Insulating walls of old Farmhouse

webels

Hi all,
Just to start off, I am a total novice at this so take it easy on me. In the spring I will be getting an old farmhouse renovated. I was thinking about the insulation it may require. Th walls are drystone about 2.5 feet thick and do not appear to suffer from dampness. I have heard it would be better th insulate the inner (exterior walls). So from the more experienced out there what are my options?

Thanks for anyones advice.

tak

Insulating the outside face of the wall is no good as the capacity of a 2.5' wall for heat is enormous. Must be the inside surface you insulate.
The cheapest solution is 3" of mineral fibre under plasterboard.
Dearest is Celotex-type material (polycyanurate) which gives the same degree of insulation for a much thinner layer. Drawback is its cost.

webels

Thanks Tak
Where is celotex available in this country?

bradnailer

If the inside of your walls are in fairly good condition, try Xratherm warm board.
It's a high density insulation bonded to a 12mm plaster slab, it can be stuck to the walls with a bonding compound or drilled and fixed with plastic fixing called a mushroom and skimed, the fixing with mushrooms is probably better for your situation.
In areas where your going to need good wall fixing at a later stage eg. Kitchen,toilets, rads you can fix grounds before the installation of the warm board,then just remove the insulation in the area of the grounds

http://www.xtratherm.com/xtratherm/Literature/xttl.pdf

tak

Kingspan sell the same sort of product - ask for polyisocyanurate board.
The thickness matters a lot, since you're working on an old house.
You'll be asked for the cross-section of the wall, the type of filling, cavity size (if any), plastering details etc.
They will then work out the required thickness of Kingspan PIR that you would need so as to achieve a final acceptable U value. I think that 0.27 W/sq m K is the statutory minimum for U values in Ireland.
If you want lower U-values you therefore need thicker Kingspan panels.

Viking House

Old farmhouses are usually built using breathable lime mortar between the stones in the wall. This allows the wall to breathe and sweat. Using the above mentioned products stops the wall from breathing and concentrates the water vapour at the points in the wall where the sheets meet. This leads to condensation/fungus/mould at these points. The only way to dryline properly using these products is to put a ventilated cavity between the wall and the insulated plasterboard.

It would be better to use a breathable Hydroscopic insulation like Softboard that still allows the wall to sweat if you are determined to dryline but you should be aware that when you dryline you are only insulating 90% of the wall and you are left with big cold bridges where internal walls meet external walls.

But better still would be to use a breathable External Insulation that wraps around your building like a blanket.

Heavy insulation like a heavy coat keeps you much hotter for much longer so pick an insulation with a high density. Softboard is 10 times heavier than Polyeurethene for example.

muffler

Viking House wrote: »

Heavy insulation like a heavy coat keeps you much hotter for much longer so pick an insulation with a high density. Softboard is 10 times heavier than Polyeurethene for example.

Thats way of the mark VH and you know it. Please dont be misleading especially when you are in a position to understand the make up, density and properties of various insulating materials (or at least you make out to be)

Next we will hear that lead is much stronger than most metals because its heavier

Mellor

Density does not equal insulation, infact their is no relation.
I have said this many times over the years. VH by the same reasoning, we could say solid wood is an even better insulator, or go all out and insulate it with concrete.

VillageIdiot

At the risk of being labelled crazy, we have stripped the Kingspan insulated drylining from our 2.5 foot farmhouse walls on the ground floor. The character of the old stone was too nice to cover up. We painted the walls white with breathable sealer followed by white breathable paint (ridiculously expensive). Too early to tell if this will work. The exterior was finished with standard render plaster before we bought the house, so perhaps the walls are no longer breathable anyway. When we stripped the drylining, we noted some moisture on the walls, although nothing excessive. Probably rising from the ground.
The visual impact of the internal old stone walls is worth the condensation risk.

davidoco

4 years ago I drylined a building with walls as you describe. Got professional help to point the exterior walls using lime motar.

I used 3 x 2 treated timber set back from the wall, 5 mm or 10 mm depending on levels. Insulated between the timber with stryofoam (cheapest at time). 50mm or 70mm in places. No vapaour barrier inside insulation and regular plasterboard. No footpaths outside used french drains.

