attic insulation

John mac

Just a quick question .
I have been trying to find a thread about installing extra attic insulation.
it was about May ish .
some guy had posted a link to pics of how he built up the attic floor to put in extra insulation and then floor over again.

It was a first class job and looked very impressive.

anyone remember ?
I think he was in Wexford or Waterford.

muffler

I just know that sinnerboy or sydthebeat will know where it is

No6

Kingspan have a composite insulation and chipboard sheet but its very expensive. If you havn't got your ceilings in yet try filling between the joists with fibergalss, laying sheets of 12.5mm plywood and then laying 38mm sheets of insulated wallboard over it. You can cover the wallboard with a laminate floor if you intend to use it a as a room or just leave it for storage use.

Hellrazer

Dont want to start a new thread about insulation again but could someone answer a quick one for me.

Need to upgrade the attic insulation.Currently its at 100mm buthas become squashed to bits.
What I want to know is would it be ok to do the following--Doing this myself by the way so Im looking for the easy way out

1.Can I leave the existing insulation as it is and "top up" with new fibreglass.

2.Joists are only about 100mm deep and I dont really want to get into having to raise them up for deeper insulation.Whats my best options here.Im thinking of trying to get to 300mm plus if possible.Heard something about laying a second layer opposite to the joists--how well does that work?

Attic is not used for anything but storage and theres no plans to convert it or floor it for the foreseeable future.

Thanks
Richie.

muffler

Hellrazer wrote: »

Dont want to start a new thread about insulation again but could someone answer a quick one for me.

Need to upgrade the attic insulation.Currently its at 100mm buthas become squashed to bits.
What I want to know is would it be ok to do the following--Doing this myself by the way so Im looking for the easy way out

1.Can I leave the existing insulation as it is and "top up" with new fibreglass.

2.Joists are only about 100mm deep and I dont really want to get into having to raise them up for deeper insulation.Whats my best options here.Im thinking of trying to get to 300mm plus if possible.Heard something about laying a second layer opposite to the joists--how well does that work?

Attic is not used for anything but storage and theres no plans to convert it or floor it for the foreseeable future.

Thanks
Richie.

I would suggest lifting the old stuff - it has probably lost most of its properties at this stage especially if its been laid a number of years. I know its a messy job but you are better starting from scratch (Jesus I just love the puns ).

Then as you suggested yourself lay the quilts first of all between the joists and then across the joists. Downside to this is that you loose sight of the joists and if you ever had to maneuver around the attic at any stage then you wont have a foothold.

You could also consider a rigid board type insulation.

Hellrazer

muffler wrote: »

I would suggest lifting the old stuff - it has probably lost most of its properties at this stage especially if its been laid a number of years. I know its a messy job but you are better starting from scratch (Jesus I just love the puns ).

Then as you suggested yourself lay the quilts first of all between the joists and then across the joists. Downside to this is that you loose sight of the joists and if you ever had to maneuver around the attic at any stage then you wont have a foothold.

You could also consider a rigid board type insulation.

Thanks for that Muffler.Any recommendations on the best type to use?

muffler

Hellrazer wrote: »

Thanks for that Muffler.Any recommendations on the best type to use?

Are you talking about a rigid board?

bbam

Hi..
I've only fitted rigid boards once but..
To get good airtight fit don't the boards need to be a good tight fit into the rafters? I'd be afraid of cracking celings below when "thumping" in the boards..
Our supplier talked about blown shredded paper, I thought it was a good product but herself couldnt get over the idea of paper and fire :rolleyes:

DO0GLE

This was it.....

http://www.boards.ie/vbulletin/showthread.php?p=54886772

muffler

DO0GLE wrote: »

This was it.....

http://www.boards.ie/vbulletin/showthread.php?p=54886772

Thanks DOOGLE, thats the thread I had in mind.

As mentioned above Kingspan have options for this type of insulation and some of the blow in beads are fairly good.

John mac

DO0GLE wrote: »

This was it.....

http://www.boards.ie/vbulletin/showthread.php?p=54886772

Yea that was the one .
Thanks

jwt

Ignoring for a moment the eco green thing, what's the cost benefit ratio of increasing your insulation from 100mm to 300mm plus?

