Help please on insulation options

[Jeremy Harris]

4 minutes ago, Stones said:

I used a multifoil insulation on one of my builds, because at the time, it was billed as the best thing since sliced bread.  The performance was worse (in terms of amount of energy used for heating) than a previous house which had 140mm of mineral wool in the coombs and loft. You may think this is subjective, but is our experience.  Of course there are many reasons why this could have been the case - poorly fitted, areas missed etc but the interesting thing was that when we sold that house and bought our next one (from a small developer) they had to change from proposed multifoil insulation back to mineral wool as NHBC withdrew their support for the product and said they wouldn't cover the house if it were installed.

Your experience, and that of Peter W above, matches everything I read when researching insulation materials.  I'll admit to having been provoked by that Grand Designs programme from several years ago, because what Kevin McCloud was saying (which was just repeating the manufacturer's claims at the time, I'm sure) seemed to defy the laws of physics to me.  The claim at that time (I still have it here, in my spreadsheet of lambda values, with a note by it highlighting that the claim is false) was that "Gen X Multifoil" had a lambda value of 0.019527 W/m.K, working back from their claimed U value for a given thickness of the stuff.  If true, this would have made it only slightly worse than silica aerogel, which at that time was the very best insulation material I knew of.

As noted above, approvals were withdrawn, advertising claims had to be changed and the manufacturers of the stuff had to come up with hybrid solutions, using insulation materials and/or added sealed air gaps in addition to the foil to get the stuff to perform as an average insulation material.  When you work back through the build up and calculate where the bulk of the insulating effect is coming from, you find that the foil is contributing very little, it is the sealed air gap and/or other insulation material that is providing most of the insulation.

The reason is fairly simple.  Foil insulation works by reflecting radiated heat.  The vast majority of heat transfer through closed areas like a wall, roof, ceiling etc is by conduction.  Unfortunately, metallised plastic films (which is what these foils are) are relatively good conductors of heat, even though they are pretty good reflectors of radiated heat.

The issue we are currently looking at with regard to radiated heat (in the latter part of this thread:

is a good illustration of an area where reducing radiated heat can be beneficial, somewhere where the heat reflective material being used is directly exposed to infra red radiation and can reflect it back to good effect.  Unfortunately, the outer and inner skin of a wall or roof will very effectively absorb (and reflect a little) of the radiated heat, and will conduct that heat to the insulation inside the wall or roof, so internal insulation needs to primarily have as low a thermal conductivity as is practicable (and affordable).  The lambda value I've mentioned previously is the measure of thermal conductivity; the lower it is the less thermally conductive the material is.

 

[ProDave]

1 hour ago, JSHarris said:

As a tip to anyone posting tables, complete your post first, then paste in the table.  If you try and add text after the table you can mess up the formatting (this is what I found).

I found the same on ebuild. It must be an IPB thing.  Once you have posted a table, any attempt to edit anythign whatsoever spoils the formatting of the table.

I would go as far as saying post the related text in one post, then the table on it's own in a following post, so you can still go back and edit the text post without upsetting the table.

[janedevon]

This all gets confusing for sure, as ours is a dormer I presumed we were having warm roof as the bedrooms are part of the roof therefore won't be layering insulation over first floor celings i.e. an attic as we wont have one, now reading the post above I can still have either a warm or a cold roof still depending on where insulation goes.

So what are the pros and cons for hot and cold roofs in this situation.

ideally I want to use standard breather membrane as it's cost effective, then the most reasonable priced option to achieve 0.16 either rockwool or celotex between rafters then vcl before plasterboarding. 

But if it's better to insulate above the rafters then I'll go that route.

I should have paid more attention to this at the time the architect chose what to put on the plan!!!

[janedevon]

Using the kingspan calculator, it says 150mm inulation between rafters and 37.5mm kingspan insulated board will give 0.14

that sounds good?

 

Construction build-up includes:

• 3mm skim coated Kingspan Kooltherm K18 Insulated Plasterboard fixed under rafters
• Kingspan Kooltherm K7 Pitched Roof Board fully filling space between rafters
• Kingspan nilvent breathable membrane
• 38mm x38mm counter-batten
• Slate / tile batten
• Tiles/Slates

Edited June 13, 2016 by janedevon

[NSS]

1 hour ago, Nickfromwales said:

Hmmm.

