Why the surface inventory is the foundation of a solid retrofit project in 2026
Surfaces: what exactly are we talking about on site (walls, floors, roofs, windows)?
On site, surfaces are all the boundaries of the heated volume. This covers walls facing outside or a garage, ground floors, roofs and lofts, as well as windows and doors. We distinguish opaque surfaces from glazed ones. These are what concentrate most of the heat loss, and a large share of comfort.
The information to record without error: area, composition, condition, orientation, unheated space
For each surface, note the measured area, the composition (materials, thicknesses, existing insulation), the condition (moisture, cracks, continuity), the orientation and any shading, then whether it's in contact with an unheated space. A reliable survey underpins the thermal calculation, heat pump sizing, and the supporting documents for subsidies. Part of that information is rebuilt before the visit from the address alone, land registry, construction year and energy rating included, so the visit is there to confirm.
Common mistakes and their direct impact on the quote, subsidies, and final performance
Forgetting a floor over a cellar, confusing gross area with usable area, or averaging different compositions skews the quote. The result: underestimated insulation quantities, a measure that no longer matches its specification, a weakened funding file, and final performance below expectations. In 2026, with tighter audits, well-inventoried surfaces beat assumptions every time.
Moving from note-taking to structured data entry: the method that saves time
Standardizing labels and units: the key to avoiding omissions and duplicates
On site, adopt the same vocabulary everywhere. For example: exterior wall, wall against unheated space, ground floor, roof, window. Same logic for units: m² for areas, linear metres for lengths, cm for thicknesses. The result: fewer trips back to the office, and each surface entered once, in the right place.
Organizing entry by zones and levels: dwelling, rooms, volumes, associated surfaces
Think of your survey as a plan. First the dwelling, then each level, then each room. Within each room, attach the surfaces, openings, and ceiling heights. With this hierarchy, a photo or sketch immediately finds its context again. You gain a clear structure and cut down on missing fields.
Quick on-site checks: area consistency, thermal bridges, insulation continuity
Before leaving, run a one-minute check: wall area consistent with the room's perimeter. Openings properly deducted. Sensitive junctions identified: floor-wall, wall-roof, window reveals. Also check insulation continuity at joints and access hatches. These checks avoid 80% of rework. To go further on the sensitive points, see our article on thermal bridges.
Surface inventory and costing: securing your measurements and profitability
Turning the inventory into work lines: insulation, airtightness, ventilation
Starting from the surface inventory, turn each area into clear work lines. One surface equals one work package, one technique, one unit, and one piece of evidence. For example: exterior walls with internal or external insulation, roof slopes, ground floor, then air leak treatment and ventilation upgrades. You avoid the omissions that eat into margin.
Adjusting quantities and sensitive line items: roof slopes, undersides, party walls, load-bearing partitions
Discrepancies often come from the "in-between" zones. Measure roof slopes, undersides, and returns separately. Identify party walls that shouldn't be insulated, and load-bearing partitions to treat only if planned. Add a waste coefficient, and cost out access (scaffolding, hatches) to protect your profitability. For those areas, surfaces and heights are extracted from the readings taken on site and feed the costing, with no second pass back at the office.
Documenting to limit disputes: photos, notes, assumptions, and technical reservations
Attach a simple file to the quote. Dated photos, sketches, measurement notes, assumptions (thicknesses, substrates, networks), and technical reservations about hidden risks. This habit secures the subsidy file and reduces disputes at sign-off.
Entering surfaces in Argile: from field survey to a usable pre-quote
Structured data entry in Argile: useful fields, clear naming, and automatic reuse
On site, you record the surfaces (walls, floors, roofs) and what actually matters for costing. In Argile, entry uses simple fields: surface type, area, orientation, existing insulation, thickness, access. The naming stays clear, so fewer omissions and fewer duplicates. Once entered, each surface is automatically carried into the study and the pre-quote.
Renovation scenarios: comparing treated surfaces and prioritizing work
You test several scenarios and compare, at a glance, which surfaces are treated versus left as-is. Argile highlights the overall impact and helps you prioritize without getting lost in spreadsheets. Often you start with the areas losing the most heat, then adjust based on budget and site constraints. The result: a more readable pitch for the client.
Pre-costing and funding: linking the inventory, the quote, and the calculation
Starting from the surface inventory, Argile pre-costs the work packages and prepares a usable quote. You link each package to the applicable funding. The schemes rely on eligibility criteria and, in most cases, on companies registered for the measure, with technical requirements attached to each measure. Argile calculates an estimate of the amounts and of what is left to pay, to be confirmed when putting together the file.
Best practices for your teams: making the surface inventory reliable without slowing down the visit
Preparing the visit: documents to request, points to check, survey order
Save time on site by pre-filling the file. Ask in advance for plans, photos, the EPC, past work invoices, and access to key areas. On site, survey the surfaces in the same order every time, top to bottom, then outside to inside. Take dated photos and note uncertainty rather than improvising.
- Loft, hatch, height, insulation
- Walls, lining, thermal bridges
- Ground floors, crawl space, cellar
Shared entry rules: who enters what, when, and how to validate internally
Assign a pair. One person measures and photographs, the other enters the data the same day in your tool. Use a single naming convention for surfaces, areas in m², and "unknown" when proof is missing. Do a quick check with an internal checklist before quoting.
Special cases: difficult lofts, ground floors over cellars, damp walls, and technical constraints
For difficult lofts, favour laser measurements, photo markers, and insulation continuity. For ground floors over cellars, check condition, ventilation, networks, and access before costing. For damp walls, treat the cause first: ventilation, rising damp, infiltration. Poorly installed insulation can trap moisture. Note technical constraints as soon as you visit.