From what I can garner it's typically going to reduce your heating bill by 50 to 100 euro per annum and make the house temps more stable.

So if it costs me 200 Euro for materials (I'm guessing here) plus 20 hours of labour (whether its my labour or paying someone it's still a cost) we are looking at about 500 Euro all in

So payback is somewhere between 5 and 10 years? Which isn't bad.

Are those figures about right or way off the mark? Just curious


JWT

Hellrazer

muffler wrote: »

Are you talking about a rigid board?

I wasnt going to go with rigid board--just the rolls of fibre.Is rigid board better?Or could I fill in between the rafters and put the rigid on top going the opposite direction?

Is there a rigid thats safe to stand on or floor on in the future?Just incase we ever do decide to convert.

muffler

Kingspan do a composite board made up of ply with insulation behind which you screw down to the joists. This link may get you a few ideas.

Theres another thread here which may be of help.

Hellrazer

Thanks Muffler.Some great info there.

Hellrazer

One last question regarding this.Anyway measured the attic on Saturday and the joist height is only 100mm and the width is all over the place.60cm in some,40cm in others,30cm in others so there will be a bit of cutting involved.

Any way since the joists are only 100mm deep do I have to use 100mm inbetween them? Or could I go to 200mm and then lay another 200mm opposite to this or would the lower layer get too compacted and lose its properties?

smashey

Hellrazer wrote: »

One last question regarding this.Anyway measured the attic on Saturday and the joist height is only 100mm and the width is all over the place.60mm in some,40 in others,30 in others so there will be a bit of cutting involved.

Any way since the joists are only 100mm do I have to use 100mm inbetween them? Or could I go to 200mm and then lay another 200mm opposite to this or would the lower layer get too compacted and lose its properties?

What's the span of the joists?

Hellrazer

When you say span do you mean width between joists which is 60cm for most of them but some are 40cm and theres a few that are less than 35cm.

Edited my last post there--getting my mm and cm mixed up.

topcatcbr

Hellrazer wrote: »

One last question regarding this.Anyway measured the attic on Saturday and the joist height is only 100mm and the width is all over the place.60cm in some,40cm in others,30cm in others so there will be a bit of cutting involved.

Any way since the joists are only 100mm deep do I have to use 100mm inbetween them? Or could I go to 200mm and then lay another 200mm opposite to this or would the lower layer get too compacted and lose its properties?

You can lay it in 200mm layers. There will be some compaction but this is unavoidable. And makes little difference.

Hellrazer

topcatcbr wrote: »

You can lay it in 200mm layers. There will be some compaction but this is unavoidable. And makes little difference.

So 2 200mm layers( one compacted) would be better than a 100mm (not compacted) and a 200mm cross laid??
Only reason Im asking is because its the same price for 100mm and 200mm which I thought was a bit odd.

sydthebeat

topcatcbr wrote: »

You can lay it in 200mm layers. There will be some compaction but this is unavoidable. And makes little difference.

Id have to disagree here....

if quilted insulation is compacted, it is only then acceptable to consider the compacted depth as the actual depth of insulation. ie if 200mm is compacted down to 100mm then in reality you only have 200mm insulation.

if you want to use the attic for storage, then you will have to build up the floor over the existing joists.
id advise putting 150mm joists perpendicular to the existing. this gives you a depth of 250mm to incorporate insulation into....

Hellrazer

sydthebeat wrote: »

Id have to disagree here....

if quilted insulation is compacted, it is only then acceptable to consider the compacted depth as the actual depth of insulation. ie if 200mm is compacted down to 100mm then in reality you only have 200mm insulation.

if you want to use the attic for storage, then you will have to build up the floor over the existing joists.
id advise putting 150mm joists perpendicular to the existing. this gives you a depth of 250mm to incorporate insulation into....

