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Guide to problems and solutions: reflection on glass panes

High performance glass owes its efficiency to its fine Low-E metallic coating. Therefore, we can observe on this type of glass a different tint and reflection from regular uncoated glass. It is this coating that contributes to reducing heat loss by reflecting it towards the inside. It is considered normal to see reflections with this type of glass. Obviously, the industry offers no warranty attributable to this type of "defect".


Guide to problems and solutions: condensation

On humidity problems, Canada Mortgage and Housing Corporation offers a comprehensive guide to solutions. We suggest that you download and read it before any other article. (Below)

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In the North-American zone, we are faced with a challenge during every cold season: condensation. This phenomenon, apart from obstructing our view through windows and door windows, happens when there is too much water vapor contained in the ambiant air. A certain level of humidity is necessary for the comfort and health of the occupants, but some control is required to prevent problems related with the formation of condensation on surfaces. In the case of a house that has been renovated in regard to its openings, the air infiltration may be solved, but a new problem can sometimes arise: humidity.

Reunited in this chart are the corresponding indoor humidity levels in relation to the outdoor temperatures, which will help prevent condensation problems.

Outdoor temperatureIndoor relative humidity
- 28°C or less 15 % at the most
- 28°C à - 23°C 20 % at the most
- 22°C à - 17°C 25 % at the most
- 16°C à - 12°C 30 % at the most
- 11°C à - 6°C 35 % at the most
- 5°C à - 4°C 40 % at the most
Table 1

If you manage to reduce the relative humidity to these recommended percentages, it may help to solve the annoying problem of condensation on surfaces.

Prevention techniques
The reduction or elimination of condensation will often require a number of complementary techniques. The methods for reduction or elimination will therefore target the product itself (windows and doors), protective indoor devices (curtains, shades, valences, etc.), the indoor relative humidity and the interior pressure in relation with the exterior.

1- Indoor protective devices
To maintain the temperature rating of the product or its performance level when it comes to resisting condensation, the indoor protective devices must not stop or obstruct the air flow on the product. The temperature rating will decrease as an effect of any restriction of the air movement.

2- Control of the ambiant relative humidity
The replacement of old windows by new high efficient windows usually brings about notable improvements to the air tightness of the building, thus providing substantial energy savings and increased comfort for its occupants.

However, when day to day habits remain unchanged with regard to producing water vapor inside the residence (showers, baths, cooking, plants, etc.) , and there is a drastic difference to the level of air exchange, there is a possibility that during certain months of winter, the level of relative humidity will exceed the recommended value in table 1, which can cause condensation on the inner surface of windows. Occasionnal occurence of this problem (once or twice a year) can be solved by momentarily opening two windows located on opposite walls, or by turning on the kitchen or bathroom fan. Otherwise, in cases where the condensation appears too frequently and is judged unacceptable, the occupant should consider other means such as the installation of a ventilation system.

3- Control of the interior pressure
The behavior of doors, windows and other componants of a building envelope will be influenced by the direction and intensity ot the pressure variation that is exerted on a given componant.

The pressure variation that is exerted on a componant of the building envelope can be positive (+), that is, towards the interior of the building, or negative (-), towards the exterior of the building. It can also happen to be neutral, which means without any pressure variation. In the first case (+), the targeted componant will be subjected to an infiltration rate that will depend on the air of the openings (cracks, splits, etc.) and the intensity of the pressure variation. In the second case (-), the targeted componant will be subjected to the exfiltration rate that will depend on the air of the openings and the intensity of the pressure. In the case where the pressure variation is neutral, there will be no air exchange between the interior and the exterior of the building. Obviously, this last solution represents our goal since the behavior of the different componants would be ideal. However, a control of the pressure variation that is neutral through all the componants is almost impossible to realise, which underlines the importance of knowing the undesirable effects associated with any air leakage that crosses the building envelope.

4- Effects associated with air infiltration
A positive pressure variation (+) is associated with air infiltration. This pressure variation may come from the wind flow, the chimney effect, depressurization caused by an exhaust fan or a combination of all these effects.

5- Effects associated with air exfiltration
A negative pressure variation (-) is associated with air exfiltration. Just like the previous example, this pressure variation may come from a combination of different forces (wind, chimney effect, positive pressure caused by a fan).

When the walls are submitted to air exfiltration, we observe these phenomenons : exfiltrating hot and humid air that comes in contact with materials whose temperature decreases as it progresses towards the exterior. These materials will cool the air, and, before it reaches the outer sides of the building, there will be condensation and/or solidification (frost) of the water vapor on and within certain elements of the envelope.

The condensation or formation of frost on or within certain elements will lead to the following problem concerning windows: the obstruction of our view, a basic fonction, and also, sashes that can be nearly impossible to open.

The goal of this document is to help detect, within your residence, the signs and probable causes of humidity and air quality linked to the humidity and therefore, offer some practical solutions that you may chose to apply to improve the situation.



Quality standards for sealed glass units and stained glass units.

1- Introduction

This document was prepared to provide information to our customers on the inspection methods of our products and to provide knowledge on different industry criteria of acceptance, thus explaining why certain defects or imperfections are not covered by the limited warranty.

2- Quality standards for sealed glass units and stained glass units (inspection)

This procedure has been summarized on the basis of Canadian standards and of the National Building Code. According to Canadian standards, certain defects are acceptable upon using the inspection method below. This method allows all concerned persons to inspect the sealed glass panels and stained glass panels in the same way and by using the same acceptable criteria. References: CAN CGSB 12.3-M, CAN CGSB 12.8-M, National building code.


Chips or bubbles: gaseous inclusion appearing as a round or elongated air bubble in the glass.
Scratch or scrape: any mark or crack on the glass surface that seems to have been caused by a sharp or rough object.
Dirt: Deposit of a foreign matter on the inner surface of the panels of the sealed glass unit or stained glass unit.

Visual inspection procedure: If there is a defect, place the glass in a vertical position and exposed to daylight without direct sunlight or to any other indirect light enabling to observe all imperfections. Defects must be inferior to the dimensions specified in the following table and scratches must not be detectable at the distances specified in the said table.

DefectCentral areaOuter area
Chip or bubble Maximum of 1,5 mm Maximum of 2,5 mm
Scratch or scrape Non visible at 3 feet Non visible at 5 feet
Dirt Non visible at 3 feet Non visible at 5 feet
Other Non visible at 3 feet Non visible at 5 feet

The central area is considered to be, in the center of the glass unit, a maximum surface of 80 % of the total surface. What remains is considered to be the outer area.

3- Quality standards for doors, aluminum and PVC windows (inspection)

These standards have been summarized on the basis of norms provided by our various suppliers. According to their norms, certain defects are acceptable when applying the inspection method below. This method allows all concerned persons to inspect the doors and windows in the same way and by using the same acceptance criteria.

Visible defectsCentral area
Bruises Non visible at 5 feet
Scratch Non visible at 5 feet
Paint defects or retouches Non visible at 5 feet
Distorsion Non visible at 5 feet
Other defect Non visible at 5 feet


370, chemin Mont-Granit Ouest
Thetford Mines, Québec, Canada
G6G 5R7
Phone : 418 338-4628
Fax : 418 338-0347
Toll free : 1 800 905-5234
E-mail :
RBQ Licence : 8102-0000-00

Printed on : November 30, 2020