CLIMATE CHANGE Vs CLIMATE CONTROL

WHEN humans solve one problem, our solution often creates a new problem that we didn’t expect. This observation has been described as “The Law of Unintended Consequences”. I would caution that it’s happening again in the tension between climate change and climate control, or, in another sense, between the outdoor environment and the indoor environment.

In the spring of 2023, Global Warming is front and centre. This March 20, the International Panel on Climate Change (IPCC) released its final Synthesis Report, which indicates previous goals to minimise carbon have not been met. The report calls for increased effort to reduce carbon emissions and energy use.

To keep future carbon goals below the 1.5 degrees C (2.9 degrees F) threshold, which is considered “manageable”, we need to have significant carbon reduction by 2040, reducing our carbon footprint by two-thirds. Maintaining this threshold level of 1.5 degrees C, or below, will require a sizeable reduction in energy use – no easy task, considering carbon- or energy-reduction results have historically fallen short of previously targeted levels.

While the world wrestles with this long-term threat of global warming, I am reminded of March 2020, the recent past, when we all received a quick and brutal education on an existential threat few of us ever considered: A pandemic. The quickly unfolding calamities of spring 2020 showed us how devastating a pandemic can be to human life and society at large.

Sadly, there may be a correlation between the unintended consequences of reducing energy intensity and increasing the intensity of the pandemic. In our zeal to make buildings energy efficient over the last 70 years, we may have inadvertently caused them to be more vulnerable to poor Indoor Air Quality (IAQ). By the 1960s and 1970s, as buildings grew, we transitioned from operable to inoperable windows, which are now the norm for most large buildings. The reason is simple: You’d get knocked over if you left the windows open on the 40th floor. So, we engineered ways to bring fresh air into these buildings through mechanically controlled ducts, and problem solved. But we didn’t stop with skyscrapers. Most modern buildings have inoperable windows now, because it can be more energy efficient – and more economically efficient – to control indoor air… with properly maintained equipment.

You can still pop open a window in a “prewar” (1940s or earlier) building, but we are, in effect, hermetically sealed within our modern indoor spaces. That’s fine, until it isn’t.

The correlation between poor IAQ and COVID-19 case counts

Early in the pandemic, my firm put out an analysis evaluating the correlation between poor IAQ and COVID-19 case counts. As an HVAC practitioner who has observed abysmal IAQ issues over the past 25 years, the conclusion was simple: High-density buildings (nursing homes, multi-family, etc.) with poor IAQ were a clear breeding ground for the virus, thus we should expect the case counts to increase when these environmental conditions exist. Further – and this is critical to understand with regard to meeting the stated carbon targets – HVAC done properly requires energy, a lot of energy. There is a clear correlation with poor IAQ and reduced energy use, which is not how we want to meet our energy reduction targets.

The most common HVAC issues, which can lead to poor IAQ, are as follows:

> Inadequate outdoor air. Outdoor air ventilation serves to purge a building of contaminants, whether those contaminants are benign (that is, odours, particles) or more dangerous (that is, viruses and bacteria). Note that provision of outdoor air is a major energy impact, because this dictates the amount of makeup air (fresh air which is mechanically added to a building), which has to be heated and cooled. Heating and cooling of makeup air is typically 2040% of total building energy use.

Lack of fresh outdoor air can be due to the following:

• Intentional reduction of outdoor air: Building operators may choose to do this with the intent of saving energy and money for utility bills.

• Deferred Maintenance: Modern buildings are complicated. Without continuous commissioning, it is common to observe systems (such as the actuator, on the right-hand photo, above) which fall out of service.

• Control Issues: With faulty building management system controls, it is common that minimum provision of outdoor can be askew due to faulty data input to the BMS. Again, continuous commissioning typically will ensure that this issue is not persistent.

> Air distribution issues. In modern buildings, air distribution systems (supply fans, return fans, exhaust fans and ductwork) can contribute to 10-20% of building energy use. Common issues which can affect IAQ include:

• Loose or non-existing belts for fans: Without properly tight belts, conditioned air simply doesn’t move. Although this can reduce energy use and cost, lack of ventilation will also contribute to poor IAQ.

• Leaky ductwork: Leaky ductwork will not allow all the conditioned air to get to where it needs to be. In addition to contributing to poor IAQ, it will increase energy use.

> Inadequate central plant. Poor performance of central heating or cooling plant, especially chiller plant for dehumidification, can lead to poor IAQ issues.

Energy impact of improved IAQ

In the summer of 2020, Guth DeConzo