Published 1 October 202631 min read · the essentials in 2 minSIA 380/1 · EN ISO 10077-1 · EN ISO 14683Uw · ψg · Position in wall · External insulationUpdated 2 October 2026
Window replacement: the position in the wall matters more than the glazing
Windows are works that get decided quickly — sometimes too early. Triple glazing set into a bare reveal, with no façade strategy settled, can lose at installation a good part of the gain paid for in the glazing. The reveal is the return of wall that frames the opening. This dossier sets out the values that matter — Uw, Ug, ψg —, why the position in the wall weighs as much as the glazing, and in what order to validate decisions before ordering.
The question to ask before ordering any window
"In five to ten years, are you going to insulate the façade from the outside?" If the answer is "probably yes" or "we don't know yet", set the window outboard, with the reveal thought through. If the answer is "no, definitively" (protected heritage, documented budget constraint, internal insulation planned), then the inboard position with maximum reveal insulation is the right one. The only wrong answer is not to ask the question.
A building owner short of time? Read § 03, § 06 and "Key points". The rules and the grants — Geneva, French-speaking Switzerland, neighbouring France — have their own dossier: Windows: what the rules require.
Ug — thermal transmittance of the glazing alone [W/(m²K)] · triple glazing with two low-e coatings and inert gas: 0.5 to 0.8 according to PassipediaPassipedia, “Types of glazing and their specific values”: triple glazing, one low-e coating per cavity and inert gas (“usually Argon”): “U-values between 0.5 and 0.8 W/(m²K)”.Passipedia (Passive House Institute) — Types of glazing and their specific valuesaccessed 2026-10-01
ψg — linear transmittance of the glass edge [W/(m·K)] · aluminium spacer (standard category “aluminium and steel, not stainless”): 0.08 tabulated (timber or PVC frame, coated glazing)
Ag, Af — areas of glazing and frame [m²] · lg — perimeter length of the glass edge [m]
ψg is an inconspicuous figure on a quotation, and yet it counts. On a window of 1.2 × 1.4 m, the perimeter of the glass edge is about 4.6 m. Take an aluminium spacer: ψg = 0.08 W/(m·K), the EN ISO 10077-1 tabulated value for a timber or PVC frame with coated glazing. It adds 0.37 W/K of heat loss — the equivalent of degrading Uw by about +0.22 W/(m²K)EN ISO 10077-1 default ψg (2006 ed., Table E.2; Annex G in 2017), timber/PVC frame, coated glazing: 0.08 aluminium or non-stainless steel, 0.06 warm edge. 0.08 × 4.6 m (lg) / 1.68 m² = +0.22 W/(m²K).iBAT, Instituts-Gesellschaft für Betriebs- und Arbeitstechnik des Tischlerhandwerks (Hanovre) — iBAT-Fachinformation 2010-06-22 — Ermittlung des Wärmedurchgangskoeffizienten für Holzfenster und Fenstertüren (Uw-Wert), reproduit DIN EN ISO 10077-1:2006, tab. E.22010-06-22 · accessed 2026-10-01 across the whole window (1.68 m²). A warm edge spacer whose data sheet gives ψg ≈ 0.04 cuts that contribution to 0.18 W/K. The gain is about 0.18 W/K, or ≈ −0.11 W/(m²K) on Uw, without touching either the glazing or the frame. With the standard's tabulated values alone (0.08 against 0.06), the gap shrinks to 0.09 W/K: the gain comes from the product's own value — ask for it on the quotation.
The frame takes up a sizeable share of a window's area: about 20% on the 1.2 × 1.4 m window used as the example here (7 cm sight line). Its share is larger on small windows and wide frames. A worked example on this window, with Ug and Uf taken as assumptions rather than catalogue values. Going from Ug = 1.1 to 0.6 W/(m²K) on the glazing (1.34 m²) saves 0.67 W/K. Going from Uf = 1.3 to 0.8 on the frame (0.34 m²) saves 0.17 W/K, i.e. 20% of the total gain. Ignoring Uf when comparing quotations means reading only part of the datasheet.
