Stop Designing Mechanical Closets Like It’s 1999

The all-electric transition is quietly wrecking floor plans.

Why? Because many teams still size mechanical spaces like it’s 1999—assuming a compact gas boiler and a slim panel will suffice.

Fast forward to 50% Design Development: the electrical engineer demands a dual-panel 400A footprint, the mechanical engineer requires a secondary buffer tank, and that cozy 3x4 closet under the stairs becomes an architectural disaster.

If you do not plan for this in Schematic Design, you will find yourself giving up precious square footage—and having awkward, budget-busting conversations with your client—when it is already too late.

Winning bigger, greener projects requires proving to clients that you can handle the complexities of decarbonization smoothly. That starts with aggressive, early coordination. You cannot afford to wait for your MEP engineers to "fill in the blanks" after the walls are already drawn.

Electrification shifts the building's burden from combustion exhaust (flues and gas lines) to electrical capacity and thermal storage (larger panels, heat pump water heaters, ERVs). This requires massive, rigid clearance zones mandated by the National Electrical Code.

Furthermore, heat pump water heaters (HPWHs) pull heat from the surrounding air. If you stuff them in an unventilated closet, they will freeze the room and stop working. They need louvered doors or dedicated ducting. Your mechanical engineer knows this, but if you don't give them the space to work with early on, they will be forced to specify expensive, custom workarounds that blow the project budget.

Here is your immediate action plan—an equipment footprint and spatial planning guide for all-electric closets. Stop guessing. Start using these rules of thumb today:

Never place panels behind door swings or underneath water pipes. Remember NEC 110.26(E) prohibits foreign piping or ducting directly above the electrical panel up to 6 feet above equipment.

Hydronic heat pump systems often need a buffer tank alongside the primary water heater. Budget at least 5' x 5' dedicated to water systems.

HPWHs harvest heat from room air. If unvented room volume is under 700 ft³, call out louvered doors (or dedicated ducting) on your early elevations to manage client expectations.

Heat pump compressors run at roughly 45–55 dBA. Avoid sharing walls with primary bedrooms, and always specify low-cost vibration isolation pads under equipment baseplates.

Before your next project begins, send your MEP engineers a simple email:

You don't need a massive, specialized team to design high-performance buildings. You just need the right spatial playbook before the ink dries on your floor plans.