A Portuguese window quote is full of words nobody explains: Uw, Low-E, corte térmico, oscilobatente. Here they are in alphabetical order, with the Portuguese word you will see on the quote in brackets, a few sentences each and a link to the guide that goes deeper; where a number depends on the product we do not give one, and you should ask the installer for it in writing.
A
Air permeability (estanquidade ao ar, permeabilidade ao ar)
How much air gets through a closed window. The EN 12207 standard gives it classes from 1 to 4, and class 4 is the best. A window that lets air through wastes part of what the glass gains. See thermal insulation.
Aluminium (alumínio)
A frame material that is rigid and allows slim profiles and big openings. Without a thermal break it conducts heat very well, so always ask about the break. See PVC or aluminium.
Argon (árgon)
A gas put between the panes instead of air. It conducts less heat than air, so it improves the glass a little. See double glazing, Low-E and argon.
B
Basculante (tilt-only window)
A window that only tilts, hinged on a horizontal axis. It opens little and is common in bathrooms and high windows. See opening types.
C
Casement window (janela de batente)
A window whose sash opens inwards or outwards like a door, hinged on one side. According to ADENE, it usually seals better than a sliding window. See opening types.
CE marking and EN 14351-1 (marcação CE)
EN 14351-1 is the European product standard for windows and external pedestrian doors, and the CE marking is tied to it. The performance data (water tightness, wind resistance, air permeability, thermal transmittance, sound insulation and others) goes in the declaration of performance. Ask for the document and keep it. See warranties and certificates.
Chamber (câmara)
The sealed space between two panes of an insulating glass unit. In a 4/16/4 specification, the chamber is the 16, meaning 16 mm. Ask whether it is filled with air or argon. See double glazing, Low-E and argon.
CLASSE+
An energy label for windows created by ADENE, the Portuguese energy agency, on a scale from F (least efficient) to A+ (most efficient). It also shows the solar factor, the light transmission, the air permeability and the sound attenuation. See the CLASSE+ label.
Condensation (condensação)
Water that forms on a cold surface when humid air touches it. It can appear on the glass, on the frame or between the panes, and each case has a different cause. See window condensation.
Contra-frame (contra-aro, aro falso)
A frame fixed in the opening, into which the window is then placed. Not every job uses one, so ask whether the quote includes it and why. See replacing old windows.
D
Double glazing (vidro duplo)
Two panes with a sealed chamber between them. Two quotes that both say “double glazing” can describe very different glass: ask for the specification, the gas and whether it has Low-E. See double glazing, Low-E and argon.
F
Fixed window (fixo)
A part of the window that does not open and only lets light in. It can be a panel next to a sash that opens, or a whole window. Because it does not open, it cannot be used to air the room.
Frame (aro) and caixilho
The aro is the fixed frame, fastened to the wall. The caixilho is the window without the glass: frame and sash together, which is what a quote means by “PVC caixilharia”. The frame’s heat loss is measured by the Uf.
G
g-value, or solar factor (fator solar, valor g)
The share of the sun’s energy that passes into the house, from 0 to 1. The lower it is, the less heat comes in, which helps in summer and costs some free sun in winter. See double glazing, Low-E and argon and the solar factor and the Portaria.
H
Hardware (ferragens)
The metal parts hidden in the frame: hinges, lock, handle, arms. They decide whether the window opens and closes without effort and for how many years. Ask for the make and the warranty. See tilt-and-turn windows.
Hygrometer (higrómetro)
A small device that shows the relative humidity of the air, meaning the water the air holds compared with the most it could hold at that temperature. It helps you see whether the house needs more ventilation. See window condensation.
I
Insulating glass unit (unidade de vidro, vidro isolante)
The double or triple glazing as one sealed piece: panes, spacer and chamber. If the seal fails and water appears between the panes, the unit is replaced, not the window. See window condensation.
L
Laminated glass (vidro laminado)
Two or more panes bonded with a plastic film. If it breaks, the pieces stay stuck to the film. It is used for safety and, with an acoustic film, for noise. See double glazing, Low-E and argon.
Light transmission (transmissão luminosa)
The percentage of daylight that goes through the glass. It appears on the CLASSE+ label. See the CLASSE+ label.
Low-E (low emissivity, baixa emissividade)
A transparent coating on one face of the glass that reflects heat instead of letting it through. The quote should say which type, because some coatings insulate and others block the sun. See double glazing, Low-E and argon.
M
Monobloco
A window and shutter box that arrive on site as one piece. It can reduce the height of the glass, so confirm the final height on the drawing before you approve it. See roller shutter box.
Multi-chamber profile (multicâmara)
A profile with several air chambers inside, like a honeycomb. It helps with insulation. The number of chambers and the design vary from system to system, so ask for the data sheet. See profile classes.
O
Opening (vão)
The hole in the wall where the window sits. You measure the opening, not the glass. See how to measure windows.
P
Profile (perfil)
The “skeleton” of the window, in PVC or aluminium: the shape of the parts that make the frame and the sash. The make and the system name are on the data sheet. See PVC or aluminium.
Profile class (A, B, C)
For a PVC profile, the EN 12608 standard grades the thickness of the outer walls. Class A is 2.8 mm or more and class B is 2.5 mm or more. The thicker the walls, the stiffer the profile. See profile classes.