Component
Starting assumption
Improved assumption
Calculated effect on Uw
Ug — glazing
1.1 (double glazing)
0.6 (triple glazing)
≈ −0.40 W/(m²K) on Uw
Uf — frame
1.3
0.8
≈ −0.10 W/(m²K) on Uw
ψg — glass edge
0.08 (aluminium spacer, tabulated value)
0.04 (warm edge, product data sheet)
≈ −0.11 W/(m²K) on Uw
ψinstallation — reveal
0.15 (bare reveal: SIA 380/1 limit for a window sill junction in new build)
ψinstallation is not part of the product Uw — it is added after installation, and on site it can take back a good part of the gains won at ordering. Impacts calculated on the 1.2 × 1.4 m example window (glazing 1.34 m², frame 0.34 m², lg 4.6 m, perimeter 5.2 m). Ug and Uf: calculation assumptions. ψg: EN ISO 10077-1 tabulated value and product data sheet (§ 01). ψinstallation: values sourced in § 03, applied as assumptions over the whole perimeter.
The solar factor g — the forgotten half of Uw
Ug measures the losses; the solar factor g measures the gains. Glazing at g = 0.50 lets in 50% of the incident solar energy, through direct transmission and through the heat the glazing re-emits inwards (EN 410) — free passive solar gains in winter. The EnerPHit criterion above couples the two values, with no g threshold on its own: at Ug = 0.50, it requires g ≥ 0.31. Highly insulating triple glazing can show a lower g than double glazing: read it on the glazing's data sheet, and weigh the trade-off orientation by orientation (§ 02).
02 — Choosing the glazing
Triple glazing — when it pays and when it does not
Triple glazing has good arguments in high-performance refurbishment. But the decision deserves to be made project by project, because it costs more than double glazing, is heavier (hardware, reinforced frames) and, depending on its g value, can reduce passive solar gains. The right question is not “triple or double?” but “what overall installed Uw, for what budget, in what wall configuration?”
Triple glazing justified
North and east façades, or wind-exposed ones
On these orientations passive solar gains are limited: what triple glazing may cost in gains weighs little there against what it saves in losses.
To be assessed
Strongly exposed south façade
On a south façade without external solar shading, the difference in g counts. For the same glazed area the transmitted gains are proportional to g: going from glazing at g = 0.62 to glazing at g = 0.45 cuts them by 27% (g values taken as assumptions). If the building lacks thermal mass, summer overheating may also be harder to control. Assess the Ug / g trade-off with a PHPP balance, orientation by orientation.
To be assessed
Listed or inventoried heritage
In Geneva, the joinery of protected buildings follows its own regime, with its exceptions and its waiver. The detail is in Windows: what the rules require.
Triple glazing and weight — a practical point
4/16/4/16/4 mm triple glazing contains 12 mm of glass. At 2.5 kg/m² per millimetre of glass, that makes about 30 kg/m² — against 20 kg/m² for 4/16/4 double glazing. A large 2 m² glazed unit thus carries some 60 kg of glass: hardware, tracks and sometimes the frames have to be sized accordingly. In refurbishment, if you keep the existing frames, have their load-bearing capacity checked before specifying large-format triple glazing.
What Minergie, RE2020 and the BBC Effinergie label really ask of a window — and what the grants fund — is covered separately: Windows: what the rules require.
03 — The decisive factor
The position in the wall — more decisive than the glazing chosen
This is the central technical point of this dossier, and it does not appear in manufacturers' catalogues. The quoted Uw is calculated to EN ISO 10077-1 (or measured in a hot box to EN ISO 12567-1) on the window alone, at standard size, with no real wall around it. That figure says what the product does. It does not say what the window does once installed in your wall.
The difference is ψinstallation — the linear transmittance of the thermal bridge created by the junction between window and wall. It depends on two parameters: the position of the window within the thickness of the wall, and the insulation of the reveals. The reveal is the return of the wall that frames the opening all the way round, between the window frame and the outer face of the façade. It is not the frame, not the glazing, not the sill, but the masonry itself seen in section around the window. Geneva's RCI uses the word "embrasure" in a different sense in its art. 56A: the window assembly itself — glazing, window frames, blind boxes (see Windows: what the rules require).
Three positions, three levels of real performance
Position 1 — Within the insulation plane (optimal)
ψinstallation of the order of 0.03 W/(m·K)Passipedia, quality assurance — thermal bridges: retrofit of a 1930s building, windows “comparable to the situation in a new build”: Ψa = 0.017 W/(mK) at the side connection, 0.030 at the metal window sill.Passipedia (Passive House Institute) — Quality Assurance — Thermal bridgesaccessed 2026-10-01 — minimal thermal bridge
The window sits within the thermal insulation plane of the wall. Where external insulation is applied at the same time, that typically means an outboard installation: the window is fixed in front of the loadbearing wall rather than within the thickness of the masonry (§ 04). Where the wall is insulated from inside, it is the plane of the internal insulation. The reveals are covered by the insulation system. ψinstallation is minimal: the installed performance comes close to the product Uw.
