Insulation between rafters needed?

[gilford]

I have recently had a new roof and want to board out the inside to create a storage room in the attic.

I was simply going to board out the attic but now I've had a new roof I'm considering insulating also.

Kingspan seems a good option but expensive and time consuming.

What other options would you recommend before I get a local joiner in to screw a load of MDF down?

Thanks

 

[HERTS P&D]

Loft insulation, the clue is in the name!

Raise your new floor with cross members going horizontal against the ceiling rafters, that way you can insulate 200mm.

Anywhere that is not boarded should be insulated to at least 300mm.

Andy

 

[gilford]

I think you have misread my topic header, I'm after information about insulating between the rafters, I already have a proper floor up there.

 

[freddiemercurystwin]

Presumably you had a breathable membrane fitted with your new roof? If so then you can insulate at rafter level though you still need to leave a 25mm gap between the insulation and the membrane. Not sure what you mean about the MDF, do you mean MDF boards into your rafters? In anycase why would you use MDF?

 

[gilford]

The roof was fitted a couple of weeks ago, it has a breathable membrane fitted along with eves vents or whatever (sorry, I'm not a roofer).

The kingspan route seems pricey, I'm looking for alternatives really.

I've seen the foil bubble wrap rolls that are stapled to the rafter, is this a good option and can you then board over it? I'm not plaster boarding, I thought as it was not going to be habitable an MDF board would be better?

Thanks for taking the time to reply

 

[freddiemercurystwin]

Do you mean the foil multi layered insulation or literally bubble wrap or 2l2 insulation?

 

[gilford]

It's a foil type bubble roll, if you google rafter insulation the first video that pops up is a B&Q how to (sorry, on my iPhone and cannot link to it)

I was originally thinking about stuffing some cheap rock wool in but then read about an air gap being needed? Just need some basic info on my options if you could 😄

 

[freddiemercurystwin]

That's equivalent to about 30mm Kingspan, generally you get what you pay for. I guess it will take the chill off and stop the draughts but it won't be warm. If that's all you want though then use it.

The trouble with foils and bubble type insulations is that they need a 25mm gap beneath them so you would need to add 25mm battens to the underside of your rafters before you boarded them.

MDF is not really suitable, hardboard is lighter.

 

[gilford]

Thanks again for the reply.

I'm not too fussed about warmth, I'm just after the cheapest possible method to be honest

So cheap and cheerful loft insulation placed inbetween the rafters is ok to do and then just screw hardboard/MDF/plasterboard over?

No need for air gap etc?

 

[freddiemercurystwin]

You need to ensure a 25mm gap can be retained between the roof underlay and insulation.

 

[gilford]

My rafters aren't very thick and quite close together, I'll have to measure them and see what options I have I think. I don't think you can get thin rock wool, at a guess I'd say the rafter is between 70 and 100mm.