Plastics fact sheet - Domestic windows

Description

According to the Energy Saving Trust, around 2 million windows are installed every year in the UK, both in new builds and as replacements in existing buildings.

Ratings are given to windows in bands from A to G, just like energy-performance labels on new fridges; the minimum to satisfy Building Regulations is E, but the Energy Saving Trust recommends at least C. (Note, there are other methods of assessment that also comply with building regulations). Most buildings now require the use of either double or triple glazed units due to Building Regulations which stipulate better levels of energy performance.

Windows typically come wood, PVC-U, metal or a composite. The use of PVC-U is dominant in the domestic new build and replacement sectors. Aluminium is the dominant frame material in the commercial sector due to the need for strength and supporting structures, though steel is also used. Timber windows (can be softwood and hardwood) are mainly used where local planning regulations stipulate its use, for example, in the refurbishment of ‘historic/traditional’ buildings.

About plastics in windows

Many modern window frames and sills are made with PCV-U (Unplasticized Polyvinyl Chloride), a type of plastic. In these windows, plastic  is found in almost every aspect of the frames. 

Almost every window will contain at least some plastic. Wooden frames have the least, with very small amounts found in glues and paints, and accessories such as trickle vents and hardware.

Metal frames also contain some plastics, more than wooden frames but considerably less than PVC-U. These are found mostly in thermal breaks and powder coatings.

Product comparator

Below is a comparison three common window types. PVC-u frame, wood frame and aluminium frame. Parameteres include plastic content and where is plastic used, but also takes a look at embodied carbon, recycled content, cost, life span, maintenance, thermal performance, benefits and drawbacks. 

 

PVC-U frame windows

Wood frame windows

Aluminium frame windows

What’s it made of?

Glazing, PVC- u frame, steel reinforcement, steel/stainless steel/aluminium (hinges and locks)

Glazing, Softwood or FSC certified hardwood frame, paint, glues, dowels, filler, wrapping foil, rubbers, steel/stainless steel/aluminium (hinges and locks)

Glazing, aluminium frame, polyamide thermal break, polyester powder paint, steel/stainless steel/aluminium (hinges and locks)

Plastic content

55%-65% of frame can be plastic, with other % made up of steel reinforcement, fittings etc (frame can make up 22.9%-28.2% of total window)

<1%

8-17% (of frame) can be plastic; the total frame makes up around 20% of total window

Where is plastic used?

Frame profiles are PVC-U, and can be reinforced with polyurethane foam or glass fibre extruded into the PVC-U material. The surface of frames can be laminated with PVC foil, coated with PMMA (polymethyl metha acrylate) or painted. Seals can be made from plasticised PVC, EPDM (ethylene propylene diene monomers) or TPE (thermoplastic elastomers)

Potentially in glues and paints, as well as trickle vents and small parts of hardware like stops on friction hinges and locking systems.

Plastic used for thermal breaks, and use of polyester powder paint to coat the aluminium profiles

Embodied carbon

Research suggests that the lowest embodied carbon option 52kg CO2e per m2[1]

Research suggests that the lowest embodied carbon option is 40kg CO2e per m2 of double-glazing[2]

14-24% reduction of the embodied impacts of PVC windows[3]

Research suggests that the lowest embodied carbon option is 76kg CO2e per m2[4], 29-49% increase in embodied impacts of PVC windows[5]

Recycled content

 Up to 40%

 0%

 Up to 50%

Waste management

The RecoVinyl scheme has been set up to co-ordinate the collection and recycling of post-consumer PVC building products. PVC-U can be shredded and compressed into pellets. This recycled 73,700 tonnes of PVC from window profiles in 2018. [6]

There are concerns with legacy additives and work ongoing on the restriction of lead

Timber can also be recycled or used as biomass for energy recovery.

Aluminium will be sent to metal recyclers where it will be sorted into alloy grades which allow it to be recycled into specific product types. The aluminium is re-melted in the smelter. Aluminium has high recycling rates, which can be between 92% and 98% for architectural aluminium

Cost

Average price for new windows (per casement window) -£600-£1800[7]

50% more than PVC-u[8]

25% more than PVC-u[9]

Life span

18-30 years[10] [11]

25-65 years[12], typically 55-65, up to more than 3.5 times than PVC-U[13]

25-80 years[14], typically 45 years[15]

Maintenance period

6 months cycles of cleaning with solvents[16]

Painting every 5 years and staining every 3 years[17]

20 years for re powder coating. Windows should be wiped clean every 6 months[18]

Thermal performance

Thermal conductivity is excellent thanks to the low conductivity of the polymers; however, PVC-U windows rely on a metal frame inside for rigidity, and this can cause the thermal conductance to rise[19]

Thermal conductivity is the lowest among the three materials[20]

 

Thermal conductivity is poor, the highest of the three materials; however, the implementation of thermal breaks can decrease its thermal conductivity and reduce thermal bridges[21]

Benefits

Low initial cost

Easily installed

Lowest embodied carbon option

Usually high quality

Long life span

High level of recycling (up to 95%)

Little maintenance required

Drawbacks

High plastic content

Relatively short lifespan (18-30 years)

Low level of recycling- 3%

Higher cost than typical PVC-U window

Wood frames are the most demanding in terms of maintenance

High embodied carbon

[1] https://www.building.co.uk/focus/choosing-low-carbon-windows/5060079.article

[2] https://www.building.co.uk/focus/choosing-low-carbon-windows/5060079.article

[3] Saadatian, S.; Simões, N.; Freire, F. Integrated environmental, energy and cost life-cycle analysis of windows: Optimal selection of components. Build. Environ. 2021, 188, 107516. 

