NZ Case Study: Retrofitting Double Glazing versus 3M Thinsulate Installation

Compare the costs and benefits of 3M Thinsulate versus Double Glazing in NZ – South

NZ Case Study:  Retrofitting Double Glazing versus 3M Thinsulate Installation

Retrofitting Double Glazing versus 3M Thinsulate Installation: Cost Comparison for New Zealand, South Island.

Complete Film Solutions is excited to announce expansion plans into the South Island of New Zealand, with the aim of bringing 3M Thinsulate Window Film into the perfect market for this product. The areas of South Canterbury, Otago and Mackenzie suffer through some bitterly cold winter weather (we swear that wind comes directly up from Antarctica), yet are experiencing warmer Summers every year (thank you climate change!)

Many of our friends and family in the land of the long white cloud are trying to save money to retrofit double glazing for their homes to improve their year round comfort levels and reduce their energy bills.

In this article, we will explain the pros and cons of retrofitting double glazed units, and compare these against the pros and cons of installing 3M Thinsulate Window Film – a revolutionary new product from 3M that is manufactured using the latest technology to prevent heat loss through your glass in winter, and reject heat from the sun in summer.

Advantages of New Double-Glazed Units

The positives of retrofitting existing windows with new double-glazed units include:

  • Reduction of neighbourhood, traffic or other external noise
  • Reduced heat loss through the glass in winter
  • Reduced heat transmission through the glass in summer
  • Improved energy efficiency
  • Reduce or remove condensation build up on glass in cold weather
  • Updated and improved aesthetics from brand new window frames and glass installed
  • Usually a 5-10-year warranty

Disadvantages of New Double-Glazed Units

The drawbacks of retrofitting existing windows with new double-glazed units include:

  • High cost – see our case study below for more detail
  • Where the lower cost option is chosen to retrofit by adding additional glass and framework to create a 2nd layer of glass to existing windows, this adds additional bulk, and may not look as aesthetically pleasing when adding to existing frames.
  • Disruption to the home owner by removal and replacement of windows
  • Dirt and dust created from installation process
  • Potential damage to the home from removal of existing windows/ install of new windows
  • Very high replacement cost should a DGU be broken or damaged

Advantages of 3M Thinsulate

The positives of installing 3M Thinsulate low-e insulating window film to existing glass include:

  • Considerably more cost and time effective to install than double glazing or installation of low e glass.
  • Achieves similar benefits to double glazing in heat retention during winter.
  • 3M Thinsulate, in both the 40% VLT and 75% VLT (visible light transmission), achieves higher heat rejection performance than double glazing in Summer. Let’s review the Solar Heat Gain Coefficient (SHGC) for each. Remember, SHGC is a measure of heat gain through glass from sun, and is a figure between 0 and 1. Numbers closer to 0 reflect better rejection of summer heat. Double glazed units typically record a Solar Heat Gain Coefficient of around 0.60 (low-e double glazed unit) to 0.72 (for clear double glazing). Thinsulate window film achieves a SHGC of between 0.40 (for 40% VLT option) and 0.53 (75% VLT variant).
  • Clean installation process that minimises disruption to the home owner, as the film is applied to your existing glass.
  • Easier installation for multilevel homes or apartments, where removal and installation of an entire window unit would be difficult and risky due to working at heights, compared to installing film from the inside on existing glass.
  • Original windows and glass is retained, so your home appearance does not change. The 75% VLT option of 3M Thinsulate is near invisible on your glass, so there will be no noticeable difference between how your windows look before and after installation.
  • Improved energy efficiency resulting in much lower energy bills for heating and cooling your home.
  • Low long-term maintenance costs – if a window fitted with Thinsulate film is damaged or broken, cost of replacing with standard glass and new film is much lower then replacement of a DGU or low e glass
  • 3M provides a Lifetime manufacturer’s warranty Thinsulate window film when it is installed by a 3M Licensed Installer. This is for residential homes for the original film purchaser for the lifetime that they own the home. Commercial properties are provided with a 15 year warranty.

Disadvantages of 3M Thinsulate include:

  • Will not improve the aesthetics where existing window frames are in poor or unsightly condition
  • Is not designed to assist with noise reduction
  • Compared to double glazing, a little extra care is needed in cleaning windows with Thinsulate applied to prevent scratches in the film – this is not onerous and will only require minor changes to how you might normally clean your windows
  • For best results, 3M Thinsulate will perform better in homes where condensation build up on windows is minimal or controlled (through use of extraction fans in bathrooms and kitchens, regular airing of your home and/or installation of a home ventilation system). If your home suffers from damp or condensation build-up, then 3M Thinsulate will not work as effectively to reduce heat loss in winter.

