For existing masonry walls...

To insulate internally, for best results use Astrofoil Original.  This is has two layers of air bubble and gives the best thermal protection.

Almost as good and slightly less expensive is Astro-E - the 'E' stands for 'economical'.  Astro-E has one layer of air bubble in the middle and is not as sturdy as Astrofoil Original.

If you want to protect against conducted heat-loss as well as radiant heatloss you could use Astro-safe.  This combines a layer of reflective foil with 40mm of Polyester foam.  This material was originally designed for heating and ventilation ducts but it is an excellent product for general purpose insulation.  It compares extremely well price wise against other ,multi-layer' insulation materials.

For new construction, where the insulation can be put inside the cavity, both Astrofoil Original and Astro-E are equally applicable, however you may wish to consider Heatshield b-r-e-a-t-h-e-r foil.  This is a lot less expensive per m2 (the roll size is 92m2) and it has the additional property of being 'breathable' due to the material being micro-perforated.  Heatshield b-r-e-a-t-h-e-r foil is ideally suited for use with timber frame construction and is normally used in conjunction with a bulk insulator such as glass fiber or rock-wool and the like.  (The latter to protect against conducted heat loss and the Astrofoil to protect against radiant heat-loss.

For further information see our guide to reflective insulation.

Image	Name	Description	Price	Qty
	* * * Astro - E * * * Foil-Bubble-Foil 40m2	A more economical, lighter weight version of Astrofoil original, designed for DIY use.	£99.60
	* * Astrofoil Original * * Foil-Bubble-Bubble-Foil 40m2	Heavy duty for commercial and industrial use. Two layers of plastic air filed bubble with 99.9% pure Aluminium foil on each side, finished with a clear vinyp protective coating.	£139.00
	HEATSHIELD III B-r-e-a-t-h-e-r Foil + tape 2 x72m2	Breathable Astrofoil for roof and wall insulation (two layers of microperforated foil - no -bubbles)	£199.00
	HEATSHIELD III B-r-e-a-t-h-e-r Foil 72m2	Breathable Astrofoil for roof and wall insulation (two layers of microperforated foil - no -bubbles)	£124.00