While some try to do this with fiberglass or cellulose their efforts are for naught and quite simply it is not allowed by any legitimate building code out there.
Hot flat roof.
A hot roof is one where there is no ventilation required as the insulation is directly attached to the roof sheathing.
A warm roof is much more straightforward to install and provides a superior thermal performance and is therefore more costly.
As you might imagine this is the cheapest version possible and good for covering a shed.
A system most likely to be found in newly built homes the term hot roof is something of a misnomer as the attic space will only be a few degrees warmer than in a traditional roof.
Other options to cool your flat roof.
This together with a lack of regular inspection and maintenance has meant that flat roofs have a poor reputation and there is an unwillingness to retain or to build them which is unfortunate given the potential usefulness of flat areas the more so with the excellent performance of modern.
If you live in an arid region or an older urban area you may have a large flat roof.
The benefits of a conditioned attic.
A flat roof is usually slightly sloped.
Hot tar and gravel also known as the built up roof bur this type of flat roof features three or more layers of waterproof material mixed in an alternating fashion with hot tar and a layer of smooth stone like gravel.
These roofs have some pros and cons as explained in the article.
It s definitely something to consider when re roofing and in a new construction project and you might be able to take steps to cool things down on the roof you already have.
Traditionally the smelly hot physically demanding and sometimes dangerous work of tarring flat roofs has often meant that uneducated fitters of doubtful reputation have done work to a poor standard.
How hot your roof really gets in the summer is a variable you have some control over.
It may be covered with a granular roll roofing epdm which is smooth surfaced or modified bitumen which may be smooth or mineral surfaced.
The traditional hot tar and gravel roof is built from three or more plies of waterproof material alternated with hot tar and ballasted by a layer of smooth river stone.
The hot applied asphalt or coal tar pitch blends with the bitumen soaked roof felt and creates a monolithic roof membrane.
When placed over a cool roof laminate of pvc they will continue to keep your home cool in hot summer weather.
You can also add ultra thin solar photovoltaic panels to your flat roof.
A cold roof is best when you re initially creating a flat roof and is cheaper than a warm roof but does provide an inferior thermal performance.
Some flat roofs have hot tar built up roofing which may have a gravel surface.