Worked out fine. Wouldn't compare to a modern cavity insulated house for holding the heat but it is not difficult to heat and is dry.

Viking House

muffler wrote: »

Thats way of the mark VH and you know it. Please dont be misleading especially when you are in a position to understand the make up, density and properties of various insulating materials (or at least you make out to be)

Next we will hear that lead is much stronger than most metals because its heavier

Hi Muffler

I am not misleading anybody, I am not saying that the density of the insulation affects the U-value but I am saying that denser insulations let heat or cold through them at different speeds. For proper heat loss calculations of a material you need a combination of Lambda Value, Density and Specific Heat Capacity. Here is a link to a thread in the Construct Ireland forum that discusses Decrement Delay in great detail and Heinbloed explains some of the science behind it.


http://www.constructireland.ie/vb/showthread.php?t=238&highlight=decrement+Delay

In the Mexican deserts the daily temperature can fluctuate from -5 to +40 but the temperature only fluctuates by 5-6 degrees inside the Adobe houses that are built from 14 inch clay walls. The U-value of the clay wall is quite low but the interion climate is very nice.
I know we are only suppose to discuss Irish building systems here but I didn't know a better example to make my point, so I apologise in advance for that. The first question I ask myself when building a house is "What temperature fluctation will I get when I build this house and how can I reduce this fluctuation?" For example the MosArt house is insulated to Passive Levels and has a temperature fluctuation of 12 degrees without heating.
We are trying to get the temperature fluctations down to 3-5 degrees without heating and Insulation alone will not do that. The lower the fluctuation the lower the heating/cooling costs.

webels

Thanks to everyone for their input and it seems to me that there are many ways this job could be done so I will get back to this thread armed with all your ideas and let you know what was decided on.

tak

Hold on Webels.
You can't just open a can of worms and run off.

There are many of us looking to sort out old farmhouses.
Problem is there is a whole variety of types of build for farmhouses across the country depending on the local materials, traditions, etc.
VH talks about lime mortar. Round parts of Kerry it was often just a heavy yellow mud that was often used in 1800s.
As well so many of these were given various degrees of improvement over the years. As poor as they were most people scrimped and saved for a bit of cement to plaster the inside walls at least.
Then in the 1950s a lot of originally thatched houses were raised to 2 storeys
and while the builders were doing this they often plastered the outside and maybe redid inside as well.

So you should examine your walls well first and make a cross-section sketch.
If necessary get a local (older) tradesman to look the place over with you if you are't sure of how it was done.

After you do that we can all give proper ideas to you. Maybe Muffler will make a sticky out of it for future farmhouse conversions - and maybe barn conversions too.

But whatever you do - do not insulate from the outside. It will cost a rocket and make no real difference to your heating bill.

webels

I am going nowhere Tak, I am gonna keep an eye on this thread with great interest. The house is in Cork and from memory having helped to replaster the outside of the house (It was built around the start of the last century), the walls are made from mixtures of flat and round stones and plenty lime mortar (I think) but I will definitely check that out possibly this weekend. My Uncle will be able to help me there.
I kinda guessed that this might be a popular topic and making it a sticky might be very useful for people in the future. I wont go down the road of insulating from the outside as I already said the walls were newly plastered 15 years ago or so.
Again thanks to all for your comments and keep this going for me and all those interested in keeping these old houses standing.
We are also taking up the floors and redoing ceilings so it is a fairly major project - might use the expertise round here for that too.

Mellor

Viking House wrote: »

Hi Muffler

I am not misleading anybody, I am not saying that the density of the insulation affects the U-value but I am saying that denser insulations let heat or cold through them at different speeds.

No, the heat that passes through is defined by the u-value alone.
This is the definition of a u-value, the heat passing thround the material for every degree in temp difference.

For proper heat loss calculations of a material you need a combination of Lambda Value, Density and Specific Heat Capacity. Here is a link to a thread in the Construct Ireland forum that discusses Decrement Delay in great detail and Heinbloed explains some of the science behind it.

Those are not needed for HEAT loss. You are confusing heat and temperature, they are not the same thing. They can be used to estimate heat capacity of the wall, this is different altogether and doesn't affect heat loss but internal climate.

