EVS Double Retro Glazing

Retro Double Glazing

Retro fitting Double Glazed units to existing timber windows is a great way to upgrade your windows as well as maintain their character. The process does require a skilled joiner to remove the existing glass and install  the new panel. EVS has now developed a new Glazing bead that integrates uPVC beading with a rubber (EPDM) seal for superior protection and finish.  

Double Retro Glazing

The key feature of the EVS Double Retro Glazing is the Aerated PVC profile that provides a strong and low profile bead that secures the glass into its position. The PVC profile integrates a rubber (EPDM) seal that provides a durable seal and a sharp looking finish. The PVC can be cut, pinned and painted like timber but unlike timber it wont swell up with moisture or bend, twist or split after it has been installed making for a more durable and long lasting solution.

EVS Double Retro Glazing
EVS Double Retro Glazing

The EVS Double Retro Glazing system follows industry standards when it comes to specifying glass and securing the glass with suitable glazing blocks and edge clearances. Where EVS stands out from the others is the design of the glazing beads follows the EVS method of using air vents to provide air movement around the installed glazing panel. Trapped moisture very rarely flows out from the drain holes unless there is an excessive amount of moisture getting into the cavity, so air vents work better to remove moisture that would otherwise cause rot or panel failure. The PVC and EPDM rubber seals also serve to provide a long lasting bead seal.

Advanced materials lead the way

uPVC that looks and feels like timber, but doesn't absorb moisture nor does it warp or split. Ideal for cutting, sanding pinning and sealing, it makes for a longer lasting glazing bead with a low profile to minimize its visual impact.  Its rolled corners and non shiny surface provide a solid base for a quality paint finish that wont split of flake off.
The wedge seals are made from rubber (EPDM Ethylene Propylene Diene Monomer) which don't shrink and have a high UV resistance. The special profile shape is designed to maximize the seal around the edge to prevent dust and moisture getting past. 

EVS glazing beads are the most advanced, durable and arguably most attractive, all round solution for timber retro double glazing.   

EVS Double Retro Glazing

Installation of EVS Double Retro Glazing

The process of retro glazing a panel can take between 3 - 6 hours per panel and requires a skilled person competent with using a router and skill-saw as well as a variety of other small tools. The retro-glazing industry is unregulated which can also be risky if your installer doesn't do a proper job. The biggest risk is ensuring the new glazing unit is properly sealed against moisture which is the primary cause of premature failure.   Double Glazing IGU's are deigned to have a life span of around 25 years but are only guaranteed for around 10 years by the manufacturers. A poorly installed unit may fail within 2-3 years due to moisture getting inside the panel and causing it to fog up. It is highly recommended that units have their painted exterior finish as part of the installation process to ensure they have the best opportunity to last. 

EVS Double Retro Glazing Installtion

Remove window panels

Panels are removed by first cutting through the paint around the edges between the panel and the frame then the panel can be taped out using a block and gentle tapping or using a multi-tool to cut the nails holding the panel.


Remove existing glass

The glass needs to be removed by using a biscuit cutter router blade from the inside and a skill-saw cut on the outside that neatly intersects to remove the putty edge as well as create a suitable rebate for the new glass unit.


Repair rot and prepare timber

There is sometimes rot and flaking paint that needs attention before the new glass is installed. Rot will need to be completely removed and either re-built with timber or epoxy fillers and timber treatments. Reinforcement screws should also be added to each corner. Finally all the exposed timber needs to be prepared and painted with a suitable primer.


Install primary seal

A properly installed primary seal is important to prevent water pumping inside. Often there is a pressure difference between outside and inside and if there are gaps around the edge of the window then the pressure will suck moisture into the edge of the unit which can cause leaks, rot, and potential premature failure of the glazing panel.


Install IGU (Insulated Glazing Unit)

It is important to allow room around the IGU to ensure any moisture that gets in, can either drain or vent out. Some installers will suggest that they use a sealant around the internal edges but this is a risky because water can suck into the gaps and cause premature failure of the glazing panel. It is important to also have suitable glazing blocks holding the panels in the correct position, particularly along the bottom to provide a suitable drainage gap


Install EVS Glazing Beads

The Glazing Beads are the primary defense against moisture getting in, so they need to be attached firmly with no gaps around the edges or in the corners. Some installers just use timber glazing beads, Butyl tape and sealants which need high levels of paint maintenance due to the constant movement of timber, EVS uPVC beads provide a more stable long term solution


Install Panel back into frame

The Panel needs to be reinstalled back into its frame and if its an opening panel then its a good opportunity to replace the old hinges and if its a fixed panel then its best to pre-drill for a galvanized nail rather then a screw, so they can be removed easily in the future. Screwing and gluing the frame in make it very difficult for any future maintenance.


