Corner window insulation

[vfrdave]

I have 2 corner windows with the obligatory steel corner posts.  How should these be insulated, all 4 sides or just the 2 external sides?  Was thinking of using this for insulating:-

https://www.phstore.co.uk/spacetherm blanket or CBS

[A_L]

Can you post a cross section? The important consideration is to prevent condensation on the steel because of water vapour transferring through a low vapour resistance insulation (i.e. spacetherm/aerogel) to a cold surface

[vfrdave]

@A_L does this help?

a3 - wall details 4.pdf

[oranjeboom]

I had a similar dilemna and didn't want to bulk out the post too much with thick insulation (PIR or anything similar). In the end I went and dug into the account and went for aerogel sheets. Stuck that onto the steel post on all four sides, covered with a VCL and then covered that with some timber. Better u-values than PIR, slimmer view and will protect from condensation and reduce thermal bridging.

 

Aerogel:

 

use a mask to cut the stuff!

 

wrap onto posts (had to tape them as I was doing this on my own), otherwise could maybe use a spray glue.

 

 

 

 

VCL

 

 

Timbers drillied into steel post (bit of bridging):

 

(glazing to be fitted in above pic).

 

Aluminium capping still to go over the timbers now, but need to source that.

Timbers were pretty thick, but managed to get away with that here as the door frame was almost 200mm iirc.

 

Edited January 11, 2018 by oranjeboom

[Onoff]

1 minute ago, oranjeboom said:

I had a similar dilemna and didn't want to bulk out the post too much with thick insulation (PIR or anything similar). In the end I went and dug into the account and went for aerogel sheets. Stuck that onto the steel post on all four sides, covered with a VCL and then covered that with some timber. Better u-values than PIR, slimmer view and will protect from condensation and reduce thermal bridging.

 

Aerogel:

 

use a mask to cut the stuff!

 

wrap onto posts (had to tape them as I was doing this on my own), otherwise could maybe use a spray glue.

 

 

 

 

VCL

 

 

Timbers drillied into steel post (bit of bridging):

 

(glazing to be fitted in above pic).

 

Aluminium capping still to go over the timbers now, but need to source that.

Timbers were pretty thick, but managed to get away with that here as the door frame was almost 200mm iirc.

 

If you need a piece of ali supplied and folded then P & W Nash in Hoo would do it. PM me and I'll tell you who to contact etc. What finish are you wanting, powder coating?

[A_L]

12 hours ago, vfrdave said:

@A_L does this help?

a3 - wall details 4.pdf

 

You can use any insulation on the two external sides. Doesn't look easy to insulate on warm side, but if you want to, use, like Oranjeboom  a VCL or a high vapour resistance insulation e.g. pir with foil/XPS/foamglas. Also prevent air circulation around corner post.

[vfrdave]

Found these guys who are fairly local to me.

http://enviroform-insulation.com/product/steel-window-posts-lintels/

 

Am I right in thinking @oranjeboom @A_L that as this appears to be foil faced and taped with foil tape it then acts as a VCL.

[oranjeboom]

Not really sure what Alpha Flex is. Not come across that before, but looking here http://www.ledaflex.com/ it seems a waterproofing medium, so in that a good VCL! I did not use it, just used a green polysheet as my VCL. Door fixed to that (fixings through to steel) and then frame also foamed and eventually taped on inside to the adjacent window frame.

[Weebles]

This was a really useful post as it has helped us solve a similar problem.  Here is our experience.

 

We copied @oranjeboom and shelled out for aerogel.  Went for the 10mm thick foil backed stuff (foil backed on both sides).  The aerogel people said it would be easier to cut and a bit cleaner and that proved true.  Bit pricier but worth it for the ease of working with it.  Cut with a Bahco insulation saw - really easy to get it accurate to within 5mm.

 

 

Hard to wrap around the steel posts but with 2 of us we got it tight enough by taping it onto the post first and then pulling it around before taping it to itself.

 

 

Then timber packers put around the outside so windows can fix to those.  Not got to that bit yet but it looks like it should work.

 

 

[Woodsome Lodge]

On 13/08/2018 at 23:02, Weebles said:

This was a really useful post as it has helped us solve a similar problem.  Here is our experience.

 

We copied @oranjeboom and shelled out for aerogel.  Went for the 10mm thick foil backed stuff (foil backed on both sides).  The aerogel people said it would be easier to cut and a bit cleaner and that proved true.  Bit pricier but worth it for the ease of working with it.  Cut with a Bahco insulation saw - really easy to get it accurate to within 5mm.

 

 

Hard to wrap around the steel posts but with 2 of us we got it tight enough by taping it onto the post first and then pulling it around before taping it to itself.

 

 

Then timber packers put around the outside so windows can fix to those.  Not got to that bit yet but it looks like it should work.

 

 

Very interested in doing something similar to this for a crank beam we'll be putting up in our self-build. Does the timber packing around the aerogel cause any thermal bridging issues at all?

 

[JohnMo]

We used a combination of PIR and Aerogel. We put wood battens on the outside of the steels and the windows sit inside the wood - not the steel. If you look up the thermal resistance of various materials and the thickness you are using you can build the whole window structure without cold bridges.

 

Some screenshots first outside view, all the gaps between the wood was later foam filled, steel is 90mm square.

 

Inside, mostly 25mm PIR. Fully taped.

 

Couple of years later