[en] The effect of QCD loop corrections to the weak interactions of hadrons is studied in a non-perturbative framework in which the matrix elements of the bare effective weak Hamiltonian between hadronic states are computed. The QCD renormalisation is carried out in the static cavity alleviating the scale matching problem of the standard short distance analysis. Specifically, the ΔI=1/2 rule was studied by computing the QCD corrected K-π matrix elements. The modified static cavity model used is characterised by four parameters; the effective quark-gluon coupling constant, the confinement pressure, the zero-point energy and a parameter governing the centre-of-mass corrections. These parameters are fitted to the π and ρ masses and the charge radii of π and K. Results are given for the ultra-relativistic (m_u=m_d=O) sector and for a region (m_u=m_d∼140 MeV) where the ΔI=1/2 rule is uniquely reproduced. 17 refs., 19 figs., tabs