What does the professor imply when he says this?

Listen to part of a lecture in an architecture class.
Professor: Ok, so as we’ve consistently seen over the past week, the conventional approach taken by architects is generally to design first then figure out how to make it work. So what I’d like to talk about now is a structure, a facility that totally reverses that mindset. For this project, engineers started out by imposing an energy consumption limit on the facility and architects built all the design plans around that number. In other words, energy considerations determined the design and it did so in ways that are so advanced that the facility really raises the standard for energy efficiency. The building I’m referring to is a research facility in Colorado, the first of its size to achieve the goal of net-zero in the United States meaning it creates as much energy as it uses. Let’s take a look at the basic footprint, just an outline of the foundation to start. So, you see there are two long buildings connected at their centers, forming kind of a crooked ’H’ letter. These aren’t typical buildings, either. As you can see from the footprint they’re long, as well as thin, Can anyone think of a reason why that decision was made?
Student 1: So that there’d be more surface area for solar panels on the roof?
Professor Well, you’re on the right track, yeah! Sure, solar panels were used for this facility. They supply electricity, but you know the shape of the buildings has even more to do with the sun than just that. It was carefully designed to allow an abundance of natural light available throughout the entire facility. First, the architects decided to narrow the width of those rectangular buildings, 50% thinner than the average modern office building, so that light could penetrate through the many windows into the middle of each building and secondly, they consciously positioned the buildings on the site to maximize their exposure to daylight. So the long sides get the most sun.
Student 1: Hmm... sounds good, so lots of light. But from what I’ve read windows are a primary source of both heat loss and heat gain for a building. I mean how can having so many windows be energy efficient?
Professor: Well, the architects used special type of window.
Student 2: You mean insulated windows, the kind with multiple layers of glass and gas between each layer?
Professor: As I mentioned earlier, this facility sets a new benchmark. The technology you mentioned is already outdated. For instance, throughout much of the facility they’ve installed electro-chromic windows. Electro-chromic windows use a single pane of glass that darkens automatically and blocks out the sunlight as the temperature rises and an electric current actually changes the tint. They’re placed where the building’s windows get the most sun.
Student 2: Wow, talk about innovative!
Professor: And it only gets better! You see under each of the buildings, architects designed a broad, shallow basement space that’s kind of like a maze. Air, either from within the building or from the outside, is pulled into the basement space through air ducts and then forced to move slowly around concrete barriers. The air is sort of guided through the maze. Now these concrete barriers, they absorb heat from the air if the air is warm or if the air is cold, the cold is absorbed into the concrete, so it could be either way. Let’s say it’s hot air, hot waste air being pulled in from the computer rooms, say. Well, that air moves slowly back and forth around these barriers. In this particular situation then, the heat from the incoming air is transferred to the concrete, which then holds onto it. Storing the heat until later when it’s slowly released throughout the building. That’s the concept of thermal mass in a nutshell.
Student 2: Ok, so let me try to get this... the air could be hot or cold? So then it’d be like walking into an old stone castle during summertime, lt’s so much cooler inside the castle during the day because the walls had retained the cold from the night air.
Professor: That’s right. It’s precisely the same thing: thermal mass. As a matter of fact, the outer walls of the facility consist of large panels of concrete, nearly a foot thick, for that very reason and they play a huge role in maintaining the temperature of each building.