Can I rely on the Heat Recovery Ventilation system to heat, or even cool, my house?
Heat Recovery Ventilation (HRV) only recovers heat from air leaving the house and pre-warms the incoming air. HRV, in its basic form, does not add any heat in winter or subtract any heat (cooling) in summer.
It is possible to bolt on heating/cooling mechanisms so that the air supplied is heated or cooled. These are usually finned coils similar to your car radiator, which either have hot/cold water or refrigerant gas passing through them.
What we need to be mindful of, when designing such systems is that the amount of heat which can be moved with the air is limited. We need to be careful to make sure this amount of heat is sufficient. One way to ensure this is to have the energy flows in the house modelled with varying levels of insulation, airtightness and thermal bridge mitigation. Your BER/EPC assessor will have the skills to do this.
That said, there are exciting new products coming on the market to deal with overheating through HRV so watch this space!