Position 2 — Mid-wall, partially insulated reveal
Intermediate ψinstallation — to be calculated on the detail
The window sits at mid-thickness of the masonry wall, with reveal insulation whose thickness is limited by the depth available (PUR board or rigid mineral wool). The reveal thermal bridge is reduced but not eliminated; its value depends on the actual detail and is calculated to EN ISO 10211.
Position 3 — Set back inboard, bare reveal (to be avoided)
High ψinstallation — no limit value in refurbishment
The window replaces the old joinery in the same position (on the inner face of the wall) with no reveal insulation. It is the simplest installation to carry out in refurbishment. The masonry reveal (brick, concrete) forms a continuous thermal bridge all round the window. In new build, SIA 380/1 caps the ψ of a window-to-wall sill junction at 0.15 W/(m·K)EN-NE102 (April 2023, based on SIA 380/1:2016), table 4: ψli = 0.15 W/(m·K), type 5 “appui de fenêtre contre mur”, new build. Alterations (§ 6.2): no thermal-bridge limit under the single-component route.Service de l'énergie et de l'environnement, canton de Neuchâtel — Aide à l'application EN-NE102 — Isolation thermique des bâtiments (SIA 380/1, édition 2016), édition avril 2023accessed 2026-10-01. In alterations it sets no limit value on thermal bridges under the single-component route. Worked example on the 1.2 × 1.4 m window. Assumptions: Uf = 1.0 for both windows and ψg = 0.06 (tabulated value); installation ψ of 0.15 for the bare installation and 0.03 in the insulation plane. Triple glazing at Ug = 0.55 installed this way goes from Uw = 0.81 to 1.27 W/(m²K); double glazing at Ug = 0.9 set in the insulation plane goes from 1.09 to 1.18. The triple glazing ends up worse off.
5.2 m
perimeter of a 1.2 × 1.4 m window — the length over which ψinstallation acts
+0.78 W/K
heat loss for ψinstallation = 0.15 — the SIA 380/1 new-build limit — over that perimeter: +0.46 W/(m²K) on effective Uw
≠
catalogue Uw ≠ installed Uw: on this window, the gap between the bare installation and the one in the insulation plane is ≈ 0.37 W/(m²K) with the assumptions above
Ordering high-performance windows and setting them into bare reveals lets the installation take back part of the performance paid for. The position is validated before the order, not after.
Across a whole building, the item shows
Worked example: on a building with 30 windows totalling 150 m of perimeter, moving from ψinstallation = 0.15 to 0.03 W/(m·K) removes 18 W/K of heat loss, continuously throughout the heating season. The SIA 380/1 calculation includes linear thermal bridges: a high ψinstallation across all the windows weighs on the overall balance of the building. It is an item settled when the installation is specified, before the order. What that balance decides in Geneva — the HPE standard — is explained in Windows: what the rules require.
04 — Preparing for external insulation
Outboard installation — preparing tomorrow's façade without blocking today's works
Outboard installation means fixing the window in front of the load-bearing wall — projecting on the outside — rather than within the thickness of the masonry. The window is thus placed in the planned insulation plane (present or future), and the reveals are covered by the insulation system. It is the logical configuration when external insulation goes on at the same time; it is also a position to consider when external insulation is envisaged in the medium term but not yet decided.
Why outboard installation is the right decision in a partial refurbishment
Replacing the windows in the old position (on the inner face of the wall) while planning future external insulation creates a junction problem that is hard to solve. Once the insulation goes on, the reveals will be too short to cover the full depth of wall plus insulant. Either the reveals are extended with made-up pieces (thermal bridge retained, heavy finishing work), or they are left bare (thermal bridge and condensation risk). New windows installed in the old position become an obstacle to the full façade refurbishment.