In the Mexican deserts the daily temperature can fluctuate from -5 to +40 but the temperature only fluctuates by 5-6 degrees inside the Adobe houses that are built from 14 inch clay walls. The U-value of the clay wall is quite low but the interion climate is very nice.

This is where high heat capacity of walls helps, when the outside temp is high and has a high range. Here the walls absorb the heat passing through. And the climate fluctuates less (it is not keeping the heat out, same heat is getting through as any wall with the U-value, but the high heat capacity means this heat reaches a lower final temp. This is the difference between heat and temp.

There are two things wrong with this, rarely (possibly never) will irish houses want to keep summer heat out.
And secondly, the inverse of this is that the high heat capacity means than a house takes longer to heat up.

We are trying to get the temperature fluctations down to 3-5 degrees without heating and Insulation alone will not do that. The lower the fluctuation the lower the heating/cooling costs.

Fluctuations do not equal lower bills. Infact they could increase them in certain cases, high heat capacity means more heat (money fuel money) is require to reach the desired temp.




And a final point, probably the most critical. Heat capacity is important for certain structures, and it is a worthwhile temp control strategy.
BUT its the heat capacity of the WHOLE wall that is important. Not just the insulation.
Using softboard increases the heat capacity of the stone wall in the example above, but the increase is tiny compared to the basic heat capacity of the wall due to the sheer mass of the stone.
I can do a calulation and post it up if you dispute this.

Viking House

Hi Mellor

Maybe we have to agree to differ on this one but I enjoy the debate. Here are some comments on your comments!

Mellor wrote: »

This is the definition of a u-value, the heat passing thround the material for every degree in temp difference.

One vital element is missing from this calculation! It should be U-value x Time!

Mellor wrote: »

They can be used to estimate heat capacity of the wall, this is different altogether and doesn't affect heat loss but internal climate.

How do you explain then the difference in the heating/cooling cost between house A and House B in this link? http://www.viking-house.ie/decrement-delay
They are both insulated to the same U-value.

Mellor wrote: »

This is where high heat capacity of walls helps, when the outside temp is high and has a high range. Here the walls absorb the heat passing through. And the climate fluctuates less (it is not keeping the heat out, same heat is getting through as any wall with the U-value, but the high heat capacity means this heat reaches a lower final temp. This is the difference between heat and temp.
There are two things wrong with this, rarely (possibly never) will irish houses want to keep summer heat out.
And secondly, the inverse of this is that the high heat capacity means than a house takes longer to heat up.
Fluctuations do not equal lower bills. Infact they could increase them in certain cases, high heat capacity means more heat (money fuel money) is require to reach the desired temp.

Most Irish houses never get a heating advantage from the Summer sun through the wall as most of the heat that comes through the outer skin goes up the cavity.
Using the correct building materials can buffer external temperature fluctuations and lower cooling/heating costs as you can see here http://www.viking-house.ie/decrement-delay, have a look at the graphs in the blue boxes under House A and House B.

As you said above "the high heat capacity of the wall means the high midday heat reaches a lower final temp inside", but doesn't this also works in reverse for heat loss going in the opposite direction, lowering your heating costs. The high heat capacity of the wall means the high internal heat reaches a lower final temp outside. Meaning less heat loss for the same U-value.

Mellor wrote: »

And a final point, probably the most critical. Heat capacity is important for certain structures, and it is a worthwhile temp control strategy.
but its the heat capacity of the WHOLE wall that is important. Not just the insulation. Using softboard increases the heat capacity of the stone wall in the example above, but the increase is tiny compared to the basic heat capacity of the wall due to the sheer mass of the stone.

The OP was being advised to dryline with a lightweight non breathable insulation. I suggested that he dryline with a natural breathable insulation that was 10 times heavier than Kingspan and would help to buffer temperature fluctuations. My suggestion would not require a ventilated cavity behind the insulation as the Stone wall/Softboard would act together to give a breathing sweating wall.

Mellor

Viking House wrote: »

Hi Mellor
One vital element is missing from this calculation! It should be U-value x Time!

Thats true I forgot to include that it is heat loss per second. But I think we are all aware that I already knew this.
And my previous comment still stands, U-value is a measure of heat loss. Heat = energy. Your comments confuse heat and temp.

