Attic Insulation - "Loft Walk" Insulation Boards

rickyjb

I'm insulating the attic in a 3 bed semi d house and am planning to use these insulation boards on a section in the middle that will be used for access to the tank and for storage:

https://www.build4less.ie/loft-walk-insulation-p-7197.html
(It's just insulation board with chipboard attached)

I'll be putting 100mm earth wool between the joists and will put these boards on top. The question I have is do I need to put boards on top of the joists (chipboard or similar) and then lay the loft walk stuff or can I lay it straight on top of the joists?

Also is there anything else I should be considering when putting down the fibreglass to avoid damp issues? I've done a bit of research but couldn't find much info. I'll be putting 200mm earth wool across the joists for the rest of the attic.

Thanks in advance.

Calahonda52

What material is under the roofing?
Black felt, breather membrane or what?
Whats the plan for insulation the ceiling where it meets the eaves?
Are the eaves ventilated?

I never liked this idea, all very well, 4 by 2 sheets but do they match up with your rafters etc.

I raise the rafters where i need flooring, using 2 by 2 rough, or PAO if I get a good price, screwing each run to the one below with 4 inch screws.

Then you can cut flooring to suit

rickyjb

Calahonda52 wrote: »

What material is under the roofing?
Black felt, breather membrane or what?
Whats the plan for insulation the ceiling where it meets the eaves?
Are the eaves ventilated?

I never liked this idea, all very well, 4 by 2 sheets but do they match up with your rafters etc.

I raise the rafters where i need flooring, using 2 by 2 rough, or PAO if I get a good price, screwing each run to the one below with 4 inch screws.

Then you can cut flooring to suit

I thought about raising it up alright but I only have 1 day to get the job done and it would probably take me awhile to do. 2 by 2 wouldn't be high enough, I'd need 2 by 4. With 6 inch screws?

If they don't match I'll cut them to fit, shouldn't be too much trouble.

It's a 50's built house, it just looks like black felt to me but I'm not certain. I'm not sure if the eaves are ventilated but I think they are, I can feel a draft.

Assuming they are what would you recommend for where the ceiling meets the eaves, leave a bit of a gap or block it up completely?

Calahonda52

Its 2 by 2 at a time, one on top of the other.
I have done 16 inches this way
It works best with cut timber roofs rather than prefabbed trusses
Pre cut the timber to length, my source had them 16', so
I first mark the top surface with a felt pen all they way along as they are not square
I cut in whatever works, 3 foot say
Then drill a 5mm hole in the top surface on the first one 50 mm from each end.
The next one 75mm in so as the screws dont clash.
If putting more screws just off set them

Its very quick once you get the hang.

Leave gap at eaves.

Unless the layers sit snuggly on top of each other the wind will get underneath and the top layer is wasted.

Its important to keep wind from blowing through it, lts like wearing a plastic rain coat over a woolly jumper in strong winds.
Best practice is to cover insulation with a breathable wind proof membrane but I usuall just add more insulation where I cant cover it

I never use rolls, always use loose as I get perfect filling, whatever the set up. However its more work

whizbang

Those boards will only be effective if the spacing between the joists is 2' or less. Otherwise they have to be very carefully fitted, staggered with minimum 3 boards wide.

Are you only putting in 100mm between, or 100mm extra on top of joists?
The boards are almost equivalent to 100mm wool, they are meant to make up the gap between the extra layers.
You should have 300mm...!

rickyjb

whizbang wrote: »

Those boards will only be effective if the spacing between the joists is 2' or less. Otherwise they have to be very carefully fitted, staggered with minimum 3 boards wide.

Are you only putting in 100mm between, or 100mm extra on top of joists?
The boards are almost equivalent to 100mm wool, they are meant to make up the gap between the extra layers.
You should have 300mm...!

I'm putting 100mm between the joists all around then putting the loft walk stuff on top of this in a storage section in the middle and 200mm across the joists everywhere else.

I'll have 300mm total (100 + 200) in most of the attic and 100mm plus the loftwalk boards on a section in the middle which should give the same U value as 300mm fibreglass.

Does that sound right?

Thanks for the extra info but my original question still remains - do I need to put extra board underneath the loft walk stuff or can it be laid directly onto the rafters? The gap between the joists is 355mm so it's manageable with a bit of cutting if I do it lengthways. It might be easier to put cheap chipboard on top of the 100mm layer and then lay the loft walk stuff on top of that, I'm not sure.

Robbie.G

rickyjb wrote: »

I'm putting 100mm between the joists all around then putting the loft walk stuff on top of this in a storage section in the middle and 200mm across the joists everywhere else.

I'll have 300mm total (100 + 200) in most of the attic and 100mm plus the loftwalk boards on a section in the middle which should give the same U value as 300mm fibreglass.

Does that sound right?

Thanks for the extra info but my original question still remains - do I need to put extra board underneath the loft walk stuff or can it be laid directly onto the rafters? The gap between the joists is 355mm so it's manageable with a bit of cutting if I do it lengthways. It might be easier to put cheap chipboard on top of the 100mm layer and then lay the loft walk stuff on top of that, I'm not sure.

The loft boards can be fitted directly on top of joists no need for board under

whizbang

355mm = The loft boards can be fitted directly on top of joists no need for board under

All sorted, toasty now.?

rickyjb

Thanks very much for all the replies, got it all done Friday including fitting all the loftwalk stuff. Had to widen one joist in the middle to give enough room to screw it down and cut some lengthways on one side but worked out very well in the end. Would recommend using them if anyone is doing the same and wants a good bit of storage space.

Got all the stuff on build4less.ie, worked out at about 1/3 the cost of paying someone to do it. Just make sure you cover up and use a good dust mask and goggles if you're attempting it. I didn't have the latter and my eyes were itchy for a couple of days.

I have a roll of 200mm left if anyone is short a bit. It's yours for free if you want to collect it (Dublin 9 area), just send me a pm.

Definitely noticing the difference upstairs in the mornings, can no longer see my breath in the bathroom