splitlid wrote: whether the insulation is laid on the ceiling or under the roofing material is argueable as to which is best, some will say that having both is the best way to go.
The smaller volume you have to heat or chill is obviously better therefore insulating directly at point of heat exchange is preferable ie ceiling and walls.
It also makes sense that in hot climates where the air gap between roof and ceilings can be raised to a much higher ambient temperature to add a reflective barrier to reduce this and so make the ceiling insulation more effective by reducing the delta between the house and roof space temperature.
The most common ceiling insulation is spun mineral wool insulation as it is primarly fire resistant and generally rot, bug resistant.
The foil faced bubble wrap I,m sure should not be used where heat sources such as light fittings are present in ceilings as it is not a fire resistant. It may also be potentially problematic if you do not have proper earth leakage protection fitted to electrical system
If you have solid block Walls where it's not possible to add insulation to the cavity then simply by adding polystyrene backed plaster board sheets or a similar built up inner skin using batterns, sheet insulation like the bubble wrap and the plaster boarded over to maintain fire resistance to the inside walls on at least the most exposed faces can have excellent results
Windows can have blinds or good doubled lined curtains as cheap method during the hottest part of the day. Solar reflecting film although more aesthetic to closed curtains etc is not as efficient against direct radiated heat as you may think.