High CO2 emissions from the residential sector have forced UK authorities to promote measures to improve energy efficiency through retrofit. Air-tightening can reduce infiltration rates, thereby decreasing ventilation heat losses, but also reducing indoor air quality. This paper presents an initial investigation of the increase in airborne transmission risk of Tuberculosis (TB) due to air-tightening in two of the most commonly-occurring dwelling types in London (purpose-built flat and terraced). EnergyPlus is used to calculate the ventilation rate of the main bedroom over a year for a range of building permeabilities representing the current and air-tightened stock. The Wells-Riley equation is then used to calculate the risk of infection under three different rates of TB generation. Results indicate the potential for increased airborne TB transmission between building occupants following air-tightening, with occupants of flats more susceptible to infection, particularly at high TB generation rates.