How do you explain then the difference in the heating/cooling cost between house A and House B in this link? http://www.viking-house.ie/decrement-delay
They are both insulated to the same U-value.

I already explained it in my previous post.
In the example the outside temp is much higher than the inside. This doesn't happen in ireland. There is no heating cost in the example as it is in the middle of summer. There should never be a cooling cost for an irish domestic building. There should never be a cooling cost for most large buildings either.

Most Irish houses never get a heating advantage from the Summer sun through the wall as most of the heat that comes through the outer skin goes up the cavity.

Why would you want a heater advantage in summer?

Using the correct building materials can buffer external temperature fluctuations and lower cooling/heating costs as you can see here http://www.viking-house.ie/decrement-delay, have a look at the graphs in the blue boxes under House A and House B.

Here is the same link as above. So my previous comments stand. This doesb't apply to ireland. In the example the external temp range is from 10 degrees to 35 degrees. Can you please provide met eireann records that show when this happened in ireland (or scandinavia)?

As you said above "the high heat capacity of the wall means the high midday heat reaches a lower final temp inside", but doesn't this also works in reverse for heat loss going in the opposite direction, lowering your heating costs. The high heat capacity of the wall means the high internal heat reaches a lower final temp outside. Meaning less heat loss for the same U-value.

No this doesn't work in the other direction, as I already said out. The fact that you suggest it doesn't reflect well.

When the external temp is higher heat enters the house through the wall. The heat entering the house is the same for all construction if the u-value is the same. But when the wall has a high heat capacity the wall can absorb more of this heat for every degree rise in temp. So the same heat results in a lower temp.

When it is warmer inside, heat(as a unit of energy) escapes the room or building in accordance with the U-value rate. As I have said again and again, the rate of heat loss for the room is always the same if the u-value is the same (this is a u-value). When the heat capacity is higher (in heavy construction) the room doesn't retain any more heat. The same heat leaves the room and as before the temp of the wall is lower. This lower temp doesn't reflect heat loss. It just reflects the slower rise in temp of the structure for every joule of heat. All heat lost has to be replaced by the boiler. In some cases the boiler must produce more heat with heavy construction so as to comp for extra heat required by the structure for every degree rise required.


[/quote]The OP was being advised to dryline with a lightweight non breathable insulation. I suggested that he dryline with a natural breathable insulation that was 10 times heavier than Kingspan and would help to buffer temperature fluctuations. My suggestion would not require a ventilated cavity behind the insulation as the Stone wall/Softboard would act together to give a breathing sweating wall.[/QUOTE]
I am not disputing the breathability argument.
What I am disputing is comments such as

Heavy insulation like a heavy coat keeps you much hotter for much longer so pick an insulation with a high density. Softboard is 10 times heavier than Polyeurethene for example.

and

I am not saying that the density of the insulation affects the U-value but I am saying that denser insulations let heat or cold through them at different speeds. For proper heat loss calculations of a material you need a combination of Lambda Value, Density and Specific Heat Capacity

The first because it is worded in a misleading way.

The second because denser insulation do not let heat or cold through them at different speeds. And because for a stone wall the insulation used does not affect the heat capacity.
You only ever apply the advantage of dense materials to insulation and I have repeatedly called you out on this. The whole building structure should be assessed. The mexican huts for example have no insulation, simply mass. You bring up the advantage of mass in relation to insulation, but you never mention it as a disadvantage to timber construction, or Poroton blocks. The difference in mass between polyiso and paroc is nothing to that between timber frame and mass concrete.

Viking House

Mellor wrote: »

Thats true I forgot to include that it is heat loss per second. But I think we are all aware that I already knew this.
And my previous comment still stands, U-value is a measure of heat loss. Heat = energy.

Isn't it W/(m2K), No mention of time here.

Mellor wrote: »

But when the wall has a high heat capacity the wall can absorb more of this heat for every degree rise in temp. So the same heat results in a lower temp..

Exactly!

