ventilation and Overheating) suggest sealed unit glazing (especially where there will be no other openable windows) should be an option of last resort.

Discuss :) 

Phil Mason MSc, MIEnvSc, MCIEH, AMIOA
Environmental Consultant (Air Quality, Noise, Contaminated Land) – Infrastructure
Urban Vision Partnership Ltd

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