MVHR (Mechanical Ventilation with Heat Recovery) provides fresh filtered air into a building whilst retaining most of the energy that has already been used in heating the building. Heat Recovery Ventilation is the solution to the ventilation needs of energy efficient buildings. Mechanical ventilation with heat recovery (MVHR), heat recovery ventilation (HRV) or Comfort ventilation are all names for the same thing. A heat recovery ventilation system properly fitted into a house provides a constant supply of fresh filtered air, maintaining the air quality whilst being practically imperceptible.
AT WHAT LEVEL OF AIRTIGHTNESS IS MVHR
Although MVHR can be installed in any building, there is a rule of thumb that its use is not justified unless the air permeability of the thermal envelope is at or below 3 air changes per hour when tested at 50 Pascals. If this level of airtightness is not achieved, then the natural breathing of the building is such that alternative strategies to ventilation are more appropriate.
If your building has poor insulation/thermal bridging and or other damp ingress due to for example lack of proper damp proofing, then it can be tempting to look for technological solutions. In such a situation you will have problems with condensation and probably mildew where the condensation is forming. Yes, heat recovery ventilation can help reduce these symptoms; however, our advice would be to sort out the problem not cure the symptom.
THE IMPROTANCE OF A GOOD MVHR DESIGN
If you are intending to fit MVHR heat recovery ventilation into a new build or refurbishment then it should be considered from early in the planning stage. For any MVHR heat recovery ventilation system to give its best performance the devil is in the detail. System design will make the difference between a highly efficient system working un-noticed in the background and one that is constantly in the awareness of the inhabitants and wasting both heat and electrical energy. These systems necessarily require ducts to be run through the building and the routing is important both from the point of view of the building and the efficiency of the ventilation system. Indeed, layout of rooms can be influenced by ventilation needs.