Insulation for loft conversion

[dinger541]

Hi all,

Still at the planning stage of a possible loft conversion in the near future. I will be doing the bulk of the work myself over time so it wont be a quick job. I'm not an experienced DIY'er but i'm not a novice either. I have a small question to do with u values and hopefully some of the more knowledgeable people within this forum can keep me on the straight and narrow.

Background.

Loft roof beams are 100mm (4") deep to sarking battons and tiles. I have to have a 50mm air gap, so my availible depth of insulation is 50mm. A Kingspan derivitive called Xtratherm will give me a u value of around 0.25 with 50 mm inbetween the rafters and 30mm below and across. This will obviously infringe slightly on the availible space. There are other products but i dont know much about them. One idea is 50mm Xtratherm between the rafters and a Screwfix product called 'super quilt' http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=101893&ts=97478&id=25009 with a u value of 0.2 across then 12.7mm duplex plasterboard.

Question.

Never having used this product or know anyone that does will that give the proper u value or close to it.

2nd question.

Is the U value calculeted from an average of the whole room? not just U values of individual walls all being under the stated limits (for my county 0.2 U. The reason for this is i can extra insulate the eaves and loose some on the slopes where i need the space.

I thank you all for any and all advice given.. its much appreciated

Dinger

 

[salem2000]

What is it going to be used for?

Not too sure on the calcs you require, but when we converted our loft we had to use 100mm of Celotex and the rafters had to be Strengthened.

Converting a loft can be a very complex job for a DIYer, but not impossible. I would advise that you contact the local Building Control Office, they will help if they can and the INFO is free. As for the planning, I would also have the plans drawn up by a Pro, as they would know what is required to comply with the Building Regulations.

 

[dinger541]

Fair comment m8 and thanks.

The calcs i require are for the U value, is it an average of the whole room or taken ona roof face to roof face basis. So each individual area of the loft must come under the level, or if its an average of all facets of the construct.

the second was a query if anyone has used this product above. and it complies with building regs.

I will go to the building dept and ask all the questions, i'm lucky three neighbours have done it before so i know we can do some things but i will still have a raft of questions for the inspector when i see him.

Thanks

Dinger

 

[dinger541]

Sorry i forgot... Its going to be used as a childs bedroom

To be honest the only thing i cant do is the windows (velux) and the stairs, the rest i can manage (slower than a professional) myself.

Im still at the planning stage so just getting my facts together.

Thanks again

Dinger