A significant amount of heat can be lost from your home, from warm air escaping through cracks and gaps in the construction. This can also lead to draughts which can reduce your perceived level of comfort. A fresh supply of air is required for good indoor air quality, however this should be provided through a PAS2035-compliant whole home ventilation strategy. Any uncontrolled 'leaks' should be sealed by an airtightness champion to reduce infiltration.