Unless you're aware of a specific and purposeful alteration in a post, and then it's deemed a misrepresentation, then could we please stick to facts. Are you aware of a change in the posted texts, or have you assumed the posts were altered for the purpose of disposing of a statement? If it's the latter then I'd politely invite you to edit your comment to be less abrasive please!

There are no members here who wish to "bash" anything . We give free impartial advice here, and in this case only the facts have been posted according to the manufacturer, warts and all, and it's always been the best way to provide real life info. The supporting comments about the multifoils' other shortcomings, like poor sound insulation, are vital components of any critique, and should be in no way stifled as that would be worse IMHO. 

Many thanks. 

 

I wasn't suggesting the post had been altered to dispose of a particular statement, merely to indicate that my reply was posted in response to JSH's post, not PeterW's. And my point about 'bashing' and potentially libelous statements relates to the use of language in relation to multi-foil insulation such as "snake oil", "their mis-selling", " "what can only really be called an open lie" and "they fiddle the tests". Those comments may have been directed at products/practices that were in use years ago, but the inference is that the same is true today. Scandia-Hus recently constructed a new show home using the same spec of insulation that is going into mine, and in February they used a thermal camera to see how it was performing - see http://www.scandia-hus.co.uk/news_items/adelia-show-home-thermal-imaging-survey-results

As for sound insulation, if you live near a busy road, or under a flight path, then noise insulation will be far more important than if you live, as I will, in a very quiet residential area. That said, I've been amazed at just how quiet it is in our house already, and that's with much of the H-Control layer (which is quilted layers of foil and fleece) still to be added, never mind the plasterboard and much of the external cladding.

[NSS]

Oh, and while I think of it, one big advantage of Actis over, for example, Celotex is that it is so clean to work with, which if you're doing it yourself as I am is a real bonus.

[PeterW]

5 minutes ago, NSS said:

Oh, and while I think of it, one big advantage of Actis over, for example, Celotex is that it is so clean to work with, which if you're doing it yourself as I am is a real bonus.

Out of interest have you added any logging / sensors to the house ..?

Would be good to get a view on how it does perform in your build and in "real life" rather than in a test. 

[PeterW]

2 hours ago, janedevon said:

Using the kingspan calculator, it says 150mm inulation between rafters and 37.5mm kingspan insulated board will give 0.14

that sounds good?

 

Construction build-up includes:

• 3mm skim coated Kingspan Kooltherm K18 Insulated Plasterboard fixed under rafters
• Kingspan Kooltherm K7 Pitched Roof Board fully filling space between rafters
• Kingspan nilvent breathable membrane
• 38mm x38mm counter-batten
• Slate / tile batten
• Tiles/Slates

That's about right. One thing that is worth considering is just using 25mm PIR and ordinarily plasterboard as it's a lot cheaper than the insulated stuff and you can foil tape all the joints. 

[Ferdinand]

For the record, this is the ASA ruling on ACTIS Insulation:

https://www.asa.org.uk/Rulings/Adjudications/2013/5/ACTIS-Insulation-Ltd/SHP_ADJ_71306.aspx#.V16VApErJhE

ACTIS claims were found to be misleading throught presenting inadequate test results in a misleading manner. One of the issues was that the tests were done in High Wycombe, which is not the worst imaginable environment :-) .

And this is the one on YBS Insulation Ltd (Superquilt)

https://www.asa.org.uk/Rulings/Adjudications/2012/2/YBS-Insulation-Ltd/SHP_ADJ_147993.aspx#.V16VA5ErJhE

Ferdinand

Edited June 13, 2016 by Ferdinand

[Jeremy Harris]

7 hours ago, NSS said:

 

I wasn't suggesting the post had been altered to dispose of a particular statement, merely to indicate that my reply was posted in response to JSH's post, not PeterW's. And my point about 'bashing' and potentially libelous statements relates to the use of language in relation to multi-foil insulation such as "snake oil", "their mis-selling", " "what can only really be called an open lie" and "they fiddle the tests". Those comments may have been directed at products/practices that were in use years ago, but the inference is that the same is true today. Scandia-Hus recently constructed a new show home using the same spec of insulation that is going into mine, and in February they used a thermal camera to see how it was performing - see http://www.scandia-hus.co.uk/news_items/adelia-show-home-thermal-imaging-survey-results

As for sound insulation, if you live near a busy road, or under a flight path, then noise insulation will be far more important than if you live, as I will, in a very quiet residential area. That said, I've been amazed at just how quiet it is in our house already, and that's with much of the H-Control layer (which is quilted layers of foil and fleece) still to be added, never mind the plasterboard and much of the external cladding.

