External Insulation of Timber Frame

[middi]

....Also ,may I add, one cannot blame the insulation materials if they are not fixed in position correctly, one just needs someone else to dot it correctly.

As to what insulators you use, this is entirely determined by what will not " deface" the building, cost and inulation value.

I do not disagree with most of the comments made on other posts, it is a question of adaptability and value for money.

 

[Jon Maine]

Some multifoils are punctured by pinpricks to make them 'breathable' (allegedly).

When I first encountered multifoils I was suitably bedazzled by the shiny space-agey look and thought this must be the best thing since sliced bread. But I couldn't work out in my head just how the interior foils foiled the heat flow, so sat down and attempted to write a simple iterative computer model that might clarify my thinking. I just couldn't see how it could work as advertised. So I set up a crude experiment with a cafetire full of hot water, a thermometer, a clock and various types of insulation. I found that the multifoil (Tri-iso9 is what I had at the time) did not perform significantly better than some other, much cheaper materials. This confirmed my theoretical understanding but disappointed my hopes.

The Green Building thread has rambled on through many arguements but I still hold to the narrow view that the internal layers of a multifoil contribute little to the insulation and much to the cost.

If you want to draught proof and improve airtightness then there are other materials designed for the job. Don't defend a poor insulator on the gounds that it is good for some other purpose.

The best (though it's not cheap) insulator for thin spaces is 'Spacetherm', an aerogel product supplied by Proctors. This actually does what it says on the packet.

(Multifoils do have a place - in cryogenics and deep space, where up to 30 foils are used, separated by paper, and in a vacuum - the physics is very different in that environment.)

I have an open mind as to whether there are materials which are as thin which may perform as well or better than multifoil and take on board the points you make regarding that.

What I can clearly say is we are losing an acceptably low amount of heat through our roof which is covered in tri-iso 9 4.5 years ago. At that stage it was before the s**t hit the fan about its thermal ability.

My point is where we had no space to install insulation thicker than 25mm we have something which performs probably like a celotex two to three times that thickness.

I have been nervous about the bad press regarding over ambitious claims on performance. My experience is one of it has fitted the bill and done the job admirably here in the extremely cold conditions.

Pin pricks or not I cant see that they can claim it would breathe adequately whatsoever though.

 

[middi]

I feel much in the same way about this insulation Jon, it "appears" to do the job, and IT DOES ( perhaps within limits on these kind of buildings). I more concerned about Biff"s valuable comments regarding it's ovestated thermal qualities.

 

[Jon Maine]

I agree, my experience of it is that it does the job I bought it for well, it could be argued it should do that job better but regardless of that it does it to a level that I find acceptable.

My experience is limited to celotex, sheeps and mineral wool and multifoil. I had a look at Spacetherm which Biff has pointed out, not at availability or pricing though ( does anyone have this info?) and it looks a remarkable product.

Biff, what other thin material in the £8 to £20 a metre square region do you think perform like multifoil or better?

I do consider it has insulative properties when installed into a building as per its instructions and think its a bit harsh to base your comments on a brew of coffee :wink: , did it have the prescribed air gap all of the way around it and all of the joints taped? Without these it will not perform as well. Maybe it is not a top class insulator but I cant agree with your comment that it is a poor insulator as it seems to be doing a fair job on our roof with no other help.

 

[middi]

I also use mainly celotex if the building line permits this, the main reason for using multifoil is where bulking of the roof line and the wall will not compromise the original eaves sprocket line. Windows can carefully be moved out with care to meet the slightly increased building line.
I also use 9 or 12mm boards on the exterior side of the stud line and/or roof if possible. This stabilises the building ( although there is some school of thought that this makes the building too "stiff"), which also adds that extra insulating factor.

 

[Jon Maine]

So do I, the multifoil has for me been a solution to a specific problem, the need for insulation without major build up.

Boxing with the thin board will brace the building well, I have had no experience to suggest it would be "too stiff" :shock: , I cant imagine it will have a negative effect.

