Please Help! Insulate loft conversion with insulation boards

[johnjones323]

Please help!!
I have a house which was built in 1890, it has a loft conversion but has no felt or insulation whats so ever. I have bought kingspan 65mm Insulation boards but i'm not sure what I should do to fit them.
Looking from below I see the rafters which are 3 x 2 and batterns going accross with slates on top, there is no felt. My plan is to cut the insulation board to fit between rafters and then plaster board on top.
If I did this there would be a 2cm gap (depth of battern) between my insulation board and slates.
Am I MAD or am I doing the right think, please advise.

Thank you

John

 

[freddiemercurystwin]

No you're on the right track. However you are advised to fix some more Kingspan (say 40mm) beneath the rafters and then board beneath that. You may wish to check your rafters are up to taking the extra weight.

 

[johnjones323]

Thanks for that. Another question.

Should I tape up the joints between the insulation boards. Everyone seams to have a different opinion on it?

Regards

John

 

[freddiemercurystwin]

You ought to, something like this http://www.tapes-direct.co.uk/index.php?main_page=product_info&cPath=132&products_id=934

 

[johnjones323]

This is hard to explain but will attempt.

In my loft the sides have been partisioned of with timber, probebly because of head space and it would be good for storage.
Basically it is a trianangle, Can I use insulation boards on the roof where tiles are visible, on the floor as it would probebly be good to save heat from escaping bedroom, and should I insulate the partisioned wall made from timber. This would mean the whole storage spot would be insulated.

Not sure if this makes sense but which parts would you recommend me insulating?

Thank you

John Jones

 

[geraldthehamster]

Please help!!
I have a house which was built in 1890, it has a loft conversion but has no felt or insulation whats so ever. I have bought kingspan 65mm Insulation boards but i'm not sure what I should do to fit them.
Looking from below I see the rafters which are 3 x 2 and batterns going accross with slates on top, there is no felt. My plan is to cut the insulation board to fit between rafters and then plaster board on top.
If I did this there would be a 2cm gap (depth of battern) between my insulation board and slates.
Am I MAD or am I doing the right think, please advise.

Thank you

John

Current standards would demand 5" inches of Kingspan, which you obviously don't have room for, without adding extra battens under the rafters.

You could get nearly to this standard by fitting 2" between the rafters, then another 2" over (using 75mm plasterboard screws). Tape all the joints with foil tape. Then plasterboard over (using 100mm plasterboard screws). That way you'll have an adequate level of insulation, and a vapour barrier provided by the foil backing (which stops mosture from the warm air in the room rising into the insulation, condensing and rotting your timbers.

If you have no roofing felt then theoretically you don't need the air gap behind, though I think it's a good idea to have one.

Re-reading what you have posted, you have 65mm board, so doubling that up would take you to 5".

Theoretically this should be notified to Building Control, as you are modifying what the regs term a thermal element, by adding insulation. however, people often don't bother.

Cheers
Richard

 

[geraldthehamster]

This is hard to explain but will attempt.

In my loft the sides have been partisioned of with timber, probebly because of head space and it would be good for storage.
Basically it is a trianangle, Can I use insulation boards on the roof where tiles are visible, on the floor as it would probebly be good to save heat from escaping bedroom, and should I insulate the partisioned wall made from timber. This would mean the whole storage spot would be insulated.

Not sure if this makes sense but which parts would you recommend me insulating?

Thank you

John Jones

If you're using the space as a habitable room, then insulate the roof over, and the sides - either continuing along the rafters if you can get in there, or within the stud partitions. If the latter, insulate above the ceiling in the eaves space, with roll insulation suitable for this purpose. Don't insulate above the ceiling in the main loft room if you are insulating overhead in the rafters.

Think of the loft room as part of the (warm) house - you want the insulation to be on the outside of it.

Cheers
Richard

 

[johnjones323]

continuing along the rafters if you can get in there, or within the stud partitions. If the latter, insulate above the ceiling in the eaves space, with roll insulation suitable for this purpose. Don't insulate above the ceiling in the main loft room if you are insulating overhead in the rafters.

I can get in to the sides along the rafters, (meaning I can insulate the intire roof. Should I also insulate the stud partions and the floor within.

Hope you understand my question?

Very greatfull

John

 

[freddiemercurystwin]

This is how I normally detail my loftys. Personally I think this is best as you are not wasting energy heating the voids behind the dwarf walls.

Untitled

• freddiemercurystwin
• 25 Apr 2010
• 24

 

[geraldthehamster]

I can get in to the sides along the rafters, (meaning I can insulate the intire roof. Should I also insulate the stud partions and the floor within.

Hope you understand my question?

Very greatfull

John

Again, one or the other but not both. I'd do whichever is easier, and it's probably easier to bung some roll insulation above the ceiling in the void, and put some Kingspan between the studs in the stud wall, and plasterboard over.

If you do that, don't also insulate between the rafters, in the void behind the stud wall.


Cheers
Richard