With outboard installation from the moment the joinery is replaced, the window is already in the right position for the future external insulation, which then meets the outer face of the frame cleanly. No additional reveal work is needed. The low ψinstallation of position 1 (of the order of 0.03 W/(m·K)) does, however, assume that the insulation overlaps the frame. Until the external insulation is in place, the junction remains a thermal bridge to be dealt with provisionally: the gain only materialises once the façade is insulated.
The technical conditions for outboard installation
Technical
Fixing bracket
An outboard window is fixed to the load-bearing wall by metal brackets (stainless steel or anodised aluminium, thermally broken where possible). The fixing has to carry the permanent loads (glazing weight) and the variable loads (wind, operation). Sizing to EN 1991-1-4 for wind-exposed sitesNF EN 1991-1-4, Eurocode 1 part 1-4: "donne les bases pour l'évaluation de l'action du vent sur les structures des bâtiments et des ouvrages de génie civil". To be read with the national annex.AFNOR Éditions — NF EN 1991-1-4 — Eurocode 1 : actions sur les structures — Partie 1-4 : actions générales, actions du vent2005-11 · accessed 2026-09-02. Thermally broken bracket systems exist and reduce the thermal bridge of the fixing itself.
Technical
Airtightness and watertightness
The frame-to-wall junction has to be airtight on the inside (airtightness tape or acrylic sealant) and watertight with drainage on the outside (impregnated pre-compressed sealing tape or EPDM strip). The principle: airtight on the inside, insulated in the middle, rain-tight and vapour-open on the outside. In refurbishment this detail is sometimes sacrificed to speed of execution, and that is one cause of water ingress on replaced windows.
Caution
Appearance and acceptance
An outboard window on a still-uninsulated wall visibly projects — it can surprise the building owner or the tenants if it has not been anticipated and explained. The larger the projection — to prepare for thick external insulation — the more it has to be presented and approved in the project file.
Caution
Building envelope limits and boundary distances
In Geneva, the LCI deals separately with the thickness of external insulation. The text, its proviso and the office to consult are in Windows: what the rules require.
05 — The reveals
Insulating the reveals — the solutions, and the warning signal
A window and its insulated reveal are a single item of work. Here are the common solutions, compared at equal thermal resistance, then the signal that gives away a reveal left bare.
Insulating the reveals — the common technical solutions
Solution
Thickness for R = 1 m²K/W
Declared λ (manufacturer data sheet)
Applicability
Rigid PUR/PIR board
2.2 cm
0.022 W/(m·K) — swisspor PIR Aluswisspor, PIR Alu product sheet: PIR rigid foam board faced with aluminium on both sides, λD = 0.022 W/(m·K). Manufacturer's value.swisspor — PIR Alu — fiche produit (fiche fabricant)accessed 2026-10-01
Lowest λ of the three: useful where reveal depth is constrained. Plaster finish or PVC reveal lining.
“Universal-use” insulation according to its manufacturer.
Rigid mineral wool
3.5 cm
0.035 W/(m·K) — Rockwool RockfaçadeRockwool France, Rockfaçade product sheet (06/2026): stone wool for ventilated cladding, λD = 0.035 W/(m·K), reaction to fire A1. Manufacturer's value.Rockwool France — Rockfaçade — fiche produit (fiche fabricant)2026-06 · accessed 2026-10-01
Non-combustible (class A1 on the data sheet cited). Thicker than PUR for the same thermal resistance.
PVC or aluminium reveal profile without insulation
—
Thermal bridge retained
Not reveal insulation at all. The masonry thermal bridge stays active: ψinstallation unchanged, condensation risk retained.
Thicknesses calculated for the same thermal resistance R = 1 m²K/W (d = R × λ), to compare the materials, not as thicknesses to install. λ: declared values from the manufacturer data sheets cited. The resulting ψinstallation is calculated on the actual junction detail (EN ISO 10211).
Condensation on the reveals — the warning signal
Traces of condensation on the reveals after a window replacement do not point to a faulty product: they point to an untreated reveal thermal bridge. Condensation forms where the inner surface drops below the dew point of the indoor air — about 12 °C for air at 20 °C and 60% relative humidity (Magnus formula). An uninsulated masonry reveal can drop below that threshold in winter, and mould follows the moisture. This is the opposite of what the window replacement was meant to achieve.
In Geneva, RCI art. 56A carries the word "embrasures" in its title. What it actually requires, paragraph by paragraph, and what the other French-speaking cantons and neighbouring France provide: Windows: what the rules require.
