EWI to clipped eaves with room in roof (insulation to rafters)
Detail summary
A detail for external wall insulation to deal with a potential cold bridge at eaves where new insulation to rafters meets external wall insulation. To be used where there is an existing room-in-roof or loft/roof insulation to be applied to existing rafters.
Where there is a limited overhang at the existing eaves, an integral gutter is required to enable water run-off. The EWI is used to form a verge, which is then capped with a Stainless steel gutter.
Target values:
Target Roof U-Value: 0.18 W/m²K Target Wall U-Value: 0.18 W/m²K
Technical description
Section detail. EWI to existing wall. Up to eaves, clipped, with new/ existing loft insulation join to EWI. Loft insulation to rafters where existing room in roof
Suggested Installation Sequence:
Preparation of roof and loft space: Remove any existing loose material and prepare in accordance with manufacturer's requirements.
Any alterations to cabling, existing ventilation, drainage and other fixtures, affected by the work to be agreed with contract administrator prior to work being undertaken. Prior to start on site inspect the form and condition of the roof internally and externally, especially any structural timbers; institute repairs and/ or additional works necessary to make the substrate suitable to receive insulation.
Installation:
- Carefully remove minimum 750mm of tiles or slates, putting to one side for reuse. Note positions of existing roofing battens.
- Remove roofing battens to at least 600mm up the roof from the existing eaves. Roll existing membrane back but do not cut.
- Insert rigid insulation (RF06)between rafters, allowing at least 125mm from the edge of insulation board to the next batten position up the roof.
- Fix external wall insulation (EW01)- cut to fit to eaves insulation and cut back to form gutter parapet.
- Install breathable membrane/ roof underlay (RF06c) approx 500mm up roof slope from front edge of EWI. Pin in place to rafters with galvanised clouts at upper edge. Dress over EWI outer layer so as not to protrude beyond the front face.
- Insert stainless steel gutter system over the top of the breather membrane/ roof underlay and EWI as shown on drawing. Fix in place with self drilling fixings to every third rafter at inner upper edge.
- Roll original membrane back over new stainless gutter to lap new gutter by 200mm. If required replace roofing battens in original locations up to approx 600mm above bottom edge of gutter. Dress the existing membrane over this reinstalled batten. Insert last batten at approx 350mm up from the edge of the gutter.
- Roll the original membrane over the top of the polycarbonate vent strip.
- Replace slates/tiles, dressing last slate/tile so as to be just below the upper edge of the gutter.
- Install loft insulation to rafters (RF02a) - making sure it meets the back of the eaves insulation (RF06c).
Reference Specification:
All guttering to BS EN 12056-3, clauses 3–7 and National Annexes. Collection and distribution of rainwater: complete, and without leakage or noise nuisance.
For all works to existing roofs refer to Approved document C (resistance to contaminants and moisture), with reference to Section 2, and section 6.
Reference should be made to Document H (drainage and waste disposal). Approved Document F (ventilation) should be referred to with regards to ventilation to existing roofs and over eaves ventilation. Document L1b should be referred when working on existing dwellings, with particular attention to sections 5 and 6 regarding material alterations. Document L2b should be referred to with existing buildings other than dwellings.
Notes:
Care should be taken to ensure air-tightness. Seal all service penetrations through EWI and existing wall. Lap and tape all membranes around edges of EWI system.
All insulation to be continuous to avoid thermal bridging.
Preparation of external wall: Remove any existing loose material and prepare in accordance with manufacturer's requirements.
Any alterations to drainage and other fixtures, or work to prepare the existing roof or eaves , to be agreed with contract administrator prior to work being undertaken. Prior to start on site inspect the form and condition of the existing eaves; institute repairs and/ or additional works necessary to make roof suitable to receive insulation system.
Parts list
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External Wall Insulation (Woodfibre), rendered finish [EW01]
Composite woodfibre board for use on solid and hard to treat cavity walls.
- Insulation back board: UdiTherm SK.