 

[biffvernon]

(Can't find the banging head on wall emoticon)

No, Jon, in my not particularly humble opinion, multifoil does not perform like a celotex two to three times that thickness. The percieved gain is because with multifoil it is easier to achieve airtightness. In the real world Celtex type stuff, when badly fitted, allows air to waft its way round the edges, circumventing the insulation. My point is that with mutifioil you are paying a lot of money for something that a sheet of polythene will do. The internal foils are a con. The talk of having to have an airgap next to the multifoil is another red herring. You are gaining thermal resistance by having still air but it won't be still if its a big gap. For the outer foil layer to stop losing energy by radiation the gap only needs to be of the order of half a wavelength of infra-red radiation (bugger-all). You don't need to trust my coffee pot but the National Physical Laboratory at Teddington did an improved version of my experiment. I don't know if their coffee is any good.

If space is the limiting factor then the only product to rely on that I know of is this.

 

[Lime]

Talking about insulating a roof and insulating a house wall are two distinctly different things.
I can understand the argument about keeping the "line" but at the expense of what?
The future?
Just how different is it covering a property with cement to sealing it in with a impermeable membrane?
Not a lot.
Perhaps the cement "breathes" a bit more.
you may as well just use polystyrene or plastic.
While I wholeheartedly agree that insulating an old building is difficult, if not impossible, covering damp walls with impermeable insulation, particularly one that can collect condensation, is a bad idea.

 

[Jon Maine]

I agree, my experience of it is that it does the job I bought it for well, it could be argued it should do that job better but regardless of that it does it to a level that I find acceptable.

My experience is limited to celotex, sheeps and mineral wool and multifoil. I had a look at Spacetherm which Biff has pointed out, not at availability or pricing though ( does anyone have this info?) and it looks a remarkable product.

Biff, what other thin material in the £8 to £20 a metre square region do you think perform like multifoil or better?

I do consider it has insulative properties when installed into a building as per its instructions and think its a bit harsh to base your comments on a brew of coffee :wink: , did it have the prescribed air gap all of the way around it and all of the joints taped? Without these it will not perform as well. Maybe it is not a top class insulator but I cant agree with your comment that it is a poor insulator as it seems to be doing a fair job on our roof with no other help.

Whilst around 0 degrees outside the inner surface temperature of my multi foil is sitting at around 15 degrees. And the snow melts no faster than the building across the road with insulation to 8 year ago building regs as that was when it was converted.

How can that be achieved with just air tightness?

Believe me if I felt that the product was not doing something more than a vapour barrier I would be livid and suing all and sundry for rectification works totaling tens of thousands of pounds.

 

[biffvernon]

Of course it's doing more than just airtightness. You've got a certain thickness of wadding and a radiant barrier on the front and back. My substantive point is that the internal layers of foil add very little to the overall thermal resistance but add quite a lot to the cost.

Two layers of foil with bubble wrap between is probably a pretty cost effective insulation for a thin space - especially if you buy the bubble wrap from a packaging manufacturer.

 

[Jon Maine]

Have you heard what the legal position is for people like me who were supplied this material on false figures?

We certainly did install it before it was brought into question, Whilst I am uncertain that now we have I installed we could even improve the heat loss with a different product in the limited space we have I guess I have been mis sold something big time and perhaps whilst it is performing ok according to their figures it should be performing even better.

Although as we installed it 4 years or more ago maybe its even to late to take a legal pop shot at them as It may be the case three years is the limit to do so?

 

[Flyfisher]

This issue seems to boil down to whether the inner foil layers are absolutely necessary rather than whether the stuff actually works, which no-one seems to be disputing. This is perhaps not really surprising because if the stuff didn't actually work, i.e. provide the thermal performance it advertises, then presumably there would have been serious repercussions by now.

And if the inner foil layers really aren't required for performance reasons and therefore only contribute to the cost, surely this is a golden opportunity for someone to make a lower cost, but just as effective, version. Surely such a product would become a runaway success?

 

[middi]

Back to Celotex ( or similar), if it is of no consequential arguments with CO and planners a 25mm layer of the stuff wrapped around an old framed wattle and daub building, sealed with aluminium tape, battened to studs and any difficult to get to gaps filled with expanding foam does an exellent job. A 125 mm thickness will do a better job ( if possible to fit) but not that much better to jusify the cost. conversely ( it appears ?) multifoils also do a good job but not that good in order to justify it's cost either, may be because of the little thickness is very practical for some applications.

