Which type of internal wall insulation?

[MR GUS]

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  )

[mespilus]

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.

[briand]

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

[dan_aka_jack]

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

[rhys]

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.

[Solal]

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.   

[MR GUS]

"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,

[dan_aka_jack]

Here's a very interesting document:

Energy Saving Trust: Practical Refurbishment of Solid Walled Houses (2006 edition)

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.

[wookey]

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)

[rhys]

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.

[merkland]

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.

[rhys]

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.

[wookey]

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.

[chickensoup]

        Which is the best cavity wall insulation, i've come across the white very brittle foam, little clumps of fibreglass, recycled newspaper and i'm sure there is an expanded foam? which has the highest u/ value, it would be great if it was the newspaper.

[Richard Owen]

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.