Understanding home occupancy and the role of nmax
Actual occupancy, "reference" occupancy
Occupancy of a home is first and foremost the people who actually live there, with their routines and their usage patterns. For calculations (DPE, audits, simulations), "reference" occupants are also used. This is a standard assumption, designed to compare homes with each other without depending on each household's habits.
What nmax is for
Nmax corresponds to the maximum number of occupants used in these models. It is used to estimate hot water, humidity, ventilation, and therefore to size consistent works. Without nmax, you risk scenarios that heat well but max out on hot water, or the reverse.
Why it varies by home
Nmax changes with surface area, number of rooms and layout. A small one-bedroom flat is assumed to be more "densely" occupied than a large house. Needs per m² do not follow a linear rule, hence visible gaps in results and pricing.
Max occupants by home type: concrete benchmarks for your projects
For a single-family house, start from the main rooms and the surface area, then validate with actual usage. An office can become a bedroom. If you underestimate occupancy, you risk an undersized mechanical ventilation system and heating that struggles at morning peaks.
- Flat: shared walls limit heat loss, but occupancy weighs more heavily on humidity and odours. Watch out for ducts, air inlets, and common areas (cellars, shafts) that disrupt ventilation balance.
- Studio/one-bedroom: avoid a fanciful nmax. 1 occupant, sometimes 2 for short stays. Size ventilation on the regulatory flow rates, not on a permanent "full house".
- Three- to five-bedroom+: link nmax to household composition and available bedrooms. A guest room used 3 nights a week already changes the picture.
How to determine a reliable nmax on site without spending an hour on it
Quick checklist and points to record
On site, aim for an nmax consistent with actual occupancy, without conducting an interrogation. Start with the number of bedrooms and the sleeping arrangement (double bed, bunk beds, sofa bed). Then validate the habits. Who is present on weekdays, weekends, and during holidays. Remote work changes the picture. More hours at home means more hot water, more ventilation, sometimes a continuously heated room. For shared housing, count the permanent occupants, and note the rotations. For shared custody, use the most frequent scenario, and mention the rhythm. For a second home or seasonal rental, indicate the usage period, the estimated occupancy rate and the source (calendar, platform, records). In the file, record the answers, the date, and any verifiable element (photos of sleeping arrangements, exchanges, leases). This keeps you solid in the event of an inspection.
- Bedrooms and actually usable sleeping arrangements
- Weekly presence, holidays, remote work
- Documented special cases: shared housing, alternating custody, second home, seasonal
- Simple evidence: photos, leases, calendar screenshots, records
Impact of occupancy on technical choices in energy retrofitting
Occupancy changes everything, starting with ventilation. The more people there are, the more you should aim for steady flow rates, with well-distributed outlets and genuinely unobstructed air inlets, otherwise humidity and CO2 build up. For heating and domestic hot water, the right approach is to set the output and tank volume to match usage. Back-to-back showers, remote work, staggered schedules. Without fine-tuned control, you end up with short cycling, discomfort and excess consumption. For insulation and summer comfort, internal gains rise quickly. Cooking, appliances, number of occupants. A heavily occupied house can overheat despite a good envelope. Hence the value of weighing options by scenario: night-time ventilation, solar protection, thermal mass. In a whole-house renovation, occupancy dictates the right order of work packages. First airtightness and ventilation, then heating, to keep the project consistent. To secure sizing, you can also rely on the outdoor base temperature to avoid over- or under-sizing.
Occupancy, housing and grants: securing your quotes and applications in 2026
In 2026, the solidity of a file often comes down to one detail. Home occupancy must stay consistent everywhere. Same assumption in the audit, the scenarios, the quote and the certificates. Otherwise, the stated gains, the home category and the supporting documents no longer tell the same story. On the MaPrimeRénov' side as on the CEE side, inspections cross-check the address, status (main residence, rental), the date of works and the commitments made. A discrepancy can block payment or trigger a request for additional documents. To avoid blockages, refer to the mistakes to avoid when building and checking files. Good RGE practice is simple. Write down in black and white the assumptions used (number of occupants, heating periods, domestic hot water usage). Have them validated by the customer in writing, keep the exchanges and versions. You secure your quotes and avoid disputes after the works.
How Argile helps you frame occupancy (nmax) and sell the right scenario
With Argile, you quickly test several occupancy assumptions (nmax) right from the fast energy diagnosis. In a few minutes, you see how this setting affects the home's conventional items, without starting from scratch on every attempt. On the works scenario side, Argile compares the effect of nmax on ventilation, heating, domestic hot water and perceived comfort, to avoid oversizing a heat pump or underestimating flow rates. Quote generation then integrates the grants (MaPrimeRénov', CEE) consistently with the home and the occupancy used: you can also automate your quotes and CEE grants to make things more reliable and save time. You limit the gaps between the study, the pricing and on-site reality. Finally, technical visit assistance and administrative management centralise this information in a clean, traceable file, ready to be shared.
