attic insulation

sohappy

i want to insulate my attic and put down flooring for storage, the joists are 100 ml deep, is it better to get a thicker insulation say 170 ml and compact it down before laying the floor on top of the joists? any deals around on insulation at the moment? whats the best type to use?

Buford T Justice

You'll need to be careful of the wiring between and across the joists if you intend on compacting it. Be sure not to insulate under your water tank. Do you have any recessed downlighters in the ceiling?

sohappy

yeah gona run 2x1 accross the joists so the wiring not an issue and I know to keep the area around the downlighters clear, what im trying to figure out is are you better using thicker insulation and compressing it or just using enough thickness to fill the cavity?

aujopimur

Compressing the insulation reduces its value.

RKQ

sohappy wrote: »

the joists are 100 ml deep, is it better to get a thicker insulation say 170 ml and compact it down before laying the floor on top of the joists?

No, 170mm thick insulation compacted down to 100mm thick is the same as 100mm insulation.
300mm is the current standard so do try to achieve this where possible. You might not need to floor your whole attic.

sohappy

thanks for all the answers, 100ml it is so!

RKQ

sohappy wrote: »

thanks for all the answers, 100ml it is so!

Nope! 150mm if I were you.
4' joist + 2' batten = 6' or 150mm.
Thats half the recommended depth but better that one third.:)

woody_2000

Just to add some passing/general comments on fiberglass attic insulation.

Firstly, you shouldn't compress fiberglass insulation as this will reduce its intended insulation quality. The thermal insulation quality of fiberglass insulation is based on still warm air being trapped in the air spaces of the fiberglass. Fiberglass itself would have relatively little insulation value as it is made of glass - hence, it would have insulation/conductivity characteristics similar to glass. The fiberglass just acts to trap still air for its insulation quality - so compressing fiberglass would just simply reduce its insulation quality as there is less capacity to trap air. So, fiberglass should always be left loose and uncompressed for optimal insulation quality.

Secondly, for optimal effectiveness, you should lay the appropriate/corresponding thickness between ceiling joists, and then cross lay the next layer over the first layer and joists. E.g. 4" / 100mm laid between joists, and then 4" / 100mm, 6" / 150mm or 8" / 200mm cross laid over the first layer and joists.

Lastly, 1' (300mm) of insulation is apparently considered optimal. The more thickness of insulation added the less return you get from each additional inch (25mm). You get the best return from the first inch, and a slightly lesser return for each inch added - as each subsequent inch has slightly less insulation to do, due to the insulation provided by the previous inch(s). Obviously, one inch alone is not sufficient for proper insulation - but this first inch actually offers the best, and fastest, return for your money/investment. You get a slightly lower return for each subsequent inch added, but you need to meet certain insulation standards. The more insulation you add, the longer it will take to recover your investment on each subsequent inch - and one foot is apparently considered an optimal balance between insulation quality and return on investment. You could be waiting a very long time before you recover your money beyond this thickness, due to the inherent diminishing returns. Obviously when you fully recover your investment through energy/efficiency savings, you're then "in the money" and your investment from then on is paying you back in the form of savings...

Carlow52

RKQ wrote: »

No, 170mm thick insulation compacted down to 100mm thick is the same as 100mm insulation.
300mm is the current standard so do try to achieve this where possible. You might not need to floor your whole attic.

Nope. 170 compressed to 100 is less than 100 because the optimal air glass ratio in an uncompressed 100 is not achieved.

woody_2000

You get the best return from the first inch

burly

woody_2000

[/QUOTE]


+1

Bugnug

Just about to redo the attic in a house we just bought. Would not be gone on the idea of using fibre glass. Can anybody recommend something better?

Also is it a good idea to lag the attic tank?

Cheers.

RKQ

Bugnug wrote: »

Would not be gone on the idea of using fibre glass. Can anybody recommend something better?

Rockwool is less irratating to use but is more expensive.
Foil backed insulation board is very good but a lot more expensive.

Bugnug wrote: »

Also is it a good idea to lag the attic tank?

Very important to insulate sides & lid only. Do not insulate under tank.
Also fully insulate all exposed pipework.

paddy147

Bugnug wrote: »

Just about to redo the attic in a house we just bought. Would not be gone on the idea of using fibre glass. Can anybody recommend something better?

Also is it a good idea to lag the attic tank?

Cheers.

You can buy rolls of insulation that isnt made of fibregalss,its 100% recyclable and does not itch or irritate skin.

I got a load of rolls of 100,150 and 200mm insulation in from Wickes in the UK.

They were doing a deal of buy 1 roll and get 2 more rolls free.

So 3 large rolls of insulation only cost me 25 quid sterling or around 36 euro

Where as 1 roll of insulation here in Ireland is around 25-30 euro alone.Rip Off Republic still.

No1J

Thinking of doing the same myself. should I leave about a 4" gap in the corners for air flow between the joists and rafters? Is Thermal wrap foil any good on the rafters, have seen this in Woodies and again should I leave a few inches from the corners?

TTTT

paddy147 wrote: »

You can buy rolls of insulation that isnt made of fibregalss,its 100% recyclable and does not itch or irritate skin.

I got a load of rolls of 100,150 and 200mm insulation in from Wickes in the UK.

They were doing a deal of buy 1 roll and get 2 more rolls free.

