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General Renewable Topics => General Discussion => Topic started by: dan_aka_jack on September 03, 2008, 12:02:15 PM



Title: Which type of internal wall insulation?
Post by: dan_aka_jack on September 03, 2008, 12:02:15 PM
Before this Winter, I want to install some interior solid wall insulation on the exterior wall in our living room.  It's a very long wall and I suspect the very poor insulating properties of this wall are the primary reason why the living room takes such a huge amount of energy to keep warm during the winter.

We don't have any wall cavities so cavity wall insulation is out of the question and exterior wall insulation is Too Damn Expensive and Too Tricky for my modest DIY skills.  So I'd like to install some interior wall insulation.

The room is reasonable large so we can, if needs be, use some quite deep insulation.  My main criteria is: which type of insulation provides the largest decrease in thermal conductivity per £ spent?  Should I simply screw Kingspan onto the walls and do a plaster render over the Kingspan? Or should I build a 250mm-deep wooden stud frame, filling the frame with loft insulation and then putting plasterboard over the stud frame?

Searching the 'net for some figures... it looks like Kingspan Kooltherm K17 Insulated Dry-lining Board (http://www.insulation.kingspan.com/uk/k17.htm) has a thermal conductivity of 0.024 W/m.K (insulant thickness 15–24 mm), 0.023 W/m.K (insulant thickness 25–44 mm) and 0.021 W/m.K (insulant thickness ≥ 45 mm) whilst 250mm of loft insulation has a thermal conductivity of 0.040 W/mk (http://www.energysavingtrust.org.uk/esr/esr/product_criteria_registration/insulation/loft_insulation) (but I'm not sure I believe that figure) so it sounds like Kingspan is a significantly better insulator than 250mm of loft insulation.

And do I have to worry about condensation building up?

Any advice would be great!
Thanks,
Jack


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 03, 2008, 12:31:38 PM
For most drylining Kingspan is the way to go. You can "glue" to walls with the right dabs of adhesive and the use long frame anchors  a couple per board, the hold the panels back,  all as Kingspans guidance notes on their web pages.
Kingspan is vapour impermeable so interstitial condensation should not be a problem, provided bathrooms and kitchens are vented as they should be. You can also finish the boards with a surface "slurry" that acts as another vapour barrier, if you want to. I'd avoid wet plaster, easier and quicker to "tape and joint" the boards. Kingspan is relatively expensive, but much easier than studding out.
See my blog for details of what I did.


Title: Re: Which type of internal wall insulation?
Post by: MR GUS on September 03, 2008, 01:05:41 PM

 go look at celotex website, I think it might be a bit better, & it has regs approval documentation which the others didn't have last time I bought some! (told that at the builders merchants)


Title: Re: Which type of internal wall insulation?
Post by: dhaslam on September 03, 2008, 01:55:24 PM
B

Searching the 'net for some figures... it looks like Kingspan Kooltherm K17 Insulated Dry-lining Board (http://www.insulation.kingspan.com/uk/k17.htm) has a thermal conductivity of 0.024 W/m.K (insulant thickness 15–24 mm), 0.023 W/m.K (insulant thickness 25–44 mm) and 0.021 W/m.K (insulant thickness ≥ 45 mm) whilst 250mm of loft insulation has a thermal conductivity of 0.040 W/mk (http://www.energysavingtrust.org.uk/esr/esr/product_criteria_registration/insulation/loft_insulation) (but I'm not sure I believe that figure) so it sounds like Kingspan is a significantly better insulator than 250mm of loft insulation.

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I think that the figures refer to a metre thickness of the insulation materials.  The dense material has about double the insulation value of fibreglass.   The sort of values you need are in the range of .1 to .2.  For this you need 110 to 220 mm of the dense stuff.   For example if you have 100 square metres of outside wall and a temperature differential of 10 C you only need 100 to 200 watts heat input.     The important part is around doors and windows where the high density materials have a big advantage.  Otherwise I would go by price.


Title: Re: Which type of internal wall insulation?
Post by: CeeBee on September 03, 2008, 02:54:50 PM
I think that the figures refer to a metre thickness of the insulation materials...

Yes - one certainly has to be very careful with the units here to avoid incorrect answers.

Formally, 'thermal conductivity' is measured in watts per square meter per (Kelvin per meter), hence (cancelling out the meters) W/(mK). This is a property of the material itself - not of any particular amount of the material. If you like, its the rate of transmission of energy though a square meter of the stuff, one meter thick, with a one degree temperature difference between the sides.

