Whilst great strides are being made in upgrading energy performance requirements under Part L of the Building Regulations, the issue of ventilation has remained largely ignored by legislators for years, leaving designers with antiquated standards to work to. At its worst, efforts to air-tighten and increase the insulation of homes is being undermined by the absurd practice of knocking holes in walls. John Hearne looks into what changes need to be made to modernise Part F.