L10 Windows Rooflights Screens Louvres (Checklist) G#1604 N#1533

GBE CPD L10 Windows

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L10 Windows Rooflights Screens Louvres Checklist

L10 Windows Rooflights  Screens Louvres Checklist


  • Thermal bridging around windows
  • Air leakiness around windows
    • (see GBE Robust Specification P14)
  • Thermal discomfort due to poor U value windows makes a well insulated building fail to meet expectations
  • Excessive heat loss through windows compared to opaque building fabric
    • (See U Values to Energy consumption to Carbon GBE Calculator)


  • Robust Details do not refer to durable tough details they refer to competent acoustic details that may fall short on other performance requirements.
  • A passivhaus window does not automatically perform as well as designed if installed incorrectly or misaligned with the insulation in the wall


  • Competent detailing (not necessarily robust details)
  • Correct placement of windows in relationship to insulation in surrounding walls
  • Passivhaus windows can eliminate cold down drafts and cold feet
  • Avoid placing radiators under windows and on inside face of external walls
  • Spend us much as you can on high performance windows


  • ‘Fabric First’ & ‘Build tight – Ventilate right’
  • Highest performance windows you can afford,
    • to reduce fuel demand (during heating season) over life of building
  • Many Scandinavian manufacturers offer high specification at good price,
    • not many UK manufacturers can compete, a few exceptions.
  • Trickle vents controllable by occupant, visible and easy to use without risk of jamming
  • Internal temperature of glass needs to be as close to the temperature of the wall
    • (17-18 degrees C) for thermal comfort
    • U values of 0.8 to 0.5 W/m2.K should achieve these temperatures
  • Double and Triple glazing
  • U Values of 1.0 to 0.5 W/m2.K are achievable
  • Use Double Glazed Sealed Units to BS EN 1279-2 and BSI Kitemarked
  • Use Low E (Emissivity) glass generally
    • (to minimize heat loss by reflecting it back in)
  • Use Argon, Pentane or CO2in sealed units
    • (but be aware of the high environmental impact: See Bath ICE Database)
  • Exclusion of UV light, using PVB interlayer in laminated glass
    • (to reduce fading of objects inside)
  • Permitting UV Light: for plant and food growing green houses
  • Co-ordinate window and door opening with brick sizes and/or blocks modules to minimize cutting waste
  • FSC approved timber sources and timber based materials See Z10
  • Timber: Hardwood, Heartwood of softwood, Slow grown timber, reclaimed timber
  • Uncoated recycled aluminium
    • (but no coating reduces component life marginally)


  • Choose local or FSC certified timber.
  • Choose High performance windows with manual control trickle vents
  • Choose from the British Woodwork Federation BWF’s Timber Window Accreditation TWA Scheme: Manufacturers, Suppliers and Installers.
  • http://www.bwf.org.uk
  • Get them fully finished in the factory on all faces, but avoid oil paints, choose microporous high build paints or stains
  • Consider aluminium sill and bottom beads for durability in the most vulnerable locations.
  • Choose BBA Certified and/or BSI Kitemarked windows
  • Choose with BSI Kitemark Double Glazed Sealed Units
  • Choose Windows with Secure by Design Accreditation


  • Scandinavian and east European windows: are usually high performance compared to many UK makes.


  • Excessive glazing on north face (heat loss and thermal discomfort in winter)
  • Excessive glazing on any face (heat loss and thermal discomfort in winter)
  • Excessive glazing on south and west faces (heat gains in summer unless it is managed and exploited)
  • Single glazing: higher chance of condensation on inner face
  • Double Glazed Sealed Units only offering U Value between 1.0 and 2.0 W/m2.K
  • Indonesian Hardwood
  • Most is reported to be illegally logged: destroys forests, communities and habitation
  • CCA (Copper Chrome Arsenic) Treated softwood, See Z12
  • Powder coated aluminium (hazardous residue or emissions when recycled)
  • Primed timber windows being installed and then painted insitu, leaving vulnerable absorbent timber against potentially wet masonry.
  • Apply full paint scheme to ALL faces in the factory.
  • Virgin plastics See Z50
  • PVC See Z50
  • Give yourself and the fire fighters a better chance of survival in a fire
  • Some Responsible Social Landlords have had enough bad experience to refuse to use PVC windows.
  • Some RSL have maintenance regimes in place to wash PVC windows inside and out every 3 months so they have a chance to check for failing Ironmongery.
  • They will also check for pinking or yellowing of the frames.
  • Dulux created a paint specifically for painting PVC windows, I wonder why?
  • 25 year life is optimistic for PVC windows, Ironmongery fails sooner if not steel reinforced sections.


  • Use of virgin aluminium in window frames
  • Use of PVC in all applications
  • Use of preservatives in timber frame windows


  • GRP Pultruded faced composite timber for:
    • aluminium faced composite timber window frames
    • PVC windows


  • Long life powder coated or anodized aluminium in preference to painted metalwork


  • Don’t ignore the feel good factor of seeing and touching timber


Precautionary principle:

Resource Efficiency:


  • Use of virgin aluminium in window frames


  • Reclaimed wooden windows
  • Web Portal: Salvo Ltd.


  • Reclaimed windows

Repairing Windows:

  • Repair PVC windows rather than remove and landfilling them.

