Cold Extension - Insulation Issues?

[Iceverge]

11 minutes ago, SteamyTea said:

Not kept up much this week, it is school holidays, so I am silly busy.

 

But yes, have sniffed most foams in the past, so what was the question?

 

Closed cell foam, poured or injected into the wall outside the PIR, it should in theory expand, shove the PIR into place and make a pretty good job of airtighting the wall too. 

 

Seems to be a wonder solution to PIR board in the wall improperly fitted 

 

 

 

 

 

Edited April 10 by Iceverge

[SteamyTea]

31 minutes ago, Iceverge said:

Closed cell foam, poured or injected into the wall outside the PIR, it should in theory expand, shove the PIR into place and make a pretty good job of airtighting the wall too. 

The idea is sound.

 

While PU/PIR foams do expand from liquid state, they also warm up. As they cool/cure, they contract a bit (I have mentioned some SIP panels being wavey).

This, along with the general aging of the material, may, over time, leave a void.

 

The usual way to overcome much of the contraction, and improve mechanical and thermal stability, is to introduce a filling agent. Melamines are a useful one as they are well understood and improve fire ratings.

Other matrixes can be created with long fibres.

 

The biggest problem is long term performance (this can be checked) and chemical leaching (again can be checked).

The biggest problem is getting the right people to do the work, processing is everything in the foam industry. A slight variation in temperature or humidity makes a huge difference.

We have made 3 'foam sausages' for fire rate testing, same chemicals, same ratios, same machines, same operators, maybe 2 hours apart between 'squirts'. 

One would pass, 2 may fail. It is down to the reactions between the extra humidity and temperature during the day, this changes the 'bubble' size, which changes the ratio of flame retarders to surface area.

 

Would be an interesting project to be involved in.

Edited April 10 by SteamyTea

[Iceverge]

Foams are amazing. 

 

Perhaps too hi-tech for houses in my purist opinion.  

 

However they have their applications where dumber materials won't cut the mustard.

 

 

Edited April 10 by Iceverge

[Onoff]

"foams" is an anagram of sofa...sort of... 😉

[SteamyTea]

39 minutes ago, Iceverge said:

Foams are amazing

They are.

39 minutes ago, Iceverge said:

Perhaps too hi-tech for houses in my purist opinion.  

There are structural foams. A lot of early computer cases and enclosures where made from they.

Relatively cheap tooling and injection machines, so great for low volume, but good mechanical properties.

 

This has sparked me interest in these polymers again.

43 minutes ago, Iceverge said:

However they have their applications where dumber materials won't cut the mustard.

They fit between 3D printing and full injection moulding. 

When you get in your car, just think of all the things in it that are foams. Most of the stuff you can see, touch hit, and in an impact.

 

If I was not so tired I would write up a bit more about them, like composite plastics, they are very under used, and more importantly, misunderstood, in the building industry.

[gravelld]

Icynene?

[EinTopaz]

21 hours ago, Iceverge said:

Foams are amazing. 

 

Perhaps too hi-tech for houses in my purist opinion.  

 

However they have their applications where dumber materials won't cut the mustard.

 

 

 

Looks great, i think i'll need a proffesional to do this for me by the looks of it though. Do you know of anyone in the north west of England? 

[EinTopaz]

Changing topic ever so slightly as I need an answer on this for the roof. As I'm about to order all the extra Kingspan for it (i'll be removing all the tiles and taping/sealing all the gaps between insulation of what's there already AND adding more whilst im there.

My question is how much of an airgap do i need to retain between the top of the Kingspan that's between the rafters AND the underside of the vapor proof membrane? In the photos below i've shown how my tiles are arranged, they're sat ontop of 25mm counter battens so a good 25-40mm or so higher than the membrane.

The rafters are 170mm tall, there's 100mm Kingspan between them. Given that there is an airgap between the membrane and tiles. How much of an airgap do i need to leave between top of kingspan and underside of membrane? 1" or 2"? Or can I entirely fill the void between rafters with no airgap at all? 

 

Edited April 11 by EinTopaz

[gravelld]

Bear in mind that spray foam insulation is getting a very bad reputation amongst the normies out there. It's mentioned as the reason for a lot of collapsed house sales because mortgage companies and surveyors can question it.

 

That's not a good reason, of course, just that there may be growing anecdotal feelings toward it that you might find challenging later.

[MikeGrahamT21]

9 minutes ago, EinTopaz said:

Changing topic ever so slightly as I need an answer on this for the roof. As I'm about to order all the extra Kingspan for it (i'll be removing all the tiles and taping/sealing all the gaps between insulation of what's there already AND adding more whilst im there.

