Prioritising people in HVAC design

How did you first become interested in occupant comfort and the role HVAC has to play in that?

When I had my own engineering practice we were producing drawings and commissioning systems. Even though we were following codes and standards, we were still getting people complaining about the indoor environment. And I’m not just talking about thermal comfort, I’m talking about air quality, lighting and sound.

I made it my business to figure this out. We’re doing what we’re supposed to do, so why are people still complaining?

I spent many years reading medical textbooks and taking as many classes as I could. Through this, I realised that we (practitioners) don’t know enough about human physiology and psychology in relation to the built environment.

When I started to learn that and put it into our practice, it evolved into our motto: “Design for people – good buildings follow”.

We looked at what people needed from a physiological and psychological point of view and let that drive design, as opposed to creating design and then making the design professionals responsible for meeting codes and standards. That drove everything: window-to-wall ratios, fenestration performance, all our strategies.

But codes and standards are based on physiological data and perceptions of comfort, right? Is it just that the data is bad?

One would think that codes would represent the needs of the occupants. But codes are primarily a means of reducing risk. Whether people are comfortable or not is irrelevant as long as the buildings don’t kill you or make you sick.

A practising HVAC engineer would do their load calculations, and then all those load calculations get converted to flow rates. But we know that thermostat readings can be in compliance with the codes and people will still be uncomfortable for all kinds of reasons. So it’s really important we understand that load calculations and HVAC design in of itself is not thermal comfort design.

For that, you actually have to do thermal comfort calculations – that’s what ASHRAE Standard 55 or ISO 7730 is all about. They’re actually not that difficult.

How do you achieve genuine thermal comfort in practice?

There are two approaches. You either review a set of drawings and create environments based on those drawings, or you influence the drawings in the pre-design stages. It was always our preference to get in front of the design, so that we could say what would work.

In the northern hemisphere, for example, southwest-facing buildings are high solar load areas. We need to increase the performance of the glass and provide external shading so we don’t end up loading the building with a whole bunch of shortwave radiation. We’d also look at issues like thermal bridging.

We would actually incorporate what we learnt about how people sense the indoor environment, then that would drive the architectural design, including the geometry of the architecture, the colours and the textures.

If we were given a set of blueprints and asked to create an environment, we would do our traditional load calculations, then do thermal comfort calculations and indoor air quality analysis. Based on our findings, we would then make recommendations.

For example, maybe 80% of the building would work fine, but you’ve got 20% of the building that really needs to be tweaked. We’d recommend fixing the 20% of the architecture so we don’t have to design the mechanical system for the 20% rogue zones, because that drives the rest of the building. We may have to run the cooling system at the lowest temperature needed for the rogue zones, which the other 80% of the building doesn’t need. If we didn’t do that, we’d end up having to put in mixing valves, which required more circulators and more controls. The complexity of the systems would go up, the amount of maintenance for the building would go up, and that would last for its lifetime.

You mentioned indoor air quality and how it affects occupant comfort. What sorts of issues were you identifying with IAQ, and what kind of improvements could you make?

In almost every air quality standard and code that I’m aware of, there’s a requirement for what we call source control. That’s not just about analysing what’s coming in through our makeup air systems and the ventilation system, but what’s inside the building, including the interior finishes.

A lot of people don’t understand that when you expose synthetic materials like carpets or wall coverings to shortwave radiation, they break down into gases and particles, contributing to odours. That “new building” or “new car” smell is actually the outgassing of chemicals that are in the products. Moisture and sunlight shortwave radiation are enablers of those VOC emissions. We would spend a lot of time working with the interior designers using software tools to model the outgassing of various interior finishes.

We also encouraged them to make different flooring choices. So instead of going with synthetic carpets, we might encourage masonry-type surfaces like tile, slate, terrazzo or stained concrete. We had a preference for more natural woods as opposed to engineered woods, because one of our objectives was to reduce formaldehydes, whose volatility is sensitive to temperature.

Source control also involves looking at what’s on the outside coming into the inside. We have to look at these things not just at a single point of time, but consider what could happen around that building as society evolves.

Take a farm that’s in the middle of nowhere. Let’s assume that the farm is not using chemicals, herbicides and pesticides, in which case there’s a higher probability that the air coming into that space is of good quality.

But over time, land parcels get purchased and it’s not uncommon to find industrial facilities being built around farming communities. A good example of that is meat packing plants; the smells that come out of a meat packing plant are horrendous. So you can have a farm that was designed when the outdoor air quality was good, then see it degrade over time because of what gets built around that community. It also happens with commercial spaces downtown with vehicle traffic.

What have you noticed about Australia’s built environment since you’ve been here? Please, don’t hold back!

I’ve been told I notice stuff that people don’t really care about. But if you have an engineering architectural eye for things, it’s just part of your DNA.

I’m currently in Brisbane, and what I love most about this city is the exterior shading. It’s simply some of the best, some of the most creative strategies that I’ve seen to reduce solar loading. You can see what works and what doesn’t work, because as the sun moves, you can see who’s closing their blinds or closing their shutters. North America has a lot to learn about how Australians do the exterior part of their buildings.

Another thing I’ve noticed in the taller buildings is these thermal buffer zones. You see a lot of rooftop social areas so that the top floor is not actually an occupied suite – it’s more of a socialising area. Oftentimes it’s naturally ventilated, but it’s always shaded. That reduces the roof load onto the occupied suite on the floor below. That’s brilliant. We don’t see those types of strategies in other parts of the world, so kudos to the architectural and engineering teams that have done that.

When I look at the two buildings out my window – which are both engineering firms, by the way – the window-to-wall ratio on one of them is about 50%. They’ve actually done a pretty good job of being conservative with their windows. The other one is basically 100% window-to-wall ratio – it’s all glass. You can see the consequences of that by people pulling down the shades on the inside.

One thing I’ve noticed that could be better is hallway control. I’ve been in several apartment buildings and hotels where there is definitely cross-contamination of odours in the hallways. We don’t typically see that in other parts of the world where hallways are pressurised.

Finally, what are you teaching through your role in ASHRAE’s distinguished lecturer program, and what messages are resonating?

One of my most popular lectures asks whether we should let indoor environmental quality drive the bus instead of energy use. It challenges people. I make the case that people at birth come with these gifts, which are our ability to see, smell, hear and feel.

As soon as we can smell, we’re building up an inventory of odours. Eventually you get exposed to odours like mould, smoke and diesel fumes that are offensive.

I make the argument that people will do whatever they can to create environments around them that are safe and healthy, to the best of the resources that they have, and that energy use is actually an intellectual construct unrelated to what people sense.

Most people aren’t engineers – they don’t have a scientific background. You can see that in the words people use when they talk about their indoor environments: it stinks in here, or it’s muggy, or it’s dark, or it’s loud. They don’t use technical jargon.

So the argument is that indoor environmental quality should actually drive sustainability, not energy. The reason for that is that when we design for people to resolve the things that they complain about, energy conservation and energy preservation becomes a byproduct.

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