How big for mechanical room?
I am looking to build a slab on grade home and are in the preliminary design phase. What does everyone say in regards to the size of a mechanical room? We are contemplating radiant heat in slab vs heat pumps(ducted or ductless), probably heat pump water heater and then ERV. We are trying to stay close to 1800 sq ft so we don’t want to waste space that isn’t needed but also want to make servicing and functionality as best as can be
Before you discount an option, you can have radiant heating using your slab sourced with a heat pump.
https://www.arcticheatpumps.com for example.
A while ago, the heat pump water heater would have dictated minimum size for the mechanical room, but there are models that are set up for air routing to the heat exchanger using duct work.
To avoid wasted space, but have a layout that works, you need to get specific. This means some homework.
Start with working choices for specific equipment for all mechanical systems you want to include. Include equipment-specific guidance for clearance requirements, and lay out access lanes. Include the need to remove and replace at some point.
If you locate the mechanical room where noise will not be an issue, say near an entrance from the garage, or adjacent to laundry area, you may be able to count on larger doors and hall space as part of the required service access space.
You might end up with one or more mechanical closets vs rooms.