Airtightness Detail for Velux

[richo106]

In our bathrooms we have had velux’s installed but the bathroom ceiling is flat so creating like a light tunnel etc

 

I am going to have vcl at first floor ceiling level, would it just be the case of continuing this up to the window? Do I need to air tight tape the velux to the wood at all?

 

I have attached pictures to show what I mean 

[eandg]

No idea if I've done it right or not but I put 20mm Kooltherm in attached to the structural timber, airtight taped the Velux plasterboard groove to it and then boarded. About an hour a window once I had the hang of it and only a few quid in the scheme of things. 

[TonyT]

I’m sure Velux sell a foam sealing kit with shaped foam, remember seeing it a few years ago pretty sure they have a pencil that comes with the kit to push it into a pre cut slot…….

[crispy_wafer]

Great post, thanks for raising it, must admit i was looking at my velux wondering how the hell do I deal with it.

 

I guess something like this

 

VELUX LSB 2000 Lining including Facings | Roofing Superstore®

 

 

[Kelvin]

57 minutes ago, TonyT said:

I’m sure Velux sell a foam sealing kit with shaped foam, remember seeing it a few years ago pretty sure they have a pencil that comes with the kit to push it into a pre cut slot…….

They do. Mine came with the windows. It’s all piled up in my garage though because we are fitting them side by side with an 18mm post in the middle they don’t fit so we’ll need to use Kooltherm insulation and tape. 

[richo106]

Does it have to be 20mm Kooltherm? Could it be 25mm PIR  or is that different completely?

 

Also sorry for my naivety...where does the velux need to be boarded and plastered up to?

 

 

 

[eandg]

13 hours ago, richo106 said:

Does it have to be 20mm Kooltherm? Could it be 25mm PIR  or is that different completely?

 

Also sorry for my naivety...where does the velux need to be boarded and plastered up to?

 

 

 

There's a groove in the Veluxes approximately 22mm or thereabouts from the edge of the window unit. I think 25mm insulation would leave it too tight to fit the plasterboard. I had Kooltherm kicking about but if I had 20mm PIR could have used that too (Kooltherm has better performance though - so 20mm Kooltherm is like 40mm bogstandard PIR - and it's really robust, but I don't think there's any issues just screwing plasterboard straight onto PIR either). We got our Kooltherm from Seconds and Co and the price was not much different to buying PIR from a merchant. 

[Thorfun]

8 hours ago, eandg said:

so 20mm Kooltherm is like 40mm bogstandard PIR

Sorry to be pedantic but that’s not true. 
 

With a fibre-free rigid thermoset phenolic core, and a thermal conductivity of 0.019 - 0.022 W/mK, 
 

Taken from

 

https://www.kingspan.com/gb/en/business-groups/kingspan-insulation/kooltherm/

 

so it can be better than standard PIR but definitely not twice as good!!

 

[eandg]

On 18/05/2023 at 07:29, Thorfun said:

Sorry to be pedantic but that’s not true. 
 

With a fibre-free rigid thermoset phenolic core, and a thermal conductivity of 0.019 - 0.022 W/mK, 
 

Taken from

 

https://www.kingspan.com/gb/en/business-groups/kingspan-insulation/kooltherm/

 

so it can be better than standard PIR but definitely not twice as good!!

 

Pedantry is fine. A wee bit better and a bit more solid for getting a drywall screw through works for me.