Conservatory build

[James87]

Hi I'm building a conservatory to the rear of my house. The floor will be raised by 600mm due to steps on 4x4 posts and 6x2 joists then a 600mm dwarf wall built ontop to sit windows. What would the best way to insulate this with?
I was planning to use 50mm alreflex platinum insulation boardshttps://www.thermal-economics.co.uk/main_products/alreflex-platinum/ I can get cheap locally in walls and floor with cladding externally & Plasterboard inside with 18mm osb ontop of floor joists. Would I need to add any kind of sheet behinds the cladding and vents for moisture buildup??
Thanks

 

[^woody^]

For any 50mm of insulation the most efficient type would be a PUR foil-faced product such as Celotex, Kingspan or Xtratherm etc. Compare those with that EPS product as EPS is generally the least efficient insulation for any given thickness.

It's not clear what wall construction you are forming or what sheet you are referring to.

 

[James87]

The link for the board I may use ishttp://www.thermal-economics.co.uk/main_products/alreflex-platinum/
It is foil faced on one side so I was going to double 2 boards back 2 back to give 100mm insulation with foil on both side,.
In relation to the wall sheet i meant like a waterproof membrane or breatherble etc, it's going to be a timber stud timer Clad 600mm high for the windows to sit on

 

[^woody^]

You need to compare K or R values of insualtion to determine which is the more efficient. A PUR product can be twice a efficient as EPS for the same thickness.

Timber frame walls need a vapour check membrane on the inside of the frame, and then a waterproof and breathable membrane on the outer face. Then a ventilated cavity would be prefferable to not having one.

 

[James87]

OK thank I'll check that out, as for the vapour check and breatherble membrane and vent, how would this work as the kingspan would bet tight withing the studseaving no gaps, is it to release moisture the forms on the kingspan?

 

[^woody^]

It might be best if you have a quick google for some timber frame section details, rather than me try to explain in words.

Also you are better to design it with insulation within the frame and across the inner face. Otherwise you risk getting dark marks on the decorations due to the cold bridge created by the frame.

 

[James87]

Google gives mixed opinions going off forums, ino it's specific and many factors determine the outcome butI'd rather a professional try to explain to me than listen to 10 amatuers that say mines still OK after a year. But thank you you've helped me enough to Google what I need to which so far is.

Insulate studs flush internally which is foil backed and foil tape over the joists to form a complete barrier this acts as the moisture barrier then externally osb/ply which apparently is best to but can be skipped, vapour barrier, batton and clad???

 

[James87]

Sorry to be niaeve and to the people who think that "ohh hes incaperble he sould just pay a professional to do it" , I'd rather spend a couple nights researching and asking willing people to guide me as I will have another valued piece of information logged even if it probly will never be needed again

 

[noseall]

Insulate studs flush internally which is foil backed and foil tape over the joists to form a complete barrier this acts as the moisture barrier

Insulate BETWEEN studs and foil tape, then another layer ACROSS the studs, (foil tape again) to prevent shadowing. adding a layer of foil back plasterboard (duplex) will finish the VB process.

externally osb/ply which apparently is best to but can be skipped, vapour barrier, batton and clad???

You would staple a breather membrane across the studs externally. A layer of ply would add stiffness and prevent racking, probably not needed in this case.​

 

[James87]

Brilliant is it the same process for the floor but only between the joists as wouldn't the crush if you lay the optop aswell

 

[^woody^]

Like this

 

[James87]

Thanks for the help and time much appreciated hopefully I'll get it done today now.
Is the lead optional

 

[noseall]

Cedral10

• noseall
• 3 Dec 2017

Cedral7

• noseall
• 3 Dec 2017

Cedral2

• noseall
• 3 Dec 2017

 

[James87]

Thanks alot

 

[^woody^]

Is the lead optional

The idea of the lead, or it can be DPC or suchlike, is to form a drip from the cavity so any water running down the cavity can drip away, and it needs to be something that wont be degraded by UV.

Also its good practice to keep the frame 150mm above any ground level or paving (two course of bricks), else you tend to find the rain splashes can cause problems to the bottom of the cladding - either rot or staining.