- Insulation top board: Diffutherm NF (T&G, renderable).
- Thermal conductivity: 0.045W/m2K. GWP 0.
- Base Coat: levelling on substrate: 90% contact required around edge of boards between board and substrate to prevent thermal bypass. If substrate is very uneven, use base-coat material around edge of board to achieve contact.
- Fixing: Fixed mechanically to substrate in accordance with manufacturers recommendations.
- Render/carrier: to manufacturers standard.
- Render: Udi Perl
- Decorative finish: tbc
- System guarantee: 25 years - ECO compliant insurances and guarantees.
- System Certification : ETAG
Unger-Diffutherm. Product Reference: UdiFRONT.
Supplied by: Back To Earth. Tel: 01392 861763
Web: http://www.backtoearth.co.uk/ -
Gutter system [RF06c]
Flashing at junction between flat roof verge and external wall insulation. To BS 460, and BS EN 12056-3, clauses 3–7 and National Annexes.
- Manufacturer: Contractor's choice.
- Profile: As drawing.
- Gauge: 1.2mm min.
- Jointing: Joints to be avoided where possible. If required must be fully welded and tested. Could be glued and blind riveted subject to approval.
- Size: Contractor's choice- to suit existing roof dimensions and cover depth of external wall insulation. Ensure provides adequate capacity for rainwater discharge from roof.
- Finish as delivered: Self finished Stainless Steel grade 304.
- Setting out: To falls.
- Fasteners: as manufacturers recommendations.
- Accessories: As welded stop ends.
- Testing: Test on completion.
Contractor's choice
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Breathable Membrane/ Roof Underlay [RF06c]
Roof underlay. Sealed to phenolic foam insulation and dressed to drainage point at the end of each run of guttering to allow water to exit construction.
Green Building Store. Tel: 01484 461705.
Web: http://www.greenbuildingstore.co.uk
Product Reference: Solitex Plus underlay -
Insulation Boards/ Batts Fitted Between Rafters [RF02a]
- Type: Formaldehyde Free Glass mineral wool semi rigid batts friction fitted between rafters.
- Thickness: 35mm less than rafter depth.
- Width: to suit rafter spacing.
- Thermal conductivity: 0.032 W/m2k. GWP 0.
Knauf Insulation Ltd.
Product Reference: DriTherm Cavity Slabs. -
Integral vapour control with Insulated Dry-Lining Board [RF02a]
Phenolic foam backed plasterboard.
- Thickness: As required to meet target U-value (80mm where 35-75mm mineral wool insulation, 60mm where 75-100mm mineral wool insulation, 50mm where 100mm + mineral wool insulation).
- Thermal conductivity: 0.020W/m2k. GWP< 5.
- Adhesive scored bonding coat to ensure no air-gap to rear of board. Joints taped and filled.
- Integral Vapour Control Layer: ensure all joints between sheets detailed and taped to minimise vapour transmission using vapour-tight tape.
Kingspan Insulation Ltd
Web: http://www.kingspaninsulation.co.uk
Product Reference: Kooltherm® K18 Insulated Plasterboard -
Insulation to Eaves (Flexible) [RF06c]
- Woodfibre offcuts from external wall insulation.
- Installation: Insert into gaps between wall plate/top of wall and rigid insulation to ensure continuity and avoid air movement.
EWI manufacturers or: Back to Earth:
Tel: 01392 861763.
Web: http://www.backtoearth.co.uk/
Product Reference: Diffutherm -
Insulation to Eaves (rigid) [RF06c]
- Manufacturer: Contractor's choice.
- Phenolic foam.
- Size: 50mm thickness
- Width: cut to suit rafters.
- Length: 750mm PLUS distance to eaves board or 200mm (whichever smallest).
- Thermal conductivity: 0.023W/m2k.
- Installation: Continuous with roof insulation, no gaps, to avoid cold bridging. Friction fit between rafters from inside loft, being careful not to damage existing roof membrane or structure or block existing ventilation paths.
