Understanding window energy ratings is not as easy as one would hope. Unlike other insulating features of the home, the efficiency of windows can be expressed multiple ways with each rating system focusing on different efficiency aspects of the window. Add in different glazing options (glass, coatings, Argon gas and spacers) and judging a window can become very tricky for the average home owner. Change the opening style of the window (e.g. form a slider to a casement) and the ratings and efficiency changes too.
Energy Ratings & Testing
Modern pride's itself on making a window on the West Coast for the West Coast. We are also extremely proud to make a window that is one of the more energy efficient windows in BC with particularly good Energy Rating, Watertighteness and Wind Load ratings.
Besides Energy Ratings, what else contributes to making a "good" window?
Ratings are just one way to assist with determining “good” windows form “bad”. Here’s a list of other things to look out for:
Understanding Window Glazing Options
Glass within today’s' windows is not the same as the glass in windows form 20 years ago. Technology has changed and window glass, or “glazing”, has been a leading contributor to increasing the energy efficiency of a window. The following a brief over view of the some of today’s more commonly used terms and glazing options that manufactures will offer.
Argon: Argon is a gas that is heavier than air and assists with the slowing down of heat transfer. Its placed between the layers of gas. Argon helps lower U-Value.
LowE : Low-emittance (lowE) coatings are virtually invisible, metal or metallic oxide layers added to glass assist with lowering the U-Value. In general terms LowE keeps your home cooler in summer and warmer in the winter. Modern currently uses Solarban 60 (Soft Coat) and Sungate 500 (Hard Coat - Northern Series) as its two options for LowE.
LowE - Soft Coat vs. Hard Coat: There are many types of Soft and Hard Coat options on the market – each with its own unique ratings and pros and cons.
Soft Coat lets less heat in but less heat out (typical in the West) as it acts as a thermal mirror reflecting heat back into the home. Conversely in the summer Soft Coat allows for less heat to enter the home then Hard Coat, therefore keeping it cooler.
Hard Coat let’s more heat in but also let’s more heat out. Typical in Manitoba and Alberta, Northern Ontario Hard Coat looks to maximize solar heat gain. In the summer homes with Hard Coat may require additional air conditioning as it will let more heat in.
As a general theory, HVAC units or heat pumps are typically used in combination with Soft Coat as Soft Coat keeps the overall temperature of the home/commercial building more balanced and stabilized versus the HVAC unit having to compensate for larger hot/cold swings if Hard Coat was used.
A good approach is to apply Hard Coat to windows on the sun-facing side of the home and Soft Coat on the shady sides of the home. This maximizes heat coming into the home and slows down its escape.
LowE and UV: Soft Coat (79% reduction) provides a greater reduction in UV then hard Coat (51% reduction)
Spacers: Modern Windows are made with Super Spacer Technology. We call it TrueWarm because Super Spacer is the worlds only 100% polymer foam, Super Spacer's NO-Metal formula blocks the heat escape path and provides one of the best thermal performances in the industry. That means it keeps the heat in during the winter months and keeps the cool in during the summer months. Super Spacer assures comfortable winter humidity levels with hardly any worries about condensation and mold.
Note: Differences in ratings are based on decimal points and fractions of percents. Overall differences are typically so minor that they don’t allow for any actual noticeable or physical difference. Ratings can also change window to window depending on glazing combinations and sizing samples.
Energy Ratings - Rating System Terms & Definitions
Zone Rating – A, B, C or D: Canada has been divided into four climate zones based on annual average temperature. Zone A is the mildest, and Zone D is the coldest. Vancouver Island and the Sunshine Coast are within Canada’s mildest Zone and requires a Zone A Rated window only. Modern does offer however Zone A,B and C rated windows.
Physical Testing Properties– A, B & C: All windows and sliding glass doors must be rated for their airtightness, watertightness, wind load strength, resistance to forced entry, insect screen strength (windows only) and ease of operation (sliding glass doors only) when they are installed in new homes or other buildings. Provincial and local building codes require different airtightness, watertightness and wind load strength categories depending on the climatic conditions; the higher the better. Air: A1-A7, Water: B1-B7, Wind: C1-C5.
Solar Heat Gain Coefficient (SHGC): The SHGC indicates the amount of solar gain through a pane of glass. It ranges from 0 to 100. SHGC is specific to how well the window allows for heat to travel into the home (outside-in).The higher the number, the better the solar gain.
U-Value: A U-value indicates the rate of heat transfer. The lower the U-value number, the slower the transfer of heat from a warm area to a cold area (inside-out). The lower the number the better.
An R-Value is the inverse of a U-value and indicates the resistance to heat transfer. The higher the R-Value number, the more insulative the product is. R & U Values will come in imperial or imperial units. Neither the U- or R-value account for heat energy from the sun (solar gain).
Energy Rating (ER): The Energy Rating (ER) value is calculated using a formula that balances a product's U-value with its potential solar heat gain coefficient (SHGC) and its airtightness. The higher the number, the more energy efficient the product. The ER scale was recently modified so that all products now have a rating of between 0 and about 50. The higher the ER number, the better the product's thermal performance.
U-Value vs. ER: Our Soft Coat windows have a better U-Value and a lower ER then our Hard Coat (Northern Series) windows as Soft Coat is better at keeping heat in the home but lets less het in the home then Hard Coat.. Conversely, our Hard Coat windows have a higher ER as they are better at letting more heat in the home but a weaker U-Value as they let more heat out then Soft Coat.