Presumably Kingspan give different (but very similar) figures for the thermal conductivity of their materal depending on thickness because the material is 'composite' (not sure whether it is or not?), or because whatever happens at the surface has more effect when it's thinner.

The U-value on the other hand reflects the rate of loss through an actual piece of stuff of given thickness. Its units are watts per square meter per Kelvin (note not the same as thermal conductivity above).

To (simplistically) get from thermal conductivity to U value, you'd divide the thermal conductivity by the thickness of the material in meters.

So (to take Dan's 250mm loft insulation example): if the material has a thermal conductivity of 0.040, then 250mm of it will have a U-value of 0.160 (units as above - if you start using centimeters, fahrenheit, whatever, then make allowance as appropriate).

For the same thickness, indeed the Kingspan seems to get getting on for twice as good as fibreglass. Hence less thickness of Kingspan needed for same effect.


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 03, 2008, 03:16:10 PM

 go look at celotex website, I think it might be a bit better, & it has regs approval documentation which the others didn't have last time I bought some! (told that at the builders merchants)

Celotex is a perfectly good material but is a PIR insulation material with a slightly lower performance for any given thickness.
Celotex is usually used between battens on solid walls, which obviously gives cold bridges, unless cross battened, and then the cavity will improve the thermal performance.
Celotex as far as I know is not available as a laminated drylining material which is what Kingspan K17 is, so the cost of timber plasterboarding and additional labour needs to be added.
Kingspan is a Phenolic Foam insulation, which apart fromSpacetherm, has the best insulation value. of .21 -.24 W/mK
For a comparison of insulation performance see this link:
http://www.wbs-ltd.co.uk/newbuild_components_insulants.htm
BTW - both Kingspan and Celotex have all the Building Reg approvals, standards, Low Ozone depletion, etc that you could possibly want, Builders Merchants tend to stock sheets of Celotex as standard, which is why they like to sell it rather than order laminated products like K17, pick your merchant carefully, the mark up on insulation materials is at least 40%!! in many cases.


Title: Re: Which type of internal wall insulation?
Post by: MR GUS on September 03, 2008, 03:33:33 PM
..sORRY I keep saying celotex, but actually mean xtratherm.
got any idea about that one?

additional...

 www.xtratherm.com
tel 0871 222 1033
 Their guides for newbuild, renovation etc are the clearest I've come across very good site for info gathering (eg stone wall requirements)

Gus


Title: Re: Which type of internal wall insulation?
Post by: dan_aka_jack on September 03, 2008, 03:58:11 PM
This is all very good information, thanks loads.

So, just to make sure I'm not missing anything... please can I confirm that this would be the correct way to use Kingspan K17 (insulated dry-lining plasterboard for plaster dab / adhesive bonding):

1) Remove existing skirting board and mains sockets and clean the wall
2) Stick the Kingspan directly onto the existing wall (which is a "finished" wall i.e. it's been plastered and painted).
3) Tape up the gaps between the Kingspan boards
4) Install the mains sockets in the Kingspan
5) Paint
6) Add a skirting board
7) Done!

Is that roughly correct?  Do I have to remove the existing paint and plaster before attaching the Kingspan?

Thanks again for all the excellent advice!


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 03, 2008, 03:59:04 PM
..sORRY I keep saying celotex, but actually mean xtratherm.
got any idea about that one?

additional...

 www.xtratherm.com
tel 0871 222 1033
 Their guides for newbuild, renovation etc are the clearest I've come across very good site for info gathering (eg stone wall requirements)

Gus
HI Gus
Havent come across Xtratherm looks good, but their dryling product is again PIR which is slighly less effective compared to Phenolic, not much in it though. Strangly they do do a Phenolic Foam but not in laminate like Kingspan do strange, must be how their laminating factories are set up.
I guess if thickness is not critiacal it all comes down to price.


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 03, 2008, 04:21:40 PM
This is all very good information, thanks loads.

So, just to make sure I'm not missing anything... please can I confirm that this would be the correct way to use Kingspan K17 (insulated dry-lining plasterboard for plaster dab / adhesive bonding):

1) Remove existing skirting board and mains sockets and clean the wall
2) Stick the Kingspan directly onto the existing wall (which is a "finished" wall i.e. it's been plastered and painted).
3) Tape up the gaps between the Kingspan boards
4) Install the mains sockets in the Kingspan
5) Paint
6) Add a skirting board
7) Done!