Refurbishing Windows

  • See C51
  • See Refurbishment Checklist L10


  • Use recycled aluminium in preference to virgin aluminium, significant reduction in energy consumed and potentially CO2 generated


  • Do not incinerate:
    • PVC windows high risk of Dioxin release to the atmosphere (See Trashed Film/Video)
    • Painted wood windows
    • Preservative treated wood windows
  • Do not burn off coatings on aluminium windows
    • Ensure emmissions to air are controlled

Waste Issues:

  • WRAP guide on dismantling PVC windows to segregate waste

Waste Catagory:

  • Window: Mixed waste
  • Double glazed sealed units: Mixed waste
  • Single glass: Inert

Waste statistics:

Waste minimization:

  • Measure the openings accurately and forward the survey information before manufacture

End of Life options:

Hazardous waste & Deleterious Substances:

Design for recycling:

  • avoid coatings as they create problematic expensive hazardous waste or emissions when recycling aluminium
  • e.g. PPC Polysester Powder Coating and PVF2 Poly Vinyl Fluoride Coating
  • Anodising is a chemical oxidation process generating an oxide of aluminium
  • Anodised aluminium generates less problematic waste when recycled
  • Mill finish is best for recycling but not everybody likes the oxides that form on aluminium
  • Mill finish aluminium may have a marginally shorter life than coated aluminium


  • Passivhaus windows in Passivhaus buildings
  • Insulated, airtight weather resistant gap filling between window and surround
  • Airtightness membranes designed for window perimeters and adjacent materials


  • Align windows with the insulation in the surrounding wall or link them if they do not align
    • Thermal bridges can seriously reduce the performance of the window
    • A well placed poor performing window can be better than a badly placed Passivhaus window
  • Choose BBA Certified and/or BSI Kitemarked windows
  • Choose with BSI Kitemark Double Glazed Sealed Units
  • Choose Windows with Secure by Design Accreditation
  • Choose Windows with TWAS accreditation or equivalent
  • Choose Windows with Passivhaus accreditation or equivalent
  • Get them fully finished in the factory on all faces, but avoid oil paints, choose microporous high build paints or stains
  • Always use an approved accredited or manufacturer trained installer


  • In wood windows consider aluminium sill and bottom beads for durability in the most vulnerable locations.


Maintenance issue:

  • Anodized or coated aluminium give a long life but the guarantee relies upon a regular cleaning regime
  • Painted and stain timber have a relatively short life between recoating
  • Stains that can accept overcoating with more of the same and at worst needs sanding down; are easier to maintain than paint that may need to be removed or at least sanded down to accept over-coating

Industry Initiatives:


  • An EU fund for recycling extruded rigid PVC from window and other waste exists and a number of waste handlers are engaged in the scheme in the UK.
  • Only one window manufacturer was involved in RecoVinyl so most are not using recycled content in their frames
  • Most of the PVC that is recycled goes to make something other than windows, this does not make the windows any better
    • (despite BRE Green Guide to Specification)
  • Use of virgin PVC sheath over recycled PVC is adopted
  • Use of recycled PVC in the core of a window section may not be a clever solution because the best PVC windows are steel reinforced in the core of the section

Information sources:

ARTICLES: (on GreenSpec)

  • Window Materials
  • Wood paints
  • Wood preservation
  • Glass:
  • Ventilation:


  • BedZED BioRegional Guide

© GBE NGS ASWS BrianSpecMan aka Brian Murphy
16th December 2012 – 20th February 2017

L10 Windows Rooflights Screens Louvres Checklist



GBS Green Building Specification

NGS GBS JP14 SWS Cover png

P14 Air/wind tightness systems

Robust Specification Work Section
  • P14 RSWS Airtghtnss A15 BRM 060414 doc
Robust Specification Guidance Notes
  • P14_RSG_Airtightnss_A03_BRM_091212.doc

If you wish to reproduce images, feel free, but please acknowledge the source.

© GBE NGS ASWS  BrianSpecMan aka Brian Murphy
29th July 2014 – 20th February 2017

L10 Windows Rooflights Screens Louvres Checklist
See Also: 

GBE Compare

GBE Jargon Buster


  • BBA
  • BSI
  • BRE
  • BWF
  • DGSU
  • FSC
  • GGtS
  • PVC
  • PVCu
  • TGSU
  • TWAS
  • UPVC
  • BSI Kitemark
  • BRE Green Guide to Specification (GGtS)
  • British Booard of Agrement (BBA)
  • Composite Window
  • Double Glazed Sealed Unit (DGSU)
  • High build stain
  • Micro porous paint or stain
  • Passivhaus
  • Polyvinyl Chloride (PVC)


Seminar Topics

  • L10 Windows


New Build

  • C50 Repairing/Renovating/Conserving metal
  • C51 Repairing/Renovating/Conserving timber


  • FSC UK
  • BSI
  • Secured by Design








  • U Values to Energy consumption to CO2
  • Embodied Energy & Embodied Carbon

GBE Datasets

GBE Jargon Buster


  • 2D and 3D SketchUp Product files
  • SketchUp files of Construction Sections

GBS Green Building Specification

Robust Specification Work Section

GBS Robust Specification

Robust Specification Clauses

GBE Library

GBE Information

GBE Projects

© GBE NGS ASWS BrianSpecMan aka Brian Murphy
16th December 2012 – 20th February 2017

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