Low SightLine Sealed Units

By using a new concept in the construction of double glazed units we are able to supply low sightline sealed units.
This is done by using the latest equipment and components that are available which allow us to have very small cavities or space between the glasses with a 5mm perimeter sealant depth. We also manufacture the low sightline sealed units using inert gases, this helps to reduce the centre-pane 'U' value of the units which subsequently helps to conform to building regulations.

Windowright low sightline Double Glazed Units use a combination of a 4mm clear outer pane with a choice of cavities of either, 3.9mm, 4.8 mm or 6.4mm using a warm edge super spacer bar. The warm edge bar is available in various colours, the 3.9mm only being available in white and all the other thicknesses are available in black, Charcoal, White, Gold and Light Grey.
If the value of the insulation provided by the sealed unit is a key factor then the wider the cavity the better the insulation, using an inert gas with a 4mm Low Emissivity glass will also help the insulation value of the low sightline sealed unit.
The low sightline units are particularly useful when completing Conservation projects and timber windows
Low Sightline sealed units will fit almost any suitable window rebate and are popular for conservation work or sash and casement timber windows.


Allowing a maximum of 2mm between back of rebate depth and unit.

Glazing sizes should be hard size of opening less 2mm from height and 2mm from width and allowances made for any irregularity in height or width.

U Values
The insulation of double glazed sealed units are measured in 'U' Values, the lower the 'U' value figure the better the insulation. Below is a list of 'U' values that can be achieved when using certain components.

Pilks 'K' or Low 'E'
4mm Clear / 3.9mm Warm Edge Spacer / 4mm low emissivity2.72.21.8
4mm Clear / 4.8mm Warm Edge Spacer / 4mm low emissivity2.51.91.6
4mm Clear / 6.4mm Warm Edge Spacer / 4mm low emissivity2.21.71.4

Climaguard A or Planitherm Total +
4mm Clear / 3.9mm Warm Edge Spacer / 4mm Soft Coat2.62.01.6
4mm Clear / 4.8mm Warm Edge Spacer / 4mm Soft Coat2.31.71.4
4mm Clear / 6.4mm Warm Edge Spacer / 4mm Soft Coat2.01.51.1

Glazing Information for Double Glazed Sealed units into Timber Frames

Your low sightline double glazed sealed unit is manufactured to a high standard using top quality materials to EN1279 requirements. Our units are guaranteed as long as they are glazed correctly. Below are some principles that have to be considered when glazing sealed units into timber frames. General Principles of Glazing.
The following points need to be followed to ensure the correct glazing of double glazed sealed units. Moisture Attack.
If water is trapped against the edge seal of a unit for a long period, failure of the adhesive bond of the sealant to the glass will result causing the unit to break-down. Moisture can penetrate to the rebate area, either through or around the glazing system, or through frame joints into the glazing system, from a variety of sources such as rainwater, window cleaning, condensation within frame sections and condensation on the room side glass surfaces. All glazing systems must protect the edge seal of the unit, either by preventing access of water to the seal, or by ensuring that water which penetrates as far as the seal, is soon removed by drainage of the rebate area by means of a specially designed frame.

Compatibility of Unit edge seal with glazing materials.
The edge seals of a unit have different compatibilities with different glazing materials. The hot-melt edge sealant used in Sealed Unit manufacture is not compatible with solvents, and because certain glazing compounds contain such solvents we recommend a good quality Low modulus Neutral Cure silicone sealant such as Hodgson Silfix U9 ISO 11600 F & G or a Security Glazing Strip such as Hodgson Flexistrip.

Exposure to sunlight.
The edge seal on most units will degrade if exposed to ultra-violet light rays for a long period. It is essential, therefore that the rebates provide full cover of the edge seal from sunlight. It is normal practice for the spacer bar not to protrude past the rebate.

Prior to Glazing.
An edge clearance is necessary to prevent frame-to-glass contact, and to prevent water from bridging between the rebate and the edge seal of the unit. The edge clearance should be sufficient to allow for thermal movement also, so, when measuring the frame you should allow 6mm on the height and width (3mm all around the unit).

1. Firstly ensure that the rebates, beads and unit are clean.
2. Run a continuous seal of glazing strip around the back of the rebate or a continuous seal of low modulus silicone and place two glazing blocks on the bottom rebate. The glazing blocks should be of a resilient, non-absorbing, rot-proof, compatible material.
3. Sit the unit on the glazing blocks and push gently against the back rebate and centralize, making sure not to push silicone out of the rebate. If using security glazing strip apply direct from the reel onto the correct surface of the unit (if using Low 'E' double glazed sealed units ensure that the Low 'E' surface is on the inside of the property) and press sufficiently along its whole length to achieve good initial adhesion. Remove backing paper and offer to the back rebate, push firmly to seal across the joint. There should be 3mm gap around between the unit edge and the timber, to allow for thermal movement and to prevent water from bridging between the rebate and the edge seal of the unit. (See Fig1)
4. Next fix the glazing beads around the unit. The beads should be a snug fit, and fixed using non-corrosive material (sheradized and brass glazing pins are recommended).
5. With a fine nozzle, run a neat continuous seal of silicone sealant between the face of the glass on the inside and the back rebate (see Fig 2.) and also between the face of the glass and the glazing bead on the outside thus forming a water tight seal on the edge seal of the unit from any moisture which may occur. Flexistrip can also be used for this process. Make sure any residual voids are filled (see Fig 3).


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