The lion’s share of vinyl windows are sold as white inside and out, however, substantial market opportunities exist for colors and decorative finishes both inside and out. Because many window fabricators have national sales programs, it is important to consider weatherability and heat buildup in the color conversation. Typical techniques for achieving color along with pros and cons are as follows:

Solid Color Vinyl
Solid vinyl is achieved by pigmenting the compound to achieve a desired color. Extrusion of solid color vinyl is not difficult and colored vinyl is easily separated for recycling. Window fabrication of solid color vinyl requires no additional steps except for the necessity to ventilate and reinforce dark colored profiles. Minor scratches during fabrication and installation are generally accepted and not cause for repair as with painted surfaces. Light colors such as earthtones generally perform well, however, as the colors get increasingly darker, it is more difficult to keep compound cost and heat buildup low while still achieving excellent weathering.

Capstocked Vinyl
Although PVC can be capped with PVC, it is usually capped with more weatherable compounds such as Acrylics, ASA, PMMA, etc. The primary benefit is improved weathering. The capping compounds cost much more than PVC and extrusion requires two extruders. If the cap covers the entire exposed surface then cost savings may be realized in the substrate. Weld cleaning will generally require touch up. Shallow scratches in the cap need not be repaired.

Laminated Vinyl
Laminates are hot melt glued to the profiles after extrusion. Laminates are attractive and durable. Tooling needs to be relieved to accommodate the thickness of the laminates. Weld clean touch up is required. Lamination of horizontal and vertical sliders can be challenging and labor intensive when considering parting lines and screen tracks.

Paint
Paint can be applied to profiles or finished windows. As paint is a very thin coating it is susceptible to scratching during fabrication and installation. Protective film is recommended. Touch up after weld cleaning is necessary. Paints can be formulated to have excellent weathering and low heat buildup. Application of paint is usually very labor intensive.

Hotstamping
Hotstamping is applied to profiles by applying heat and pressure to a foil that transfers the hotstamp to the profiles. Hotstamped profiles should have protective film applied to reduces scratching and will require touch up after weld cleaning. Hotstamps can be formulated to have excellent weathering and low heat buildup.

Aluminum Cladding
Aluminum cladding can be applied to finished windows to achieve superior coating performance. This may also improve structural performance with only minimal negative effect on thermal performance. There will be tolerance issues, additional cost for painted metal, and additional labor for fabrication and assembly. Some care will be required to minimize paint scratching.

SUMMARY

There are many successful paths to colorization of vinyl. It is important to match the needs of the customer with the proper path.

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The potential for excessive heat buildup may be exacerbated by the type and reflective properties of interior window treatments. Avoiding southern and western facing exposures with direct sunlight would be wise. A thorough inspection after installation is recommended to insure weep holes are clear to allow proper drainage and ventilation. Very few if any studies have been conducted to determine the effects of storm products installed over today’s high performance glazing vinyl windows. Therefore, Veka does not recommend applying storm windows over prime vinyl windows.

Due to its chemical composition, PVC alone is insufficient to produce a quality profile. It is necessary for PVC to be protected against deterioration during high temperature thermoplastic processing (e.g. extrusion and frame welding). In the US, Tin-derivatives are typically added to enhance the performance of the PVC.

In addition, lubricants are required in order to prevent PVC-melt from sticking to the hot extruder surfaces and to ensure a good heat transfer within the melt. During this time the lubricant plays an important role in the necessary disintegration of the PVC-particle into its sub-segments, which ultimately is important for maintaining the physical properties of the final profile.

TABLE I – Examples of Lubricants

PVC itself has remarkable impact resistant properties. However, for window and door and fencing/railing profiles, this is not enough, especially in severe weather conditions. Acrylic-based impact modifiers are usually added in the range of 6 – 10% to achieve the superior performance that is required.

Acrylate based flow modifiers and processing aids are also used to adjust the melt flow in the extruder to the required needs. Additional fillers are added for the perfecting of surface gloss, mechanical profile properties, color, weathering properties and so on.