Is that roughly correct?  Do I have to remove the existing paint and plaster before attaching the Kingspan?

Thanks again for all the excellent advice!
1 yes
2 Depends how sound the plaster is mine was ok'ish but very thick so I removed it saving 30mm on the room. Think I'd check how well the adhesive sticks to the paint, if the paint is vinyl matt or satin I'd either remove or at least score it and scratch through to the plaster. You don't want the paint to act as a vapour barrier on cold side of insulation. Bit picky 'cos not much moist air is going to get through anyway. Scoring will help the dabs stick.
Make sure there is a ribbon of adhesive around the edge of the boards to stop any air getting behind - very important this. I also foamed up any gaps at the tops and bottoms of the board with an intumescent foam ( same price as ordinary expanding foam)  to make sure.
Don't forget the mechanical fixings  i.e long frame anchors. They are to hold back the boads both whicle the adhesive sets and to hold the boards in place in case of fire.
3.Yep then when filled get your palm sander out unless your very good at tapeing and jointing ;D
4. If you run any wiring actually in the insulation it should in theory be rated correctly. Also ribbon of adhesive aroud the boxes, I avoided this by relocating sockets on adjacent internal walls.
5.6.7 Yes done!!
Oh and one other point, work to an element of a building thant affects its thermal performance under Part L of the building regs needs a building notice.  :police:
But... I coudn't possibly comment.
A good reason for notifying though is that you can later prove,you've done it properly, when you come to sell. There's a lot of C*ap dryling out there, that could put off a buyer, also you can prove to a Hip's home energy rating surveyor that there is added insulation, without it they must assume the insulation to the wall, based on the age of the property.


Title: Re: Which type of internal wall insulation?
Post by: MR GUS on September 03, 2008, 04:43:39 PM
Why does anyone still use plasterboard these days?
...ok Hardyboard may be a bit more expensive but far more durable than P/board, & less nasties, no hazardous reclamation, can be ground down, not to mention tougher, water resistant etc.
 ???

 www.jameshardie.com


HardieBacker™ 500 Cement Board for walls and floors delivers superior protection against moisture damage and mold growth. It contains no paper facing, which serves as a food source for mold, or gypsum, which can disintegrate with continuous moisture exposure. HardieBacker board is an ideal choice for wet area walls; its smooth surface may be painted, textured, wallpapered, or tiled. HardieBacker™ 500 board is available in a 3´x 5´ and 4´x 8´ sheet size and is backed by a limited lifetime product warranty.

Thickness: 0.42"
Weight: 2.6 lbs./sq. ft.

3' x 5'4' x 8'

Mold ResistanceHardieBacker products achieve a perfect score on both industry standard mold tests. HardieBacker board scores a 0 (best possible score) on the ASTM G21 for mold resistance and a 10 (best possible score) on the ASTM D3273 test against mold growth.


Non-CombustibilityHardieBacker™ cement board is recognized for use in non-combustible construction in NER-405.

Surface Burning CharacteristicsWhen tested in accordance with ASTM test method E-84:

Flame Spread
Fuel Contributed
Smoke Developed  0
0


Thermal Resistance(Approximate value) 1/4'' thick: R:0.13


 Hardyboard sidings on houses in fire zones (forset fires) are the only ones in burn zones that really have a chance of surviving compared to a regular home! ..something to consider if you live in a nice tree filled setting


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 03, 2008, 05:09:21 PM
Well you answered your own question it is very expensive.
I use Fermacell in limited areas i.e bathrooms when there's a need for fitting disabled rails etc. cheaper than the layer of ply most builders use.
Not easily available in an insulated laminate, although I expect Proctors would do it if you asked, they'll laminate anything to anything if you order enough sq. metres.
Now if you really what to spend money on an expensive durable insulated thin dry- lining material here it is:-
http://www.spacetherm.com/spacetherm-f.htm - Just add the gold plate for that very rich client.


Title: Re: Which type of internal wall insulation?
Post by: GW on September 03, 2008, 07:34:27 PM
I am looking into this for my own house and have read this with interest, however I do not have the luxury of losing room space to fit internal insulation.  Has anyone considered the "Superfoil" insulation SF19 and would this be an option?

