Frequently Asked Questions


Laminated Glass

Two or more panes of glass are bonded together by a durable plastic interlayer with a resin called PVB (polyvinyl butyral). This technique is used to create single sheets of glass with multiple layers. The PVB keeps the glass from breaking apart easily and provides high sound insulation. However, if it should break, the glass will tend to remain in its frame, minimizing the risk of injury from sharp edges and flying or falling glass particles.

Tempered Glass

Tempered glass is often referred to as safety glass because it is more resistant to breakage than normal float glass. Yet if it is broken, it usually breaks into relatively small pieces, which are less likely to cause serious injury. Tempered glass is known to be several times stronger than laminated glass. Tempered glass is created using chemical and thermal treatments.

Sound Transmission Class (STC) is a single-number system used to rate the airborne sound transmission performance of a window, wall, panel, ceiling, etc. The higher the STC number, the better the product's ability to block sound transmission.

Solar Heat Gain Coefficient (SHGC) measures how well a window blocks heat from entering a home or building, whether directly transmitted or absorbed and subsequently released inward. SHGC is expressed as a number between zero and one. The lower the SHGC, the better a product is at blocking unwanted heat gain. Blocking solar heat gain is particularly important for homes located in warm, southern climates and during the summer cooling season.

U-Value measures how well a product prevents heat from escaping a home or building. U-Value ratings generally fall between .20 and 1.20. The lower the U-Value the better a product is at keeping heat in. U-Value is particularly important for homes located in cool, northern climates and during the winter heating season.

It is important to have as much detailed information as possible. Proper measurements for sash/panel replacement, as well as your product series number are necessary for us to place an order for you. If needed, visual aides, such as emailing pictures of your product, can also be of assistance.

Any form of documentation that states the date you purchased the product/home is helpful. The builder would have the records of sale which would have this information as well. Tax assessment papers showing the year that the home was built, customer receipt, or invoice would also include this information.

Windows are reflective. When sunlight hits a surface, such as window glass, it sometimes reflects onto another object. The amount of sunlight reflected by the window glass is increased when it has a Low-E coating, which is purposely designed as an energy-saving device to decrease the amount of sunlight entering a home. The reflection of sunlight off glass with Low-E indicates the window is doing its job.

A Window Opening Control Device (WOCD) is an option available for some MI windows designed to restrict the opening of a sash to less than 4" to lessen the risk of accidental falls. A WOCD can be released to allow the sash to fully open for emergency escape and rescue. Some IRC and lBC editions have minimum sill height requirements for certain window openings, with use of a WOCD as one exception. Building codes vary by jurisdiction: consult your local code to determine if a WOCD is appropriate for your application.

WOCDs are effective only if properly installed and remain engaged except in cases of emergency. Installers should follow MI installation instructions. Occupants should be familiar with and follow MI's important safety information. MI's WOCDs have been tested for compliance with ASTM F 2090.

MI offers a WOCD for the following windows:

Factory Installed WOCD: 3500, 4300, 1650, 1555, 1556, Western Region 5500 & 5800 (can only be applied with equal sightline adapter)

Aftermarket WOCD (installed in the field): 3500, 4300, 9700, 1675, HM147, EC147, Southern Region 5500

Note: A WOCD can be applied and replace a nite latch on the 1650, 1555, or 1556.

The answer will vary depending upon several factors, including, but not limited to, the characteristics of your old and new windows, house size, geographic location and personal use. ENERGY STAR® has calculated some estimates for replacing single-pane or double-pane clear glass windows with ENERGY STAR qualified windows. Ask your builder, contractor, or distributor for information on MI windows bearing the ENERGY STAR label.

Please look for a gold or silver identification label which is the AAMA certification label. You can also find this information on a white warranty label. Your product labels can be found on the header of the mainframe or sill area. We do prefer the label information rather than the subdivision or builder name, which we do not keep on file. For examples of our labels, please see the Window ID Labels section of our website.

If your sash will not stay up, it is likely that your balance is broken or sized improperly. Depending on what type of window you have, the issue will be fixed differently. Visit our video library for information on how to fix and replace broken balances.

The word “tempered” will be physically etched on the bottom right corner of the glass.

Obscured glass is frosted or textured in appearance.

If you measured 1/2”, you likely have 5/8” grids. If you measured 3/4”, you likely have 7/8” grids

Multiply the width by the height and divide the answer by 144.

If the seal on an insulated glass unit (IG) fails it is no longer able to keep out moisture, dirt or other elements from the space between the panes of glass.

The weep holes may be blocked. Gently clean the weep holes by using a dry paintbrush or vacuum brush attachment to remove any debris. If the weep holes are clear, or if cleaning the weep holes does not result in the removal of the water, contact MI’s Customer Care Department at 717-365-2500 or by email .

Tape a piece of white paper to the inside of the glass and then look at the window from the outside. If the paper appears white, your glass is clear. If it has a light to dark gray appearance or is greenish in color, you have Low-E glass.

R-value is the resistance of heat flow through a given material. The higher the R-Value of a product, the greater resistance it will have to heat flow.

At this time we do not offer any ADA-compliant products.

Yes, there are a couple different options for screens. These include roll-form, extruded latching and FlexScreen.

The American Architectural Manufacturers Association is a trade association that advocates for manufacturers and professionals in the fenestration industry.

The National Fenestration Rating Council is a non-profit organization that developed the uniform rating system used to measure the energy performance of fenestration products. These ratings are standard for all products, regardless of the material they are made of.

