Technical / Installation Information

What standard are the units made to?

EN 1279 Parts 1 to 6

How should my timber frames be constructed?

A frame needs a U-value or WER (the Architect, Specifier or Frame Maker will give you the U-value or WER for the frame); from this information we can give you the required makeup of the insulating glass unit. Make it clear if your U-value is a centre pane U-value for the glass alone or a combined frame & glass U-value. The size of the rebate in timber frames especially, is critical, the height of the rebate must be at least 15mm & the width, thickness of the unit, plus 6mm for glazing materials, plus the width of the timber bead (normally a minimum of 12mm).

Heritage glazing rebates should be a minimum of 9-10mm.

How should units be glazed TIMBER?

Glazing should be in accordance with BS8000. See our Arbo Heel Bead Glazing System page for the basic method; contact us for other types of glazing and glazing of self-cleaning glass.

Frames should be of sound structure and primed with suitable materials. Aggressive timbers such as green oaks especially, so as to prevent acids leaching through into units sealants.

Units that are not glazed with suitable materials or following our guidelines will be void of warranty.

How should units be glazed – Plastic?

Frames should be dry, drained and ventilated. Units should be installed on suitable glazing blocks and equally supporting both glass panes. Blocks should be placed in the appropriate positions to offer support and rigidity to the glazed assembly throughout service.

The correct overall thickness unit should be specified upon order and where necessary glazed with the correct glazing rubbers.

Glazing Plastic frames is specific to system manufacture. If you are unsure you should seek the services of an experienced glazier/installer.

Are there special requirements for glazing glass in a roof?

  1. The outer leaf is normally toughened to resist thermal fracture.
  2. The inner leaf can be toughened or laminated depending on the application, but both glasses must be a safety glass. If laminated it must be stepped back to be within the building. Special consideration should be given to thermal risk if using laminated. Deep cast shadows can in certain situations cause thermal fracture.
  3. If the bottom edge of the insulating glass unit is exposed, the edge should be encapsulated by a U-channel or the top leaf should be longer than the bottom leaf to run water clear of the seal.
  4. Both top and bottom leaves must be “stopped” in the rebate to prevent the glass sliding down and premature failure.

Duplex and Back to Back Bars. What to allow?

The method of construction compounds tolerances and allowance should be made for this when determining the width of the cover-bar to be applied to the surface of the glass. The width of the cover-bar should be the pitch of the Duplex or Back to Back bar plus 3mm. Deviation from parallel along the bar lines is acceptable.

What is U-value?

The rate of heat loss per square metre for a temperature difference of 1 degree Kelvin, or Celsius, between the interior and exterior.

How can I improve the U-value?

By using either low-e glass with an inert gas if necessary. There are now varying grades of low-emisitivty glass and three inert gasses to choose from. These being Argon, Krypton and Xenon. We can advise what combination will get the results you require.

What is the “greenhouse” effect?

Clear glass will allow heat from the sun to enter the building un-controlled, contributing significantly to internal temperatures.

Is there a date from which all units must be made to EN 1279?

April 2007

Can heat be kept out?

Solar heat gain can be reduced by using a solar control glass. These are glasses such as Plikington Suncool’s or Pilkington Activ’ or body tinted floats such as blue, bronze, grey and green.

Does the thickness of glass improve the insulation value?

Very little.

Is there a self-cleaning glass?

There are clear and tinted self-cleaning glasses produced by the glass manufacturers with a hard hydrophilic coating to help the removal of dirt when it rains or hosed down. There are other applications available that are applied to the surface of the glass prior to installation, the life of which should be checked with the manufacturers. Please call us if you would like to specify self-cleaning glass.

Can I have a cat flap in an insulating glass unit?

Yes, we can put square or round holes in units and supply the flap too.

After glazing what maintenance is required?

Follow the maintenance instructions below for all types of installation:

Flush Edge Units
  1. Inspections should be carried out after about one year and periodically, thereafter, as deterioration could take place as a result of incorrect application or vandalism.
  2. Damaged sealant should be cut out and replaced in the affected areas. The Sealant Manufacturers’ recommendations should be followed.
  3. Where gaskets have been displaced or damaged, or where there are gaps, they should be re-fitted or cut back and capped with silicone sealant.
  4. With vented glazing methods, checks should be made to ensure the drainage or ventilation holes or slots, have not become blocked with dirt. While checking these, it is also advisable to examine the effectiveness of the seal of the exposed frame joints, which may determine the weather tightness of the rebates.
Stepped Edge Units
  1. Same principles of inspection as flush edge units.
  2. Inspect UV blocking lead strip for damage or erosion and replace if necessary.
  3. Keep gutters free of blockages and obstructions so that the unit is not exposed to sitting water, high humidity or moisture underneath the stepped edge.
Micro Porous Frames and Stained Frames
  1. Special care must be given to the inspection of treated and stained softwood frames. Lack of routine maintenance causes the finish to flake off and joints in the frame to open up. This may allow water to permeate the seal and cause failure of the unit.

Visual quality standard for installed insulating glass units constructed from flat transparent glass.

It is necessary to apply a viewing standard when it is deemed an insulating glass unit may have a fault. The glass manufacturers apply a standard to their glass for imperfections in the main body of the glass and any coatings they may apply to it during their manufacturing processes. The quality of glass used in the manufacture of insulating glass units is the same as that for single glazing. Working with the materials supplied to us to the relevant EN standards in turn dictates the quality of the insulating glass units supplied to you and has to be taken into account for the finished product.

The viewing standard will be as follows: Annealed glass will be viewed at 2 metres. Toughened, laminated or low e glasses will be viewed at 3 metres. Other coated glasses will be viewed from 3 metres. The viewing will be at 90 degrees, in natural daylight, imperfections may not be marked to highlight their presence and will only be visible to the naked eye. A band 50mm wide around the perimeter of the insulating glass unit is excluded as an area to be viewed. The insulating glass unit will be looked through, not at the surfaces.

