Questions to Ask Before You Sign a Double Glazing Contract

Most people start looking into double glazing because something about the home does not feel quite right. A living room that never warms up, a west-facing space that bakes every afternoon, or old windows that rattle when the wind picks up.

Once you reach the stage of getting double glazing quotes, the focus quickly shifts from comfort to contracts. Numbers, product names, and installation notes begin to appear, and it can be hard to know what is normal, what is negotiable, and what is missing. At APS Double Glazing, we often see this is the point where homeowners begin asking more detailed questions about what is included, how installation will work, and what support may apply over the long term.

In practice, the questions you ask before signing a double glazing contract can be just as important as the windows themselves. Good questions help you understand what is actually being supplied, how it will be installed, and what support you might receive if something goes wrong years down the track. This is particularly important for full window replacement projects where both frames and glass are being changed.

This guide outlines practical, specific questions you can ask before committing. It is written for Australian homes, where climate, building codes, and bushfire considerations all play a role, and where different suppliers may have different products, policies, and installation methods.

Before You Look At Price, Clarify What You Are Actually Buying

Question 1. What, exactly, is included in this quote?

A double glazing quote can range from very simple to extremely detailed. Before you compare prices, you need to know whether you are comparing the same scope of work.

Helpful things to clarify. Ask whether the contract clearly spells out:

• The type of work
  • Full-frame replacement, including new frames and glass
  • Retrofit double glazing into existing frames
• The number and type of windows and doors
  • Awning, casement, sliding, tilt-and-turn, fixed, or doors
• The frame material and finish
  • uPVC, thermally broken aluminium, timber, or a mix
• The glazing system
  • Double glazing, triple glazing in rare cases, or mixed
  • Glass thicknesses for each pane
  • Toughened, laminated, or standard float glass was used
    

A clear contract should let you walk around your home, window by window, and understand exactly what will happen at each opening.

If something is only described in a brochure but not named in the contract, ask for it to be written in.

Question 2. What is the precise IGU and glass specification for each area?

Many Australian contracts mention “double glazing” without explaining what sits inside the insulated glass unit. A few small details can change performance, safety, and cost.

You can ask:

• What glass thicknesses are being used for inner and outer panes
• Whether any glass is laminated for security or noise
• Where toughened safety glass will be installed, for example, in bathrooms, near floors, or near doors
• Whether low-E glass is included, and if so, on which facades
• Whether the IGU cavity is filled with argon or left as air
• Whether warm edge spacers are included or a standard aluminium spacer is used
  

You do not need to become a glazing engineer. The aim is to ensure that the same IGU configuration described verbally is clearly documented so it can be checked during manufacture and installation.

Understanding Performance, Compliance, and Suitability

Question 3. How will these windows typically perform in my climate and orientation?

Performance labels and brochures are helpful, but they are still generic. Ask the installer to relate the proposed glazing to your specific house. For example:

• How will these windows usually perform in a hot, dry, or humid climate
• What U-values and SHGC values are being targeted for key rooms
• Whether the same specification is used for all elevations, or if west and north-facing glass is treated differently
• How the proposal may influence summer cooling and winter heating use in practical terms

Different double glazing companies may offer different configurations even at similar price points. Listening carefully to how clearly they can explain the impact on your home can be very revealing.

Question 4. Are these windows compliant with current Australian standards and local requirements?

In Australia, window and glass compliance is not optional. Your contract should reflect this. You can ask:

• Which Australian standards the windows and glass comply with
• Whether the proposed products are suitable for your wind region and building exposure
• Whether any bushfire (BAL) rating applies to your property and, if so, how the proposed windows are intended to address it
• Whether safety glass is specified wherever required by the National Construction Code
• Whether there are any pool, deck, or balustrade interfaces that need additional consideration
  

If your home is part of a strata property or subject to a heritage overlay, ask how the installer will manage any additional approvals that may be required. In some cases, this will be your responsibility, so it is important to be clear.

Question 5. Can you provide actual performance data for the selected products?

Many manufacturers have windows rated under Australian schemes that provide U-values and solar heat gain figures. Ask whether:

• The proposed configuration has a tested performance label
• The performance figures relate to the complete window, not just the glass
• Any acoustic ratings are available for the specific glass and frame combination
  

Not every configuration in every project will have a formal label, especially for very customised builds. However, reputable suppliers should still be able to explain the basis of the performance they are describing.

Installation, Site Work, and How Your Home Will Be Treated

Question 6. Who will actually do the installation, and how experienced are they?

The contract should clarify who is responsible for installation. You can ask:

• Whether the company uses its own teams or external subcontractors
• How long the installers have been working with the chosen window system
• Whether they hold the appropriate trade licences where required
• Whether there is a dedicated site supervisor or project manager
  

Good installation is critical. Even well-designed double glazed windows in Australia can underperform if they are not installed square, sealed, and supported correctly, which is why understanding the role of professional installation may help set realistic expectations.

Question 7. What will happen to the surrounding finishes, and how will they be made good?

Window replacement and retrofit work often disturbs plaster, paint, tiles, or external cladding around the opening. It is worth asking for details on:

• Whether internal architraves and trims will be replaced, reused, or altered
• How any damaged plaster or render will be repaired
• Whether repainting around the window is included or excluded
• Who is responsible for matching existing colours and profiles
  

Some installers include basic making good. Others limit their work to the window itself. The contract should be very clear so there are no surprises once the old frames are removed.

Question 8. What preparations do we need to make before installation day?

