Aluminium thermal insulation for loft

pmorrison_2

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Hi, Ive been given a large amount of aluminium thermal insulation (this stuff) for topping up the insulation in our loft.

We currently have 100mm of regular insulation, how much of this should we put on top of the current insulation to make it most effective?

Cheers,

pmorrison

homeenergise

I think you are missing the point of this product.. It is not insulation you lay at floor level on top of your existing insulation. Insulation Foil is for spanning across your rafters or purlins that slope down to the attic floor. It helps reflect heat back into the attic and prevent cold coming in through from the outside. I have done this and you need a staple gun to fit the insulation to the rafters or battens then tape to air seal the joints or laps.. If there is any spare foil left when your done, put it behind your radiators!

With regards to the floor insulation in the attic you need 280mm (Space Blanket is the least mess and less itching!)

You

pmorrison_2

That does make far more sense! I was looking at it and couldn't work out how it could actually insulate the house!

Looks like I now have 2 jobs to do in the loft, that and the floor insulation as well!

ormus

if you do the loft floor with extra insulation (which you should) then dont use the foil in the rafters.
itll most likely cause you condensation.
better to see if you can swap the foil for the proper stuff?

vaio

it will work as floor insulation but you'll need to add 6 layer on top of the existing 100mm to bring it up to the recomended u value

pmorrison_2

So what would be best to use then? Ive got tonnes of the aluminium foil but I would assume that the floor insulation will make more of a difference? And it definetly isnt advisable to do both?

Our roof doesnt have any sarking felt so it is drafty up there, does that make any difference?

pmorrison_2

Shameless bump!

iamcornholio

To bring it up to current standards, you need to add another 150mm of fibreglass quilt or rockwool quilt

That stuff in the first post is not insulation at all - definitely a trades description issue going on there. Its bubble wrap with some foil around it!

Insulate above the ceiling to keep the house warm, leave the roofspace cold and draughty to ventilate it.

vaio

iamcornholio wrote: »

To bring it up to current standards, you need to add another 150mm of fibreglass quilt or rockwool quilt

That stuff in the first post is not insulation at all - definitely a trades description issue going on there. Its bubble wrap with some foil around it!

Insulate above the ceiling to keep the house warm, leave the roofspace cold and draughty to ventilate it.

It is insulation and much better than normal loft stuff, as i said earlier 6 layers (thickness maybe 25mm in total) has the same insulation value as 150mm of normal loft insulation. Other advantages......it would be easier to lay, probably fit below the level of the ceiling joists so boarding would be easy.

Only downside is cost but as the OP got it for nothing that doesn't apply here

pmorrison_2

It does seem that everyone has varying opinions on this stuff! Been doing a bit of research and cant really find a definitive answer.

I have now ordered some of the rockwool insulation that was on offer from npower, total of £58 so I am considering laying this over the current insulation on the floor and attaching the aluminium foil to the rafters.

Im not 100% certain that this is what Im going to do, but thats the plan at the moment!

vaio

This stuff http://www.diy.com/diy/jsp/bq/nav.jsp?isSearch=true&isYmal=true&fh_search=0000003716250 has an R value of 5 and is 8 inches thick

The stuff you got free has a thermal resistance (U value) of 1.455 W/M2K

To convert R values to U values you divide the R value into 1 so R of 5 is same as U of 0.2

Two layers of the free stuff will have U value of 1.455 divided by 2 so about 0.7

Seven layers will be 1.455 divided by 7 so about 0.2 which is about the same as the stuff above except that 7 layers of the free stuff will only be about an inch thick rather than eight inches