Mellor wrote: »

When it is warmer inside, heat(as a unit of energy) escapes the room or building in accordance with the U-value rate. As I have said again and again, the rate of heat loss for the room is always the same if the u-value is the same (this is a u-value). When the heat capacity is higher (in heavy construction) the room doesn't retain any more heat. The same heat leaves the room and as before the temp of the wall is lower. This lower temp doesn't reflect heat loss. It just reflects the slower rise in temp of the structure for every joule of heat. All heat lost has to be replaced by the boiler. In some cases the boiler must produce more heat with heavy construction so as to comp for extra heat required by the structure for every degree rise required..

This contradicts your comment above.

Mellor

Viking House wrote: »

Isn't it W/(m2K), No mention of time here.

This post just proved that you don't understand the topic.

W/m2k= watts per metre squared per degree kelvin
The watts represents the time factor.
The watt is the SI unit of power. It is equal to one joule per second., energy per unit time.

Viking House wrote:

Mellor wrote:

But when the wall has a high heat capacity the wall can absorb more of this heat for every degree rise in temp. So the same heat results in a lower temp.

Exactly!

You still don't understand here. The wall absorbing more heat per degree rise is an advantage when the heat is entering, it keeps the room cooler.
When the heat is leaving there are two outcomes, the heat leaves the room at the same rate!!.

• The structure of the wall will be cooler. There are no savings here in terms of energy, or
• More heat is required to get the room to the optimum temp. This results in a higher required output from the boiler.

This is common knowledge, Houses of mass concrete for example take longer to heat up,

This contradicts your comment above.

No it doesn't. You are mis-applying the info.
Hot day, heat enters the house, the rate set by the u-value, the wall absorbs lots of heat, and the temp rises slowly in the room. Heat is the room rises, it is comming from outside.
Cold day, the heat leaves the house, the rate set by the u-value, the walls absorb lots of heat, the temp falls in the room as the heat in the room falls, the heat is going to the outside. The heat is leaving the room so the wall doesn't affect climate.

Mellor

Is there a reason you failed to comment on the following:

Mellor wrote: »

In the example the outside temp is much higher than the inside. This doesn't happen in ireland. There is no heating cost in the example as it is in the middle of summer. There should never be a cooling cost for an irish domestic building. There should never be a cooling cost for most large buildings either.

Here is the same link as above. So my previous comments stand. This doesn't apply to ireland. In the example the external temp range is from 10 degrees to 35 degrees. Can you please provide met eireann records that show when this happened in ireland (or scandinavia)?

I realise I sound like I am bias regarding dense insulation . This isn't the case, I dislike misinformation and mis-application of sound information. Its a terrible problem in the building industry, espiecally regarding anything relating to energy. One only had to look at and compare an ad for concrete built verses timber built.
I am not disputing that their are advantages to rockwool paroc or similar as an insulator, as there are definate advantages. But the advantage of density in one sense doesn't always apply. Same as the breathability of the insulation in one sense is a loss in another.

jerryob

Hi. First post, so I hope I don't break any rules...

I realise this deviates from Mellor .v. Viking House's interesting debate, but I'd like to add an option for for damp proofing webels 2.5" stone walls.

I too am renovating an old house, not lived in for 30 years. It's southernly facing, with a cavity wall extension built on eastern end. I dug out alot of rock outside the northern wall, making sure to have it well under floor level. I am now starting the process of putting down the floor - the surface is currently very damp, and I expect this dampness to creep up the walls over time, even though the surfaces have been newly plastered.

My Dad is retired from the trade for years now, but used to swear by a membrane he refers to as dry-lath. It has evolved over the years and I have tracked down the latest version to what's called "plaster lath". See product brief at http://www.deltamembranes.com/waterproofing_membranes/delta_plaster_lath/delta_plaster_lath1.htm. I intend to add dry lining on top of this membrane. I don't have any technical or scientific argument to make for this method, only my fathers years of experience.

