Solid wall insulation

Can someone point me at a reputable website that shows the amount (%) of
heat loss through a solid double brick wall? I can find lots of sites about
cavity walls but my house was built in 1923 and has solid walls.
I'm asking because we're about to do some work, part of which will be
insulating the roof (it's flat so no crawl space so insulation will be a
pain!). At the same time I'm trying to find out whether insulating the
walls will be worth the large amount of effort involved as it seems to
involve removing existing plaster (optional) and replacing with combined
insulation/plasterboard and then skimming.
Thanks,
Paul DS
Reply to
Paul D.Smith
Have a look at page 221 (8 of 16) of:
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a 215mm solid brick they give a thermal conductivity of 0.75, which with a cavity they say drops to 0.54. I'm thinking of using their ThermaLine Super to get my solid walls up to U-values of 0.35. They give figures for leaving the plaster on, but I believe it is better to remove to allow the bricks to breathe and thereby prevent moisture buildup (obviously some venting of the created cavity is required, but you don't want gales blowing through it).
Reply to
Cod Roe
as the double brick wall has a cavity any moisture can dry out though the outside so why cant we make the inside of the brick wall non-porous and windproof and glue the insulation board straight onto it without an airgap for draughts and gales?
[george]
Reply to
George (dicegeorge)
Thanks for that although I've not clear about this cavity - as far as I can see the boards are simply dabbed to the wall.
Paul DS.
Reply to
Paul D.Smith
Brick has an average k value of about 1, so a U value of about 5 for solid 200mm brick.
Similar to a single glazed window or a solid wooden door.
To be honest, in a single brick house, the walls represent the greatest heat loss of anything. People insulate rooves because its simple and cheap, but there is no doubt that wall insulation has the greatest potential benefit, but its also the greatest cost unless you dry line etc.
If you can be bothered, the difference will be remarkable. Even 3mm of polystyrene, will knock about 30% off that heatloss.
Put in 2" of celotex, and you are knocking 90% off it. Up to the point where its almost worth double glazing the windows..;-)
You don't HAVE to skim, if you are careful..just plasterboard up, fill the cracks and use lining paper..
The 2" of dry lining is also a great place to re-lay cables and pipes..
If you do it a room at a time,. it doesn't seem so painful, either.
Basically get 2x2 timber, screw thriugh into the walls, lay cables and pipes, and infill with celotex, covering over he joins with te foil tape, so the whole wall is airtight and vapour proof, then line with 12mm or 15mm plasterboard,fill holes, lining paper and paint.
Electrical sockets can use steel boxes 2" deep screwed straight to the brick..
Wrap pipes in insulation and run in slots in the celotex, notching through studs as needed.
The actual difference will astound you. Walls ae no longer cold, and you will feel warmer even if the room is cool, as there will be no cold air draughts falling down the walls to freeze yer tootsies.
Done to a complete house, with roof a well, I would NOT be surprised to see you halve the heating bills.
Reply to
The Natural Philosopher
No reason at all.
There are two ways to look at damp, one is to let it get in and make sure it can get out again.
I.e. no damp proof course and breathable walls..
The other way is to stop it getting in (DPM, vapour barriers), and what little does, give it a path to outside, I.e. breathable bricks *outside*.
Modern insulation requires that massive internal ventilation via open chimneys and fires cannot be used to dry out internal dampness, so the latter way is the de facto standard under the regulations.
You almost always HAVE to use a vapour barrier inside insulation, otherwise the far side of it will get condensation. Celeotex comes foil wrapped.
Mind you, it can play merry hell with radios. Probably one of the reasons wifi can be so unreliable.
Lay in plenty of CAT 5 when dry lining ;-)
Reply to
The Natural Philosopher
Yes, but the dabs will have air voids between them, and this leaves the opportunity to have a small circulating air flow between the back of the sheet and the brick work. This allows an opportunity to remove any moisture that has worked its way into the bricks. This flows needs to be limited though, otherwise you compromise the insulating properties. I'm thinking of a few small vents to the loft which is covered by a sealed Tyvek Supro permeable membrane, which allows moisture out (like Gortex) and thereby allows you to seal everything else up to prevent the wind blowing through.
Reply to
Cod Roe
If you are using celotex and plasterboard combinations, that's how you do it.
However consider using studs and sheet insulation, you can get more depth, and its easier to arrange pipes and cables, and easier to mount stuff onto the wall - there are wood pieces to screw things to. Its more labour intensive, but if its DIY te better result may be worth the effort..
Also do look at windows and doors..yo MAY want to mount cills on top of insulation to prevent losses there as well.
Reply to
The Natural Philosopher
"The Natural Philosopher" writ:
shouldnt the vapour barrier be * outside * of the insulation in this case, i.e. between the cellotex and the bricks in this case?
Reply to
George (dicegeorge)
I assume you mean doesn't have a cavity? My house has internal and external bricks, those on the outside have extra glazing to increase their water proof properties, which of course is very desirable, you want to keep the rain out. The glaze is water resistant in both directions, so only allowing the house to breathe through the outside bricks isn't going to work. Damp can get into the inner skin in all sorts of ways, and although a vapour barrier will help to stop it, it won't be 100% effective. The air gap itself also has insulating properties.
