Today is June 24, a date connected to the summer solstice and festivals in Europe. It is known as Saint John’s Day/Midsummer Day in the United Kingdom, Festa di San Giovanni Battista in Italy, Sânziene in Romania, Juhannus in Finland, and also my birthday. But we are not going to spend any time counting that. I quit doing that a while ago!

But that small calendar coincidence has led me to discover midsummer traditions, unexpectedly medieval church architecture, and a larger question about how we design with seasonal light.

Because if you have ever had a client ask for “more natural light,” you already know that sounds simple until you really start thinking about it.

More light when?

More light in the morning?

More light in winter?

More light in July, when the afternoon sun is trying to turn the room into a toaster oven?

More light for about 30 days during a holy festival?

At the Church of the Holy Cross at Pătrăuți Monastery in Romania, built in 1487, a complex and choreographed light effect unfolds for about thirty days around the summer solstice.

Corresponding with the Feast Day of Saint John the Baptist, morning light enters through the altar window and lands on the mural of the church patron, whose name was also John. As the sun moves, the ray descends from the wall to the floor, then begins an almost three-hour journey toward the altar.

This is one of several timed light effects at the church, but I think this one is the most dramatic. I watched a time-lapse video of the effect and it has a performance-like quality. The light illuminates the patron then slowly becomes a moving block on the floor, almost as if the figure is making his way toward the altar before the altar itself lights up.

I have been noticing a light effect in my own mudroom lately, though mine is obviously less sacred and more “where did I put the dog towel?”

I usually take my plants out for the summer, but one of them is just too big to move now. It’s a Monstera.

We also added a fish tank because of our rescue goldfish. The mudroom was the only place to fit the big tank. The room has a big southeast-facing window and a southwest-facing full glass door. In winter, it is usually light and bright. It’s perfect for plants, and the room has a bit of a greenhouse feel.

Now in June, the sun is not even coming through the window after about 10 a.m. The room does seem to stay a bit cooler, which is good for the fish. But my poor plant was not doing so well. I added some supplemental plant lights, and it seems to have perked up.

So after all these years, it took a shift in the use of the room to notice it. But, there it was, in one room, light was both a problem and a benefit.

Openings and windows can be calibrated to use light for a dramatic effect, highlight materials, or affect the temperature of a room. But what if the whole building was designed around seasonal light?

At the Kiasma Museum of Contemporary Art in Helsinki, American architect Steven Holl did just that. Rather than fighting Finland’s extreme seasonal daylight, he used it as one of the main features of the building. The low winter sun, abundance of snow, the long dark season, and near-endless summer light all became part of the visitor experience.

In his award-winning design, called Chiasma (Kiasma is the Finnish spelling), light almost becomes one of the building materials. The building’s curved wall helps capture and reflect natural light into the museum, allowing the galleries to work with the low northern sun. Then, during the snowy season, light reflects off the snow, and the building begins to glow back into its surroundings.

Interestingly, Steven Holl was inspired by one of the last passages in the treatise The Visible and the Invisible by Maurice Merleau-Ponty, composed in 1959-1961.

The word chiasma, or specifically the optic chiasma, is the part of the brain where the optic nerves cross. Merleau-Ponty theorized that the chiasma was intertwined with thought and perception. Holl shaped the building around this idea of perception and intertwining.

Merleau-Ponty’s philosophy also emphasized the indivisibility of humans and nature.

Some of today’s fastest-growing design trends in wellness, aging in place and biophilic design echo Merleau-Ponty’s ideas.

So we may not be designing sunlight to travel across medieval frescoes or align with ceremonial dates, but we are still designing for morning routines, afternoon glare, summer heat, winter comfort, work spaces, sleeping spaces, and real people living through real seasons.

Finland has much more dramatic seasonal light shifts than we experience, but our seasonal light can still affect our well-being.

And sometimes plants and fish too.

Architecture may be designed in space, but it is experienced in time. Our homes are not static objects. They interact with light, the seasons, and our spaces can transform throughout the year.

Hawkes House, built in 1991 in Cambridge, UK, was the focus of a study by VELUX, “Circadian Design for Aging,” that examined the importance of natural light and seasonal changes in residential architecture and also aging/adapting needs over time.

One of the main design features of the home is the way the principal rooms are laid out, facing south and connected to a courtyard garden. The angle of the sun at the summer solstice is approximately 62° at noon, and at the winter solstice, it is close to 15° at noon.

In summer, the high sun is mostly kept near the front edge of the living room, helping the interior remain shaded and cool while the garden becomes an extension of the house. In winter, the low sun reaches deep into the room, bringing light and warmth to the back wall.

So back to that mudroom. I began to wonder what the sun angle was doing at my own southeast-facing window.

I found a free online app, Sun Trace 3D https://www.suntrace3d.com/ I have to admit, this is where I got a little excited. I entered my own address, waited a few minutes, and the app generated a 3D model of my house. I could easily manipulate the model to adjust the view and see the sun angles and shadows at different times of the year. It also included the surrounding terrain, trees, roads, and structures. Toggling between June and December at 10:00 am showed such a striking difference.

In the June view, the sun was already high enough by midmorning to move past the windows and roof edge. In the December view, the lower sun angle clearly showed why the room was so sunny and bright in the winter. Another helpful feature is that you can add structures or even build onto existing ones in the model.

Check out the screenshots below.

The sun is already doing something on every site. The opportunity is to better understand it and create designs that work with it.

More light when? That is the question I will be asking more often.