Attic Insulation

[149oaks]

Looking for ideas on what I can do. 17 year old 2 storey house. Attic currently has 4" yellow fibreglass insulation between joists (15" apart). Depth of joists is 5", floor never covered in. was thinking of simply increasing the depth of insulation with another 4" of Rockwool or something but the 5" depth of joist is a problem. Any ideas. Overall attic size 42ft by 24 ft.

 

[onq]

A bit worried about the depth of rafters 149oaks.
Recessed downlighters also may cause you problems.
Also you need to identify the routes of services and insulate pipes and not insulate main cables.
For an open attic [no dormer conversion] you need to preserve a continuous gap of 10mm at the eaves or equivalent.
You also need to keep a 50mm / two inch clear air gap from the eaves into the attic.
You should also ensure the ceiling below is vapour checked before increasing the insulation depth.
Doing so makes the attic colder and moisture will tend to condense on colder surfaces within it unless checked to reasonable levels and adequately vented.
In you case merely adding more fibreglass may be the cheapest solution but other posters here have recommended it should be laid crossways to the existing.
Remember to keep the 50mm air gap clear - Part F of the building regulations is here:
http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf
Diagram 6 P. 11 refers.

ONQ.

[broken link removed]

 

[seantheman]

A bit worried about the depth of rafters 149oaks.

OP didn't mention depth of rafter, only Joist, as i see it you dont seem to use the attic for storage(ie. floor never covered in) so in this case why not just top up existing insulation. It doesn't matter if it comes above the joist if your not boarding out the attic

 

[onq]

OP didn't mention depth of rafter, only Joist,

Thanks for correcting my sloppy usage of terms Sean the man.
I must remember to check my posts more thoroughlyafter 12:15 am...

as i see it you dont seem to use the attic for storage(ie. floor never covered in) so in this case why not just top up existing insulation. It doesn't matter if it comes above the joist if your not boarding out the attic

OP showed concern at the joist depth when considering adding extra insulation, which suggests the attic, like most attics, is used for storage.
And of course, compressing 4" of fibreglass and 4" of Rockwool into a 5" layer is worse than just leaving the existing as is.
Regardless of this, issues will arise when covering over service pipes, routes to eaves vents and the like.

ONQ.

 

[NavanRd]

I got a quote today to insulate my converted attic (15years since conversion). It is awkward to get around and under the eaves, but not impossible. I was quoted nearly €2,000 to pump foam in and €800 to take down and put back the internal ceiling - I'm gob smacked at the cost. I live in a normal 3-bed semi in Dublin. Can anyone give me advice?

 

[onq]

I got a quote today to insulate my converted attic (15years since conversion). It is awkward to get around and under the eaves, but not impossible. I was quoted nearly €2,000 to pump foam in and €800 to take down and put back the internal ceiling - I'm gob smacked at the cost. I live in a normal 3-bed semi in Dublin. Can anyone give me advice?

Don't use foam - see Dia. 6 P. 11 in TGD F Ventilation.

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1647,en.pdf
ONQ.

Also make sure you have complied with the requirements of TGD B in relation to Attic conversions and alternate excape routes:

http://www.environ.ie/en/Publications/DevelopmentandHousing/BuildingStandards/FileDownLoad,1640,en.pdf

ONQ.

[broken link removed]