Welcome, Guest. Please Login or Register
Welcome To Ask The Trades!
Mar 28th, 2024, 1:18pm
Quote: There are two kinds of pedestrians: the quick and the dead.


Pages: 1 2 
Send Topic Print
Insulation in 40 degree roof rafter using cellotex (Read 16248 times)
saaya2020
GDPR opt-out









Re: Insulation in 40 degree roof rafter using cellotex
Reply #17 - Jul 13th, 2013, 11:33am
 
Thanks for your reassurance. Very grateful for your comments. I confirm that the fibreglass will be between the Cellotex and the plasterboard. I will purchase the screwfix vapour barrier as recommended above.

Cheers
Back to top
 
 
IP Logged
 
saaya2020
GDPR opt-out









Re: Insulation in 40 degree roof rafter using cellotex
Reply #18 - Aug 15th, 2013, 8:55pm
 
Quick update on my attic roof insulation project ... i have finally put in all the celotex between the rafters & taped all the joints - big job!

Quick reminder of my set up from the outside:

Roof Tile -> breathable felt -> 50 mm air gap -> 50mm original celotex -> **50MM GAP** -> vapour barrier -> plasterboard -> skim

The next step in my plan is to put my existing rockwool left by British Gas in the **50MM GAP** before plasterboarding

BUT, i had a builder that came today to quote me some attic partitions and said that if I am going to dry my clothes in the attic (my wife has a washing line up there & is always drying clothes up there) , then it is not advisable to put this rockwool in the **50MM GAP**.

He says that it will lead to massive mould problems. He strongly said i should not put it in. He said that i either put nothing or i put another 50mm celotex. Also, he said i should also put air bricks on both gable walls for extra ventilation.

I appreciate that in the above posts, i did not mention that my wife dries clothes in the attic .. so can somebody please guide me whether this builder is saying correctly or not?

Many thanks in advance for your comments



Back to top
 
 
IP Logged
 
woodsmith
Global Moderator
Trade Member
Author
*****
Offline


Posts: 4395


Total Thanks: 135
For This Post: 1


Gender: male

Trade: Joiner

Re: Insulation in 40 degree roof rafter using cellotex
Reply #19 - Aug 16th, 2013, 8:18am
 
I can't see why he would think adding insulation will create a bigger problem unless he thinks that warming the roof will make the walls comparatively colder and then you would get a lot of condensation, and mould, on the walls. However I think you are likely to get that anyway if you dry clothes in there.

It is not a good idea to dry clothes in a room at all unless you have an enormous amount of ventilation or have a specialist dehumidifier which can be set for laundry. I don't think adding a couple of vents will make much difference, other than to make the room colder.
Back to top
 
Thank User For This Post View members image gallery  
IP Logged
 
CWatters
Super Member
*****
Offline

"Daddy fick it" says James

Posts: 5150


Total Thanks: 58
For This Post: 0


Gender: male

Re: Insulation in 40 degree roof rafter using cellotex
Reply #20 - Aug 29th, 2013, 10:05am
 
I agree with woodsmith.

The basic idea is to ensure that any water vapour created in the room can find a way outdoors. It's important that this is via ventilation and not through the structure. A correctly installed vapour barrier will deal with one issue but you need sufficient ventilation to deal with the other.

50mm celotex +50mm rockwool isn't a lot of insulation. I have around 150mm Celotex in my pitched roof and wish I had more. If the room isn't adequately heated and ventilated it's just possible you may get condensation on the room side of the plasterboard when drying clothes in there.

Obviously the need for ventilation pushes up the cost of heating the space. One potential way out of that catch22 is some sort of heat recovery ventilation system (MHRV). Single room systems exist but are quite expensive and I'm not really up to speed on what's available.

I'd try drying clothes and see how you get on. Just be aware of the potential for condensation.

Back to top
 
Thank User For This Post View members image gallery  
IP Logged
 
Pages: 1 2 
Send Topic Print