Attic Insulation

Lex Luthor

I want to add some more insulation to my attic on top of what is there already. From what I can see it is 150mm thick rolls.

I priced rolls of 4m (150mm) thick insulation in B&Q the other day for about €23 a roll. Is this a good price or can it be got anywhere cheaper than this?

If I am rolling out the new stuff, should I roll it at 90 deg to the current insulation or in the same direction to it?

Is the roll out stuff the best or is there anything better?

What is the min. thickness I should be thinking about?

I have a big enough attic so the cheaper I can get it the better.

10-10-20

It depends on the R-factor. You'll have to look that up and also get prices from Brooks. They do 150mm rolls for ~€32, but the R-value may be better...

I've heard that the B&Q rolls in plastic sheeting are good value and are frequently on sale.

JohnBoy

from my experience b&q are great for some stuff, but not for others, and insulation is one of em.

you should be able to beat their prices on fiberglass at any proper builders providers.

the GALL

b&q ...your not buying from a builder supplier there diy so your paying for the fancy t-shirts and their electricty go to a builder supplier and get it there

evolving_doors

could someone name a few builder suppliers in Dublin that sell attic insulation to Joe public

Thanks

jdpl28

Chadwicks, Brooks Thomas - basically any builders supplier will sell direct to the public. They're usually good for asking questions too, cause yer teenager in woodies won't have a clue how to lay insulation.

evolving_doors

Thanks JD
With all of these types of insulation on the market it would be handy if there was a site that compared all their R-factors , when the BER comes in next year you might have spent all your time and effort putting down 150mm of burning fiberglass insulation only to be told it's not enough...

it's the type of job I will be doing once only..

Niall33

B&Q, Woddies etc charge far too much for fiberglass rolls. Try one of the insulation distriubution companies. IIS in Ballymount or UVAlue in Finglas for example. Ring around first - you'd be amazed at the savings you'll make. Most will sell direct to the public and you will generally get a better rate. Also to achieve the u Value of 0.16 (current Part L requirment) you will need a minimum of 270mm of mineral wool (Fiberglass or Rockwool) - that means fully filling between the ceiling joists and then laying a cross layer at 90 degrees to bring the overall depth of insulation to 270mm. Realistically 300mm is easier as 150mm rolls can be bought as standard. Very important to leave a 100mm gap at the eaves as air needs to be able to circulate in the attic space to avoid moisture problems, rotting timbers etc. Also don't insulate over recessed downlighters that use standard halogen (GU10) bulbs - they will overheat - covers can be bought which do the trick and try to keep all electrical cabling above the insulation.

Its really important also not to compress the insulation afterwards by storing things on top - these products rely on trapped air to do the insulating. By compressing the insulation you are driving out the "active ingredient" and reducing the thermal performance. Never compress Rockwool or Fiberglass - you are wasting your own money!

You can build a storage platform using 18mm plywood fixed to the trusses.

Makes a huge difference to the comfort of the house if done right.

Keep in mind to draught proof the hatch and if possible use some double-sided tape to stick a piece of roll onto the hatch door.

And lastly use gloves and protective clothing - Rockwool (made from volcanic rock) is itchy stuff and Fibeglass (made from sand) is a serious irritant and you should wear a mask if working with this stuff.

Oh yeah, R values indicate the thermal resistance of a product and depends on the thickness - they can be misleading. The lambda value is the one to look for which indicates the resistance of the product itself - most Fiberglass Rolls has a lambda value of 0.044 - Rockwool Rolls (which is not Fiberglass) have the same lambda value but it do not shrink like fibreglass does over time. Fibreglass will start go off after about 10 years. Ever seen the matted yellow stuff in old attics?

gsxr1

Niall33 wrote: »

B&Q, Woddies etc charge far too much for fiberglass rolls. Try one of the insulation distriubution companies. IIS in Ballymount or UVAlue in Finglas for example. Ring around first - you'd be amazed at the savings you'll make. Most will sell direct to the public and you will generally get a better rate. Also to achieve the u Value of 0.16 (current Part L requirment) you will need a minimum of 270mm of mineral wool (Fiberglass or Rockwool) - that means fully filling between the ceiling joists and then laying a cross layer at 90 degrees to bring the overall depth of insulation to 270mm. Realistically 300mm is easier as 150mm rolls can be bought as standard. Very important to leave a 100mm gap at the eaves as air needs to be able to circulate in the attic space to avoid moisture problems, rotting timbers etc. Also don't insulate over recessed downlighters that use standard halogen (GU10) bulbs - they will overheat - covers can be bought which do the trick and try to keep all electrical cabling above the insulation.

