Refining Your HRV / ERV Choices

February 12, 2018

New year, new resolutions, new builds. If new HRV/ERV systems is on the top of your list, then this recap article by Gord Cooke, originally published Better Builder Article, Winter 2016, is a must read.

Please don't blame me, but the new 2017 Ontario SB-12 Supplementary Standard for Energy Efficiency requires all Part 9 dwellings to meet the Principal Ventilation requirements with an HRV or ERV. Certainly I have been an advocate for proper balanced ventilation for over 30 years, but I think most readers will know that this specific new requirement is a natural progression. The requirement for mechanical ventilation first appeared in 1990. With recognition that ventilation without heat recovery can easily represent 15-20% of the annual energy loss of a home, it stands to reason there needs to be an energy efficiency requirement on ventilation in the same way as other house components such as furnaces, water heaters and even windows and walls are required to meet minimum energy efficiency levels.

The changes in SB-12 - 2017 should spur you to review and fine tune your HRV and ERV selections to take advantage of the hard work manufacturers have put in to provide cost effective solutions to meet the new prescriptive and performance pathways described in the code.

One significant change in the 2017 code requirements is the addition of the following words: the minimum SRE (Sensible Recovery Efficiency) required is based on a test temperature of 0°C at an air flow rate equal to the 
principle exhaust flow but need not exceed 30 L/s. 
In previous codes, an HRV or ERV efficiency could be selected at any airflow. Now it is tied to the Principle Ventilation Rate of the house. The example below should help with this. It shows the Sensible Recovery Efficiency required for Prescriptive Package A1.

If you are going to use one of the Prescriptive Packages A1 through A6, for homes in southern Ontario, you will be looking for HRVs or ERVs with an SRE of between 65% and 81%, with the most likely packages requiring a 75%. Fortunately, leading manufacturers such as vanEE and Venmar are responding quickly with cost effective units that will still fit nicely into the ever-smaller mechanical spaces builders like to provide. Actually this is something you will want to check up on, higher efficiency HRVs are by definition bigger and not all manufacturers will have choices available in compact models. The good news all HRVs or ERVs installed in Canada must be independently rated and listed by the Home Ventilating Institute (HVI). Just confirm that your HVAC contractor is able to provide you with this independent listing showing that the equipment they are installing meets code requirements.

Of course, more thoughtful builders may well decide to use the more flexible Performance Path options in SB-12. Using REMRate or HOT 2000 or building simply to ENERGY STAR specifications allows total flexibility in choices of efficiencies of HRVs or ERVs. For example, if you are using a 65% efficient HRV as part of your ENERGY STAR for New Homes specifications now, you can continue to use those specifications and that appliance under the 2017 code requirements. In other performance path software evaluations you will find that higher efficiency HRVs or ERVs may be more cost effective than other envelope upgrades. For example, choosing one of the new high performance HRVs or ERVs would offset or allow a builder to reduce basement insulation from R20 back down to R20 or eliminate the need for a Drain Water Heat Recovery unit. Ask your energy rater to run some comparisons for you so you can best match your selections with your building process.

I do feel inclined to ask you to tune up a few other things now that HRVs are as normal and as common as furnaces or water heaters. Its time we cleaned up a few things. Improper installation and balancing of HRVs continues to be the most common defect in ENERGY STAR and other energy programs. This despite extensive efforts by manufacturers and representatives such as ourselves to offer training and installation assistance. Here are 3 things to check in on with the HVAC contractor. I will ask you, the builders, to step up and expect to pay perhaps $30 to $50 dollars more for your installation but expect the following 3 improvements.

  1. There has been an important change to the fire ratings of insulated flexible duct. You will find that the cheapest of duct, typically characterized by a black or grey plastic outer liner can no longer meet the required flame spread ratings. As of this fall you will see that your contractor will be switching to a higher quality flex that is more durable and has an attractive metalized (silver) jacket, for just a $7-$8 more per 25' length.
  2. Ask for better quality exterior hoods. The cheapest hoods have a plastic bird screen on the face of the duct that restricts airflow significantly. In order to get good airflow performance out of the better and better HRVs you are buying, pay $4-$5 more per hood and get one with a 1/4" mesh wire screen or better yet a sloped hood that has a proper rain-screen fitting that minimizes potential water intrusion - pictured here.
  3. Lastly, ask your HVAC contractor to partner with a leading manufacturer to have their installers regularly and repeatedly trained on how to properly balance and verify flow of the units they install. Leading manufacturers offer field experienced personnel to do this at no charge. I suggest a touch up training every 6 months or so. It can be done in the field or in their office and takes 45 minutes or less. You will benefit from fewer call backs due to window condensation and cold air complaints.

Still need some assistance in making your HRV / ERV choices? Contact us today!