Reply to
Cod Roe
How does one engineer a breathable brick that doesn't let the rain water in from the other direction? I haven't come across the Tyvek of the brick world, could you point me to a link please. Were they available and used in 1890?
Reply to
Cod Roe
No. See the diy wiki for why not. Basic explanation: Inside a warm house there is a high temperature, and quite a lot of water vapour (measured in g/m3, not relative humidity). Outside there is a low temperature, and less water vapour. With the insulation but no vapour barrier, the temperature falls steeply, but the water vapour falls gradually. The net result is that the temperature can fall below the dew-point and you get condensaton.
With the vapour barrier INSIDE the insulation, the vapour level falls very steeply at the barrier, so the temperature never gets below the corresponding dew-point.
The the vapour barrier OUTSIDE the insulation, things are much worse, and you are positively guaranteed condensation, with no way for it to get away!
Reply to
Martin Bonner
Snip good discussion of why to dry line.
Although putting in new, well made, windows does allow you to eliminate draughts which are an even bigger source of heatloss than solid walls.
If you are putting in new windows, you might as well get them double- glazed unless you need thin glazing bars for visual reasons. We were originally disappointed with our new double glazing, but we have got used to the glazing bars (and it certainly looks better than UPVC).
Reply to
Martin Bonner
Dear Paul It is against the spec but I have sucessfully used TP10 (its all the same regardless of name) 2" p-urethane ins on walls using a) gypsum plasterboard adhesive AND external stainless steel fixings and washers b) followed by plasterboard and skim also fixed with adhesive and fixings (spaced differntly to those under) If you want to minimise space loss it is the best way forward If you want to you can use drywall topcoat vapour check on the inside It worked a treat for me Chris
Reply to
mail
No.
The purpose of the vapour barrier is to keep your steamyy interior, full of steamy dogs, and cups of coffee, from getting PAST the insulation to the cold part of the wall, where it will condense and form a nice habitat for fungus. Which will rot the studowork in time.
Water ingress from outside is what the brick wall is there to stop, and the theory is that if it gets in that way, it can get out that way.
You COULD shove a DPM in between te stids and teh brick, but hat runs the risk that if water DOES get in by e.g. dripping down from the eaves, it cant get OUT again via the brick..and then you might get rot at the stud bases.
Reply to
The Natural Philosopher
Wll AFAIK its quite simple. All bricks are pourous. If siake on te outsie, they will in time get damp n te inside.
However bricks are built into walls, and water runss off walls, so teh damp never penetrates that far. It tends to cling to teh brick a well when its arrived via the rain, so the inside wont drip. It will just be damp, and once teh brick is full of water, it is in fact waterprof..in te snsen that to actialyy force water through it takes pressure. Maybe on really DRIVING rain a bit gets through, but no big deal.
When the rain stops, the water evaporates, and the water migrates through the brick back to the outside.
Think 'sponge' ...if you play a hose on a sheet of sponge, mostly the water soaks in, then runs down the outsdie. Not a lot drips down the far side.
If there is a DPM at the bottom,its traditional to NOT bridge the inner and outer leaves, and in fact the inner DPC is usually higher than the outer..so any water in the cavity ends up below inner DPC level, but abive the outer, and goes out via the brickwork.
On a single brick te wall is much thicker per leaf, and you relyy on interior ventilation to deal with the odd heavy shower..
If dry lining it there is PROBABLY an argument to put DPM between the lower part of it and the studs, to make sure than any water collecting at the area above the DPC doesn't get into the studs, and instead soaks outwards, but its going to do that anyway in all probability. A little humidity after rain is not a huge problem: Rot happens when water collects and cannot escape. I.e. when you tank the outside of a brick wall becaue you think you have a penetrating damp problem at low level, when its leaking guttering getting into the wall at high level, and soaking BEHIND your new tanking, and now, having nowhere else to go, is blowing the plaster inside the house at skirting level..
Reply to
The Natural Philosopher
I put in new windows ..SG units, and the lack of draughts and the lovely visual appearance more than compensated for the 100W extra or so the room needs to be heated on cold days..
Reply to
The Natural Philosopher
It is, but it has the downside of having nowhere to route wires and pipes other than by carving it about.
Its a very simple and effective quick fix, bit I reckon proper studs and 2" of celotex, is the better way by far
Reply to
The Natural Philosopher
so is the steamy breath in this room seaping through the porous plaster ceiling into the glass fibre insulation and condensing there? or is that that the plaster cieling is a good enough vapour barrier? or should i go up in the attic and put plastic under the fibreglass...
or even better paint the ceiling with a waterproof paint?
and then fit a fan for controlled ventilation?
george
Reply to
George (dicegeorge)
Hmm... Compare the cut edge of a brick to the outside surface and you'll see the difference between a glazed and an unglazed surface, and the purpose of the glaze is to stop water, in the same way it does on plates for example. Concrete blocks are porous, hence the reason why you have to render them, despite the fact they are built into walls, to stop the water penetrating them.
Reply to
Cod Roe

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