H/ERV Selection guidelines

 
RENOVATION SCENARIO:
The requirements (airflow rates, capacity, control features) will differ according to your installation, your dwelling characteristics and local building code. These guidelines are applicable for most of the residential dwelling type and within most of the location in Canada; in case of conflict between the following guidelines and your local building code requirements, the latter shall prevail.
 

1.  Maximum airflow capacity:

​ The ventilation requirements will differ according to your installation and local building code requirements, but the following rules are applicable most of the time:

• A Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV) could be used to provide exhaust ventilation capacity to any of your bathroom or water closet room in lieu of a typical bathroom exhaust fan and provide the following advantages:
  • Your bathroom and/or water closet room will be kept in slight negative pressure 24/7, odors and pollutant will be exhausted continuously and their propagation through the house will be significantly limited.
  • In the wintertime, when the ambient relative humidity is very low, an ERV will transfer some of the moisture from the exhausted air back into the house to prevent over-drying the air. 
• Provided that your dwelling layout allow you to run ducts from your bathrooms to the H/ERV installation location, you need to account for at least a 50 cfm (24 L/s) exhaust capacity for each bathroom that will be ducted through your H/ERV.
  • Example: 3 bathrooms ducted through H/ERV will require at least 150 cfm maximum airflow capacity (3 x 50 cfm = 150 cfm)     
• If your dwelling layout doesn’t allow you to duct the H/ERV exhaust grilles to your bathrooms or water closet rooms, we recommend selecting the maximum airflow required according to your number of habitable rooms, count 20 cfm for the master bedroom and 10 cfm for every other room. 
• Always remember that these recommendations are providing minimum target values to maintain an acceptable indoor air quality. Selecting an H/ERV with higher airflow capacity is usually an advantage as it provide more flexibility to deal with different situations. Oversizing airflow capacity should also be considered under some circumstances such as the presence of sensitive occupant(s) (respiratory problems, heart, or lung disease) or occupancy rates higher than average households.

 

2. Heat Recovery Ventilator (HRV) vs Energy Recovery Ventilator (ERV):

Both HRV or ERV recover heat from the stale air exhausted from the dwelling and transfer that heat to warm up the incoming fresh air in the winter and shoulder seasons or temper the air in the cooling season. Hence either one or the other will provide significant energy savings compared to a ventilation system without heat recovery such as an exhaust fan, a fresh air intake ducted through your forced air furnace or even the opening of a window.
 
An HRV will generate condensate water in the shoulder seasons and the winter as the humidity from the exhausted stale air condense to the contact with the cold surfaces of the heat recovery core exposed to the cooler outdoor fresh air being brought into the house. Hence, an HRV shall be installed with a drain tube (provided) that is either routed through a plumbing drain nearby or into a pail that will have to be emptied manually.
An ERV will not require a drain tube (except for extremely cold location combined with high occupancy rates), hence, you do not have to worry about finding a location with an access to a plumbing drain or reminding to frequently empty the pail that collects the water. An ERV provides an enhanced comfort compared to an HRV as it will also transfer the moisture from one airstream to the other. The engineered membrane used within an energy recovery core allow water to be transmitted through the membrane but blocks other undesired gaseous pollutants from being transferred. As a result, the ERV will smooth the extremes low and high relative humidity throughout the year and contribute to maintain it within the optimal 30 – 55% RH range.

 

3. Sensible Recovery Efficiency (SRE):

There’s a range of sensible recovery efficiency offered in the marketplace from the most affordable at around 60% up to the 80%+ high efficiency models. A simple rule is the higher the better: the higher the SRE, the more energy you recover from your exhausted stale air and transfer to the outdoor fresh air stream to temper it before it is brought inside your house, which maximize your comfort and energy savings. However, this doesn’t mean that the lower tier models with a rating of 65% SRE shouldn’t be considered, these models do recovery 2/3 of the exhausted stale air energy which is way better than any exhaust fan or window which recover 0%...   
See our H/ERV models

 

4. Filtration:

All HRV or ERV include standard filters to protect the heat or energy recovery component from being clogged with large particles which would hinder the airflow and the recovery efficiency. These filters usually capture the bugs, pollens, grass, and large duct particles before being brought inside your house.
 
Most manufacturers offer optional filters with the capacity to capture a higher percentage of the smaller particles from the outdoor fresh air intake before being brought inside the house. Such optional filters should be considered for specific conditions such as:

• Areas where frequent environmental events affect the outdoor air quality and generate a high concentration of small particles.
• The presence of sensitive occupant(s) with respiratory problems, heart, or lung disease, especially the elderly or newborns.

See our optional filters
 
According to Statistics Canada, 71% of the population lived in areas of Canada where outdoor concentrations of air pollutants are within the 2020 Canadian Air Ambient Quality Standards (CAAQS). Hence, bringing outdoor air without supplemental filtration is acceptable for most of the locations.

 

5. Wall Controls:

There are many control options offered on the market and it could become confusing at some point for the average consumer to select which is the best option for his situation.
 
There are two main categories of ERV or HRV controls:
Basic controls:

• Controls that either offer a manual choice of ventilation speed or a threshold activation based on measurement such as indoor relative humidity without supplemental flexibility or adjustment.

Premium controls:

• Controls that offer the basic features and supplemental functions that will adjust the ventilation mode automatically according to several factors such as: indoor temperature and RH%, outdoor RH%, etc.              

The most important word is ‘’automatically’’, if, as a user, you will reach out to your HRV or ERV control to adjust the ventilation mode or RH% set point according to events that affect your indoor air quality (temporary higher occupancy rates, season change, etc.), then you will manage to maximize the outcome from your HRV or ERV. If not, then we would recommend selecting a premium control and use the automatic mode which takes care of such tasks, and it is the equivalent of a ‘’set it and forget it” approach.

See our wall controls

Finally,  
According to EPA, the concentration of some pollutants in your home are often 2 to 5 times higher than typical outdoor concentrations. An ERV or HRV will contribute to lowering such pollutant concentration within your house by exhausting the stale air and at the same time bringing fresh and tempered outdoor air with lower pollutant concentration. If your H/ERV is only used 20% of the time through the year because the model and or control installed doesn’t suit your needs or isn’t user-friendly, you will only get a subset of the health benefit you should get from this system… Choose wisely.