[4] https://www.building.co.uk/focus/choosing-low-carbon-windows/5060079.article

[5] Saadatian, S.; Simões, N.; Freire, F. Integrated environmental, energy and cost life-cycle analysis of windows: Optimal selection of components. Build. Environ. 2021, 188, 107516. 

[6] Richard McKinlay, Head of Consulting, AXION

[7] https://www.everest.co.uk/double-glazing-windows/new-windows-cost/. Accessed 31/01/2023

[8] https://www.everest.co.uk/double-glazing-windows/new-windows-cost/. Accessed 31/01/2023

[9] https://www.everest.co.uk/double-glazing-windows/new-windows-cost/. Accessed 31/01/2023

[10] Asdrubali, F.; Roncone, M.;Grazieschi, G. Embodied Energy and Embodied GWP of Windows:  A Critical Review. Energies 2021, 14, 3788. https://doi.org/10.3390/ en14133788

[11] https://www.bereco.co.uk/case-studies/plastic-not-so-fantastic. Accessed 31/01/2023

[12] Souviron, J.; van Moeseke, G.; Khan, A.Z. Analysing the environmental impact of windows: A review. Build. Environ. 2019, 161, 106268. [CrossRef]

[13] https://www.bereco.co.uk/case-studies/plastic-not-so-fantastic. Accessed 31/01/2023

[14] Souviron, J.; van Moeseke, G.; Khan, A.Z. Analysing the environmental impact of windows: A review. Build. Environ. 2019, 161, 106268. [CrossRef]

[15] https://www.siegersystems.co.uk/how-long-will-aluminium-windows-last/#:~:text=Aluminium%20windows%20and%20doors%20are,to%20the%20windows%20or%20doors. Accessed 31/01/2023

[16] Fernandes, D.; de Brito, J.; Silva, A. Methodology for service life prediction of window frames. Can. J. Civ. Eng. 2019, 46. 

[17] Fernandes, D.; de Brito, J.; Silva, A. Methodology for service life prediction of window frames. Can. J. Civ. Eng. 2019, 46. 

[18] Fernandes, D.; de Brito, J.; Silva, A. Methodology for service life prediction of window frames. Can. J. Civ. Eng. 2019, 46. 

[19] https://blog.ecosupplycenter.com/blog/high-performance-windows-comparison-wood-vs-upvc-vs-aluminum-clad-wood. Accessed 31/01/2023

[20] https://blog.ecosupplycenter.com/blog/high-performance-windows-comparison-wood-vs-upvc-vs-aluminum-clad-wood. Accessed 31/01/2023

[21] https://blog.ecosupplycenter.com/blog/high-performance-windows-comparison-wood-vs-upvc-vs-aluminum-clad-wood. Accessed 31/01/202

Other references

EPD's

PVC-U frame

  • PVC-U plastic windows with the dimensions 1.23 x 1.48 m and insolated double-glazing. QKE Qualitätsverband Kunststofferzeugnisse e.V. EPPA European PVC Window Profiles and Related Building Products Association ivzw. LINK. Accessed 31/01/2023
  • PVC-U plastic windows with the dimensions 1.23 x 1.48 m and insulated triple-glazing. QKE Qualitätsverband Kunststofferzeugnisse e.V. EPPA European PVC Window Profiles and Related Building Products Association ivzw. LINK. Accessed 31/01/2023
  • Laminated PVC Profiles for Windows and Doors. Fırat Plastik. LINK

Wood frame

  • Fixed wooden window frame, painted, European softwood, sustainable forestry, NBvT. Wooden window frame + turn part, hinges and locks, painted, European softwood, sustainable forestry, NBvT. · Wooden window frame + tilt and turn part, hinges and locks, painted, European softwood, sustainable forestry, NBvT. Agrodome. LINK. Accessed 31/01/2023
  • Outward opening Side hung window Wood – EFS. Elitfönster AB. LINK

Aluminium frame

  • wooden and wooden-aluminium single frame windows and doors. Bildau and Bussman. LINK. Accessed 31/01/2023
  • Aluminium windows. The Aluminium Spanish Association. LINK. Accessed 31/01/2023
  • Aluminium windows. Strugal. LINK

Suppliers and manufacturers

ASBP members manufacturing windows

  • Velux (PVC-U, wood, and aluminium frames)
  • Bereco (wood frames)

ASBP members supplying windows

Visit ASBP’s interactive house to see a full break down of suppliers and manufacturers

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