Flat transparent glass, including laminated and toughened shall be deemed acceptable if the following phenomena are neither obtrusive nor bunched: totally enclosed seeds, bubbles or blisters; hairlines or blobs: fine scratches not more than 25mm long: minute embedded particles.

Due to the manufacturing process seeds and bubbles are deemed acceptable in patterned glass.

Duplex and Back to Back Bars

The method of construction compounds tolerances and allowances should be made for this when determining the width of the bar to be applied to the surface of the glass. The width of the bar should be the pitch of the Duplex or Back to back bar plus 3mm. Deviation from parallel along the bar lines is acceptable.

What sealants should be used (i.e. are compatible) with the Ethylene Vinyl Acetate (EVA) laminating interlayer films you use?

We use EVA films manufactured by (Toby to advise) … for the bespoke laminations we undertake (floor panels, barriers and the like). Bridgestone have produced compatibility charts (link opens in a new window) to show which sealants should be used with their EVA films. We stock clear and diffused EVA films.

What sort of glass can be used in a barrier or a balustrade?

BS618 font-weight-bold0 defines the type of glass depending on the type of framework and building it is used in. Your Architect, Specifier or Building Control will specify the Uniformly Distributed Load (UDL) in kN/m2 and/or the Point Load in kN. On receipt the type of building, eg domestic or commercial and the loadings, we can make a recommendation as to the type of glass to be used.

Glass floors, is there a maximum area and special frame?

We have data for the appropriate thickness up to 1m2. Submit the UDL in kN/m2 and Point Load in kN and advise if a domestic floor, dance floor, corridor, or stair tread, for our recommendations.

Glass Processing

What are the basic edge finishes to a piece of glass?

  1. Arrissed Edge – The sharp edges are machined, not a finished edge, suitable for glazing or handling purposes or to reduce the risk of thermal fracture in annealed glass.
  2. Smoothed Edge – The edge of the glass is machined flat and the edges arrissed but not polished.
  3. Polished Edge – The edge of the glass is machined flat, the edges arrissed and the edge is polished.
  4. Mitred edge – The edge of the glass is machined flat and polished to 22.5 or 45 degrees. This is generally used for butt-joint glazed installations like shop fronts and sneeze screens.
  5. Bevel – The face surface of the glass is ground way and polished to various widths and thickness at the edge. Unless the thickness at the edge is specified, it will be to our normal setting.

What diameter hole can be put into a piece of glass?

Virtually any diameter of hole can be drilled or cut. The internal finish to a hole is generally a smooth one. We can polish holes 25mm diameter and up. In toughened glass there are limitations as to how close to the edge the holes can be positioned. The same applies to for cut-outs. (SEE LIMITATIONS DRAWING)

Can you polish or bevel shapes?

Shapes can be bevelled and polished. Internal radii must exceed the minimum radius for the type of machine the glass is being worked on. Submit details of the shape required.

Can you cut a shape from a .dxf file emailed to you?

Yes. We have CNC machines for glass cutting and processing.

Can stencils be cut for sandblasting designs onto glass?

Stencils can be cut from your drawing, after being entered into our graphics machine, a copy will need approving before being put in hand or from your computer generated file. We can also sandblast the reverse of materials like silvered float in detail to create detailed lighting sections for vanity mirrors etc.

Can “cut outs” or “notches” for plug sockets or other items be incorporated in the glass?

Yes, normally in toughened glass to increase the strength of the finished piece so there are rules as to how close to the edge or corner they can be, submit a dimensioned drawing for approval and check limitations drawing.

What is “Cracked Ice”?

An EVA multi laminate where one of the toughened glasses used is broken after laminating, this gives a “crazed” appearance. Alternatively we now insert a foil effect between two laminated glasses to achieve the same effect but with a lighter and thinner build weight with less edge-work constraints. At the time of enquiring we need to know what it is you are looking to achieve with detailed drawings if needed. We can then advise on the best achievable solution.

Is there such a thing as, “One-way Mirror”?

Yes, 6.4mm Laminated One Way. The glass has a grey body tint with a reflective surface coating. The glass is installed with the surface coating facing the observed area. The glass has low light transmittance and high reflectance. When the glass is installed with a lighting ratio of 7:1, the dark side being the side where the observer is (the observer should also wear dark clothing), the reflection will look like a mirror to the observed.

Can you do toughened Mirror?

Yes – We can now supply Pilkington Mirropane™

Safety or Foil Backing

A mirror can be safety backed with a white woven film to give impact resistance on one face to BS6206 Class B. Glass with a white woven safety backing cannot be fixed with a mirror mastic or low modulus silicone. The film is coated with a release agent to enable the roll to be unwound and consequently no manufacturer of safety backing has approved their film to be fixed with an adhesive and conversely no manufacturer of mastic or silicones has approved their products to be used with a safety backing.

A mirror can be backed with an aluminium foil; as such it does not have an impact resistance classification. Foil protects the reflective surface of a mirror and as it has no release agent it can be fixed with mirror mastic or low modulus silicone. Foil is generally used to act as a barrier against moisture in wet environments such as bathrooms. This prolongs life of mirror in these situations. Foil also acts as a barrier against any harmful substances that may be in the substrate that could affect the silvering of the mirror. Certain plastics and plasters have high acidity which can cause a reaction with the silvering.

If desired a mirror can be fixed directly to the substrate with mirror mastic or low modulus silicone provided there is an ample covering to ensure, in the event of breakage, no large and dangerous pieces are able to break off and fall or cause injury.