How to Compare Window Replacement Bids

Why do window replacement bids differ for the same house?

Pella, a window manufacturer, says in its guide to replacement window cost that window quotes price a complete project, not only a product. The guide lists seven factors that affect cost: window size, style and configuration; frame material and product selection; installation method; glass package and energy performance features; exterior conditions and accessibility; regional labor, permits and market demand; and project size and scheduling.

Two bids with different totals may differ in any of these. That is why the details below matter more than the bottom line.

Window replacement bid comparison table

Copy this table into a document or spreadsheet and fill in one column per bid. Any blank cell is a question to send back to that contractor before you compare totals. Each row is a detail to get in writing.

What do the NFRC numbers on a window label mean?

The National Fenestration Rating Council (NFRC) label gives a window’s energy performance ratings in several categories, so you can compare one product with another. A lower U-Factor means the window keeps more heat in, and a lower Solar Heat Gain Coefficient means it lets in less solar heat.

NFRC lists five ratings on its window label:

• U-Factor measures how well a product keeps heat from escaping a room. The lower the number, the better it is at keeping heat in.
• Solar Heat Gain Coefficient measures how much solar heat a product allows in. Low numbers resist solar heat, and high numbers allow solar heat.
• Visible Transmittance measures how well a product lights your home with daylight. The higher the number, the more natural light is let in.
• Air Leakage measures how much air will enter a room through a product.
• Condensation Resistance measures a product’s resistance to condensation. The higher the number, the better a product resists condensation.

The U.S. Department of Energy’s Federal Energy Management Program says that the “energy savings of fenestration products varies according to climate.” Its guidance for federal buyers of windows also points to the NFRC’s directory search for a list of ENERGY STAR certified windows by climate zone. NFRC describes itself as the official certification body for ENERGY STAR windows, doors and skylights, and the ENERGY STAR page on what makes a window certified says that certified products have NFRC ratings that meet guidelines set by the U.S. Environmental Protection Agency.

Ask each contractor for the NFRC ratings of the exact model in the bid, and write them in the table.

Which frame material is each bid quoting?

Ask each contractor which frame material the bid quotes, because frame materials differ in how well they insulate and in the upkeep they need. A fact sheet on the U.S. Department of Energy’s Building Science Education site, “Types of Windows” (PDF), says that vinyl, wood, fiberglass and some composite frame materials provide greater thermal resistance than metal.

That fact sheet describes the materials this way:

• Aluminum or metal. Metal frames conduct heat very well, so they should have a thermal break, which is an insulating plastic strip placed between the inside and outside of the frame and sash.
• Fiberglass. Fiberglass frames are dimensionally stable and have air cavities that can be filled with insulation.
• Vinyl. Vinyl frames do not require painting and have good moisture resistance. Their hollow cavities can be filled with insulation.
• Wood. Wood frames insulate relatively well, but they expand and contract in response to weather conditions and require regular maintenance, although aluminum or vinyl cladding reduces maintenance requirements.
• Composite. Composite frames consist of composite wood products, such as particleboard and laminated strand lumber. The fact sheet says: “These composites are very stable, they have the same or better structural and thermal properties as conventional wood, and they have better moisture and decay resistance.”

If a bid quotes a metal frame, ask whether it has a thermal break. If it quotes a wood frame, ask what upkeep it needs and whether it has aluminum or vinyl cladding. Ask each contractor why they chose that material for your house.

What should you ask about the glass package?

Ask each contractor how many panes the glass has, what fills the space between them, and whether there is a coating or tint. The Department of Energy’s Building Science Education page on high-performance window glass says that features that help reduce heat transfer include two or three panes of insulated glass and low-emissivity coatings.

The same “Types of Windows” fact sheet describes the parts of a glass package this way:

• Insulated glazing refers to windows with two or more panes of glass, spaced apart and sealed, leaving an insulating air space.
• Gas fills. Some manufacturers fill the space between the panes with an inert gas, such as argon or krypton, that has a higher resistance to heat flow than air.
• Low-emissivity (low-e) coating is a microscopically thin, virtually invisible, metal or metallic oxide layer deposited directly on the surface of one or more of the panes of glass. These coatings control heat transfer by reducing the transmittance of infrared radiation.
• Heat-absorbing tints change the color of the glass and reduce the solar heat gain coefficient and the visible transmittance. The same fact sheet says the tint does not lower a window’s U-factor.

