Flat Roofing Insulation

Flat Roofing Insulation

lower energy bills and improved energy ratings. Building regulations can

mean insulation is compulsory

Building Regulations

In April 2006 the Government of England and Wales implemented changes to Building Regulations Approved Document L (Conservation of fuel and power). These revisions have a significant affect on homeowners and domestic roofing contractors, and could affect the future sales value of homes.

The regulations were changed to implement the EU Energy Performance of Buildings Directive (EPBD), which aims to reduce energy use in domestic buildings by 20% compared to the 2002 regulations.

There are essentially two designs used in the construction of a flat roof to include insulation.

Cold deck (fig 1)

This is the most common construction and can be the least thermally efficient. This roof design can also be prone to the manifestation of condensation within the roof void. From the room ceiling up the build is as follows: the ceiling is attached to the roof joists that support the roof construction. A polyethylene vapour barrier is laid into the roof void and mineral insulation is loose laid between the rafters. The roof deck is then fixed to the rafters and the water proof membrane is then installed. In some cases this construction may have to be ventilated to avoid condensation.

(fig 1)

Warm deck (fig 2)

This is the most modern method of construction and should be used were possible (although not all situations are able to accommodate this design).

From the room ceiling up the construction is as follows: The roof joists support the roof construction the internal ceiling is attached to these. On top of the joists the roof deck is fixed. A vapour barrier is laid on to the deck and the appropriate thickness of insulation is fixed to the roof deck. The waterproof roof cover is then installed.

This method of insulating the roof alleviates the formation of condensation in the roof void, and complies with the current building regulation.

(fig 2)

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The benefit of these changes will be a reduction in the energy used to heat or cool your home, which in turn will reduce the carbon footprint of your home. However to achieve this you will need to invest in the installation of a thermal insulation beneath the waterproofing membrane.

There are some exemptions, unheated parts of the building including garages and porches, some listed buildings or where the payback period (cost of insulation versus savings made) exceeds 15 years to achieve. (view all exceptions). It is down to your Local Authority Building Control (LABC) to make a judgement on what is required.

Flat Roofing Insulation

Roof Technology will include the cost of gaining approval from Local Authority Building Control (LABC) and we strongly advise that you ensure any other roofing contractors consulted do likewise. An unscrupulous roofing contractor may tell you that you do not need to bother, this is untrue and could carry serious and expensive consequences.

Roof Technology will be liable to fines from Local Authority Building Control (LABC) for not complying with Building regs, not the homeowner, but as a homeowner you will have other potentially expensive problems.

When a property comes to be sold athough the roof intallation guarantees will be in place, there will be no record of the installation having LABC approval, this could prove to be a major problem to a potential purchaser or mortage lender.

The lack of insulation will also affect the energy rating of the property.

Building Regulations approved Document L (ADL) Part L1B - Existing Dwellings (Residential Refurbishment/Extensions) now requires minimum U-values to be achieved. The regulations state that when refurbishing a flat roof, a check on the insulation within that roof must be made to ensure that it meets the requirements of Approved Document L 2006.

These requirements are that:

A new build should achieve a U-value of .20 generally requiring a minimum insulation thickness of 120mm

A refurbished roof with little or no insulation must achieve a U-value of .25. Generally requiring a minimum insulation thickness of 100mm

A roof repair that accounts for more than 25% of the individual roof area must comply with the new requirements


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