Case Study 1

Let’s compare the cost of retrofitting double glazing with 3M Thinsulate film install.

Claire obtained a quote for retrofitting double glazing to 4 window sets in her home, just south of Timaru, New Zealand. The rooms being quoted were the main bedroom (5 panel window); Dining Room (5 panel window); Living Room (5 panel window) and a Bay Window (5 panel window). This quote was a retrofit solution, installing new glass and additional framing within existing framing for fixed windows, while doing a full removal and replacement of windows and framing for opening windows.

The quote received was as follows:


Details / Inclusions

Total Project Price (including GST)


Clear toughened glass, bronze anodised 12M frames, total 14.1 sqm.


Next, the same measurements for all 20 panels were used to calculate a quote for supply and installation of 3M Thinsulate low-e insulating window film.

The final quote came to: $4,403.93 including GST. This is 39.2% cheaper than retrofitting double glazing.

Case Study 2

Andrew and Kate obtained a quote for retrofitting double glazing to their Kitchen, Dining and Lounge Rooms – 21 panels of glass in total for their home in Timaru. The quote received was a retrofit solution, where additional framing and new glass was installed within existing frames for all fixed panels. All opening windows would be a full remove and replace of both glass and framing with a new double glazed unit. The quote received was as follows:


Details / Inclusions

Total Project Price (including GST)


Clear Glass – addition to existing fixed panels x 11 panels, Grey tint glass/ clear glass double glazed units x 10 for replacement of existing opening panels, with low-e glass and argon gas upgrade.


Next, the same measurements for all 21 panels were used to calculate a quote for supply and installation of 3M Thinsulate low-e insulating window film.

The final quote came to: $4,411.86 including GST. This is 55.2% cheaper than retrofitting double glazing.

Outcome: 3m Thinsulate Most Cost-Effective Solution

3m Thinsulate is the clear winner, in terms of benefits and cost effectiveness. Before making the decision on whether to go for retrofitting double glazing or installing 3M Thinsulate window film, consider the following:

Benefits of 3M Thinsulate Window Film

  1. 3M Thinsulate Window Film is 39-55% cheaper than the cost of retrofitting double glazing
  1. A LIFETIME warranty for 3M Thinsulate versus only 5-10 year warranty for double glazing
  1. 3M Thinsulate OUTPERFORMS Double Glazing for Summer Heat Rejection – an important consideration as New Zealand’s Summers continue to heat up.


Complete Film Solutions are 3m Licensed Installers servicing the following areas of New Zealand’s South Island – Canterbury, Otago, and Mackenzie districts . Contact our expert team today to discuss your requirements and the benefits of installing 3M Thinsulate in your home.


To celebrate our expansion into the South Island, New Zealand, we will offer a 25% discount to the first five 3M Thinsulate Installations (minimum of 15 square metres) booked when we are there from 14th to 26th May 2019, in exchange for your consent to use your home (identifying features removed), and photos of your install, in a case study for our website and Complete Film Solutions- NZ South Facebook page. Get in early by sending through your individual panel measurements via email for a quote (final price will be subject to on-site confirmation of your provided measurements), OR  contact us (send a web enquiry with your phone number and we’ll call you back) to book in for a free site measure between 14 and 17th May 2019, for an install prior to 26th May 2019.

**Update – Testimonial

Remember Andrew and Kate from our case study? They stood to save more than 55% of the quoted cost for retrofitted double glazing by installing 3M Thinsulate instead.
On 16th May 2019, Andrew and Kate were our first completed install in New Zealand, and they are delighted with the results! Here are Kate’s words:
“We would like to say a very big thank you to CFS for their advice and expert installation of 3M “Thinsulate” window film.
We wanted to reduce our heating costs, but after getting quotes for double glazing, we decided that we could not justify the cost.
We later read about a Thermal Window Film and researched this product. Acting on advice from Brent, the owner and installer, we took the plunge and had Thinsulate Window Film applied to all windows and doors in our living area today and the results are unbelievable. It is like Summer all year long!
Once again, our grateful thanks, Andrew and Kate”

Comments are closed.