Write each bid’s answers in the table. If one bid says “low-e” and another says nothing about coatings, ask the second contractor to state the glass package in writing.

Insert or full-frame: what changes in the bid?

An insert replacement fits a new window into the existing frame, while a full-frame replacement removes everything down to the structural opening. Because the two methods involve different work on the frame, trim and siding, ask each contractor which one the bid quotes for each opening. Do not compare an insert bid with a full-frame bid as though they were the same job.

Andersen Windows, a window manufacturer, says in its guide to new construction and replacement windows that an insert replacement window “fits inside the existing window frame, so only the old sash is removed”. It says this type works when the frame is in good condition, and that the existing frame must be structurally sound.

Pella, another window manufacturer, describes the same split in its guide to replacement window cost: an insert, or pocket, replacement fits a new window into the existing frame, and a full-frame replacement involves removing everything down to the structural opening. Ask each contractor which method each opening gets, and what the contractor will do about the frame behind the old window.

What else can change a window bid?

Trim, siding, hidden damage, permits and disposal can each change the price. Andersen’s guide says: “Generally, the costs that fall under replacement will include labor, materials, permitting, and disposal fees.”

• Trim and siding. Andersen says that in a replacement project “you’re opening a hole in the wall, which could necessitate finishing work such as repairing or replacing trim and siding, repainting, and more.”
• Hidden damage. The same page says that opening a wall can uncover another problem, such as rot under a window, that has to be repaired before installation. Ask how each contractor prices that repair if it is found. Pella’s guide also says older homes may have hidden issues, such as frame rot, that only become visible during the replacement.
• Building code. Ask whether the bid includes any work your local building code requires.
• Installation quality. The Department of Energy’s Guide to Energy-Efficient Windows (October 2010) says: “Even the most energy-efficient windows can result in a drafty house and moisture condensation if they are not properly installed.”

What does the EPA say about work on a home built before 1978?

The U.S. Environmental Protection Agency’s page on its Renovation, Repair and Painting Program says that the rule “requires that anyone paid to perform work that disturbs painted surfaces in homes, childcare facilities and preschools built before 1978 be certified and their employees be trained (either as a certified renovator or on-the-job by a certified renovator) in the use of lead-safe work practices that minimize occupants’ exposure to lead hazards.” The same page says who the rule covers and names the states that run their own programs. If your home was built before 1978, ask each contractor how paint dust will be handled during the work.

What should you ask about a window warranty?

Ask each contractor for the written warranty for the exact model in the bid, and read it. Ask what it covers on the glass, on the other parts and on labor, how long each part of the cover lasts, and who handles a warranty call. Ask whether the contractor gives its own workmanship warranty and, if so, ask for it in writing.

Is the lowest window bid the best one?

Not necessarily. A low total may reflect fewer windows, a different frame material, a simpler glass package, an insert installation where another bid is full-frame, or no trim or siding work. Compare the table first, then the price, so you know the low bid covers the same job as the others.

Look at the gaps. If one column has blanks the others filled in, ask that contractor to complete them in writing. A bid that cannot answer the questions may still be honest, but you cannot tell what you would be buying. Our guide, How to Compare Roofing Bids: A Side-by-Side Worksheet, uses the same row-by-row approach for a roof.

What to ask every window contractor

Copy these questions and send them to each bidder in the same message. Asking everyone the same things gives you answers you can line up in the comparison table, and it shows which contractors explain their bid clearly and which leave gaps:

• How many windows are in this bid, and what are the size and style of each one?
• What frame material, glass package and manufacturer model are you quoting?
• What are the NFRC ratings of that exact model, and is it ENERGY STAR certified?
• Is each opening an insert or a full-frame installation, and why?
• What happens to the interior and exterior trim and to the siding around each opening?
• How is repair priced if rot or water damage is found behind an old window?
• Does the bid include any work that local building code requires?
• Who applies for permits, and who removes and disposes of the old windows?
• If the home was built before 1978, how will you handle paint dust during the work?
• What does the warranty cover on the glass, on the other parts and on labor, and who handles a warranty call?
• What are the deposit, the payment schedule, the start window and the duration?
• What is excluded, and how are change orders priced?

Where Otter Quotes fits

You compare the bids online, next to reviews and licensing information, and you do not need a salesperson to visit your home. Contractors pay Otter Quotes a fee on the accepted bid. We do not sell upgrades, and we are not a contractor.

How Otter Quotes works