We are discussing using contemporary insulation materials to make old existing buildings more thermally efficient, well, anything is much better than nothing . Let's face it, in theory we can insulate any building where only your body heat will keep the temp. stable.
( just immagine fa***ng in such a building :wink: )

 

[Jon Maine]

The period I bought it it was out selling all other products, both Kingspan and Celotex I believe tested it as it was seriously knocking their sales figures and that led them to dispute the values quoted and legally challenge everything.

I bought mine before the challenge.

I am happy with the fact it is working, but it is obvious it is not working to the standards that they quoted when they sold it to me.

Where does that leave me?

Do I just carry on with the insulation because its just ok, or can I look to replace it at their expense with a suitable product?

Of course if I were to do that it would mean removing all of the tiles, batten and felt, possibly even erecting a scaffolding temporary roof structure to protect the building and cost maybe £50,000 at a guess.

I cant deny that it works, however talking to Biff its is apparent that it is a lower grade insulator, substantially so than it was made out to be.

This project has been the project of a lifetime I imagine and I am starting to feel really p**sed off that it has been compromised by others potential dishonesty and false claims.

 

[Flyfisher]

Your choice, of course, but your previous posts suggest that your roof insulation is working just fine. I would worry about letting doubts over a few decimal points of U-values gnaw away at your pride and lead you down a very risky legal road, possibly to ruin, and for what? A slightly better performing roof, or a few thousand pounds refund? These sorts of "non-disputes" can take over lives.

 

[biffvernon]

surely this is a golden opportunity for someone to make a lower cost, but just as effective, version. Surely such a product would become a runaway success?

Kingspn, celotex, spacetherm various foil backed bubble wraps - the stuff is out there.

Jon, I know nothing about law, but some though not all BCOs have accepted the claims of multifoil manufacturers. There's a postcode lottery in operation. Read the BBA certification VERY carefully.

 

[Jon Maine]

The local bco let me have it before it came into question however now they do not. I just tried to call them but their office is closed today :?

 

[middi]

Are we talking about " market share" disputes here between differnt companies where one is trying to discredit the other about it's thermal properties claims?

If so, then what is the efficiency shortage in percentage terms compared to manufacturers statements ?

If the efficiency figures are exagerated, to what degree are exagerated which renders the product unserviceable?

If they are exagerated ( as appears to be the case) could it be just a case of exploitation of the market therefore " justifying a higher price" and consequently the public is being ripped off mainly in their pockets as opposed to a slight deficiency in thermal value?

Could it be that just pride and pockets have being hurt here ?

Some direct and honest answers ( from manufactures )would solve the problem, but like anything else in any markets, the buyers of any products have to do a lot of homework with no total guaranty that the right choises have been made

 

[Jon Maine]

Are we talking about " market share" disputes here between differnt companies where one is trying to discredit the other about it's thermal properties claims?

If so, then what is the efficiency shortage in percentage terms compared to manufacturers statements ?

If the efficiency figures are exagerated, to what degree are exagerated which renders the product unserviceable?

If they are exagerated ( as appears to be the case) could it be just a case of exploitation of the market therefore " justifying a higher price" and consequently the public is being ripped off mainly in their pockets as opposed to a slight deficiency in thermal value?

Could it be that just pride and pockets have being hurt here ?

Some direct and honest answers ( from manufactures )would solve the problem, but like anything else in any markets, the buyers of any products have to do a lot of homework with no total guaranty that the right choises have been made

If I say I will do a job to current building standards and then find I have not done it to current building standards because independant tests refute the manufacturers figures where does that leave me? If I were working for a customer and they became aware I would imagine that they would be very unhappy and blaming me for poor advice.

 

[middi]

Exactly Jon

A lot of users of this material ( including myself) should have a legal right to compensation if it can be proven that the manufacturers have misled the market and sold the material under false pretences. The real question is under what conditions was the material tested when, like many sales hype, it is the whole truth that is witheld, as you know this does not constitute lies to deceive.

I don't really know Jon.