Thin Insulation

rosullivan

I want to insulate the walls of an old farmhouse. As described in another post, the walls are standard traditional stone with lime mortar and are about 2 foot thick. In order to keep the walls breathable, I have been advised to use Delta membrane as my DPC. I am told this will allow the external walls to continue to breathe, but will provide an effective damp proof layer to keep the internal room dry.

What kind of insulation can I put on the inside of the external walls (over the Delta membrane)? I can't really afford to have thick layers of insulation as it will eat into the internal room space. So, I need a thin, but effective, insulation. Any ideas? I don't expect passive house standards, but I would like to maximise insulation without losing too much space. Does my insulation have to be breathable or can it be regular insulation on the basis that it is onthe inner side of the Delta membrane?

sydthebeat

The higher performing insulations such as PU and PIR, even EPS are non breathable so i wouldnt consider them. Therefore you need to incorporate the best performing breathable materials. These include hemp, sheepswool, rockwool, fibreboard, perlite board etc.

In my opinion a blown in rockwool type such as 'energy saver' into say, a 100mm cavity behind breathable sheeting such as panelvent.

rosullivan

sydthebeat wrote: »

The higher performing insulations such as PU and PIR, even EPS are non breathable so i wouldnt consider them. Therefore you need to incorporate the best performing breathable materials. These include hemp, sheepswool, rockwool, fibreboard, perlite board etc.

In my opinion a blown in rockwool type such as 'energy saver' into say, a 100mm cavity behind breathable sheeting such as panelvent.

Thanks for that. The only problem is that 100mm of insulation plus the Delta membrance plus plasterboard on each wall of the room will shrink them room quite a bit. Is there any thin insulation that I could use along with the Delta membrane? Does the insulation really have to be breathable, given that the air spaces in the Delta Membrane have to be vented separately anyway (anyone got any experience of this)?

Mellor

Who told you to use delts membrane?

Delta membrane is a drainage product for flat roof, if you were to use this in the wall, it will not keep the wall breathable, it will however bypass the insulation (if vented) rendering it useless.

DPC does not need to be breatable, it is perpendicular to the passage of air.
Use regular DPC and a breahable membrane

rosullivan

Mellor wrote: »

Who told you to use delts membrane?

Delta membrane is a drainage product for flat roof, if you were to use this in the wall, it will not keep the wall breathable, it will however bypass the insulation (if vented) rendering it useless.

DPC does not need to be breatable, it is perpendicular to the passage of air.
Use regular DPC and a breahable membrane

OK. Now that's the exact opposite of what I was advised so I'm confused . I was told that the wall was designed to breathe and so if I simply put a sheet of standard DPC on the floors the damp would simply rise to the sides i.e. the walls. in the walls themselves, I was advised to continue my Delta Membrane up the walls. On the exterior side of the membrane there are air pockets. I can vent the membrane internally or externally. On the inner side, I can put insulation and plasterboard. If I used a regular DPC on the floor, the amount of moisture building up and going around the side into the walls would be excessive.

Does that sound right, or nonsense;)?

Mellor

Nonsense. Delta is not a DPC, its a drainage layer (unless they do another product being refered to, but it doesn't sound like it)
Firstly DPM and DPC are being confused.
DPM is a big layer under the floor.
DPC is a thin strip under the wall (actually 150mm up)

The wall breath from the inner face to the outer. This is fine.
The DPM is lapped with the DPC to fully separate the walls from the ground, amd then wall breaths through fabric, this releases air-bourne moisture, not groud water
but in your case a DPC may not be there. Ideally it should, even an old bitumen dpc.
A retro application will help

But installing a vented layer before insulation with negate the insulation. And afaik, delta membrane is not designed for that (may even make it worse, its not breatable)

The best solution is as syd detailed above. Or similar.

rosullivan

Mellor wrote: »

