There is a product called foil board it is 10 mm polystyrene with reflective foil adhered both sides.
Retrofitting sarking under metal roof.
Unfasten all clips that take hold of the roof tiles.
This will give you space to lay the sarking on.
The use of anticon roofing blanket or vapour permeable sarking directly under the roof sheet is recommended to reduce this risk.
Dismantle all roof battens to enable you to install sarking beneath them.
This video answer the question what is sarking.
What is roof sarking.
Here are just some of the considerations your roofers make when it comes to getting the best and most effective result from roof sarking.
To do this you will have to remove the capping on the ridges.
You may use a staple or nail gun to fasten them with the rafters.
If some are damaged replace them with new ones after putting the tiles back.
Since sarking sits directly underneath your roof it s impossible to retrofit sarking without tearing off your current roof.
Sarking is pliable laminated membrane well that s how bradford describes anyway.
Remove the ridge capping to easily get rid of roof tiles and clips.
It is light and easy to work with and you can fit it to roof battens between rafters or trusses.
Cavity which can allow the metal roof sheet temperature to drop below dew point increasing the risk of condensation formation.
If your home s existing shingles are pretty curled you could install a textured metal roof such as a metal shingle shake or tile directly over the curled shingles along with underlayment.
Now you can lay the sarking sheets.
Lay the sarking sheets on the roof cavity with care and precision.
Unfasten all the roof clips that hold the roof tiles down.
If you re just changing them.
You also could install a corrugated through fastened metal roofing product and probably not have issues.
You can t retrofit sarking without lifting roof sheets but there is a solution.