MI offers a Limited Lifetime Customer Assurance Warranty on all our products. This warranty allows the homeowner to order necessary replacement parts to ensure proper product operation at no charge. Some products also come with a Glass Breakage Limited Warranty. This allows customers to order new replacement glass units at no charge.

The X Panel signifies an operating panel on a patio door. This panel can only slide to the left or right and has a handle to open the door on it. The I Panel is an intermediate panel, which can slide but does not have a handle on it. When you open one of the X Panels, it picks up the two I Panels along the way and all four panels can be opened to one side.

In many areas of the United States, strong wind and fine soils create issues regarding dust infiltration, which can affect all fenestration products (i.e. windows and doors). Even when closed and locked, all operational window and door products can experience air infiltration because the operating component is designed for movement (i.e. the operational sash). Air infiltration occurs as air under pressure enters the home, which may occur through certain points on a locked window. The operating components have weatherstripping to reduce air infiltration, but it is not feasible to eliminate all air leakage due to the operational function of the window. Windows with these characteristics routinely meet the common industry standard.

Dust infiltration is found at these operating points; usually when winds exceed residential standards of twenty-five miles per hour. Also, high winds may cause a slight deflection of the sash component allowing the opportunity for dust particles to be forced into the home. Please note: if excessive dust is allowed to build up on the exterior sill between the sash and screen, even normal wind pressures will force dust inside the home.

Dust infiltration is most prevalent in arid regions, new construction areas, and farming areas. Once landscaping is established and the amount of dust particles are reduced in the air, problems often decrease substantially. Below are tips on how to reduce dust infiltration.

Tips for Controlling Dust Infiltration

  • Remove excessive dust on the sill outside of you window between the sash and screen as often as necessary to prevent build up.
  • Establish a lawn as quickly as possible.
  • Use mulch and water flowerbeds around the home.
  • Clean the bottom sash weather-strip periodically to insure a tight seal on the sill of the window.

Window and door manufacturers are required to test their products to meet industry standards for air infiltration, water intrusion, and structural integrity. These tests have parameters that must be met for the window to become certified. The products, which achieve certification, are then labeled to reflect their compliance in meeting these standards. MI Windows and Doors tests its products to meet those standards.

The terms "Design Pressure" (DP), “Structural Test Pressure” (STP), and "Performance Grade" (PG) have in the past been loosely used by some in the field, when in fact they have different meanings.

Design Pressure and Structural Test Pressure are strictly structural testing qualifications, irrespective of the results of any air leakage resistance testing or water penetration resistance testing. The Performance Grade of a product is limited by the lowest/least performance of its structural, air leakage resistance, or water penetration resistance test results; operating force and/or forced-entry resistance requirements may also apply.

More specific definitions of these terms are defined by the American Architectural Manufacturer’s Association (AAMA):

Design Pressure (DP) – “A rating that identifies the load, induced by wind and/or static snow, that a product is rated to withstand in its end-up application. Loads induced by static snow are applicable only to unit skylights, roof windows, and [tubular daylighting devices (TDD)]”. (AAMA AG-13)

Structural Test Pressure (STP) – “The overload pressure differential applied to a window, door system, TDD, [secondary storm product (SSP)], or unit skylight.” (AAMA AG-13) The structural test pressure is 150% of the design pressure for windows and doors.

Performance Grade (Grade or PG) – “A numeric designator that defines the performance of a product in accordance with [AAMA 101/I.S.2/A440] … Performance grade (PG) is achieved only upon successful completion of all applicable tests specified in Clause 9 [of 101/I.S.2/A440-11].” (AAMA AG-13)

Clause 9 includes the following tests: “(a) operating force for operable window, roof window, unit skylight, sliding door, and secondary storm product test specimens; (b) force to latch door for operable side-hinged door specimens; (c) air leakage resistance test(s); (d) water penetration resistance test(s); (e) uniform load deflection test; and (f) uniform load structural test.” (AAMA 101/I.S.2/A440-11, sec. 9.1.2)

Our measurements for new construction windows are in feet. For example, the 3050 stock size would be 3 ft x 5 ft or 36" x 60".

The size guides can be found for some of our new construction products on our website. For replacement windows, we do not have stock sizes and all of the measurements are in inches. If you see a replacement window size of 28x42, that would be 28"x42".

Both of these measurement listings are pretty much industry standard.

Note: If your existing windows have a nail fin, the size of the window does not include the fin. It is the tip to tip frame size. On most vinyl windows, the fin extends 1 ½” past the frame all the way around the window, so to find the tip to tip fin size you would add 3” to the frame size.

The key to proper window installation is to think beyond the actual act of installing. There are steps you can take both before and after the installation to ensure proper function and performance of your windows.

First, be sure the rough opening has been properly prepped - is clean and smooth and the proper size. Before windows are installed, be sure the installer reads any and all installation instructions thoroughly and notes any special care to be taken with the windows. Often, manufacturers have their own set of instructions in addition to the ASTM E2112 Standard Practice for Installation of Exterior Windows, Doors, and Skylights. Additionally, make sure all materials are on-hand and compatible with the product. Check with the proper resource to gather a list of materials (including flashing, sealant, etc.) that is compatible with the product you purchased.

After the installation is complete, if there is more work to be done, use extra caution around the job and make sure it's not disturbed. Keep in mind that any contact with the window that happens between the installation and finalization could possibly affect the original work. Lastly, take great care with any final caulking or trim work.