If you’re building or buying a new home in Franklin, Brentwood, or anywhere in Williamson County, there’s a code update that took effect September 30, 2024 — and most people in the building industry haven’t caught up to it yet. Williamson County adopted the 2018 International Energy Conservation Code (IECC), and that change has real implications for how permanently installed landscape lighting gets specified and permitted on new construction projects.

At Middle Tennessee Christmas Lights, we work with homeowners and builders across Williamson County and the greater Nashville area every week. Energy code compliant landscape lighting in Tennessee is one of the fastest-growing parts of what we do, and questions about permits, code compliance, and what actually needs an electrician come up constantly. We put this guide together to give you straight answers — and to show you why Haven lighting systems are, in our experience, the cleanest path to compliance on new builds.

What Changed in Williamson County — and Why It Matters

Tennessee’s statewide residential energy code is still based on the 2009 IECC with amendments — the state has been slow to update, and that’s not unusual in the Southeast. But Williamson County moved ahead on its own. As of September 30, 2024, new residential construction in the county falls under the 2018 IECC with 2009 tables, making it one of the more current local codes in the region.

The relevant section for permanently installed lighting is IECC 2018 R404.1. Under that provision, at least 75% of permanently installed light fixtures in a new home must be high-efficacy — defined as fixtures producing at least 45 lumens per watt. That threshold applies to interior and exterior permanent fixtures alike. If your landscape lighting is wired in as a permanent system during construction, it counts.

There’s also a useful exception worth knowing: under IECC 2018 R404.1.2, exterior lighting that is controlled by the dwelling unit — meaning the homeowner can turn it on and off from inside — is excluded from the exterior lighting power allowance calculation. We’ll come back to why Haven’s app control is relevant here.

One more note on the horizon: the U.S. Department of Energy has set a 2026 deadline for states to adopt equivalents to the 2022 IECC. Tennessee will face increasing pressure to update its statewide code in the next few years. Getting ahead of that now is just smart planning.

Haven’s Efficiency Numbers Against the Code Standard

Here’s the part that surprises most builders when we walk them through it: Haven lighting isn’t just code-compliant — it exceeds the 2018 IECC minimum by a wide margin.

The Haven 6 Series fixture produces 690 lumens at 6 watts. That’s 115 lumens per watt. The 2018 IECC high-efficacy threshold is 45 lumens per watt. Haven comes in at roughly 2.5 times the minimum. In practical terms, that means a permanent Haven system on a new Franklin build sails through the high-efficacy fixture requirement under R404.1 with room to spare — and if a home’s lighting plan needs to balance some lower-efficiency fixtures elsewhere, Haven’s numbers give you that cushion.

The 6 Series also offers selectable color temperature — 2700K, 3000K, or 4000K — and three output levels (2W, 4W, or 6W per fixture), all adjustable through the Haven App. That kind of flexibility matters on high-end builds in Brentwood or Nolensville where lighting design is part of the project, not an afterthought.

The X Series uses the XCONT240 controller — 240 watts, 24V DC output, IP55 rated — for larger or more complex installations. The 9 Series Pro handles full RGBW plus adjustable white on the same low-voltage platform. All three series run through a single Haven App interface with sunrise/sunset scheduling and automatic daylight saving time adjustment.

How Low-Voltage Lighting Sits Under the NEC

This is where permit confusion comes from, and it’s worth being precise. NEC Article 411 covers lighting systems operating at 30 volts AC or less, or 60 volts DC or less. The Haven 6 Series runs at 12–15V AC through the Stratus transformer. The X Series runs at 24V DC. Both systems fall squarely within the NEC Article 411 low-voltage category.

What that means practically: the wire runs on the secondary (low-voltage) side of the transformer — the cables running to your fixtures — generally do not require conduit, a licensed electrician, or a separate low-voltage permit in most Tennessee jurisdictions. That’s a meaningful cost and scheduling advantage on new construction projects where trades are coordinating against tight timelines.

What still requires a permit is the 120V AC supply circuit feeding the transformer. If the Stratus transformer is hard-wired, that connection is a standard electrical permit item — same as any hardwired outdoor circuit. NEC 210.8 also requires that outdoor receptacles be GFCI-protected, so the transformer’s supply circuit needs to reflect that regardless of how it’s connected.

There’s a cleaner option for some situations: the Stratus transformer is also available in a plug-in configuration. For retrofit installs — or new construction where one dedicated exterior outlet is being roughed in anyway — the plug-in Stratus eliminates the hardwired circuit permit entirely. One outlet, one plug, done. Our team has used this approach on numerous Williamson County projects where the homeowner wanted the system added after the main electrical rough-in was closed.

Speccing Haven on a New Construction Project

If you’re a builder or GC working on a new Franklin or Brentwood project, the conversation with your electrical sub is straightforward. The primary question is whether the homeowner wants a hardwired transformer connection or a plug-in setup. Either way, the low-voltage wire runs happen after the transformer is in place — they don’t touch the electrical rough-in schedule.

For permit submittals, we recommend pulling the Haven product spec sheets directly from the manufacturer. They include the fixture wattage, lumen output, voltage, and IP ratings in the format most building departments want to see. We don’t make independent claims about certification listings — the spec sheets are the right source for that documentation, and they’re what your plans examiner will reference anyway.

A few practical notes for new construction coordination:

  • Identify transformer location during framing — a weatherproof exterior enclosure near the main panel or garage simplifies the 120V supply run
  • Low-voltage wire can be stubbed through conduit sleeves in foundation or exterior walls during rough-in for a clean finish later
  • Fixture layout and zone planning can happen at any stage — the Haven App makes it easy to add or reconfigure zones after install
  • For hardwired Stratus installations, confirm GFCI protection on the supply circuit with your electrician before rough-in inspection

Why App Control Matters Beyond Convenience

The Haven App does more than let you pick colors and set brightness. Sunrise/sunset scheduling with automatic DST adjustment means the system can be programmed to shut off at a set time each night — which is directly relevant to the IECC 2018 R404.1.2 exception we mentioned earlier. Exterior lighting that’s controlled by the dwelling unit is excluded from certain exterior power allowance calculations under that provision. Haven’s app-based control, operated by the homeowner, appears to satisfy that “dwelling-unit-controlled” definition, though we always recommend confirming with your plans examiner on a project-specific basis.

Williamson County has grown by 8.6% since 2020 — 269,136 residents as of 2024 — and Franklin’s new construction market shows no sign of slowing. Property values in Franklin rose 7.2% in 2024 alone. Permanent outdoor lighting in Franklin TN has become a standard expectation on new builds in this market, not an upgrade. Getting the code piece right from the start protects builders from correction notices and gives homeowners a system that’s documented and ready for resale.

Work With a Team That Knows the Local Market

We’ve installed permanent lighting systems on homes throughout Franklin, Brentwood, Nolensville, and across the Nashville metro. We know how Williamson County’s building department works, we stay current on the code updates that affect our installs, and we’re comfortable coordinating with your electrician and GC to get the low-voltage side scoped correctly from the beginning.

If you’re a builder looking to offer permanent landscape lighting as a standard or optional package on your projects, or a homeowner about to close on a new build and wondering how to approach this, we’re glad to talk through the specifics with you.

Contact our team today to schedule a consultation — we’ll walk through your project, answer your permit questions, and put together a Haven spec that works with your build timeline.