06 — The order of decisions
The classic mistake: ordering the windows before deciding the façade
This is a mistake met on the ground in residential refurbishment in Geneva and French-speaking Switzerland, and it is hard to put right afterwards. New windows set in the wrong position create constraints for their whole service life.
Why the mistake happens
Cause
Degraded windows get noticed
Condensation, draughts, glazing that fogs up in winter: degraded windows are noticed at once by the occupants, who ask for them to be replaced. The building owner orders windows without a prior energy balance — sometimes without knowing that external insulation would make sense.
Cause
A window quotation is easy to get
A window quotation comes quickly; a CECB® Plus takes longer. The CECB is the cantonal building energy certificate, a grade calculated from the building rather than a metered consumption. The decision can follow the fastest quotation rather than the most complete assessment. With no owner's adviser or design engineer appointed early on, the building owner proceeds on the information available, which is then the suppliers' information.
In a rental building, the owner or the managing agent decides on the windows on a maintenance signal. The strategic decision (external insulation, HPE, Minergie) belongs to another level — for instance a deliberative body (owners' meeting, foundation board) with a longer decision cycle. Operational decisions come before strategic ones, creating expensive faits accomplis.
Cause
Unawareness of the position problem
Joiners set the window where the old one was — that is their trade, not their role to prescribe the façade strategy. Without instructions to the contrary from the design engineer, the window goes in at the same depth. Outboard installation is technically more demanding; without a specification, nothing prompts the contractor to propose it.
The recommended order of decisions
Step 1 — Overall assessment before any decision
CECB or PHPP balance — setting the trajectory
In Geneva, the CECB® and the CECB® Plus have to be submitted to obtain the grant decision on measure M-10GEnergie, conditions of measure M-10: "Le certificat CECB® et le CECB® Plus doivent être fournis pour obtenir la décision de subvention".GEnergie, OCEN, République et canton de Genève — Amélioration de la classe CECB® pour l'enveloppe et pour l'efficacité énergétique globale — mesure M-10accessed 2026-09-02, the one that rewards a class improvement. The CECB gives the current classes and the gap to close. A PHPP balance (where the target is Minergie-P or EnerPHit) makes it possible to simulate the effect of the various measures in their order and combination. A position mistake, by contrast, is paid for over the window's whole life, in excess consumption and remedial work.
The façade strategy determines where the windows go
Three scenarios determine where the windows go. (A) Immediate external insulation — windows within the insulation plane, installed at the same time. (B) External insulation envisaged later — outboard installation prepared in advance, brackets and sill sized for the future insulation thickness, reveals left accessible for the later junction. (C) No external insulation planned — internal insulation or no wall insulation at all: windows at mid-wall with maximum reveal insulation. Scenario (B) is the most delicate, because it requires a decision on the likely future of the façade — a decision the building owner has to take deliberately, not by default.
Step 3 — Technical specification of the windows according to position
Target Uw, Ug, ψg, reveal, bracket — the complete specification
Once the position is settled, the specification becomes precise. It sets the target product Uw, worked back from the installed Uw sought and the expected ψinstallation. It also sets the minimum Ug and ψg, the reveal system, the bracket type if outboard, and the sealing detail (airtight inside, vapour-open outside). The joinery contractor's quotation answers that specification — not the other way round.
Step 4 — Ordering and coordinated installation
Joinery, reveals and façade: a single works sequence
Joinery replacement and reveal insulation are carried out by the same contractor, or within the same works package. Where outboard installation goes together with external insulation, the insulation contractor is on site for the junction. Handover includes a check of the junction details. Where the target is Minergie, the airtightness measurement (Blower Door test, the pressurisation test of the envelope) is to be entrusted to a specialist contractor. No window installed without its insulated reveal — the two are a single item of work.
Step 5 — File and grants
A file documented as the work proceeds
Documenting the installation during the works (photographs, junction details) is easier than afterwards, and useful if a file asks for it. Counters, measures and conditions, in Geneva as in neighbouring France: Windows: what the rules require, § 05.
07 — Three questions from site
What professionals and building owners ask
Why doesn't the manufacturer state ψinstallation in the quotation?
