Page 40 - Domestic Smoke Nuisance and Emissions Final_Neat

Summary 2: Pressure Systems within Pressure Systems

• Summary

• wind flowing over the top of a chimney can produce a driving pressure, increasing draft

• wind may also create adverse pressures at the top of a chimney because of its direction of flow or turbulence created as it flows over nearby

obstacles, or when the top of the chimney is in a positive pressure zone

• wind pressure induces air flow through leaks in the building envelope

• wind causes pressure changes inside a building which in turn changes the position of the neutral pressure plane

• wind is an unreliable source of draft because it is highly variable and may be driving or adverse to chimney venting

• specialised chimney caps may reduce the effects of adverse winds, but are sometimes used in error as a cure-all for troubled venting systems

• the best defence against wind-induced failure is good system design

Welcome to the Next Level CST. CITB-SDC 2020