Rafter insulation pointless?

[Cocat2517]

Hi
The loft in my house has been boarded out for storage.

- Mineral wool insulation (200mm) in joists, boarded over with floor boards.

- Mineral wool between rafters (and pressing against felt membrane) and boarded over with plasterboard.

First of all, should the insulation from the rafters be removed due to potential condensation issues? Second is there any point to it to start with? The 200mm in the joists is keeping most if the heat in the house below and the loft space is only boarded for storage it's not lived in or heated.

I was thinking remove plasterboard & rafter insulation, replace with 25mm polystyrene board insulation between rafters, maybe another 50mm over rafters, re-plasterboard.

 

[wwwebber]

If it is breathable membrane then its fine I believe as there will be no requirement for an air gap. If you're not bothered about heating or protecting your loft from the cold and your joist insulation is sufficient then it is indeed pointless.

 

[Cocat2517]

No, it's old fashioned felt, so not breathable.

I'm not too worried about keeping the loft space warm, I doubt 75mm of polystyrene insulation would have much effect anyway, after most of the heat has been kept in by the 200mm in the floor.

The main reason I was considering it was for EPC rating, the 200 + 75 would give above recommended amount of insulation, so potentially extra points?

 

[wwwebber]

ok, so you could have an issue with condensation as you should have a minimum 50mm air gap with that type of membrane.

 

[Cocat2517]

That's what In was thinking, yes. I pulled some back a few weeks ago and it was dry underneath, but now the colder weather is setting in I'm not sure it'll stay dry.

Think I'll pull it all off, put 25mm polystyrene insulation (Jablite boards from B&Q) between the rafters then board over it with Knauf Fire panel plasterboard. Not too expensive or time consuming.

 

[wwwebber]

That's what In was thinking, yes. I pulled some back a few weeks ago and it was dry underneath, but now the colder weather is setting in I'm not sure it'll stay dry.

Think I'll pull it all off, put 25mm polystyrene insulation (Jablite boards from B&Q) between the rafters then board over it with Knauf Fire panel plasterboard. Not too expensive or time consuming.

If you're not bothered about insulating the room then why even bother to put any back in ?

 

[Cocat2517]

Just for a little extra help with the EPC rating I guess?