Nonsense. Delta is not a DPC, its a drainage layer (unless they do another product being refered to, but it doesn't sound like it)
Firstly DPM and DPC are being confused.
DPM is a big layer under the floor.
DPC is a thin strip under the wall (actually 150mm up)

The wall breath from the inner face to the outer. This is fine.
The DPM is lapped with the DPC to fully separate the walls from the ground, amd then wall breaths through fabric, this releases air-bourne moisture, not groud water
but in your case a DPC may not be there. Ideally it should, even an old bitumen dpc.
A retro application will help

But installing a vented layer before insulation with negate the insulation. And afaik, delta membrane is not designed for that (may even make it worse, its not breatable)

The best solution is as syd detailed above. Or similar.

OK - my fault for not getting my terminology right. Basically it's an old farmhouse so the only damp proof course in the walls is an old slate one that is (a) cracked and (b) not very good. It would cost a lot of money to put in a new DPC in the walls and it could damage the existing old structure.

What I was told about the Delta Membrane is that it gives a dry inner room while still allowing the walls to breathe and therefore avoiding the damp just staying in the walls and God knows what nasties occuring behind the dry/damp-proof lining in the walls.

I wanted to attached the two info sheets I was given - they are too big to attch (PDF of 550k???). I can email them to you if you would like. I have absolutely no affiliation with this products - I was just told it was good for damp-proofing old buildings with old walls that have to breathe.

sydthebeat

if the membrane is the 'pocketed' type that im thinking about then
a. its not a breatable membrane. It may allow the walls to breathe by introducing a cavity (which you have to vent to the external as well) but it DOES NOT allow the room to breathe, and therein lies the problem. all this would do is create a 'tank' around the room, similar to a basement, or a swimming pool.

You need to incorporate materials that are breathable. The lime render, the clay/stone walls, the breathable membrane, the breathable insulation and the breathable inner finish. This make up will hydroscopicall diffuse moisture from the internal to the external and minimise interstitial condensation and sick building syndrome.

sinnerboy

their is no thin insulation , breathable , with good thermal performance as you ask for it .

if you were not tight for space then delta membrane , with vents to external together with a free standing 100deep stud wall insulated would be an answer

so you have to compromise on insulation performance

the latest issue on Construct Ireland magazine features a hemp lime plaster . it can be applied up to 50mm thick ( in layers ) . it is hygroscopic ( breathable - the lime plaster can safely absorb and release moisture without damage to itself or to occupants ) . lime has anti septic properties , which means spores can't develop .

i don't know what it's thermal properties are - not comparable to high performance insulations thats for sure . but it will improve the wall , thermally .

Mellor

The slate DPC will not be perfect, but should be acceptable.

The best thing you can do here is keep it traditional as suggested above, hemp/sheepswool/fibre insulation, lime render, materials that can deal with moisture.
Trying to keep it out will lead to problems as the wall will let some in, which may be then trapped. Go breathable and accept the moisture. If the walls are breathable then the levels will not get too high ever.


The delta membrane, could work. But all it does it create a cavity, that can be created without the use of Delta. It must be externally vented, and the downside is that the room is no longer breathable (wall will still be). Doing this with out delta is better imo. If space is an issue then the cavity/Delta can be omitted.

rosullivan

Mellor wrote: »

The slate DPC will not be perfect, but should be acceptable.

The best thing you can do here is keep it traditional as suggested above, hemp/sheepswool/fibre insulation, lime render, materials that can deal with moisture.
Trying to keep it out will lead to problems as the wall will let some in, which may be then trapped. Go breathable and accept the moisture. If the walls are breathable then the levels will not get too high ever.


The delta membrane, could work. But all it does it create a cavity, that can be created without the use of Delta. It must be externally vented, and the downside is that the room is no longer breathable (wall will still be). Doing this with out delta is better imo. If space is an issue then the cavity/Delta can be omitted.

Thank you Mellor, sinnerboy & sidthebeat. That makes sense now that you explain it. There is no point in creating a "tank" as you put it. No point in having walls that can breathe when the room can't. It also makes sense that the normal levels of heat from the room will help prevent internal moisture beoming a problem - a breathable membrane on the walls will help that.

