Choosing an HRV...My Thoughts....

So, which HRV do you want for your home?  This is a question not often asked by the homeowner.  When the house is built, somebody installed an HRV and that was it.  The home owner is rarely involved in anything other than turning a knob on the HRV wall control if they dare fool with it at all.  An HRV is probably one of the most important appliances in your house;  it expels moisture, eliminates odours, evacuates stale air from bathrooms, provides clean air to keep you healthy and it recovers a lot of heat that would have otherwise been blown out through the vent on the house.  It serves three main functions:

1.  Supplies the home with fresh dry air.
2.  Removes stale air and removes excess moisture.
3.  Recovers heat or heat/moisture

For a low energy home we need an HRV that is as efficient as possible.  With the ventilation unit taking care of exchanging most of the air in the building, having an efficient one will pay for itself in the energy saved over it's lifetime.  Zehnder HRVs are probably (http://zehnderamerica.com), some of the best HRVs on the market (available in North America) but they are way too expensive.  They have some amazing features; like preheating winter air using a ground source brine loop and summer time bypass mode that completely bypasses the HRV core to bring in cool nighttime air.    They also use electrically commutated variable speed motors which are super-efficient and provide more CFM per watt consumed than many standard HRVs.

Recently, several Canadian HRV manufacturers have started building more modern HRVs.  The HRV design has changed very little in the past 20 years.  An HRV was typically one size fits all.  There was very little that could be done to change the CFM other than increase the static pressure of the ducts by installing an inefficient system or changing the depth of the duct diffusers in each room.  Some new models offer the best technology seen in European HRVs.  Both LifeBreath and Venmar make several models of HRV/ERV with ECM motors.  This increases the efficiency of the units drastically compared to older models.

The LifeBreath 195ECM (http://www.lifebreath.com/products/residential-ventilation-hrv/195-ecm) is one of the most efficient on the market.  It has an Sensible Recovery Efficiency (includes heat and the use of electricity for the motors, etc) of about 85% at 0 Celsius.  The Venmar X24ERV (https://www.venmar.ca/135-air-exchangers-x24erv-ecm-new.html) has an efficiency of about 84%.  The Venmar is an ERV.  Opinions on the use or ERVs have changed a lot in recent years.  Here is the old map:
Newfoundland would require a HRV according to the old map.  The new map below indicates that an ERV is more favourable in our climate since it transfers some of the outgoing moisture to the incoming air stream.


ERVs seem like the answer to our dry indoor winter climates.  However, will humidity lead to condensation on the windows?  Doubt it!  triple glazed windows are usually within a few degrees of the room temperature so maintaining a higher humidity inside the home shouldn't be an issue.  I may be considering a heat pump water heater for my domestic hot water which will also dehumidify the air inside the home.  If we use an HRV, the relative humidity inside the home will be even less again in the winter.  I am thinking that an ERV is the way to go.  The X24ERV model from Venmar is fully programable, electronically balanced, and the fan speeds are fully programable.  You can ventilate according to the ASHRAE standard (for our home it will be about 60 CFM) and program boost mode for 200 CFM if you want to really make away with stale air quickly.






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