So 3 large rolls of insulation only cost me 25 quid sterling or around 36 euro

Where as 1 roll of insulation here in Ireland is around 25-30 euro alone.Rip Off Republic still.

hello, I'm just wondering how you got Wickes to deliver to you as I
was on their website and it says they only delivered to the UK mainland.

they're offering "buy 1 get 3 free" now!

slimjimmc

paddy147 wrote: »

You can buy rolls of insulation that isnt made of fibregalss,its 100% recyclable and does not itch or irritate skin.

I got a load of rolls of 100,150 and 200mm insulation in from Wickes in the UK.

They were doing a deal of buy 1 roll and get 2 more rolls free.

So 3 large rolls of insulation only cost me 25 quid sterling or around 36 euro

Where as 1 roll of insulation here in Ireland is around 25-30 euro alone.Rip Off Republic still.

Er, those 100mm, 170mm & 200mm rolls are glass fibre, it even says so on the website (the term "glass mineral wool" is glass fibre wool). And, being made from glass, all glass fibre roll is 100% recyclable. I'd hate for someone to think he's getting something different when he's not.

The Space Blanket is also glass fibre but is encapsulated between 2 layers of polythene film which makes it very low itch.

Alternatives to glass fibre/mineral wool are:
- insulation rolls made from recycled plastic
- rock wool
- sheep's wool
- loose blown particles (polystyrene or wood fibre)
- insulation board.

You should also check prices with builders providers.

DublinDilbert

Does anyone know wheres the best value is for attic insulation in the Dublin area?

Was going to put down a second layer in the attic.

Also while I'm up there, what's the best way to insulate the storage thanks?

paddy147

slimjimmc wrote: »

Er, those 100mm, 170mm & 200mm rolls are glass fibre, it even says so on the website (the term "glass mineral wool" is glass fibre wool). And, being made from glass, all glass fibre roll is 100% recyclable. I'd hate for someone to think he's getting something different when he's not.

The Space Blanket is also glass fibre but is encapsulated between 2 layers of polythene film which makes it very low itch.

Alternatives to glass fibre/mineral wool are:
- insulation rolls made from recycled plastic
- rock wool
- sheep's wool
- loose blown particles (polystyrene or wood fibre)
- insulation board.

You should also check prices with builders providers.

Eh no they aint,they were not glass fibre,they were Knauf fully recycled insulation that Wickes were doing special deals on.Itch free and can be handled with out need for gloves or suit.;)

Oh and I did check around with allmost every builders providers in Dublin/Meath/Wicklow area and DID stores,and no one could come close to the Wickes prices.

paddy147

TTTT wrote: »

hello, I'm just wondering how you got Wickes to deliver to you as I
was on their website and it says they only delivered to the UK mainland.

they're offering "buy 1 get 3 free" now!

Yes,1 for 3 offer,Buy 1 take away 3.

Oh and I never said anything about Wickes delievering to me.;)

I was visiting family over in Surrey and when my brother in law brought me to Wickes just for a look around 1 Saturday afternoon.
I was gobsmacked by how cheap prices were and some of the amazing deals that I could get over there,even when comparing the sterling to Euro price conversion at the time.

So hense me buying a heap of rolls of the insulation.My family also come over from Surrey to visit me in Ireland on a regular basis too.:)

slimjimmc

paddy147 wrote: »

Eh no they aint,they were not glass fibre,they were Knauf fully recycled insulation that Wickes were doing special deals on.Itch free and can be handled with out need for gloves or suit.;)

Oh and I did check around with allmost every builders providers in Dublin/Meath/Wicklow area and DID stores,and no one could come close to the Wickes prices.

These are the rolls I'm referring to, are yours different?
100mm Buy 1 get 3 free
170mm Buy 1 get 3 free
200mm Buy 1 get 3 free

According to Knauff their insulating rolls are advertised as glass mineral wool. Their DIY products "Space Blanket" and "Space Loft Roll" are also advertised as glass mineral wool. These products are treated to make them less itchy and easier to handle.

TTTT

slimjimmc wrote: »

These are the rolls I'm referring to, are yours different?
100mm Buy 1 get 3 free
170mm Buy 1 get 3 free
200mm Buy 1 get 3 free

According to Knauff their insulating rolls are advertised as glass mineral wool. Their DIY products "Space Blanket" and "Space Loft Roll" are also advertised as glass mineral wool. These products are treated to make them less itchy and easier to handle.

They're the ones I have my eye on. I'm going to ring Wickes in Limerick to see if they have any special offers here.

I'm not holding my breath but I'll let you know tomorrow.

TTTT

as expected with Rip Off Ireland™ there were no "buy 1 get 3 free" in the Limerick Wickes. they were charging roughly €20 for 1 roll of 150mm or 200mm. I didn't even bother with the exact prices.

paddy147

TTTT wrote: »

as expected with Rip Off Ireland™ there were no "buy 1 get 3 free" in the Limerick Wickes. they were charging roughly €20 for 1 roll of 150mm or 200mm. I didn't even bother with the exact prices.

The british governmeant subsidise these schemes for eco friendly houses and grener energy,thats why you get the buy 1 get 3 free deals in the UK.

The governmeant picks up the tap in the long run.When I got all my insulation,I got 15 quid cash back aswell,as I was asked to sign a form for the insulation and Wickes gave me money back as part of this scheme.So in fact,now that I think of it,I got the insulation for absolutely feck all in the long run.

Sweet.:D

That price you got is till better than paying 30-40 euro in either BnQ or Homebase.

Rip Off Republic indeed.:(


Im seriously considering doing a pre Christmass run over to the Uk very soon,to stock up on some more diy/home improvement supplies,if you get me.