As I made very clear above, the facts speak for themselves.  The manufacturer has provided a lambda value, that lambda value shows that the insulation effectiveness is similar to EPS, and a lot worse than PIR (Celotex, for example).  150mm of the Hybris gives the same insulation value as 100mm of PIR like Celotex, but with a significantly shorter decrement delay.

The history of multifoil products (and I'm not singling any one manufacturer out, just as I didn't originally) is one of claim and counter-claim, investigation by BRE, withdrawal of approval, re-approval with changed specifications, adding real insulation to the highly thermally conductive foils, changing the certification to show that the claimed performance is achieved under specific conditions with airtight spaces of particular dimensions and additional insulation in some cases, etc, is clear for anyone to read up on.  This does tend to raise suspicion when any multifoil product comes to market, even if that suspicion turns out to be unjustified.  If these materials (again, not singling out any specific manufacturer) had always reliably performed in accordance with all the manufacturers claims then I would not be spending so much time pointing out the potential issues here.

What is very clear from all the testing is that, unlike some other forms of insulation, the performance of multifoil products is highly dependent on the installation being exactly compliant with the BBA certificate approved detail.  If the stuff is compressed at all, or the air gaps that may be required aren't sealed up tight and of the right dimensions, or if the additional insulation layer isn't fitted exactly as specified, then the performance will suffer.  In the case of any sort of compression of the material the performance will suffer very badly indeed, as the proper insulation inside that spaces out the foil layers has to be at its full depth in order to work.

[Crofter]

Jane

as you will see, multifoil is a bit of a can of worms! Your suggestion to use K18+K7 sounds good, but as Peter says you can buy the insulation and plasterboard separately and save some money. That's what I did on my loft conversion a few years ago.

[NSS]

150mm Actis Hybris in situ.

[janedevon]

Thanks all for your thoughts, I'm still reading through pages on google about insulation it seems most favour some insulation over the rafters in a new build, I guess thats where architect put the tlx gold, just seeing what other options there are its all good im learning.

[ADLIan]

I was involved for many (too many!) years with the ongoing Actis saga and their wild & spurious claims. They now declare thermal performance in accordance with both accepted Standards (EN 12667 and EN 16012) and in-situ/comparative testing (the latter not to be used for U-vals under the Regs).

Above roof may only achieve U=0.17 with rafters at 400mm(?) c/c and ventilated airspace above the Actis product and Actis VC product directly under the rafter.

Ian

 

[NSS]

Rafters are at 600mm centres and 45mm H-Control is being added over the top (and fully taped), then 35mm counter battens to create service void and to take 15mm plasterboard.

[ProDave]

48 minutes ago, janedevon said:

Thanks all for your thoughts, im still reading through pages on google about insulation it seems most favour some insulation over the rafters in a new build, i guess thats where architect put the tlx gold, just seeing what other options there are its all good im learning.

My entire house, roof and walls, is clad on the outside of the frame with 100mm thick Pavatex wood fibre board (other makes are available) In the case of the roof it takes the place of a sarking board (a requirement in Scotland) then is covered with a breathable membrane then battens and tiles.  In the case of the walls the render is applied directly to the wood fibre board.

[ADLIan]

NSS - OK, just looked to be at 400mm c/c looking at 150mm actis between. Check Actis U-vals against their 'certified' thermal values very carefully.

[Declan52]

My build is attic truss do is a room in the roof type build like what you are planning. I went with a cold roof as at the time money was short. I have 140mm of high density earth wool between the rafters and 50mm pir below on the underside. I then have my vcl and my plasterboard. All my joins of the pir insulation is taped and my vcl is taped at the overlaps and glued to the floor and the walls at either side. 

The problem with putting pir between the rafters is it's not easy cut to fill the gap and not leave a path for cold air to travel through. It will be labour intensive to do correctly.

 

If I had to do it again and had the funds available it would be a warm roof construction pretty much like Prodave's that I would end up with. 

Both a cold and warm roof build up can meet and exceed the poor building regs. The choice is yours to make. Consult with your architect and builder and see what decision you can agree on. 

[Jeremy Harris]

48 minutes ago, ADLIan said:

I was involved for many (too many!) years with the ongoing Actis saga and their wild & spurious claims. They now declare thermal performance in accordance with both accepted Standards (EN 12667 and EN 16012) and in-situ/comparative testing (the latter not to be used for U-vals under the Regs).