Graham


Title: Re: Which type of internal wall insulation?
Post by: MR GUS on September 03, 2008, 07:56:43 PM
Well if you local friendly builders merchant is O.O.S. get them to write you an advantageous price & show it to your nearest topps tiles to match, with the sales guys name & no for "verification" ..that's how it's done  whistle (cheap) whilst standing by the pile of backer board.


Title: Re: Which type of internal wall insulation?
Post by: billi on September 03, 2008, 08:14:45 PM
Me  personally prefer organic based inside insulation  ... not that iam only wearing woolen socks , but i like breathing   ;D materials

There is a woodfiberbased insulation board and adequate plasters ( more lime or clay based ) 

like this http://www.conluto.de/conluto-System.46.0.html


Or similar   ;D


http://www.pavatex.co.uk/herstellung.aspx

Billi


Title: Re: Which type of internal wall insulation?
Post by: MR GUS on September 03, 2008, 08:29:07 PM
I know what you mean billi, but we live in a 1970's house whereby people think that not having gas "instant heating" ...not having hot water on tap 24/7 , not having crew cut lawns & the latest cars is strange, the next sort of folk to move into our house will be in for a shock as it is! ..so some more latch-onable material is a pre-requisite.

Plus our local planning / regs dept is a complete mare when it comes to anything sensible trying to patch up & sort out old housing stock.

..if it were a new build they'd actually insist on stuff like that!
(two faced) ...

E.g I want to utilise my workshop, single skin brickwork & really good even heat / ventilation, sypathetic to not bungling it I ring council who at the merest suggestion of sealing drughts & improving insulATION / VENTILATION deem work "habitable" & therefore additional regs, ..I still want to chop wood in there & keep my dogs cool / warm (season dependant) without wasting energy/ heat whilst htey want me to pay lots of money for trying to keep wastage down, utilising left -overs from other jobs & charge us lots of extra council tax for the privelige!

they see what they wish to sometimes, ...otherwise our house will be un-necessarily re-classified for tax! (daft  :fume )


Title: Re: Which type of internal wall insulation?
Post by: mespilus on September 03, 2008, 10:31:26 PM
I am looking into this for my own house and have read this with interest, however I do not have the luxury of losing room space to fit internal insulation.  Has anyone considered the "Superfoil" insulation SF19 and would this be an option?

Graham

I'm currently using Superquilt from YBS

http://www.ybsinsulation.com/www/products_roof_superquilt.htm

for my loft, as the eaves give just under 6 ft headroom.

I got it in last years B&Q 2 for 1 offer.


Title: Re: Which type of internal wall insulation?
Post by: briand on September 04, 2008, 10:09:01 AM
I recently saw an article on using slabs of sheeps wool that sounded really good, the local farmer says they only get 25p per fleece - and it costs 125p for the shearer

BUT the sheeps wool slabs turned out to cost 3 times the price of mineral wool and was the dearest option by far

I use 2" thick celotex which is more compact but Thinsulex is probably slightly thinner but a fair bit dearer to achieve a reasonable insulation level - I think I was aiming at a U value of under 0.3 W/m2/K but new builds are looking at lower than that now


Title: Re: Which type of internal wall insulation?
Post by: dan_aka_jack on September 05, 2008, 09:48:17 AM
Thanks again for all the replies.

Please may I ask two really basic questions about installing Kingspan?

1) How does one cut Kingspan?  I assume you can't just use a penknife like you can with "normal" plasterboard?

2) How does one make a smooth "joint" between the top of the Kingspan and the existing ceiling (assuming we're not going to hire a plasterer)?  Is it as simple as making sure that the Kingspan is a really snug fit between the floor and the ceiling so there are no visible gaps between the Kingspan and the ceiling?

Sorry for asking such basic questions - I just want to make sure I don't do a bodge job!

Many thanks,
Jack


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 05, 2008, 09:53:44 AM
Cut with an ordinary wood saw preferably an old one as after doing a whole house it will blunt!!
Push the boards up from the bottom with a wedge - The Kingspan website has fixing instructions.
A gap at top and bottom is not a problem if you foam up later as my previous posts, in fact I left 10mm min to take the foam. Just cut the foam back with a knife or saw, and fill with the Joint Filler.
There needs to be a gap anyway to allow you to swing the boards up into position.