A smooth installation often depends on how the home is prepared. To avoid stress, ask:

• Whether furniture and window coverings need to be removed in advance
• How much access is required around each opening
• Whether pets, alarm systems, or security devices will be affected
• What will happen during wet weather or extreme heat days
  

This helps you plan your schedule and understand how disruptive the work is likely to be.

Timeframes, Scheduling, and Managing Delays

Question 9. What are the estimated lead times and installation dates, and what can affect them?

Manufacturing and double glazed window installation times can vary based on workload, glass supply, transport, and weather. Helpful questions include:

• How long is the manufacturing process likely to take from the final measure
• Whether the contract includes a target installation window
• What happens if there are delays in supply or shipping
• How you will be kept informed if timeframes change
  

Some companies may provide indicative timeframes only rather than fixed dates, especially in periods of supply pressure. Understanding this upfront can reduce frustration later.

Question 10. How long will installation take, and how will it be staged?

For multi-window projects, work may be spread over several days. Ask:

• How many days does the team expect to be on site
• Whether windows will be installed room by room or by elevation
• What happens overnight if an opening cannot be completed in one day
• Whether there will always be a secure temporary closure if needed
  

This is especially important if you work from home, care for children, or have specific access needs.

Price, Variations, and Payment Terms

Question 11. What does the price include and exclude, and how are variations handled?

A clearly written window replacement contract for double glazing should list inclusions and exclusions in plain language. You can ask:

• Whether the removal and disposal of old windows is included
• Whether scaffolding, cranes, or special access equipment is allowed for in the price
• Whether electrical work, such as moving power points or sensors, is included
• Whether structural alterations, lintel changes, or repairs are included or excluded
  

It is also sensible to ask how variations are managed. For example:

• What happens if hidden structural damage is found once old windows are removed
• How additional costs will be communicated and approved
• Whether variation prices will be supplied in writing before work proceeds
  

Knowing how surprises will be handled can be just as important as the initial quote.

Question 12. What is the payment schedule, and is it linked to milestones?

Different suppliers may have different payment structures. Before signing, ask:

• How much deposit is required, and when it is due
• When progress payments are expected, for example, at the final measure or before delivery
• When the final payment is due
• Whether payments are tied to specific milestones, such as the completion of installation
  

If you are using a finance or a staged renovation budget, make sure the payment schedule is practical for you and that you understand any fees for late or missed payments.

Warranty, Maintenance, and After-Sales Support

Question 13. What warranties apply to the windows, IGUs, and installation, and how do we make a claim?

A double glazed window system involves several components, each of which can have different warranty periods in addition to your basic consumer guarantees. Consider asking:

• How long is the warranty on the frame material
• How long is the sealed IGU covered against internal fogging
• What warranty applies to hardware such as locks and hinges
• Whether there is a separate workmanship or installation warranty
• What conditions may void warranties, such as unapproved alterations or harsh cleaning products
  

Just as important is the process itself. Ask how you would lodge a warranty claim, how long the assessment usually takes, and what sort of issues are typically covered.

Question 14. What level of service and maintenance support is available after installation?

Windows are long-term components that benefit from occasional adjustment and care. Before signing, ask:

• Whether the installer provides after-care visits or optional service plans
• Whether there are recommended maintenance intervals for seals, drainage slots, or hardware
• Whether there is a local service team that can attend if a handle fails or a sash goes out of alignment
  

Understanding what support exists in five or ten years can be as comforting as knowing who will be on site next month.

Design Choices, Future Stages, and Everyday Practicalities

Question 15. Are there design options we should reconsider before we commit?

Contracts often get signed at the end of a long quoting process, when people are tired of making decisions. It is worth pausing to ask:

• Whether any window styles could be changed to improve ventilation or safety
• Whether the current design allows for easy cleaning of the external glass
• Whether key rooms, such as bedrooms and living areas, have the most suitable glass for comfort and noise reduction
• Whether window sizes and configurations align with future plans, such as decks or extensions
  

Sometimes, small adjustments at the contract stage can save frustration later, especially around furniture placement, walkways, and how doors swing.

Question 16. If we stage the project, how will future work integrate with this contract?

Not every home is upgraded in one go. If you are planning to replace some windows now and others later, ask:

• Whether the same profiles and colours are likely to be available in the future
• Whether the contract can note the system used, to help with future matching
• How the current stage will be finished at the edges that may later connect to new work
  

Clear documentation today can make the next stage simpler, even if you choose a different installer in future.

Bringing It All Together Before You Sign

It can feel daunting to ask so many questions, especially if you are not familiar with construction or contracts. In reality, most reputable double glazing companies appreciate informed questions. They show that you are serious about your home, your budget, and the long-term performance of the windows.

A helpful approach is to:

• Read the contract at your own pace, away from sales pressure
• Highlight any terms, inclusions, or exclusions that are unclear
• Write down your questions and work through them with the installer
• Ask for any agreed changes to be added to the contract in writing before signing
  

Taking this time may feel cautious, but windows are a long-term investment that affects comfort, safety, and energy use every day. A clear contract does not remove all risk, yet it helps align expectations so everyone understands what success looks like when the work is finished.

If you are considering double glazing for your home and would like support understanding quotes and options, you can contact APS Double Glazing. We can discuss suitable products, typical timeframes, and the types of questions that may be most relevant for your home, climate, and project size.

Disclaimer: This guide provides general information only. Double glazing products, installation methods, regulations, and contract terms can vary between suppliers and locations. It is important to review your specific contract carefully and seek professional advice where needed before committing to any agreement.