Air Change in Low and High-Rise Apartments

Yonghang Lai,Ian A Ridley,Peter Brimblecombe

doi:10.3390/urbansci4020025

Yonghang Lai, Ian A Ridley + Show 1 more

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https://doi.org/10.3390/urbansci4020025

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Abstract

Air exchange in tall apartment buildings is critical in controlling indoor environments in urban settings. Airtightness is relevant to energy efficiency, thermal comfort and air quality experienced by urban dwellers who spend much of their time indoors. While many air change measurements have been made in residential homes, fewer are available for high-rise apartments. The blower-door and CO2 exchange methods were used to measure air change in some Hong Kong apartment buildings, for comparison with those from other parts of the world. Hong Kong apartments are often small and typical rented apartments show a median of seven air changes per hour under a 50 Pa pressure difference, similar to Mediterranean houses, though much greater than the airtight buildings of Northern Europe. Extrapolation of blower-door measurements made at 50 Pa to the natural pressure difference measured for individual Hong Kong apartments provides an approximation (within 8%) of the natural air change rate measured with a tracer. Air flow is a function of the pressure difference ∆Pnf and the exponent n was found close to the typical 0.6. There was a positive relationship between air permeability and construction age, but some of this also seems to reflect varying levels of maintenance by the building management companies. The median exchange in the apartments under naturally ventilated conditions was 0.26 h−1, not atypical of some houses on the US West Coast.

Highlights

Tall apartment buildings are increasingly a characteristic of high-density urban living and represent an environment where those dwelling in cities may spend a great deal of time
This is expressed as the number of air changes per hour (ACH), it is affected by factors such as the design of the building and occupant behavior, weather variation and building ventilation mode
In this paper we explore the air change rate in some Hong Kong apartments and compare these with other cities, aiming to establish a context for our measurements in apartment buildings and their relevance to regulating the built environment

Summary

Introduction

Tall apartment buildings are increasingly a characteristic of high-density urban living and represent an environment where those dwelling in cities may spend a great deal of time. The exchange of air is often expressed as the air change rate, i.e., the rate at which air is replaced. This is expressed as the number of air changes per hour (ACH), it is affected by factors such as the design of the building and occupant behavior, weather variation and building ventilation mode. There are three main ventilation modes [1]: (i) mechanical ventilation, (ii) natural ventilation driven wind or buoyancy-induced flow through open windows or doors, and (iii) infiltration through gaps and cracks in the building envelope. Infiltration cannot be controlled, as it represents the ventilation mode when all windows and doors are closed

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