ChipBoard + Loft Insulation

[civicwalker]

My loft has 10 inches of insulation.
I want to chipboard out (light storage only) a 7ft x 15ft area. The problem is that the joists are only 4 x 1.5 inches and 2ft apart.
Is there any insulation product which will fit inder the boards (i.e. 4inch gap) and provide the same insulation qualities as the rest of the loft

 

[oilman]

No.

The insulation is not provided by the material, but by the air trapped in it. Some aluminised instulating materials are quoted to be equivalent to much thicker normal insulation, but only if it doesn't touch anything. It stops radiated heat, not conducted heat.

 

[civicwalker]

Thanks Oilman.

Maybe my only option would be to somehow raise the boards.

I could run 4 x 2 across the joists befors boarding thus giving 8 inches - the problem would be securing them on top of the originals?

 

[rickyd]

civicwalker - just the question i need answered! If this is advisable, should the raised joists run along the existing joists, or supported at right angles along the existing joists.

Also, how are these new joists best supported on the old joists - wood glue, screws (if so, how many per unit length) etc.

Thanks, Rich.

 

[civicwalker]

After advice from the ebuild Board, i've gone for 50x100mm rough timber running with the original joists.

 

[civicwalker]

Completed the job this weekend - I now have 190mm clearance awaiting the insulation to be laid

 

[Damo1176]

Are your original joists capable of holding the extra 4 x2 you've put in? I want to raise mine so I can fit 200mm insulation and the only way I can do this is by adding either 4x2 or 5x2 on my current joists and I am not convinced t will take the weight.

 

[civicwalker]

I boarded out the loft shortly after I moved in some 15 years ago. When I emptied it out (and filled my garage) a couple of weeks ago I discovered that there was some considerable weight up there. Once I've relaid the boards on the 4x2 [this weekend] i'll certainly ensure that i cut out the heavier items.

 

[Damo1176]

Anyone know of anything like thre al insuatlnio that wil have the same heat keeping characteristics of 200mm loft insulation but be a damn sight thinner??

 

[lovinit]

Civicwalker - Please could you clarify how the new timbers are fitted to the existing? I'm assuming because you purchsed 100mm you fitted these directly along the length and on top of the existing timbers to acheive the new height of approx 200mm? Many thanks.

 

[civicwalker]

I used 3"" mending plates - 2 screws in existing joists and 2 screws in the new timber (49p for two @ Wilkinsons)

 

[DocNick]

Our loft has some fibreglass insulation down already, not especially deep. I've boarded out about a quarter of the loft with big chipboard sheets, and propose to do the rest. I would have thought that a fully boarded loft, with a couple of inches of fibreglass beneath, would trap an awful lot of air and since wood is also a poor conductor, should gnerally provide a good solid barrier to heat rising, but following this thread, it seems like most people think it's worth raising the rafters to be able to lay deeper fibreglass and put the boards over that. Would really appreciate a quick explanation why.

Cheers

 

[lovinit]

Thanks civicwalker - will probably do the same.