HIGH-PERFORMANCE HVAC Ask and I will answer

Any trainer or presenter will tell you that good questions from the audience are helpful in the learning experience, both for the presenter and the audience. They are specifically rewarding to the presenter since they provide reinforcement that the audience is engaged and interested in the topic, even if it’s a question that a presenter has been asked time and time again over the years. The only snag is if the presenter struggles to find an answer that satisfies the curiosity of the questioner. It is interesting to reflect on questions that are coming up in this exciting time in the HVAC industry.

The most common question asked of me in 2022 came not from HVAC industry professionals but from family and friends, and also from builders and the sales professionals representing those builders. That question was, “how does a heat pump work?” The frequency of the question is not that surprising given the popularity of energy efficiency programs and incentives such as the Greener Homes Program and the Canadian Home Builders Association’s Net Zero Energy Home program. These programs all emphasize the need to apply heat pump technology, at least for space heating, to take advantage of the incredible energy performance they offer. Indeed, it is the promise of the coefficient of performance of over three that sparks much of the questioning. How can a heating appliance be 300 per cent efficient? How is it possible to buy 1 kW of electricity and get three kW of heat energy distributed into my home on a cold winter’s day? I, and apparently others who have been asked these questions, have struggled to communicate an answer that is fully satisfying to the person asking the question. I have tried the comparisons to refrigerators and air conditioners. I have gone deeper into the explanation of refrigeration technology, compressors, evaporators, and the amazing release and absorption of energy during phase changes. While I often get a slight nod of the head, seldom do I get acknowledgement that the questioner feels confident in explaining the technology and their incredible efficiency to others. In the end, one homeowner offered to me that although she didn’t fully understand how her air conditioner worked, she was very confident it would keep her house cool on the hottest of summer evenings. She simply wanted her HVAC contractor and I to answer confidently that the heat pump proposed would offer similar comfort on the coldest nights of the year. She was satisfied with a simple explanation of the reliability of the system to extract heat from the outside air and pump it into her home under all conditions.

Gord Cooke Gord is a professional engineer who has spent 35 years helping builders and HVAC contractors implement innovative technologies into high-performance homes. He has particular expertise in IAQ and airflow management in houses, and can be contacted at gordc@buildingknowledge.ca.

The heat pump discussions raised deeper questions this past year related more to climate change objectives or greenhouse gas emission reductions. Specifically, contractor and builder clients of ours wanted assurances that a switch to an electricitybased heating device, even with its incredible efficiency, would meet expectations for carbon reductions without resulting in unacceptably high heating bills. Indeed, this is an important question that requires complex considerations of how electricity is generated in specific regions of the country and the projected price of energy sources over the next 10 to 15 years. Consider choosing a heat pump in Manitoba where 97 per cent of electricity in the province is generated by hydroelectric sources and the cost of electricity is lower than in all but one other province. By contrast, consider that in Saskatchewan over 40 per cent of electricity is coal fired generated and the average price of electricity is almost double that in Manitoba. In the short term, a builder or HVAC contractor advising homeowners to use a heat pump in Manitoba, and a high efficiency natural gas furnace in Saskatchewan would be justifiable. However, within the lifespan of the mechanical equipment it is quite likely carbon reduction initiatives will simultaneously raise the price of natural gas and provide cleaner electricity sources across the country to the point where heat pumps are the right choice in most parts of Canada. While it is still difficult to definitively answer the question, there are now excellent energy modelling and carbon prediction tools available for at least new homes to help builders make these complex decisions. That leads to the next most common question from mechanical contractors this year: “If ventilation is a year-round, 24-hour requirement, what adjustments should be made to the mechanical design to ensure proper indoor humidity control?” The solutions include application of energy recovery ventilation to minimize moisture losses in winter and to reduce moisture loads in summer. In addition, it has been my experience that airflow and refrigerant checks need to be made to ensure air conditioners are operating such that the supply air temperature is consistently below the dew point of the return air to ensure appropriate dehumidification. It is also clear to me that given the changes in lifestyles and the way houses are constructed, going forward many homes will need separate whole house dehumidification systems to maintain a healthy 50- to 55-per cent RH levels in houses throughout the spring, summer and fall in any regions with high outdoor humidity levels – at least the eastern half of Canada.

A question I have been answering for at least 35 years took a nice surprise turn this year. With homes now serving as offices, schools and recreation facilities, air quality was on the minds of many homeowners I spoke to this year. So, while for the first 30+ years homeowners would ask me when should I run my heat recovery ventilator, (HRV), in the last two years they have been asking me how can I get more fresh air and why does my HVAC contractor tell me to turn it off in the summer or when it’s really cold out in the winter? When homeowners hear about efforts to ensure proper ventilation in their kids’ schools and in their offices, they realize the need for fresh air in their homes. Yet, many mechanical contractors worry ventilation will raise relative humidity levels in summer and lower them in winter to unacceptable levels. We need to remind ourselves that the capacity for continuous mechanical ventilation in houses has been a code requirement since 1990 and it is not acceptable for an HVAC contractor to advise occupants to turn it off simply because the humidity control functions of the mechanical system can’t accommodate the required ventilation rate.

One final question that has come up a lot this year and will be familiar to anyone of my cohort, “After 35+ years in the industry, is it time to retire?” I answer sincerely there is too much going on; it’s such a perfect time for the HVAC industry. The confluence of energy efficiency, fuel choice decisions and indoor air quality, combined with great new equipment and control options, will present compelling opportunities for at least the next seven years. It is far too exciting a time to be standing on the sidelines. I want to help where I can. All the best in 2023.