Insulating a flat roof can deliver real benefits; a warm comfortable room,
lower energy bills and improved HIPs ratings. Building regulations can mean
insulation is compulsory.
In April 2006 the revised Part L of the building regulations came into force,
this has the aim to reduce energy used in buildings. The key requirements are:
- Reduce energy used in buildings by at least 20%
- In most refurbishment instances additional thermal insulation is required
to meet the required "U" value. If such an upgrade is not technically
or functionally feasible or would not achieve its pay back within 15 years.
There are essentially two designs used in the construction of a flat roof with
insulation.
Cold deck
This is the most common construction but is also the least thermally efficient.
From the room ceiling up the build is as follows: The roof joists support the
roof construction the internal ceiling is attached to these, between the joists
in the roof void insulation is laid in buildings constructed in the 60s, 70s,
& 80s, there will most likely be some type of insulation between the rafters
in the roof void. On top of the joists the roof deck is fixed and the waterproof
roof cover is laid.

Warm deck
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 build 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 regulations.