My question is how much of an airgap do i need to retain between the top of the Kingspan that's between the rafters AND the underside of the vapor proof membrane? In the photos below i've shown how my tiles are arranged, they're sat ontop of 25mm counter battens so a good 25-40mm or so higher than the membrane.

The rafters are 170mm tall, there's 100mm Kingspan between them. Given that there is an airgap between the membrane and tiles. How much of an airgap do i need to leave between top of kingspan and underside of membrane? 1" or 2"? Or can I entirely fill the void between rafters with no airgap at all? 

 

 

Full fill: https://www.kingspan.com/content/dam/kingspan/kil/products/kooltherm-k107-gb-and-ireland/kingspan-kooltherm-k107-brochure-en-gb-ie.pdf

[EinTopaz]

48 minutes ago, MikeGrahamT21 said:

 

Full fill: https://www.kingspan.com/content/dam/kingspan/kil/products/kooltherm-k107-gb-and-ireland/kingspan-kooltherm-k107-brochure-en-gb-ie.pdf

 

thanks, which figure on that link describes my setup the best?

We've 50mm beneath rafters, 100mm inbetween rafters, then membrane, then battens, then tiles

 

I'm looking to up the bit between rafters to probably 160mm 

 

edit: our soffits are vented. Forgot to mention.

Edited April 11 by EinTopaz
added info

[Mr Punter]

If the insulation is hard up to the battens it can be an issue.  It is best to leave 25mm so that any water will run down the membrane and will not get trapped by the battens. If the roof is counter battened, this will be enough. Are you planning to strip the whole roof to do this?

[Redbeard]

Gov't Best Practice guide for rooms-in-roofs says 50mm ventilation gap between the insulation and the membrane. I realise yours is not but it sounds like the set-up is similar.

[EinTopaz]

Yeah ok, if I add 40mm more kingspan that'd leave me with  30mm clearance to top of rafters.

I read the 50mm clearance required is because of sagging of the membrane etc. But ours looks pretty tight to be honest. 

[EinTopaz]

1 hour ago, Mr Punter said:

If the insulation is hard up to the battens it can be an issue.  It is best to leave 25mm so that any water will run down the membrane and will not get trapped by the battens. If the roof is counter battened, this will be enough. Are you planning to strip the whole roof to do this?

Yes going to be completely stripped 

tiles off, battens and membrane all off. 

Do you think 20mm airgap between kingspan and membrane will suffice? 50mm insulation is no more expensive than 40mm weirdly. And probably easier to sell on if I over order! 

[Mr Punter]

Crikey re-roofing is a fairly big undertaking!  Unless there are big gaps in the insulation, I am not sure that adding 40mm of insulation when you already have 150mm will make a huge difference.  The issue is more likely to be air leakage, like from around openings into the wall cavity, so make sure you foam any gaps in the underneath layer and pay attention to insulation at the wall junction.

 

 

[EinTopaz]

42 minutes ago, Mr Punter said:

Crikey re-roofing is a fairly big undertaking!  Unless there are big gaps in the insulation, I am not sure that adding 40mm of insulation when you already have 150mm will make a huge difference.  The issue is more likely to be air leakage, like from around openings into the wall cavity, so make sure you foam any gaps in the underneath layer and pay attention to insulation at the wall junction.

 

 

 

All fair point and true enough. I won't be doing the roofing myself. But i'll be up there with the team, insulating the gaps as I find them. 

As we're totally de-roofing it sort of felt silly not to add more kingspan while im there. I know it wont be night and day difference. But for £500 and a couple days of my time. Why not eh.

 

RE: wall gaps. Absolutely, take a look at this video. We've a vented tile on the roof for an extractor fan in the bathroom that I wanted to inspect.  Looking under there confirmed that I need to have all the tiles took off and insulate all these roof properly tbh. it's a complete mess. 

 

Incidentally, after i've got this sorted, im going to name and shame the company and directors. As they've since refused to rectify.
 

 

 

[SteamyTea]

I am sure there is probably a picture or drawing of the roof in question up here, but is part of the roof timbers going to be open to either a cold side or a warm side, or both even?

This can make a difference to the condensation risk.

If I remember correctly, placing insulation over the top (exposed to the outside) edge of the timbers is better than placing insulation over the exposed edge on the inside.

[EinTopaz]

1 hour ago, SteamyTea said:

I am sure there is probably a picture or drawing of the roof in question up here, but is part of the roof timbers going to be open to either a cold side or a warm side, or both even?

This can make a difference to the condensation risk.

If I remember correctly, placing insulation over the top (exposed to the outside) edge of the timbers is better than placing insulation over the exposed edge on the inside.

Currently open to cold side. 

From bottom to top ours goes

Pasterboard
50mm kingspan
100mm kingspan (between rafters)
70mm airgap
membrane
battens
tiles