anyone insulated a conservatory roof?

[chatlow]

Hi All
As the title says, we have an old conservatory with glasses all around to the bottom (no dwarf walls) and a plastic roof
We therefore experience a very hot summer and cold winter in there

I've seen many videos showing some good methods of insulating the roof using timber > Insulation > more timber, then plaster board
Are we likely to see an improvement by doing this? Or does a lot of heat get controlled more by things like dwarf brick walls, which we don't have

Please don't comment with the obvious like rip it down and build a proper room or replace the plastic roof with glass. We don't have the budget for that right now, so would be looking to do the above method (if it's safe with the extra weight of timber) or use something like coreflute


Thanks

 

[Mike13]

well it has since been done properly, but our consevatory had quite deep timbers so i fitted celotex between the joists that held up the glass, I was able to fit 125mm celotex, then fitted plasterboard up that I screwed into the joists. On the outside I painted with aluminium primer, then white emulsion over that to stop the glass from getting too hot. lasted that way for years. I got the celotex/kingspan I needed from secondsandco.

 

[chatlow]

thank you. Our conservatory joists are alu with plastic, I'm not sure. But they aren't that deep. There's probably 15mm depth from the uPVC roof panel to the bottom of joist. I still like the idea of using Celotex then plasterboard (no timber) but the concern is air circulation

 

[Mike13]

Well celotex is impermeable, so no air circulation at all. and 15mm of kingspan/celotex will not make enough of a difference,
Perhaps 15mm of celotex, then screw some dummy joists at across the aluminium with enough depth to hold say 100 mm of celotex, then plasterboard onto that, depends if the aluminium is strong enough to hold up glass and plasterboard.

 

[foxhole]

You could cross batten with timber to give extra depth for celotex. Weight is negligible.

 

[Mike13]

Cross battening will help reduce the heat lost through the aluminium beams, but if they are only 15mm deep I am concerned if they will be strong enough to take the weight of the plasterboard, specially after you have added some holes for the screws that hold the cross battening.

 

[foxhole]

Cross battening will help reduce the heat lost through the aluminium beams, but if they are only 15mm deep I am concerned if they will be strong enough to take the weight of the plasterboard, specially after you have added some holes for the screws that hold the cross battening.

They are thicker than 15mm , that’s the available space below roofing .

 

[Mike13]

They are thicker than 15mm , that’s the available space below roofing .

I think it means there is only 15mm below the glass, that means the beams are quite small, and aluminium has catastophic failure modes in overload, a timber beam would give visible bowing long before failure. Neither of us know for sure, the OP has to find out more about the structure of his conservatory before diving into this. I had 6x2 timbers holding up the glass in mine, I knew I had spare strength for the job.
The OP's conservatory has much more slender aluminium in place.

 

[chatlow]

The roof is uPVC not glass. I will need to take off the plastic to work out exact size of beams but the 15mm measurement was actually the depth of the plastic that covers the beam inside (from the uPVC). This is a standard 3x3 conservatory. At a minimum we would like to cover the uPVC roof with something to protect from the sun but ideally would like to insulate as well as possible too

 

[robinbanks]

Are we likely to see an improvement by doing this?

Test it; it would be trivial to use a minimal number of fixings and large load spreading washers to hold some PIR sheeting up there. If it gives you the usable room you want just lining paper and paint it, skip the weight of the plasterboard

 

[chatlow]

Test it; it would be trivial to use a minimal number of fixings and large load spreading washers to hold some PIR sheeting up there. If it gives you the usable room you want just lining paper and paint it, skip the weight of the plasterboard

Sounds as though less than 2cm pir isn't going to make a difference. Would love that to be wrong mind as saves me adding timber

 

[robinbanks]

I think you misunderstood me. Overboard the entire ceiling, rafters, the lot, with 75mm PIR held in place with a minimal number (3 per rafter would probably do it) of 80mm screws and wedi washers, for example

 

[chatlow]

I think you misunderstood me. Overboard the entire ceiling, rafters, the lot, with 75mm PIR held in place with a minimal number (3 per rafter would probably do it) of 80mm screws and wedi washers, for example

Ah sorry yes this would be ideal but folks above recommend checking what the depth of the aluminium frame as it might not be strong enough for that

 

[robinbanks]

Assuming your 3x3 conservatory has a 30degree roof, the length of the rafters is 1.7m
A 75mm PIR sheet 1.2x1.7m weighs about 5kg. Split across 2 rafters that's asking each rafter to carry 2.5kg

 

[chatlow]

Assuming your 3x3 conservatory has a 30degree roof, the length of the rafters is 1.7m
A 75mm PIR sheet 1.2x1.7m weighs about 5kg. Split across 2 rafters that's asking each rafter to carry 2.5kg

Thanks. The concern seems to be more around the added weight of timber as well as the PIR and whether my frame can support this easily