loft insulation top up

[allswell]

hello everyone ,been reading posts and i wreckon someone has the answer to my sticky question!!!.

i want to top up my current loft insulation with airtec bubbly stuff my question is this ,

should i lay this under or above the current insulation material as i do not fancy promoting condensation ,

my thinking points me towards under the current stuff so any warm air or vapour is prevented from contaminating conventional insulation?? ,

if it were above conventional stuff i think it may reduce the reflective properties of the product?.

all ideas or knowledge greatly welcomed as its keeping me awake!! ,
cheers,mark.

 

[PaulJR]

Personally I would staple it to the underside of the rafters.

 

[allswell]

sorry if i am being a bit `fick but,
does stapling it to the underside of the rafters mean below or above current insulation???

 

[PaulJR]

airtec or it's equivalent is an insulated vapour barrier. It relies on creating a small volume of trapped air to work. It wont really do anything if you lay it over the existing insulation, and you wont know if you have a condensation problem untill you get damp patches.
If you lift the insualation, you need to create a 25mm airspace between the ceiling boards and the foil, and then another above it, too much hassle for too little benefit.
airtec is claimed to be equivalant to 50mm of polystryene/PUR, but it requires very careful installation.

If you staple it up under the rafters - the sloping timbers that hold the felt & tiles up, you also need to seal every single joint, supposedly with aluminium foil tape, althoug I have used duct tape before now & it seams OK.

i would suggest that you invest in a thicker layer of a more conventional insulation material - wickes are doing 2 for one on their loft rolls at the minute. You will see more benefit per pound from 150mm rockwooll or glassfibre than the airtec IMHO.

 

[allswell]

thanks for clarifying that!!,off to wickes