🔍 Dig deeper — tap a topic
Each topic expands: what applies, the cost or project impact, the code or law with its official free source, and the action to take. Everything here is drawn from this briefing and its cited sources — confirm specifics with your AHJ.
The statewide code adopts the 2021 International Building and Residential Code, with the 2018 energy code (IECC) as amended, administered under RSA 155-A. That gives you a statewide baseline you can start from — but it’s the floor, not the ceiling.
An older energy code can mean lower cost — NH runs the 2021 building codes with the 2018 energy code (as amended), generally a less costly energy standard than CA or WA. For an out-of-state builder that can mean a lower envelope/mechanical cost than you’re used to — confirm the town hasn’t adopted something stricter.
RSA 155-A (NH State Building Code statute); 2021 I-Codes via the ICC free viewer.
Read RSA 155-A →Start from the 2021 I-Codes + 2018 energy code (as amended) as the statewide baseline. Energy compliance runs on the 2018 IECC as amended — don’t assume a newer edition unless the town adopted one.
New Hampshire municipalities can adopt amendments and additional local requirements. So “the state code” answers the baseline, not the whole question.
Town add-ons = price per town. Because towns layer their own rules on the state floor, compliance cost is town-specific. Don’t price one town’s job off another’s.
Local town code offices for amendments, on top of RSA 155-A. Confirm the town’s added requirements with its code office (AHJ).
NH General Court →Confirm what the specific town requires before you design or bid.
Pending legislation that could adjust how the state code is adopted or enforced. Confirm its final status before assuming any change.
Could change which edition applies — a real design-basis risk if it passes. Confirm before you commit.
Watch HB 1159 if it touches your work — but verify enactment first.
A provision allowing certain plug-in solar is set to take effect January 1, 2027, once the state certifies a national electrical standard. If you handle small-scale solar, note the date and the conditions.
A minor cost/scope item if you touch small-scale solar.
If you handle small-scale solar, note the Jan 1, 2027 date and the conditions — verify the triggering certification first.
🗓️ Recent & upcoming changes
2021 I-Codes (IBC/IRC/IMC/IPC/IEBC) with the 2018 energy code, as amended, under RSA 155-A.
Plug-in ("balcony") solar provision takes effect once the state certifies a national electrical standard; HB 1159 code update in motion (watch).
What's in effect
The New Hampshire State Building Code (RSA 155-A)
The statewide code adopts the 2021 International Building Code and Residential Code, with the 2018 energy code (IECC) as amended, administered under RSA 155-A. Unlike Arizona or Colorado, that gives you a statewide baseline you can start from — but it's the floor, not the ceiling.
Towns can go further
New Hampshire municipalities can adopt amendments and additional local requirements. So "the state code" answers the baseline, not the whole question — confirm what the specific town requires before you design or bid.
See the actual law → RSA 155-A (NH State Building Code statute) · 2021 I-Codes via ICC free viewerComing up / watch
- HB 1159 — building-code / enforcement changes. Pending legislation that could adjust how the state code is adopted or enforced. Confirm its final status before assuming any change.
- Plug-in ("balcony") solar. A provision allowing certain plug-in solar is set to take effect January 1, 2027. If you handle small-scale solar, note the date and the conditions.
What it means for you
- Start from the 2021 I-Codes + 2018 energy code (as amended) as the statewide baseline — then confirm the town's added requirements.
- Energy compliance runs on the 2018 IECC as amended — don't assume a newer edition unless the town adopted one.
- Watch HB 1159 and the Jan 1, 2027 plug-in solar date if they touch your work — but verify enactment first.
💵 How this hits your costs
- An older energy code can mean lower cost. NH runs the 2021 building codes with the 2018 energy code (as amended) — generally a less costly energy standard than CA or WA. For an out-of-state builder that can mean a lower envelope/mechanical cost than you're used to. Confirm the town hasn't adopted something stricter.
- Town add-ons = price per town. Because towns layer their own rules on the state floor, compliance cost is town-specific. Don't price one town's job off another's.
- Plug-in solar (Jan 1, 2027) is a minor cost/scope item if you touch small-scale solar.
🏗️ Real estate development — opportunities & risk
Sources: New Hampshire General Court (gc.nh.gov) — RSA 155-A and HB 1159; New Hampshire State Building Code adoption; local town code offices for amendments.