Contractor's choice
-
Protected ventilation path /Eaves vent strip [RF06c]
- 12mm Polycarbonate sheeting equivalent to 10mm continuous ventilation gap.
- OR: ventilator strip to allow airflow under roof whilst preventing ingress of insects and small birds.
Contractor's choice
-
Softwood battens (for replacement slating) [RF06c]
- Size: 50x25mm timber battens.
- Grading: Fully factory Pre-graded.
- Preservative treatment: Required- contractor's choice.
- Certification: All timber to be FSC certified \ Preservative treatment required.
- Fastening: Galvanized steel nails, sized to penetrate 40 mm (minimum) into rafters.
Contractor's choice.
Revisions
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Admin - 2015-04-29 09:29:02 [Displayed version]
DWG file updated. Contact details updated for EWI to include Back To Earth. Formatting changes.
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Admin - 2015-04-29 09:26:58
DWG file updated. Contact details updated for EWI to include Back To Earth. Formatting changes.
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Admin - 2015-03-27 16:17:15
Preview image and .pdf file updated.
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Admin - 2015-03-23 13:03:26
Introduction expanded with target u-values. Technical description updated with more detailed construction sequence and BS/approved doc links. Parts list updated with links/codes. General re-formatting.
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Admin - 2015-03-23 12:58:32
Introduction expanded with target u-values. Technical description updated with more detailed construction sequence and BS/approved doc links. Parts list updated with links/codes. General re-formatting.
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Admin - 2015-03-13 18:02:12
Technical description updated with installation sequence.
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Admin - 2015-03-12 12:44:18
Version 7- Title, description and technical description updated and expanded. BS and Approved doc information added. Parts list updated.
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Admin - 2015-03-12 12:43:01
Version 7- Title, description and technical description updated and expanded. BS and Approved doc information added. Parts list updated.
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Admin - 2015-03-03 12:02:55
Parts list updated
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Admin - 2015-03-03 11:57:19
Parts list updated
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Admin - 2015-03-03 11:42:18
Preview file updated. Parts list added.
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Admin - 2015-02-27 12:16:13
Version 2- .dwg file updated
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Admin - 2015-02-26 14:34:32
Second version - Change to summary text.
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Admin - 2015-02-26 14:32:04
First version
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For those who have seen the Earth from space, and for the hundreds and perhaps thousands more who will, the experience most certainly changes your perspective. The things that we share in our world are far more valuable than those which divide us.
For those who have seen the Earth from space, and for the hundreds and perhaps thousands more who will, the experience most certainly changes your perspective. The things that we share in our world are far more valuable than those which divide us.
- Ease of understanding detail: Easy
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For those who have seen the Earth from space, and for the hundreds and perhaps thousands more who will, the experience most certainly changes your perspective. The things that we share in our world are far more valuable than those which divide us.
For those who have seen the Earth from space, and for the hundreds and perhaps thousands more who will, the experience most certainly changes your perspective. The things that we share in our world are far more valuable than those which divide us.
- Ease of understanding detail: Easy
- Ease of sourcing materials: Easy
- Ease of sourcing skills: Easy
- Ease of implementation: Easy
- Overall cost: Low cost
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User name
For those who have seen the Earth from space, and for the hundreds and perhaps thousands more who will, the experience most certainly changes your perspective. The things that we share in our world are far more valuable than those which divide us.
For those who have seen the Earth from space, and for the hundreds and perhaps thousands more who will, the experience most certainly changes your perspective. The things that we share in our world are far more valuable than those which divide us.
- Ease of understanding detail: Easy
- Ease of sourcing materials: Easy
- Ease of sourcing skills: Easy
- Ease of implementation: Easy
- Overall cost: Low cost
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For those who have seen the Earth from space, and for the hundreds and perhaps thousands more who will, the experience most certainly changes your perspective. The things that we share in our world are far more valuable than those which divide us.
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