The only storage I need is for the xmas decorations etc and Ive gotten around that by putting wall brackets up and hanging the decorations on them so now Ive a totally clear attic to work with.Depth isnt really an issue since its never going to be converted,so i can afford to go kind of any depth.But my main question is what depth to go with inbetween the joists without having to raise the height of them--100mm or 200mm?And then a cross layer of 200mm.

sydthebeat

Hellrazer wrote: »

The only storage I need is for the xmas decorations etc and Ive gotten around that by putting wall brackets up and hanging the decorations on them so now Ive a totally clear attic to work with.Depth isnt really an issue since its never going to be converted,so i can afford to go kind of any depth.But my main question is what depth to go with inbetween the joists without having to raise the height of them--100mm or 200mm?And then a cross layer of 200mm.

if your joists are only 100mm then put in 100mm... and lay 200mm perpendicular.....
ensure to leave air gap as necessary at the eaves...
also ensure to leave the area under the water storage tank free from insulation, but lay insulation up and over the storage thank.. .this ensures the tank doesnt freeze and also that an electric shower etc doest have to work overtime to heat the shower water....

topcatcbr

Hellrazer wrote: »

So 2 200mm layers( one compacted) would be better than a 100mm (not compacted) and a 200mm cross laid??
Only reason Im asking is because its the same price for 100mm and 200mm which I thought was a bit odd.

I was talking about the natural compaction of the insulation under its own weight not forced compaction. The reason its the same price is a roll of 200mm thick insulation will cover half the area of a roll of 100mm. You are buying the same amount of fibre glass but the coverage will differ.

200mm Fibre glass or mineral wool forced into a layer of 100mm thick will equall 100mm of insulation.

I hope this clears it up.

muffler

Get your 100mm and fit as normal between the joists. Get you hands on nylon netting and spread it over the top of the joists while carefully tacking it down to the the joists to to stop sagging and then lay your 200mm over the netting.

I have seen one person use chicken wire (netting wire) which was grand is it didnt need as much tacking down however there is always that little risk with metal sitting in the middle of your insulation.

muffler

Forgot to add - avoid compression of the insulation.

Smcgie

just thought id add this here, Xtrathem have a new product out called rafterloc (kingspan to follow) this is specially designed for inbetween joices. I have seen the product but from reports the slitting in the insulation boards lowers the u-value.

Great Idea for speed, just a pity it degrades the main purpose. I am not sure how much it lowers the U-value but from hearsay i belive an 80mm sheet is = to a normal 50mm sheet.

Regards
S

Smcgie

muffler wrote: »

Kingspan do a composite board made up of ply with insulation behind which you screw down to the joists. This link may get you a few ideas.

Theres another thread here which may be of help.

If using any ridged board Insulation use Kingspan Kooltherm, (K15 or K7 for attic) Best preforming board insulation on the market with no competition. It's expensive but worth it.

I re-insulated the attic above Joice level in my new built house after living in it 6months with this product. Difference is outstanding.

Slig

While we are on the topic anybody have any ideas on how to properly retrofit extra insulation into a dormer semi-D roof.

The insulation in the roof is glass wool laid horizontally above the ceiling but I have recently found that there is no insulation on the horizontal between the eaves and the partition that supports the purlin, no insulation between the studs in the partition and no insulation behind the sloped part of the ceiling. There is also a gale blowing through the attic trap door and the downlighters but thats another days work.

Smcgie

Slig wrote: »

While we are on the topic anybody have any ideas on how to properly retrofit extra insulation into a dormer semi-D roof.

The insulation in the roof is glass wool laid horizontally above the ceiling but I have recently found that there is no insulation on the horizontal between the eaves and the partition that supports the purlin, no insulation between the studs in the partition and no insulation behind the sloped part of the ceiling. There is also a gale blowing through the attic trap door and the downlighters but thats another days work.

You can take an average measurement between joices and then call kingspan with the width, they can cut boards to widths on order, boards 2400mm x 0.6 can be taken through attic door. expensive but beats the handsaw any day. This is how i reinsulated the attic of my own house.

Worked a treat

RKQ

Or you could pop off to Argos or Aldi or similar and buy a cheap circular saw or table saw. Cuts insulation board in a straigth line in seconds. Well worth the outlay and should be cheaper and quicker than getting a special order from Kingspan.:D