The ins and outs of window replacement
Selecting replacement windows for your building may seem simple and straight forward. However, this can be one of the most confusing and complex processes which can plague even the most knowledgeable of condominium boards.
In order to ease the headaches and assist you in the selection of your replacement window system, the following helpful tips will guide you through this difficult process.
1. Wood, vinyl, and aluminum, oh my!
Windows are manufactured in a variety of different materials such as wood, vinyl, and aluminum. There are even windows which are manufactured from a combination of these materials. The selection of material will depend on a variety of factors such as type of construction (combustible or noncombustible), building height, guard requirements, the proximity of windows to adjacent windows and doors, wind loads, etc.
Wood and vinyl windows are considered to be made of combustible materials and may not be allowed in noncombustible construction which would include residential buildings over four stories. The Ontario Building Code (OBC) provides guidelines as to when combustible windows are allowed in noncombustible construction.
It is important to know when windows are required to be designed as guards. An operational window located less than 1070 mm from the floor level and more than 1800 mm from the floor or ground on the other side of the window is to be designed as a guard in accordance with the OBC which means its opening has to be restricted to a maximum of 100 mm and must be able to resist lateral force. This requirement may also limit the possible selection of window materials.
2. Performance is everything.
When selecting a window system, the most important factor should be the window’s performance. All window systems are fabricated and tested in accordance with AAMA/WDMA/CSA101/I.S.2/A440-08, NAFS—North American Fenestration Standard /Specification for windows, doors, and skylights. Compliance to this standard is required by the 2012 OBC. The key performance criteria for Windows are as follows:
- Air Infiltration
- Water Infiltration
- Design Pressure, or Window Load Resistance
- Forces Entry
- Thermal Performance
- Condensation Resistance
The minimal requirement for the above performance criteria will depend on a number of factors including location, building height, and terrain.
3. Not all operational windows are created equal.
A number of operational windows are available on the market including sliders, casements, awnings, single or double hung, as well as others. It's important to understand that these operational windows can vary greatly in their performance when it comes to air and water infiltration as well as their thermal performance and resistance to condensation.
Typically, operational windows such as sliders and hung windows have increased air and water infiltration when compared to casement and awning windows. The difference is the quality of the seal you achieve when the windows are in the closed and locked position. When the locking mechanism is engaged on a casement or awning window, the frame applies pressure to the weather-stripping gasket on all sides, creating a tighter seal. The same seal cannot be achieved in a slider or hung window due to the limitations of the locking mechanism.
Casement and awning windows are manufactured with thermally broken sashes which provide increased thermal performance and condensation resistance.
It is for these reasons that we recommend our clients select either a casement or awning operational window.
4. Bells and whistles: Which ones to choose?
Selecting a window system is in many ways similar to buying a new car. The dealer will try to sell you the model with the leather heated seats, navigation screen, and backup camera. However, do you truly need all these bells and whistles? Like a car, window and glazing manufacturers offer upgrades to their systems including extra wide window frames, triple pane glazing units, argon and krypton gas, and a variety of coatings and tints. These upgrades come with a cost and these costs may out way any benefit to the building.
The upgrade to triple pane glazing units might seem like a good idea as they provide increased sound transfer resistance and thermal performance, especially during a time when energy costs continue to skyrocket. Typically, triple pane glazing units are 15 to 20 percent more efficient. However, they can be as much as 40 percent more costly. Energy savings and the additional cost to upgrade to triple pane glazing units must be carefully weighed to demonstrate a benefit to the building.
Unlike triple pane glazing, the use of glazing coatings and inert gasses such as argon and krypton are commonly used and will also increase thermal performance and reduce solar heat gain. The costs to upgrade to a glazing coating and the use of inert gas are relatively low when compared to the benefits they provide.
There are two basic types of glazing coatings, passive low-e coatings, and solar control low-e coatings. Passive or “hard-coat” coatings are recommended for colder climates as they allow some of the sun’s short-wave infrared to pass through the glass helping to heat the building during the winter while also reflecting the interior long-wave heat energy back inside. Passive coatings are durable and can be installed on the exterior surface of the glazing unit or on one of the interior surfaces. Solar control or soft-coat coatings have low emissivity and superior solar performance. Solar control coatings are easily damaged and are typically installed on one of the inner surfaces of the glazing units. The performance of solar control coatings can be enhanced when combined with most tinted glass.
For most window replacement programs, we typically recommend the use of double pane glazing units with 6mm thick glass, a 13mm warm-edge spacer, a hard or soft low-e coating, and argon gas filled.
Your design consultant will be able to guide you through the selection process of these upgrades and which ones will be beneficial to your building.
5. Why drywall when trim will do?
The perimeter of windows in most high-rise buildings are finished with drywall returns. In many cases, the removal of the drywall around the perimeter of the windows is required to perform the replacement. This allows for proper preparation of the rough opening prior to the installation of the new window. Reinstatement of drywall finishes will increase costs and prolong the duration of the project which means increased disruption for the residents. With the substitution of drywall returns with trim, the disruption to residents can typically be limited to just a few days.