Paint and Finish

Painting is very important and often installers will require you to paint the panel within a few months in order for your warrantee to be valid. The most important thing is to ensure there is a good paint seal around the edges of the glass especially on timber bead systems, where any moisture that gets through will accelerate premature failure of your glazing system. 

Thermal Performance of Double Retro Glazing

Timber frame windows have superior insulation qualities that provide higher performance compared to replacement aluminum windows with the same glass. There are a number of options when it comes to glass panels with different properties for different solutions. Below are some indicative examples of the differences between standard and low-E IGUs   

EVS Double Retro Glazing

Existing single glazed window

The low insulation value of (R0.19) on single glazed panels causes heat loss and condensation in poorly vented rooms. Upgrading with retro glazing will improve your single glazed window.

EVS Double Retro Glazing

Double Retro Glazing (Standard)

The EVS Double Retro Glazing fitted with standard glazing (R0.36) still has a high insulation value compared to Aluminum double glazing (R0.26). It is ideal for allowing the sun to warm your home. 

EVS Double Retro Glazing

Double Retro Glazing (Low-E Argon)

EVS Double Retro glazing fitted with Low-E argon panels provides a top preforming (R0.53) for a retro fitted window solutions. The Low-E provides higher insulation against heat loss as well as heat gain. 

First there was putty, then timber and now uPVC

If you have owned a character home then you will be familiar with old putty windows that have eventually cracked and failed, Now the industry is using timber beads that will need regular painting and maintenance to ensure they don't let water in. Generally timber moves and swells up causing paint to split and allowing more water to penetrate. PVC beads wont absorb moisture and wont swell up and will hold paint work longer, providing a more durable seal and less ongoing maintenance,

Some problems with using Timber Glazing beads

The industry generally uses timber glazing beads and various sealing methods from Butyl tape to hand placed silicon. Both the timber and the seal methods have limited success when they are not painted after installation or maintained, which can lead to premature failure of the glazing units and costly repairs. The bead may be treated against rot but the paint will flake off if moisture is getting past inadequate seals. 

EVS Double Retro Glazing wooden bead failure

Insect Invasion

Large drain holes provide a perfect home for insects and can clog up with spiderwebs and prevent the units from draining. EVS uses  smaller drain hole/vent system at the top and bottom that are less affected by insects. 


Surface Crazing

Timber that gets wet can swell and then dry out causing stress on the paint finish that eventually causes crazing, which intern lets more moisture in and accelerates the deterioration of the paint. EVS's uPVC glazing beads don't absorb moisture so wont cause surface flaking


Fixture Failure

Poorly sealed timber glazing beads will allow moisture to twist and bend the timber beads which can increase the chance of the panel coming loose from its fixings. EVS's uPVC glazing beads don't bend or twist and will remain in place.


Timber Crack/Splitting

Timber can split during the fixing process and overtime water can get into the crack and cause the pins to rust and the paint to split around the crack. EVS's uPVC glazing bead doesn't split because of its aerated structure


Joint Failure

Poorly sealed timber glazing beads will move from increased moisture which will place strain along the painted joints and cause the paint to fracture and peel off. EVS's uPVC glazing beads have EPDM rubber seals that don't shrink or move and don't allow moisture to get past. 


Seal Failure

Seal failure around the edges of timber glazing beads is the main cause of failure, because most glazing beads are fixed with Butyl tape and sealant that relies on skilled installers and ongoing maintenance.  EVS's uPVC glazing beads uses a multi finned rubber seal that provide more reliable and consistent seal over a longer time frame.

Download your Copy 
 You can download your copy of the EVS Double Retro Glazing PDF (A4 Format)
Download the Booklet format

EVS Draught Seal

Dunedin and Otago Agent

Talk to us about your Retro Glazing project. For locations around the rest of New Zealand we can organise local installers for your project

Phone: +64 (0) 274346912
Email: info@evsglazing.nz

EVS Head Office 

EVS Window Technology Ltd
122 Kaituki Ridge Lane
Queensberry Hills
Central Otago 
New Zealand


Email: info@evsglazing.nz
Draught Stop orders Sales@evsdraughtstop.nz

Mobile: +64 (0) 27 4346 912