New construction homes usually have great insulation, with tight windows, proper doors and efficient vapor barriers that all meet today’s high efficiency standards. While all of this has meant that today’s homes have much better home insulation than in the past, it also means they may run the risk of being too airtight, restricting your home ventilation.
The issue that arises if your home is too airtight is that moisture cannot ventilate to the outside and the general air movement in your home from outside to inside is poor. In older homes, this was never a problem as construction materials and installation were never as highly insulating as they are in today’s energy efficient homes.
With airflow becoming an increasingly important concept to attain in new construction homes, heat recovery ventilators (HRVs) have become a popular device for ensuring the proper movement of air from outside to inside.
What is a heat recovery ventilator?
A heat recovery ventilator is a mechanical device installed onto your existing furnace ductwork that swaps stale indoor air for fresh outdoor air and spreads it around the house. The incoming and outgoing air never mix directly inside the HRV as they simply pass inside the separate channels of the ventilator and undergo a heat exchange process by conduction.
HRV units have two fans: one to push stale air outwards and one to bring fresh air inside. Two exterior vents are used in the process as well, one to exhaust the stale air and one to bring in the fresh air.
While opening a window may seem like a simpler solution to providing fresh air for a home, this is not an energy efficient solution as your furnace will need to heat the fresh cool air in the winter or your air conditioner will need to cool the incoming hot air during the summer. HRVs allow incoming air to be heated or cooled in a more efficient manner as they steal some energy from the expelled air as it leaves through the ventilator.
HRVs also contain filters, so no need to worry about dust and particles that may be entering the home from the outdoor air.
HRVs in winter
During the winter, HRVs use the heat from the outgoing air to warm up the incoming cool air. The heat exchange core of the HRV is the most important part of the device as it transfers heat from the outgoing air to the incoming air, therefore conserving energy and eliminating the need to completely heat the incoming cool air once it arrives inside. This elegant solution allows an HRV to provide fresh indoor air during the winter in an efficient and controlled manner.
HRVs also help with high indoor humidity levels and condensation on your windows in the winter. Since condensation forms from warm indoor air meeting cold surfaces (i.e. the glass on your windows), HRVs help by expelling the excess warm, moist indoor air and bringing in drier, fresh air in a balanced fashion.
HRVs in summer
During the summer months, an HRV will take heat from the incoming fresh outdoor air and transfer it to the outgoing cold air, thereby reducing the temperature of the incoming hot air and making it easier to cool.
Note that the incoming warm air will contain moisture in the summer and usually will raise the humidity level in your home. This shouldn’t be a problem if the HRV unit is properly balanced and continuously running. That means you should never turn off your HRV as they constantly maintain the balance of airflow inside your home. This balance is critical to avoid condensation in the home or the over exhausting of indoor air. As such, it is usually best to have a professional install the HRV to ensure the right balance of airflow from outside to inside is achieved and the right levels are set from the start.