Above roof may only achieve U=0.17 with rafters at 400mm(?) c/c and ventilated airspace above the Actis product and Actis VC product directly under the rafter.

Ian

 

Thanks ADLIan, I was beginning to think it was just me that had read much of the saga and formed a strong opinion as to both the performance and marketing strategy of this stuff!

My view is that all manufacturers, of any product, need to show to me that they have always been open and honest about their products.  If a manufacturer  has been deceptive (and that's fair here, as it was proven and claims had to be withdrawn) then I'd not trust them again, simply because I could never be sure that there wasn't still an element of stretching the truth when it comes to providing performance data.

When I first started looking at this stuff several years ago (after that GD programme) I was a bit surprised to find that hard data on the thermal performance just wasn't available.  There were lots of claims, including the one claiming the ludicrous lambda value for one multifoil product, and it was damned hard to get hold of independently validated test data.  When I did, I was more than a bit shocked at the way that the relatively simple laws of physics that govern heat transmission were being re-written in the advertising material from some companies in order to make certain products look far, far better than they really were.

It's interesting to see how this particular company has moved away from the thin multifoils (which were useless) and shifted towards a conventional fleece or synthetic fibre/wool insulation that happens to have some foil layers in it to differentiate it from other similar products.

[ADLIan]

Thansk JSH.

A bit of history - the original Actis tests were done on 2 identical 'chalets', from memory in Limoges, France. This info may still be available on the internet somewhere. One chalet had 200mm mineral wool quilt in the roof the other Actis multi foil but not much other data on the construction. Actis measured 'heat loss' from the chalets and came to the conclusion that 200mm quilt = 30mm(?) Actis. There was never enough data to check if they were actually measuring heat loss through the roof alone or via a myriad other routes. Complaints to the ASA only resulted in a change of product name, Actis 8, 9, 10......It seems that only when BRE did their work,  BR 443 was updated and other manufacturers of multi foil products gained certification using accepted test methods that Actis back tracked. They still use a mixture of in-situ and accpeted testing - not sure how they explain the huge discrepancy.

As you say - why trust them now! Hence my warning about thir claimed U-values!

[Jeremy Harris]

I think the problem is that they have fooled a lot of people, including building control bodies and even Grand Designs, most probably because people like to believe that there is a "wonder product" that defies the laws of physics.  I can still clearly remember that part of the programme where Kevin McCloud demonstrated that around 20mm of this "magic" insulation was equivalent to around 200mm of "ordinary" insulation.  As a (now retired) scientist it immediately got me searching for data on the stuff to see what on earth it was.  IIRC, the house that was being built in that programme was the infamous "eco house" that managed to get a SAP 2005  EPC of Band F 26 (I jest not, I have a copy of the as-designed SAP here in front of me!).

[ProDave]

Not long after I moved to the Highlands and started as self employed, I did the wiring for a loft conversion, that due to the very limited headroom used a layer or 2 or this wonder foil type stuff as its only insulation. I often wonder how that worked out.  I could tell the owner didn't have a clue as he was proud of the fact he had "insulated" the eaves storage space with the leftover bits, but on inspection he had covered some bits with what he had but left huge gaps. Fat lot of good that will have done.
 

There is a house in our road that whenever it has sold (twice now) it has been marketed as an "eco house"  Just about the only things it has that could even remotely qualify it for that title is solar thermal water heating panels, and (rather poor) triple glazed windows. It has an EPC rating of D, worse than our "ordinary" house. This is one of the reasons why I will not describe our new house as "eco" prefering to use the description "low energy" instead.

 

[Oz07]

Doesn't that prove that for the vast majority of the population energy efficiency is way down the list of priorities!

 

 

[NSS]

41 minutes ago, Oz07 said:

Doesn't that prove that for the vast majority of the population energy efficiency is way down the list of priorities!

And all the time we speak in what, to the vast majority of the population, is complete gobbledygook then that won't change. IMHO, if this forum really wants to encourage low energy homes to become the norm then it has to stop demanding a quantum leap to the Holy Grail (and scoffing at anything less) and recognise that a lot of people making small steps is better than a few scientists, academics and energy geeks fretting over minutia that means absolutely nothing to the masses.

[Oz07]

I do think you have a point. The old place used to be a good recourse for technical knowledge and practical advice. Over years it changed to a place where the focus was energy efficiency if that is the right term. 

To to be fair though I do respect the work which has gone into these passiv/nil energy projects.