Roof insulation in loft storage room

[derrynane]

Sorry if this query has been asked before but I cannot find a suitable answer.

I am getting quotes for a loft storage room. Basically boarding floor, eaves storage, velux and plasterboard roof. All quotes unfortnately differ dramatically in what and how they propose to do.

My query is about insulation between the plasterboard on the roof. One company has said they will use solarguard (multi layered protective quilt). The other quote will use standard fibreglass insulation.

Can someone tell me whether the fibreglass will give suitable ventilation to the roof. The company using the solraguard will put airflow collars and battens. the company using the fibregass will not.

I might add the company using the solarguard will be complying with Part L1B and the other will not.

any replies greatly appreciated

 

[tony1851]

You would not put fibreglass beween the rafters aa it would almost certainly block air flow, assuming your rafters are 3 or 4" deep.
The reflective quilts can take up space, as you also need an airgap below the foil (meaning additional battens) before fixing the plasterboard.
Assuming its only for storage, what's wrong with just an inch or so of Kingspan between the rafters, and then plasterboard?

 

[freddiemercurystwin]

Don't forget the continuous ridge ventilation that's required when you insulate in this way to avoid condensation. My money says none of your quotes have even mentioned this let alone priced for it.

 

[garyo]

Is ridge ventilation required if breathable membrane is fitted? (Not that the OP has said this is what he has, I'm just wondering...)

 

[JohnD]

just to check, if it is a storage room, why are you spending monery on plasterboarding it, insulating it and fitting velux windows?

did you know that a non-compliant loft conversion adds negative value to your house, because a buyer or valuer has to factor in the cost of ripping it all out and doing it again, properly?

 

[freddiemercurystwin]

Is ridge ventilation required if breathable membrane is fitted? (Not that the OP has said this is what he has, I'm just wondering...)

No provided you keep a 25mm gap.

 

[derrynane]

The quote which Is using the reflective quilt will include battens and will be signed off by building regs. The other quote which I had a feeling were cutting cost corners will not.

The building regulation compliant quote will pass the ventilation requirement so I assume vents are being installed.


If kingspan was used would the fact that the plasterboarding only went to the eaves be sufficient ventilation?