UNIFOLD Gutter Lining System
- Thermal Issues, Air-Tightness, and Approved Document L

Thermal Issues, Air-Tightness, and Approved Document L - Back To Top

Regulations concerning the energy efficiency of buildings were revised and implemented in 2002.

These regulations, specified within Approved Document L2 – Conservation of Fuel and Power, doubled our previous insulation levels and introduced a far greater emphasis on energy losses due to cold bridging and air changes.

These regulations are applicable to both new build and refurbishment programmes.

Unifold has been used within roof refurbishment programmes where the requirements of Approved Document L2 have been applicable.

Following an extensive and detailed survey, careful design consideration is obviously necessary for any roof refurbishment within the requirements of these regulations.

Eaves and gutter design are particularly relevant, as extra capacity and particularly depth, is required in the gutter to accommodate insulation levels and to retain or improve gutter capacity. The eaves arrangement needs to accommodate the new system.

These conditions are dependent on several factors including: -

1. New roof type: Built-up or Composite roof system
   
   
2. Whether the roof is to be over-skinned or stripped and re-sheeted.
   
   
3. Retention or replacement of the existing gutter.

Built-up Roof System
will require the new liner tray to discharge to the gutter to drain any interstitial condensation.

This provides some design restrictions when attempting to include the necessary insulation depth within the gutter, unless a roof over-skin system is contemplated.

Composite Roof System
As there is no liner tray to discharge, the depth of insulation within the composite roof sheet can be utilised and will usually provide sufficient capacity to include the necessary insulation levels within the existing gutter.

Roof Over-skin
If the roof is to be overskinned it is possible to use the original construction depth of the roof, plus the profile depth of the existing roof sheet, to increase original gutter depth, allowing insulation to be included to requirements.

Roof Strip and Re-sheet
There is probably very little opportunity to increase the existing gutter sizes to accommodate the insulation levels required unless a composite roof system is used. Careful design, calculation and computer modeling will most likely be required to "prove" the arrangement.

Retention or Replacement of the existing Gutter
Whether the gutter is retained or replaced is often dependant upon which roofing system is used.

If a roof over-skin system is used, the original gutter is retained, unless the gutter substrate material has degraded or corroded beyond its useful, structural, life.

Conversely, as the opportunity presents itself, the gutters are quite often changed when the existing roof is stripped and re-sheeted.

The use of Unifold in Document L2/J2 designs – whichever system of re-roofing is used and whether or not the gutters are retained or changed there is an opportunity to use Unifold and there are many advantages to its use: -

1. The gutter can be installed after the roof has been completed, preventing the damage usually caused during roof work.
   
   
2. The gutter capacity can most easily be increased to include the necessary levels of insulation. Positive air sealing can be achieved without complication.
   
   
3. The continuous cold bridge normally associated with metal gutters can be removed or at least drastically reduced.
   
   
4. The opportunity exists to improve the drainage performance of the existing gutter and outlets by utilising some or all of the insulation thickness available to introduce sumps within the system. (NB: as this will cause localised cold bridging at outlet positions, "trade – off" calculations may be necessary to prove the design.)
   
   
5. The system will provide a guaranteed solution with great longevity.

Design
It is essential when considering Unifold for use in these installations, that Ampteam Technical Department is consulted in the early stages of the design cycle, as the gutter and eaves conditions are critical for the effective and correct use of the system to conform to the regulations.

Building Sciences Ltd., leading independent building envelope consultants for thermal bridging, air leakage and roofing have made calculations for Ampteam to demonstrate compliance with the stringent criteria required to satisfy the Conservation of Energy sections of the Building Regulations for England & Wales, Scotland and Northern Ireland.