Title: Re: Which type of internal wall insulation?
Post by: Solal on September 05, 2008, 12:20:50 PM
Had a relative just complete  a new build  and he  battened  all the  inner leafs  of the exterior walls ,  then  placed 40mm  kingspan  in between.
Dry lined  with a  double  layer (one layer foil backed) of  plasterboard  and skimmed  with gypsum.   :)


Title: Re: Which type of internal wall insulation?
Post by: MR GUS on September 05, 2008, 04:12:21 PM
"cough, cough" NEVER ever tell building control you did it in areas larger than 25% at a time (as in say it was all small projects at weekends etc (ie closing up on wall and allegedly starting another elsewhere with not the same stock of material) ...OTHERWISE you are meant to have put in a notification with building control since 2006 !!!

..they are not making greening / energy efficiency easy now are they!?

 In other words, I did an outer room wall then, went away did another wall elsewhere , then thought i'd do another in the original room, NOT ONGOING!

 This was imparted to me by my building control officer in a phonecall,


Title: Re: Which type of internal wall insulation?
Post by: dan_aka_jack on September 08, 2008, 04:31:43 PM
Here's a very interesting document:

Energy Saving Trust: Practical Refurbishment of Solid Walled Houses (2006 edition) (http://www.energysavingtrust.org.uk/uploads/documents/housingbuildings/CE184%20-%20practical%20refurbishment%20of%20solid-walled%20houses.pdf)

On page 15 is the graph I've been hunting for!  It gives the resultant U value for 9" solid-walled houses (like mine) after the addition of various different types of internal insulation.  It turns out I need at least 80mm of phenolic insulation (like Kingspan k17/k18) to achieve a "recommended best-practice" U-value of less than 0.30W/m2k.  The U-value for my 9" solid walls as they stand at present is apparently a shockingly high 2.1W/m2k.

But, I'm having real trouble finding a supplier of 80mm or 100mm K17 or K18 (most suppliers seem to only go up to 60mm).  Can anyone recommend a suitable supplier?  Not even eBay is able to help me out!

Also, I've read a bit of blurb on the web about grants for solid wall insulation.  The bottom line seems to be that grants are available only if you're on means-tested benefits.  Is that accurate?

Finally: is Kingspan available in 2.7m lengths?  My walls are 2.65m high.  It seems that it's not possible to get Kingspan larger than 2.4m.


Title: Re: Which type of internal wall insulation?
Post by: wookey on September 09, 2008, 10:18:57 PM
I lined the whole inside of my previous house with 35mm phenolic foam boards (from Knauf). Cost about 800 quid for the boards in 1995 (standard 1930s semi). It was extremely effective and I'd recommend it to anyone. Don't worry too much about your rooms shrinking. If you take the plaster off first (dead easy, but incredibly messy, downstairs - it was quite loose, upsatirs was too well stuck on so I left it) then the room is only about 2cm smaller than it was before - you simply don't notice this, even in a small house.

These boards came with special glue from knauf which was very strong when set. The house became lovely and warm and very easy to heat and quick to heat up, but putting all those boards on _and_ preserving the original woodwork features was _a lot_ of work. It took months and months of every weekend. Walls with fiddly window shapes are very annoying. A house with big blank sections of wall would be a lot easier, and just throwing a way all the old skirting and covings and roof-twiddle and replacing it with new would save a lot of time (now I know why builders do that sort of thing :-)

Dan/Jack - you may find this site very useful for working out U-values of different constructions (it also gives clues about interstitial condensation):
http://www.vesma.com/tutorial/uvalue01/uvalue01.htm

I'm looking at adding some more thermal boards on at least some of the walls here. We have a cavity, which is already filled (with rockwool fluff), but so far as I can tell this doesn't work for the bottom 30-40cm of wall because it is all full of cement rubble from the building process, so the overall U-values is only 'adequate'. I'd like to get up to 'quite good', although thermal bridges due to the house design will limit what is possible overall.

The thing I haven't been able to get a good handle on is whether interstitial condensation is a problem in practice if you have internal insulation, wall, cavity insulation, wall. It seems to me that so long as care is taken over the internal vapour barrier it should be fine, but I don;t want to do somehting that turns out to be dumb.

Like Dan, I looked at external insulation but it seems to be impractically expensive, despite being technically a better solution, and there are significant issues of making the house look completely different (currently brick). I'd certainly do it that way if building new.

