I will have more to say about the context in which Andrew told us this when I have more time, but for the moment I will say only that this is the best answer to the question I have ever heard, and I’m really glad that I was recording his presentation for other reasons.
Update, 19 January 2010, 10:36am: Lucas Christensen was good enough to transcribe this (that’s my godson!). Here we go:
Q: Would you mind telling us a little bit of your philosophy on why we need beautiful churches?
A: The question of ‘why this sort of architecture?’ really brings me back to why I started becoming interested in Orthodoxy. I had previously been Anglican and I was interested in designing Anglican churches in gothic style; when I was in college, I studied gothic architecture quite intensively. But as I started to learn about Orthodoxy and Byzantine churches, I was really impressed by the degree to which architecture, iconography, music and liturgy are integrated in Orthodoxy, as one common vision. The way the liturgical movements connect to the different spaces of the building, and then the way the liturgical movements address the different icons, the way in which the icons are painted on the particular surfaces of the buildings in the proper order where they go, and then the way the hymnography refers to all of these saints and to liturgical actions. All of these things work together as an icon of the Kingdom of God in its entirety. Panel icons of saints are not the whole story. They represent the saints, the angels, Christ—but the Kingdom of God is a lot more than that.
If you read the end of the Book of Revelation it describes the Kingdom of God. The Kingdom of God is the City of New Jerusalem: it has foundations made of precious stones; it has columns and arches and beautiful pavements; it has domes—all of this is described. And it has ever been the practice of the Orthodox Church to understand church architecture as iconographic. That it, along with the icons and saints, makes for the full representation of the Kingdom of God, and then that must be filled with liturgy, music, incense, to represent we who make up the Kingdom of God along with the saints and angels worshipping God therein. So if you don’t have that, if you have a room like this {indicates a nave in a temporary office-space – ed.} with icons hanging on the wall, you’ve only got half of the picture. To me, honestly, seeing this situation of a mission church without a church, looks like the Kingdom of God in exile. We have worship, and we have music, we have saints, but where is New Jerusalem? Where is the City?
That’s why you need beautiful architecture. And that’s why the architecture needs to be honest, and solid and sincere. We don’t want to have a stage set, we don’t want to have a building that superficially looks like an Orthodox church, because that’s a stage set, that’s sort of what Baroque architecture is. That’s sort of trying to use plaster and ornament to give a theatrical impression of the Beatific Vision. But Orthodoxy’s not about that, Orthodoxy’s about building something absolutely solid, and permanent and honest that conveys the real ethos of the eternal Kingdom of God.
Leitourgeia kai Qurbana: Contra den Zeitgeist 
And Andrew’s website uses Sava Pro for headings, one of my favorite medieval-style calligraphic typefaces. It was designed by the Yugoslavian typographer Jovica Veljovič and features a large collection of specialized Byzantine ornaments. It is named after St. Sava, the first Archbishop of Serbia. How appropriate.
I like the part about the building needing to be “solid, and permanent and honest.”
There is something about beauty that lifts up the spirit, breaking through the cynicism and despair that saturates us.
I’ve come to believe beauty is very necessary for our development as people in God’s image. Sometimes people think about Church in terms of “is that necessary” but we worship a God who gives overabundantly and not meanly. This is shown in God’s creation, that despite it’s “unnecessary” beauty, was made to be delighted in. Beautiful Orthodox Churches reflect the joy of beauty and joy of creation back to our Creator, and helps us respond with joy and love in turn.
I am delighted that contemporary architects are making beautiful Orthodox churches. I looked at the New World Byzantine web site, and it is shocking to see such lovely buildings. We have become so used to the cult of the ugly here in the States that we sometimes forget that it is possible to construct differently.
I was in Rome a few months ago, where I attended liturgy at the new St. Catherine of Alexandria Russian Church. I believe that it was consecrated only last August. It was very beautiful, and well placed (http://www.patriarchia.ru/db/text/668207.html).
The papists seem to be getting their act together, too (http://thomasaquinas.edu/development/campaign/chapel/name.html).
After the last forty years, it could only get better for us all, eh?
He chose to be born in a lowly cave!
That’s true! So what does that say to you about the question of church buildings?