Window Replacement
There Are Many Reasons to Consider New Windows, Including Performance and Energy Savings
By Rana Bayadi & Bill Mann
When considering a window replacement project or drafting a policy and guidelines for owner replacement, it is not as simple as heading down to your home improvement store and picking out a window. There are many things that need to be researched and addressed, such as structural, fire, water, sound, and energy ratings. Your local building department may have a list of requirements and specific aesthetics standards that need to be met, as well. Existing window configuration may not meet the fire egress code or structural wind load ratings for your location.
In addition to structural and fire requirements, sound, energy, and fall hazard requirements play an important role in finding the right replacement window. If all the major requirements are not enough, the list goes on to include required planning aesthetics, historical preservation, and waterproofing integration. Pre 1978 developments that contain lead and or asbestos in their building materials will require proper abatement and disposal, as well.
Why should window replacement be considered? One of the main reasons is performance of the existing window reaching the end of its functional life cycle. Perhaps the association is embarking in replacing the exterior building walls so windows could easily be replaced and would save thousands of dollars in future costs. By replacing windows at the same time as the exterior wall cladding system you can ensure a continuous and waterproof building envelope. With the rapidly rising energy costs for heating and cooling, window replacement can be a cost-effective improvement that will continue to pay for itself in savings by reducing air and heat loss. The aesthetics of new windows can improve the curb appeal of your home and increase its value at the same time. The real estate industry states that the return on investment for window replacement is 69-85%. When you figure in energy savings and added home value, window replacement looks like a smart move.
Once you decide to move forward with replacing your windows, many things need to be considered to mitigate risk and reduce life cycle costs: material, fire resistivity, waterproofing, configuration, glass, wind, energy ratings, and building aesthetics.
Retrofitting is a low cost choice and is often considered instead of replacement. But the waterproofing on a retrofit window is just a bead of sealant around the window to the outside of the wall using the old window frame. If you have stucco cladding the sealant will not properly adhere to it and will fail. With a retrofit, the window has a flush fin that is simply planted over what may already be a leaky window. If the existing window frame or integration with the weather barrier is leaking, the new retrofit window will not fix the problem and hidden decay to the structure will continue.
We recommend installing nail flanged windows as they are integrated with the building waterproofing and the only way to ensure that your structure will be protected from hidden leaks caused by failing window frames. Flangeless windows, known as block frame windows, sit inside the flashed opening and do not integrate with the weather barrier. Block frame windows solely depend on sealant joints that require regular maintenance to prevent water intrusion into the wall assemblies. The best option for window replacement is a flanged window integrated with the building waterproofing.
There are seven types of window material:
1) Vinyl windows are made of polyvinyl chloride, or PVC, which is composed of a blend of ethylene and chlorine. It is a synthetic plastic that is resistant to decay caused by water and humidity. The window material makes this type of window soft and malleable; so, it is susceptible to warping and discoloration when exposed to extreme weather conditions. While vinyl is not the strongest material, it does meet average structural rating requirements and provides an affordable solution to window replacement where exposure is limited. Below is an example of a flanged, block frame or non-flanged frame and flush mounted retrofit frame.
2) Wood frame windows are typically made from pine, oak, and mahogany lumber and were the first types of windows ever made. Wood frame windows are typically block framed, but some have the option to add on a nail flange, which requires airtight waterproofing to integrate with the weather barrier. This type of window is a tried and tested classic with great visual appeal. Wood windows can also be painted and restored to maintain historic value. The downside of wood windows is that they are prone to decay, pest infestation, and require regular maintenance.
3) Wood frame windows are typically made from pine, oak, and mahogany lumber and were the first types of windows ever made. Wood frame windows are typically block framed, but some have the option to add on a nail flange, which requires airtight waterproofing to integrate with the weather barrier. This type of window is a tried and tested classic with great visual appeal. Wood windows can also be painted and restored to maintain historic value. The downside of wood windows is that they are prone to decay, pest infestation, and require regular maintenance.
4) Fiberglass windows are composed of plastic with glass fiber reinforcement and resin bonded together providing a water-resistant material. The material composition makes it versatile for extreme hot and cold weather and a good insulator. They are stronger than vinyl windows and corrosion-resistant. The downside of fiberglass windows is the limited color availability and their vulnerability to UV ray damage. Most fiberglass window manufacturers do not provide a weeping sill for the frames, so they are more susceptible to water back-up to the interior during heavy rain exposure. Fiberglass windows typically have an add-on nail fin which requires specific waterproofing provisions to seal the window frame to the attachment flange. They are generally a durable, energy efficient window and more affordable than aluminum. Installation and performance of fiberglass windows should be evaluated by a window design professional to ensure the right provisions are in place for performance.
