Mechanical Ventilation with Heat Recovery

System 4 - MVHR

System 4

Mechanical Ventilation with Heat Recovery (MVHR) is covered under System 4 of the Building Regulations, Part F. Heat Recovery ventilation provides fresh, filtered air, energy efficiency and a comfortable all year round climate. Stale, moist air is extracted out of the wet rooms of a home.

These include the kitchen, bathrooms, utility and en-suite rooms. MVHR systems should always provide the minimum whole building ventilation rate, which can be calculated using the same steps as above. The required airflow rates are as follows:

  • The maximum whole dwelling extract ventilation rate (i.e. the boost rate) should be at least the greater of Step 1 and Step 2.
  • The maximum individual room extract rates should be at least those given in Table 5.1a for ‘minimum high rate’.
  • The minimum whole dwelling supply ventilation rate should be at least the whole dwelling ventilation rate found in Step 1.

Table 5.1a - Extract Ventilation Rates

Background ventilators are not required with System 4.

System 4 - Ventilation Solutions:


The IDEO provides a constant supply of fresh tempered air into the living spaces of a home whilst extracting condensation, smells and smoke from kitchens, bathrooms and toilets.

enegiSava 250energiSava 280

Achieving exceptional thermal efficiency, the unit is designed for houses or apartments with kitchen and up to seven additional extract rooms.

energiSava 380energiSava 380

Recovering up to 93% of heat, the energiSava 380 reduces carbon emissions whilst providing continuous,all year round good indoor air quality. This system also performs to the highest efficiency on SAP Appendix Q.