(edit - corrected fibreglass->rockwool)


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 10, 2008, 10:12:25 AM
Wookey
Good points, and the U- value calculator is useful, it also will answer your question about interstitial condensation risk.
I don't know exactly what your wall build up will be, but there could be a small risk of interstitial condensation in the outer leaf of brickwork.
A good vapour barrier i.e foil in the insulating board should take care of this, there are also plasterboard finishes ( British Gypsum) which will help.
If your brickwork is soft, then decreased temperatures in frosty weather can cause problems. If its sound and well pointed, and not facing the atlantic, you are probably OK.
To make sure, most of the suppliers of wall insulation, will do a proper Condensation and U value calculation free  for you, if you give them the full build up of your wall.


Title: Re: Which type of internal wall insulation?
Post by: merkland on September 10, 2008, 10:25:38 AM
Question for Mr Gus,

Can you expand upon your statement of not doing more than 25% of a project at a time - suggesting to me that this is a way of getting around building control!"

best wishes,
merkland.


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 10, 2008, 11:16:51 AM
Question for Mr Gus,

Can you expand upon your statement of not doing more than 25% of a project at a time - suggesting to me that this is a way of getting around building control!"

best wishes,
merkland.
Any work to a thermal element that is not a minor repair, technically requires notification. In case for example adding drylining, were to be done with out regard to the rest of the wall. Or using untreated timber caused dry rot or any of the other ways bogged DIY F***s up a house.
Most Building Control officers are not to be avoided, and it most cases the small fee is worth paying for the advice they are then willing to give.
It's up to you to determin if the job warrants notification or not.
The 25% bit is about say replastering a wall. Part L  says that if the major part of a wall in a renovation needs replastering then to oppourtunity to improve its insulation should be taken, but if only 25% needs replastering then it may be reasonable not to up-grade the wall.


Title: Re: Which type of internal wall insulation?
Post by: wookey on September 12, 2008, 04:36:08 AM
Quote
Good points, and the U- value calculator is useful, it also will answer your question about interstitial condensation risk.

Well, it shows a little red asterisk for different parts of my wall depending on which construction I pick, but doesn't really explain exactly what that means. Condensation on front face?, back face?, actually inside the brick (aren't bricks reasonably waterproof)?, under what conditions? I assume it is only a problem if it stays wet for ages and never dries out? Cambridge is very nearly a desert, and this is a sheltered spot.

I'll try asking a load of people at the homebuilders/renovators show in London next week, and the point about suppliers' tech depts is a good one. One thing I wondered about - does one need to worry about 1st floor wooden joists sticking through insulation (and thus vapour barrier)?

I have a friend with an exceedingly cold sandstone house (listed so no chance of external insulation) who is also very interested in this stuff, but has been warned to be _very_ careful about condensation.


Title: Re: Which type of internal wall insulation?
Post by: chickensoup on September 12, 2008, 06:17:28 AM
        Which is the best cavity wall insulation, i've come across the white very brittle foam, little clumps of fibreglass, recycled newspaper ;D and i'm sure there is an expanded foam? which has the highest u/ value, it would be great if it was the newspaper.


Title: Re: Which type of internal wall insulation?
Post by: Richard Owen on September 12, 2008, 06:57:22 AM
Cavity wall insulation is either full fill or partial fill.

Full fill cavity insulation is usually either extruded polystyrene panels (your white very brittle foam?), rockwool (not fibreglass) or polystyrene beads.

Partial fill cavity insulation is almost invariably one of the solid foam boards such as Kingspan. There are also a variety of foil based insulators that are put in cavities but the jury is out as to how good they really are.

In terms of U-vlaues, the boards such as Kingspan are double the value of the loose fill products such as rockwool and beads. The extruded polystyrene boards are somewhere in the middle.

A cavity is there to stop rain penetrating to the inner leaf. It is designed so that any water penetrating the outer leaf, runs down the inner wall of the outer leaf, leaving the inner leaf dry.

If you fill a cavity full, it is important to use an insulator that doesn't wick the water across the cavity. Which restricts your choice to those lower value insulators above. For a retro-fit, rather that a new build, you are restricted to the loose fill products which can be blown in.

In reality, unless you build with very wide cavities, the U-value tends to even out: 100mm of full filled rockwool will end up giving you about the same U-value as 50mm of Kingspan in a partially filled cavity.

I'm a big fan of Warmcell (the recycled newspapers) and have a roof and (timber frame) walls stuffed full of it, but I've never heard of it used in a cavity. If you could use it, it would be about the same as rockwool.


Title: Re: Which type of internal wall insulation?
Post by: tony. on September 12, 2008, 07:41:40 AM
 i would be inclined to line walls with rockwool, providing good thermal and sound and fire proofing properties.