TABLE 2 – Examples of Fillers

Pigments and colorants are used to achieve a variety of colored profiles. The predominant pigment in PVC window and door, fence/railing profiles is Titanium Dioxide. It is also used in a wide variety of paints for other applications. Titanium Dioxide provides both high reflective properties in the visible light and UV-absorption. Titanium Dioxide will cause the profile to be more resistant to weather and UV light. Depending on the desired final properties, further additives may be used.

TABLE 3 – Additional Additives

As you can see, several additional components are added into the PVC to produce high performance profiles. Rather than adding every single component separately during the extrusion process, it has become common practice in the industry to produce a compound (typically called dryblend). Dryblend is a result of mixing the PVC and all the other components together prior to entering the extrusion process.

Over the years, it was discovered that only by hot mixing are the dry components ensured a good homogenous blend. Such a blend remains stable and does not separate when it is transported to various locations using trucks or railcars. The hot mixing process typically is conducted in vertical mixers using specially designed mixing blades.

This process utilizes the friction created by the rotation of the mix. The friction increases the temperature of the mix to a point where lower melting components and waxes become liquid. This allows the other additives to adhere to the PVC-particles and partially enter it. Subsequently, the hot mix is conveyed into another mixer that is rotating at lower speed. This process slowly cools the mix in order to avoid clumping.

After cooling, the produced dry blend is now homogenous, stable and has an ideal particle size and shape. Now it can be easily transported to extrusion lines, e.g. via piping, or conveyed into a storage silo for future use.

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The total window U-value is calculated by area weighing the contribution of the frame, edge of glass and center of glass. The edge of glass is measured starting from the sightline and going towards the center of glass 2.5”. As one can see, described in Table I, the area of the frame, edge and, center can change dramatically depending upon the frame height. However, in all cases the center of glass makes the most significant contribution.

TABLE I

Heat is transferred by conduction, convection and radiation. Conduction, like the heat transferring to the handle of a stovetop metal cooking pan. Convection, like the cold air falling and hot air rising causing a convection current in a room. Radiation, like the heat felt from the sun.

The best way to lower U-value is to reduce conduction, convection and radiation wherever possible.

Starting with the center of glass low e coatings are used to reduce radiation. Argon gas is injected into the airspace between the glass panes to reduce conduction.

Krypton gas (although expensive) is sometimes used instead of argon for even lower conduction. For best results balancing conduction and convection, gas filled gaps should be optimized. For argon, the best results are achieved with space a 0.50”. For Krypton, best results are achieved at 0.30”

Suspended films and triple glazing result in substantial reductions in U-value.

Internal muntins have no effect on U-values as long as there is ample clearance between the muntin and the glass. This of course presents problems for optimized Krypton air spaces.

The edge of glass U-value is effected by the aforementioned center of glass selection, the frame selection and the spacer selection. To reduce conduction from the glass to the spacer, either a dual seal or an insulated spacer is recommended. Insulated spacers are the intuitive choice for U-value reduction however, improvements in some metal spacers have made the differences almost negligible. This is primarily because although the metal spacer is very conductive, it is also very thin and transfers very little heat in a relative sense.

The frame U-value is primarily effected by the conductivity of the frame material convection inside chambers, reinforcing conductivity and foam filling / die cut foams. Typical K (conduction rate) values for various materials are listed in table II below.

TABLE II

Because total window U-value is area weighted, to achieve the lowest possible U-value in the most economical fashion, one should focus first on the glass and then on the frame and spacer depending upon design. The following table ranks U-value improvements from most to least improvement.

Assuming one starts with a typical aluminum reinforced vinyl double hung window with an optimized airspace, low-e and argon, the following improvements can be achieved as noted in Table III.

TABLE III

A typical example of how one may reduce total window U-value is listed in Table IV

TABLE IV

*Note: whereas foam filling may have a perceived marketing value, in practical application, co-extruding foam, or injecting foam into lineals has little effect on total window U-value and presents issues such as adding cost, difficulty in fabrication, minimized space for reinforcing, drainage issues, and a negative effect on the ability/quality of recycling. Therfore, if you must foam, die cut (EPS) foam is recommend.