Many office buildings have a problem with unwanted heat from the sun not only in the summer months but also in the winter when the A/C is turned off. Unless a building is specifically designed to gather and distribute the solar heat uniformly in all areas, tenants will experience hot spots on the south, east and west elevations and building owners, in turn, will receive a rash of complaints. Even with zone control, offices with south, west and east exposures can be difficult to keep at a comfortable temperature. Covering the windows with blinds or shades is not always the best option since these block the view, reduce natural daylight and continue to let heat into the interior space.

There are really three considerations, and those are Energy, Productivity, and Aesthetics

 

Energy

From an energy perspective, window films reduce up to 80% of unwanted solar heat and glare. As a result A/C demand is lowered. Additionally, peak power demand is greatly reduced and the use of A/C during the shoulder seasons is minimized. To prove this point, there have been a number of documented cases in multiple chiller installations where one of the chillers could be shut down after sun control film had been installed.

‘Low E’ window films can retain up to 30% of the heat that otherwise would be lost in colder months. Paybacks can occur very quickly (especially when capital upgrades are required) but typically they range from 3-5 years depending on glass type, film selected, building orientation/type, HVAC system, energy rates, climate, etc. Retrofitting existing windows with window film will be only a fraction of the cost of replacing them. It also offers the added bonus of saving on disposal charges and reducing environmental impact.

 

Productivity

From a productivity perspective, there are numerous studies that directly relate productivity to temperature variances. It has been proven in numerous buildings that window film smoothes out these variances and contributes to a productive work environment. Glare is another comfort factor that can be addressed with sun control film. Glare can be reduced by up to 80%, which in turn improves computer screen visibility and reduces eye strain. From a building management perspective, comfortable tenants are more likely to renew their leases.

 

Aesthetics

The higher quality films block up to 99% of the UV rays and have abrasion resistant coatings to endure regular cleaning without damage. By blocking 99% of the UV and reducing heat, the higher quality window films significantly reduce fading of expensive flooring and furnishings. Life expectancy of quality-manufactured window films range from 15 to 20+ years in Canada.

Reputable manufacturers use an adhesive layer that creates a mechanical rather than a chemical bond with glass to allow easier removal when reapplication is required. Building appearance can also be significantly enhanced by creating an attractive uniform look and eliminating the patchwork effect of the different window coverings.

 

4. Spectrally Selective Films:

• Special manufacturing process – film coatings are sputtered stacked using various metal/oxides.
• Reduce solar heat gain without compromising as much of the visible light as the first three technologies above.
• More expensive than Dual Reflective Films – allow complete viewing regardless of day or night.
• Typical heat gain reduction is less than Metallized Films but are not as shiny or reflective in appearance

 

5. Nano Technology:

• Similar to Spectrally Selective but contain no metals or ceramics – eliminates the concerns related to metal corrosion over time
• Uses hundreds of polyester layers to filter infrared and reject solar heat.
• No interference with cell phone reception – all Metallized Films tend to reduce signal strength.
• Reduces reflectivity of ordinary glass as viewed from both inside and outside.
• Film performance is higher in the summer months when the sun is at an angle during the hottest times on the day – allows more heat into the building during the winter
• Although the cost is more than Spectrally Selective films, it is possible to capture additional energy savings if daylight dimmable lighting is available.

 

6. Combination Films:

• Combination of safety/security laminate and sun control film
• Typically used on ground floor installations to deter forced entry or to minimize the effects of glass shards from the perspective of safety.
• Specialized combination films are also available to mitigate the effects of a bomb blast
• Film laminate attachment to the frame enhances overall performance

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Making the right film choice​

Interesting facts and things to consider

 

1. What are your (and tenant) issues?

• Rising costs of energy
• Premiums associated with peak power demand
• Use of A/C during shoulder seasons
• HVAC System cannot maintain an even temperature throughout the building
• Too hot or too cold - tenants uncomfortable
• Too much annoying glare – can’t see computer screens or eyestrain a problem
• Patchwork look to a building

If any of the above issues are a concern, window film will likely offer a cost effective retrofit solution. It can help your building operate more efficiently and solve many problems associated with tenant retention. It will also make your building more environmentally friendly and assist with upgrading your building appearance and classification.

 

2. What are the Typical Energy Savings?

• Rule-of-thumb: “Window Film saves up to one ton of air conditioning for every 100 square feet of filmed sun exposed glass.” This translates into 12,000 BTU’s of saved energy
• These savings do not include the reduction of charges associated with peak power demand or costs associated with running the A/C in the shoulder seasons
• Computer modelling of your building is available from some manufacturers to simulate your specific building energy dynamics in order to determine payback periods.
• Energy calculations do not factor in capital cost savings associated with deferring upgrades that may have been required to address under capacity – film should be factored in before upgrading is considered.
• The higher quality films reflect a portion of heat back into the rooms (up to 30% in the case of Low E Films) that otherwise would be lost in colder months.
• The new nanotechnogy films allow in more heat in the winter than in the summer
• Typical paybacks can range from immediate to approximately 3-7 years. Case studies are available from reputable manufacturers.

 

BTU Model

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