PS dont use any other kind on outside walls as they will prevent the walls from breathing.

good old rock wool is breathable

tony


Title: Re: Which type of internal wall insulation?
Post by: Richard Owen on September 12, 2008, 08:38:12 AM
That's an interesting point.

The big question with interstitial condensation is whether it's caused by water vapour entering from the outside or the inside. The presence of breathing mammals in rooms does tend to make them more humid than natural air.

Standard practice is to put a polythene or building paper vapour barrier on the room side of the insulation (unless it's a sealed board type insulator) to prevent warm moisture laden air from inside the room penetrating the insulation, cooling and condensing.

You probably don't want to have rockwool against a wall that gets damp from the outside because damp insulation (apart from sheep's wool) has no insulation value at all.

If I were going to use rockwool on the inner surface of an outside wall, I'd have a vapour barrier on both sides of it and let the wall breathe to the outside. I would probably have a lower grade vapour barrier against the outside wall than against the room, so that any water vapour that did penetrate the rockwool could eventually find its way out.


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 12, 2008, 10:32:04 AM
Quote
Good points, and the U- value calculator is useful, it also will answer your question about interstitial condensation risk.

Well, it shows a little red asterisk for different parts of my wall depending on which construction I pick, but doesn't really explain exactly what that means. Condensation on front face?, back face?, actually inside the brick (aren't bricks reasonably waterproof)?, under what conditions? I assume it is only a problem if it stays wet for ages and never dries out? Cambridge is very nearly a desert, and this is a sheltered spot.

I'll try asking a load of people at the homebuilders/renovators show in London next week, and the point about suppliers' tech depts is a good one. One thing I wondered about - does one need to worry about 1st floor wooden joists sticking through insulation (and thus vapour barrier)?

I have a friend with an exceedingly cold sandstone house (listed so no chance of external insulation) who is also very interested in this stuff, but has been warned to be _very_ careful about condensation.
Well the Web based calculator is a simplification. Which is why its worth getting a free calculation from people like Kingspan. When you have decided on the level of insulation you need. The asterisk mean there may be condensation at the levels of humidity set at the top of the calculator. In a swimming pool the internal humidity could be near 100% then there will be interstial condesation in many constructions.  The manufacturers programs check out the quantity of vapour likely to be present over time and will allow for the brickwork to dry out over a heating season. Showing that in  practice there is unlikely to be a problem. As for floor joists thats a good point, not only the vapour barrier but also the heat loss at this point. I have insulated between the joists against the wall with Kingspan and foamed up the gaps. In therory I suppose ther could be some minor condesation, but again thats no worse than in any solid wall, as long as it can still dry out to the outside over time.
There should never be any kind of vapour barrier on the cold side of insulation. Breathable membranes such as Tyvec used for roofs should also not be used in walls unless there is a vented air gap on their cold side. Difficult to achieve, and unnecessary, in most solid walls that are reasonably sound, and well pointed with a lime based mortar. If the external wall is already damp, fix the dampness first never hid it with drylining. Or an internally applied material. Old walls need to breath outwards.
Jack asked about suppliers, ring Kingspan, I got mine from my local family builders merchant, 92.5 overall 80 +12.5 plasterboard, they ordered it at a price that was less that some of the specialist laminated board suppliers, over 2.4 m and you will have to cut boards, how about a dado rail? if your taping and jointings not so good!!!!
The discussions in this thread I'm afraid, show why it's worthwhile involving building control, unless you really know what you are doing. Although we've talked about general principles, solid walls vary in traditional construction through out the country, some will be softer, harder, more windswept, and good local knowlege can be a great help.


Title: Re: Which type of internal wall insulation?
Post by: dan_aka_jack on September 15, 2008, 10:14:14 AM
Are there any grants available for solid-wall insulation?  Am I right in thinking that there are literally NO grants available for solid wall insulation, even if you're on benefits?  (I'm not on benefits, but I'm interested none-the-less...).


Title: Re: Which type of internal wall insulation?
Post by: rhys on September 15, 2008, 10:29:23 AM
As far as I know no, the grants system is going for the easy hits i.e. loft and cavity insulation.


Title: Re: Which type of internal wall insulation?
Post by: dan_aka_jack on September 15, 2008, 11:28:50 AM
That's what I understand the situation to be too.  Thanks for the reply!