Its really important also not to compress the insulation afterwards by storing things on top - these products rely on trapped air to do the insulating. By compressing the insulation you are driving out the "active ingredient" and reducing the thermal performance. Never compress Rockwool or Fiberglass - you are wasting your own money!

You can build a storage platform using 18mm plywood fixed to the trusses.

Makes a huge difference to the comfort of the house if done right.

Keep in mind to draught proof the hatch and if possible use some double-sided tape to stick a piece of roll onto the hatch door.

And lastly use gloves and protective clothing - Rockwool (made from volcanic rock) is itchy stuff and Fibeglass (made from sand) is a serious irritant and you should wear a mask if working with this stuff.

Oh yeah, R values indicate the thermal resistance of a product and depends on the thickness - they can be misleading. The lambda value is the one to look for which indicates the resistance of the product itself - most Fiberglass Rolls has a lambda value of 0.044 - Rockwool Rolls (which is not Fiberglass) have the same lambda value but it do not shrink like fibreglass does over time. Fibreglass will start go off after about 10 years. Ever seen the matted yellow stuff in old attics?

I would go with this advise. this lad knows his stuff.

evolving_doors

Thats some good advice I reckon Niall,

The Fool

Bought from http://www.uvalue.ie/ when they where in north strand before they moved to finglas. Saved a packet. Delivery guy told me that they supplied chadwick ect. and that you are getting stuff for same price that they are.

man o man

if you roll 150mm rockwool, over ur old 100mm glass woll it is prefectily accetable even with the least amount of resistance that ur attic holds to the elements.

divide thickness of material by conductivity gives a resistance value.

conductivity thickness resistance

external
resistance 0.040

concrete
tiles 0.833, 0.012, 0.014

roofspace 0.200
resistance

rockwool 0.037, 0.15, 4.1

glasswool 0.04, 0.1 ,2.5

timber 0.13 ,0.1 ,0.769
joist

plasterboard 0.16, 0.13 ,0.0812

internal
surface 0.100
resistance

ad up all the resistance which is 7.8, divide by 1 gives a total u value.

total resistance 1/ ,7.8

u value = 0.13

this u value calculated here passes the required u value set by documents L 2007 of a u value of 0.16

homer911

Sorry for digging up an old thread, but this was really helpful information

I am planning increasing my attic insulation, but it is currently part floored, directly over the joists and compressing the minimum insulation already there, I also a have light "tunnel" leading up to a velux in the middle of the attic space.

Can anyone advise more on raising the flooring level? Whats the best way to do this? Can you also advise on the best way to insulate the tunnel space? Should I wait until the Home Insulation grant scheme is up and running and get a pro to do it?

Final question - whats the best way to insulate a "drop-down" attic door, both in terms of the door itself and in terms of draught-proofing

Thanks a mill

gsxr1

homer911 wrote: »

Sorry for digging up an old thread, but this was really helpful information

I am planning increasing my attic insulation, but it is currently part floored, directly over the joists and compressing the minimum insulation already there, I also have light "tunnel" leading up to a velux in the middle of the attic space.

Can anyone advise more on raising the flooring level? Whats the best way to do this? Can you also advise on the best way to insulate the tunnel space? Should I wait until the Home Insulation grant scheme is up and running and get a pro to do it?

Final question - whats the best way to insulate a "drop-down" attic door, both in terms of the door itself and in terms of draught-proofing

Thanks a mill

You could frame out a new floor upstairs

But what I have done in an old house recently was to build a walk way around the whole attic using a couple of 7x2s with little legs screwed into the existing joists.

I managed to get 300 mm of inso up there with no compression.

Worked a treat

You could wrap the light tunnel in inso . I seen a few good products out there.
but I cant remember there brand names. Its like a foil bubble wrap plastic sheet.

A bit of PU kingspan type rigid insulation glued or screwed to your attic door should help there

homer911

Thats a great price - Brooks are quoting €22.31 incl VAT for 200mm (6.03m2) R=3.4 Lambda=0.044