Do you think the following is a good solution then? Damp-proof membrane on the new concrete floors (or else just leave an earth floor with air bricks and suspended timber floor), leave the old slate DPC in the walls and re-render the internal walls and include a hemp/sheepswool/fibre insulation. Do I still need a separate breatheable membrane on the walls? If so, do you know of any that are suitable?

sinnerboy

rosullivan wrote: »

Do you think the following is a good solution then? Damp-proof membrane on the new concrete floors (or else just leave an earth floor with air bricks and suspended timber floor), leave the old slate DPC in the walls and re-render the internal walls and include a hemp/sheepswool/fibre insulation. Do I still need a separate breatheable membrane on the walls? If so, do you know of any that are suitable?

Damp-proof membrane on the new concrete floors - yes - radon barrier with sump(s) in hardcore bed . use min 100mm polyurthene insul .

Do I still need a separate breatheable membrane on the walls? - no . rely on lime plaster for breathing

sculptor

Sorry to cut in, sinnerboy are you saying the hemp or wool can be put up against the lime render between battons, then vapour check and breathable plaster board.

sinnerboy

no - just apply hemplime plaster

http://constructireland.ie/news/product-news/new-hemp-plaster-product-offers-flexibility-and-carbon-gains.html

sculptor

Sinnerboy, Now your saying forget about your previous advice (in my hemp insulation post) and forget about the breather membrane, double layer studs with hemp infill, vapuor check and sasmox board. Just 50mm hemp lime mix and plaster with lime. And save myself about 1000 euro per room.
What about electrics and heating pipes do I just spray the lime/hemp over them. This sounds too good to be true there has to be a catch!

sinnerboy

no sculptor . this op is VERY tight for space . ( i didnt think you are ? not to the same extent)

his walls are stone , dificult to inrtroduce effective dpc into .

so no space , wall damp , must breath , there is no where to go . the hemp lime plaster is best option for op , but thermal value of lime plaster is not great . it will improve he stone wall u value and assist it's air tightness , so it is worth doing

spec for red brick victorian , your case, stands

sculptor

Should I put a scud coat on the old brick to seal and bind it?

fardy

Sorry for butting in. But I'm in exact same position. Breathability etc. however does this restrict wall coverings- paint/wallpaper. I was told that hanging wall paper in this situation will end in tears eventually.

rosullivan

sinnerboy wrote: »

so no space , wall damp , must breath , there is no where to go . the hemp lime plaster is best option for op , but thermal value of lime plaster is not great . it will improve he stone wall u value and assist it's air tightness , so it is worth doing

I have raised this issue again with my architect's office. They say I can still put up my Delta membrane on the wall followed by a thin, non-breathable insulation and my plasterboard. Their take on it it that the cavities created by the Delta membrane will still allow my walls to breathe (i.e. moisture comes in from outside, and then breathes back out). Any moisture that builds up on the Delta membrane will simply fall to the bottom of it and drip onto the ground under the floorboards. They say that way I get my breatheable walls and I get my warm, relatively insulated and dry interior.

Now both your explanation, and their explanation, make some sense. This is the problem with not being an expert myself. Your description makes more sense to me overall, but they seem confident I can use the Delta membrane and therefore get my thin insulation up also. Why do you think the Delta membrane won't work here? I'd really appreciate your views because my gut tells me you are right.

Mellor

Basically they are two different approaches, one is the traditional breathable approach. The other is a vented cavity approach. The delta membrane is just a modern varient on the battened cavity. If done correctly it could work, but it would have to be vented outside, you don't have the option to go in or out as you previously thought.
This was my main gripe, as given the option, a builder will vent internally, which won't work.

Now if the delta is vented externally it could work, but only if it is installed correctly, detailed correctly and vented correctly, no room for builders error (which he could cover before you see). The tradional method is more forgiving. Also, in addition to correct installation, the room must also be vented correctly and adequetly, this is easy in a new build, it may or may not be in your case.