5) Steel windows are historically made of reinforced heavy-duty steel, but in more recent years some have had a timber core with a steel coating. Steel windows have many advantages, including strength, durability, corrosion resistance, and even energy efficiency. The material strength allows for sleeker frame lines and fire resistivity. The downside of steel windows is that they are heavier, which affects operation. Due to their weight, installation may take more time depending on size, which can escalate the cost.
6) Wood clad windows are a combination of interior facing wood windows with an exterior vinyl or aluminum layer to protect them from the elements. Wood clad windows offer the interior aesthetic of a wood frame and the water resistance of vinyl or aluminum. Wood clad windows provide good insulation and improved energy efficiency but require more maintenance than other types of windows. They are also good for noise reduction but are more susceptible to decay if exposed to water. Many people select this window due to its interior versatility and paintability, allowing interior aesthetic changes without window replacement.
7) Composite windows are made of a blend of wood fibers and thermoplastic polymers with recycled materials. Composite windows are reliable windows with flexible designs and provide energy savings. They are a newer product on the market so there is a lack of data as to their long-term performance, and are currently more costly compared to other available window materials. The frames tend to be bulkier, so the same size window may seem smaller. There is lack of testing present for their structural and weather performance, so it’s difficult to verify if they meet the wind ratings. See the comparison table on page 14 for a summary of window material types.
Now that you have selected a window, let’s review the installation provisions. As noted, retrofit windows are plant-on frames using existing openings and do not integrate with the wall, so it’s recommended to avoid installation with stucco cladding. While it is not recommended to retrofit windows, sometimes it is needed due to budgetary constraints. When installing a retrofit window, make sure that there are no existing issues with the flashings or wall enclosure systems to avoid hidden decay. If the option is going with a block frame window, it is recommended to provide a flashing system that protects the structure and diverts water to the exterior. With block frames, in addition to managing water from the structure, it is crucial to maintain air barriers at the exterior and the interior to prevent negative air pressure from pulling water in. Sealant joints for block frames should be provided with the appropriate width and depth and backed with foam; this is not a simple fillet bead of caulking on the inside.
Flanged windows provide the best installation that allows integration with the wall weather barrier to ensure a waterproof envelope. Flanged windows still require some form of water relief to prevent decay to the structure from window failure.
With multi-story buildings, egress requirements for windows need to be considered, as well as fire resistivity for windows that are in exit corridors. Local ordinances provide these required provisions to ensure safe passage for residents in case of fire. These provisions are typically overlooked, so it’s important to examine the location of windows and ensure safety is maintained.
One important factor that is also often missed is the structural wind load and water rating requirements. Depending on the location and weather exposure, the rating for the window is part of the structure. Calculations should be completed per ASCE7-16 by licensed professional to avoid compromising the integrity of the wall. All too often we get calls from homeowners about newly replaced windows leaking and flexing during a pressurized storm. This is a direct result of underrated windows that are not fit for the exposure. Two story buildings generally have less exposure to the required ratings; but, it is important to note that areas along the coastline, elevated terrain, and undeveloped land may be subject to these provisions.
Windows are a considerable factor in maintaining lower energy bills. So, exposure to sun plays an important role in selecting the right type of glass in addition to the insulating factors of the frame. Sound transmission is not only a nuisance, but also a code requirement for any windows facing traffic areas or freeways. Reviewing the sound rating is an important step in installing the right window to maintain a healthy environment.
Finally, consider the effects of window installation on the interior finishes such wood sills, sheetrock, tile in bathrooms, blinds, special interior paints, etc. These are items that may be impacted by window replacement and should be reviewed by the residents as some of these costs are typically the responsibility of the owner rather than the HOA.
There are many factors that play an important role in selecting and installing a window that require the analysis of a qualified installer or designer. Remember the following check list: structural, fire, water, sound, energy, aesthetics, and lifespan. Selecting a contractor who is knowledgeable in all these areas will ensure that you get the right window replacement. It is also recommended that you engage a design professional to review and ensure that your selected window and installation method meets code. A qualified designer can provide a failsafe installation guide to protect your structure should a window fail. Performing a lifecycle cost analysis will help you decide on the best window option for a cost-effective long-term solution.
Rana Bayadi has more than 25 years of experience in building envelope design and construction. She holds a BS in civil engineering and mechanical engineering with a minor in experimental sciences, as well as an MS in structural design.
Bill Mann is the president of GB Group Construction and Painting. He has more than 40 years of experience in the HOA/CID industry, specializing in construction, finance, and operations.