Yes. The Building Research Establishment in the UK has published an experimental study showing energy savings achievable with improved airtightness [1,2].

[1] R. Coxon, “Research into the effect of improving airtightness in a typical UK dwelling,” The REHVA European HVAC Journal-Special issue on airtightness, vol. 50, no. 1, pp. 24-27, 2013.

[2] D. Butler and A. Perry, “Co-heating Tests on BRE Test Houses Before and After Remedial Air Sealing,” Building Research Establishment.