PVC
A rigid plastic, made without plasticisers, from which many frames are built. It conducts much less heat than aluminium without a thermal break. See PVC windows.
R
Remate (finishing)
The finish that closes the join between window and wall, inside and out: sill, reveals, paint, plaster. Ask who does it and who pays. See installation.
Rw (sound insulation)
A number, in decibels, that measures how much sound the window or the glass stops. The higher it is, the better. Check that the value is for the whole window and not only the glass. See sound insulation.
S
Sash (folha)
The part of the window that opens and closes, where the glass sits. A window can have one, two or more sashes. The weight of the glass and the size of the sash count when you choose the profile.
Sealing (selagem)
Closing the joints around the window with tape and sealant, to stop air, water and noise. Foam alone should not be the only protection. See installation.
Shutter box (caixa de estore)
The space above the window where the roller shutter winds up. It is a void in the wall, and it can let in air, cold and noise if it is not insulated. See roller shutter box.
Sill (peitoril)
The piece at the bottom of the opening, on the outside, sloped so that rain runs away from the wall. Ask whether the quote replaces it or keeps it. See installation.
Sliding window (janela de correr)
A window whose sash slides along a track, instead of opening outwards or inwards. It saves space, but it usually seals less well than a casement. See sliding windows.
Sound-insulating glass (vidro acústico)
Usually laminated glass with an acoustic film, often with two panes of different thickness. It does not erase noise, it lowers it. Ask for the Rw in writing. See sound insulation.
Spacer (espaçador)
The strip that keeps the two panes apart and closes the chamber. An aluminium spacer conducts heat through the edge; warm-edge spacers conduct less. The glass specification does not say which one is used, so ask. See double glazing, Low-E and argon.
T
Tempered glass (vidro temperado)
Glass treated to make it stronger. When it breaks it turns into small, blunt pieces, and it cannot be cut after tempering. ADENE says that coloured glass should be tempered, so it does not break from thermal shock.
Thermal bridge (ponte térmica)
A spot in the house where heat passes faster than through the wall around it, such as a poorly insulated corner or a shutter box. Mould often shows up there. See roller shutter box.
Thermal break (corte térmico, rutura térmica)
A rigid plastic bar that joins the two halves of an aluminium profile and slows the heat between outside and inside. Not every aluminium system has one. See aluminium with a thermal break.
Threshold (soleira)
A piece at the base of a balcony or sliding door, at floor level. Under a window the usual word is peitoril, but usage varies. See sliding windows.
Tilt-and-turn (oscilobatente)
A window with two openings on the same handle: sideways, like a casement, or tilted at the top, with only a gap for air. See tilt-and-turn windows.
Transom (bandeira)
A small window above a door or another window, separated by a horizontal crossbar. It can be fixed or open to give air. When you ask for a quote, say whether you want it fixed or openable.
Trickle vent (grelha de ventilação, microventilação)
A small opening, in the frame or in the wall, that lets air in continuously with the window closed. There are several models, so ask which one is in the quote and where it goes. Do not block them because cold comes in. See window condensation.
Triple glazing (vidro triplo)
Three panes and two chambers. It insulates more, but it weighs and costs more, and in many homes a modern double is enough. See double or triple glazing.
U
Ug
How much heat passes through the glass, at its centre. It is measured in W/m²K, and the lower, the better. If a quote only gives the Ug, it shows a more favourable number than that of the window you receive. See double glazing, Low-E and argon.
Uf
How much heat passes through the frame, without the glass. Also in W/m²K, and the lower, the better. In an aluminium profile the thermal break lowers it. See aluminium with a thermal break.
Uw
How much heat passes through the whole window: glass, frame and the glass edge where the spacer sits. In W/m²K, the lower, the better. It is the number to compare between quotes. See thermal insulation.
V
Ventilation (ventilação)
Renewing the air in the house, through windows, vents or extractors. New windows seal better, so the air renews less by itself and ventilating becomes a daily task. See window condensation.
W
Water tightness (estanquidade à água)
How well a closed window keeps rain out. EN 12208 classifies it by the test pressure up to which no water gets in, and a higher class withstands more. The test does not include how the window is fitted into the wall. See installation.
Wind resistance (resistência ao vento)
How well the window withstands wind pressure without deforming or opening. EN 12210 gives it classes from 0 to 5, and a higher class withstands a bigger load. The result is valid for the size tested, so ask for the class of the window you will receive. See sliding windows.
Sources
- Neuffer: U-Values for Windows: definitions of Ug, Uf and Uw, the W/m²K unit and the rule that a lower value insulates better.
- Finstral: Norma europeia de produtos, janelas e portas exteriores: characteristics in the declaration of performance and the air, water and wind classes (in Portuguese).
- Intertek: EN 14351-1: scope of the standard and CE marking.
- ADENE: Janelas Eficientes (guide, in Portuguese): 16 mm chamber, argon, laminated and tempered glass, sliding windows being more air-permeable, Rw.
- ADENE, CLASSE+: label (in Portuguese): the F to A+ scale and the fields on the label.
- Wikipedia: Insulated glazing, Solar heat gain coefficient, Laminated glass, Tempered glass, Window, Window sill, Transom (architecture), Hygrometer and Sound reduction index: glazing unit, spacer, solar factor, laminated and tempered glass, window parts, transom, relative humidity and Rw.
What to do next
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