I'm sending you a pm with a delta fact sheet

sinnerboy

Firstly to be crude ( not rude - i dont want sound rude ) you can't sue me - you can sue them ( your architects ) . In that context, it doesn't matter what anyone says or posts here .

you say you are VERY tight for space

ideally i would like to see a free standing stud min 75 x 50 studs insulated with foil faced polyurethane boards with a composite plaster board over - this to be erected - free standing - so it needs no fixings ( through the delta membrane !!! ) to the stone wall for support - in front of the delta membrane . then the cavity between the membrane and the stone wall should be vented to the external .

Alternatively you could use hemp insulating batts , with Intello* vapour barrier - more "eco" , less thermally effective - ( like I posted to you , Sculptor )

* sorry mods difficult not mention this without talking in "code"

but you say you don't have the space for this - thus my suggestion , which is hugely thermally inferior - i must stress that to you . i can't tell you exactly how much inferior because

- difficult to say accurately what thermal value the stone wall has
- the lime hemp plaster producer can't say what thermal performance his material has ( i am awaiting a response to that query ) . it won't be great i can predict that .

i don't want to be un helpful or dismissive , but you have engaged professional help - i would rely on that primarily

Overview

Sometimes , homing in on one aspect of specification , on a web forum like this , can be misleading . What I mean is an experienced architect will propose
spec methods , based on his career experience and taking into account his knowledge of your individual building - in its entirety .

A doctor wont just look a patients sore foot - he examines THE PATIENT - see what i mean

sculptor

Rosullivan, Sorry for hijacking your post.
Sinnerboy, Thanks for your efforts, if you keep throwing mud at a wall some will stick, I'm not being sarcastic.
Would the prefered foiled backed pu. be taped at joints?

sinnerboy

not in the case of
OP - thick sometimes damp stone walls or
Scupltor - victorian red brick - damp - needs time to dry out

walls gotta breath

in case of say post 50's walls , with effective dpc's , intact external renders , functioning cavities i.e. dry walls - then polyurethane boards are your only man - nothing can touch them for thermal performance . BUT - vapour barrier is VITAL to the warm side of the insulation - a once dry wall may otherwise become wet from interstitial condensation

muffler

sculptor wrote: »

Sinnerboy, Thanks for your efforts, if you keep throwing mud at a wall some will stick, I'm not being sarcastic.

Are you not?

Take a deep breath and you'll be fine.

sculptor

A pun?

rosullivan

Question for Sydthebeat and Sinnerboy:

My (the OP) room is tight enough for space, but not hugely tight. I appreciate you say the layer of lime/hemp plaster is a breathable solution which doesn't take up much space, but I might be able to manage some actual insulation.

What would you suggest if I had enough space? Would I strip the internal walls back to the stone walls (i.e. remove the internal plaster). What then? Battens fixed directly to the stone wall (or would I put a breathable membrane directly against the wall before the battens?), 100mm of hemp insulation between the battens and 13mm plasterboard on top? Do I need any membrane on the inside of the insulation?? Do I still use the hemp/lime plaster if I have the plasterboard? Would it look like this:

Stone wall
Breathable membrane (which one?)
Battens with 100m of hemp between them
Membrane (which one?)
13mm plasterboard and skimcoat

I appreciate that this is just one aspect of the house. But it is the one aspect I am having most trouble working out.

sinnerboy wrote: »

not in the case of
OP - thick sometimes damp stone walls or
Scupltor - victorian red brick - damp - needs time to dry out

walls gotta breath

in case of say post 50's walls , with effective dpc's , intact external renders , functioning cavities i.e. dry walls - then polyurethane boards are your only man - nothing can touch them for thermal performance . BUT - vapour barrier is VITAL to the warm side of the insulation - a once dry wall may otherwise become wet from interstitial condensation