Usually not. Most infrared heating installations can work around the church's regular schedule. Installers mount heaters on walls or ceilings and run cabling, which means scaffolding or access towers in sections of the building, but the whole nave does not need to be closed at once.
A common approach is to install in stages, working bay by bay or zone by zone, so that services can continue in the unaffected areas. Midweek installation with the church open for Sunday worship is standard for most projects. If the church has a weekday service pattern too, your installer should plan around it.
The one scenario where a short closure helps is if the electrical supply needs upgrading. A new three-phase supply or a larger distribution board might mean a day without power. Talk to your installer and your electricity provider early, and schedule that work for a quiet week. For everything else, the disruption is closer to "some people working quietly at height" than a full building site.