Because ψinstallation depends on the wall the window is set into — and the manufacturer does not know your wall. EN ISO 14683:2017 publishes tabulated values by junction typeEN ISO 14683:2017: "simplified methods for determining heat flows through linear thermal bridges at junctions of building elements", with tabulated default values.NBN / Buildwise — NBN EN ISO 14683 — Ponts thermiques dans les bâtiments — Coefficient linéique de transmission thermique — Méthodes simplifiées et valeurs par défaut (ISO 14683:2017)2017 · accessed 2026-09-02 according to the junction geometry and the position of the insulation. They are default values: they give an order of magnitude without numerical simulation, not the value of the actual detail, which is calculated to EN ISO 10211. It is the responsibility of the design engineer or the specifier to bring that parameter into the specification — and to check that the installing contractor follows the detail prescribed.
What if the windows have already been replaced in the wrong position?
Two options depending on the situation. (1) If external insulation is planned: the insulation contractor can take the insulant up to the outer face of the frame and wrap the reveals from outside — the thermal bridge is partly corrected, even though the window is not in the insulation plane. The result is not as clean as an outboard installation, but the improvement is real. (2) If no external insulation is planned: insulate the reveals from inside, with an insulation board bonded to the masonry reveal, as thick as the available depth allows, plaster finish. ψinstallation will not be optimal, but the risk of condensation and mould goes down. In both cases the remedy is decided on a reading of the building and of its actual junction detail, not on a catalogue.
Do triple-glazed timber windows last as well as PVC in the Geneva climate?
The durability of a timber frame depends above all on its maintenance: the exposed faces need paint or stain at the interval the manufacturer specifies. On insulation, timber's Uf advantage is not a given: a solid timber IV 78 profile calculates at around Uf ≈ 1.3 W/(m²K)iBAT technical note, 22.06.2010: numerical calculation (EN ISO 10077-2), IV 78 timber profile: Uf = 1.3 W/(m²K) at 500 kg/m³, 1.6 at 700 kg/m³; IV 68: 1.4 and 1.8.iBAT, Instituts-Gesellschaft für Betriebs- und Arbeitstechnik des Tischlerhandwerks (Hanovre) — iBAT-Fachinformation 2010-06-22 — Ermittlung des Wärmedurchgangskoeffizienten für Holzfenster und Fenstertüren (Uw-Wert)2010-06-22 · accessed 2026-10-01 in light softwood and 1.6 in dense timber. These values come from a numerical calculation to EN ISO 10077-2, at 500 and 700 kg/m³. Uf values below 1.0 call for profiles with an insulating core or greater depth — check the manufacturer's data sheet. Timber-aluminium frames combine timber inside with aluminium outside, which reduces maintenance.
Key points
What to take away, and in what order to act
Ask the façade question before any quotation. "Will you insulate externally in five to ten years?" A "we don't know yet" already argues for outboard installation.
Have the diagnosis done first. CECB or CECB Plus in Geneva, a PHPP balance where the target is Minergie-P or EnerPHit: the trajectory comes before the product.
Specify the position, then the product. The Uw to order is calculated backwards, from the installed Uw sought and the ψinstallation expected at the junction.
Do not buy a window without its insulated reveal. The two are a single item of work; a bare reveal exposes you to condensation and mould.
Document the installation as the work proceeds. Photographs and junction details: useful if a grant file asks for them, and hard to reconstruct afterwards.
GenevaRCI art. 56A, HPE, LCI art. 114A, the M-10 grant: the article-by-article reading is in Windows: what the rules require.
SwitzerlandLimit value Uw ≤ 1.0 W/(m²K) against the outside, in new build as in refurbishment (SIA 380/1:2016, MoPEC 2014).
Neighbouring FranceBBC Effinergie Rénovation label, DTU 36.5 and MaPrimeRénov': the conditions are in the same dossier, § 04 and § 05.
Sources and references (20)
Every figure and every claim in this dossier links back to its source. Hover or tap a footnote marker to see it.
Passipedia (Passive House Institute) — Quality Assurance — Thermal bridges(accessed 2026-10-01) Passipedia, quality assurance — thermal bridges: retrofit of a 1930s building, windows “comparable to the situation in a new build”: Ψa = 0.017 W/(mK) at the side connection, 0.030 at the metal window sill.
Settle the order of works before you order your windows
The position in the wall, the insulation of the reveals and the coordination with the façade strategy are settled before the order — not after. NRG positive advice: a reading of your building and weighing up the standards — SIA 380/1, HPE, Minergie®, EnerPHit — for Geneva and French-speaking Switzerland.