Installing Celotex in built cavity wall

[MarkAndrews76]

Hi, new to the site so hoping someone can give some advice.

Just had windows and roof removed from old conservatory in prep for replacement windows and roof. There is no insulation within the cavity and I have been told that if I put some insulation such as celotex into the cavity it will improve the insulation within the room.

Have looked at the celotex site and they advise that the boards need to be clipped against the inner leaf of the wall using the wall ties and retaining clips. However, the walls are already built and one of them is 2m high so this wont be possible.

Is it acceptable to simply drop the boards into the cavity and let them sit loose? Not looking to make the insulation perfect, just an improvement on what it is! Would loose fit simply reduce the thermal efficiency, or does it cause other problems with condensation etc?

Thanks

 

[^woody^]

No. You'll create a load of damp problems.

 

[MarkAndrews76]

OK, thanks.

Would something such as timber battens pushed in between the celotex and outer wall work to maintain the air cavity, or am I best to look at other insulation options?

 

[stuart45]

How wide is the cavity?

 

[MarkAndrews76]

80mm wide. Allowing for mortar on the inside of the cavity I had been planning on using 50mm celotex, in the 1200x450 panels as these would have been easier to position around the wall ties already in place. I'm thinking now maybe I could use wooden battens inside the cavity to hold the celotex tight against the internal wall. Unless anyone has better options!

 

[stuart45]

You can get 75mm cavity batts for a full fill cavity.

 

[theprinceofdarkness]

Get foam beads and pour them in with a garden spray spraying 10:1 water PVA solution. Not as good as foam, but in this case will work better.
Frank

 

[cjard]

we're talking about a conservatory, right? So this is the dwarf wall that the panes of glass sit on?

Assuming it's about 800mm high and is then topped with a glass box the wall will account for less than a quarter of the surface area of the room, and in the coldest part (heat rising and all) too
I think you'll find that insulating it will have such an immeasurably small benefit that you'll never recoup the cost. Conservatories are best regarded as covered outdoor areas, let them be heated by the sun and don't try to use them as an all weather extension to the house unless you want a huge gas bill. Instead of spending money on insulating what is practically a garden wall, throw the money at improving the thermal separation of the house to the conservatory.. Put some triple glazed French doors in for example

 

[garyo]

If warmth in the non-summer months is important to you then is it too late to reconsider and build something more like an orangery? That would help keep that temperatures down in July /August too.