Thoughts anyone?

sinnerboy

this used to be known as newtonite lath . it is expensive

it's best appliacation is in basement areas of protected ( histroic ) structures , where no decorative or other finish of architectural merit ( in the opinion of the LA conservation officer i must stress ) exists . it follows the conservation priciple of reversibility - it can be removed leaving the historic structure unaltered . dublin city council have prohibited the use of chemical dpcs in protected structures - as this is not reversible .

in this applcation , the membrane is used as a "3d wrap" . you dig up the floor and form a new conc floor with the membrane on a conc subfloor . then insulation and screed follow on top . the mebrane is carried up the wall to ceiling level - dry lining follows . you must ( discretely ) locate wall vents to relive vapour presure to the external

you are not "curing" the damp ness - just isolating the dampness from the internal climate

the old newton system was used a a quick fix from (top of ) floor to ceiling . very important to leave a vent strip below skirting and just below ceiling to stop vapour pressur build up . a quick fix as i say , never liked this - the damp extenal wall is "breathing" to the internal climate

i would need to know more about your situation to give solid advice but i dont belive newton/delta is your answer

jerryob

Thanks sinnerboy - all this makes sense. Yes it is expensive!

It is at ground floor level that I am putting this in at. I was considering just putting in dry lining only (or a variation on it), but didn't want to take the chance that digging out the rock over floor level outside the house would prevent dampness coming up through to the inside finished-wall surface.

Due to expense, I was considering taking following short cut, which you may advise against.
ooo The plaster-lath comes in 6' wide rolls. I plan to cut in half and only apply from floor to 3' up. Hence, there will be no venting strip on top, i.e. only venting with be floor level strip; no vent holes/pipes thru the wall

I note you recommend "form[ing] a new conc floor with the membrane on a conc subfloor . then insulation and screed follow on top". This sounds like there would be no floor-level venting strip.... I was planning on putting plaster-lath in on top of insulation/screed.

I have one issue with my approach though, accepting the short-cut of no "ceiling-level" venting strip and your misgivings. I plan to put in semi-solid maple flooring at ground-level afterwards. I expect that dampness droplets would form behind the plaster-lath and fall towards floor-level. This would come out the venting strip and damage the wooden floor. Yes, a "ceiling-level" venting strip would reduce this, but not get rid of it....

I understand your concern that plaster-lath does not fix the dampness issue, but it should improve things as I was considering only putting in dry-lining. Oh yes, I'm also under time pressure, as my sister is moving in in June, and I can only give 2days a week over to this...

rosullivan

I'm having a similar job done on a similar farmhouse. The external walls of the farmhouse are 2ft thick and are of typical stone/rubble/lime plaster construction. At some point the house was rendered - I am still waiting on final advice about whether the render is concrete or lime, but I'm guessing concrete (bad news for me).

The house has not been lived in for about 10 years and is damp inside. There is what looks like rising damp but there is certainly damp and mould on the walls. The wood inside (floors, ceilings) are ruined from dry and wet rot (and woodworm).

I have been advised to recognised the fact that these houses were designed to have breathable walls. The walls soak up mositure when it's wet and release it as evaporated moisture when it's dry. Accordingly I will be re-lime rendering the outside if necessary (expensive but may have to be done).

On the inside, it also has to breathe. Dry-lining will only hide the moisture and mould behind the drylining - not good. I have been advised to apply Delta Membrane to the interior walls as my dry lining. It is supposed to allowthe external wall to continue to breath and will allow air to circulate, but it will prevent an excess of moisture coming into the internal room. I have been told I can insulate and plaster over the interior surface of the Delta Membrane.

The membrane will run from floor to ceiling (and under the concrete floors which have to be dug up and re-laid). There will be vents to allow for air movement.

I ain't no expert on this. I am always wary of hiring a "damp consultant" as they usually either have a product to sell, or they used to work for years in acompany that had a product to sell. Does that use of the Delta Membrane all sound right? As regards insulation, I'm as interested as the OP to know what to use, but I recognise that an old farmhouse will never be as warm as a new build - but there are other advantages to an old house.

Hells_Belle

I'm very interested in this topic as well, since we're looking at rennovating a terraced house with 2.5 foot stone walls. As far as we can tell, they just plastered over the stone on the interior - no studs, lathes or insulation. There is a small amount of rising damp coming up over the skirting boards in places, about 3" which isn't much considering the age of the house and the fact it has no central heating. Were the damp a serious problem, I'd expect much higher levels on the walls.

We're hoping that central heating will sort this to some extent, but I'm looking for the best insulation and damp-proofing solution. The Delta Membranes look like an excellent approach, but can anyone tell me if they're appropriate for party walls, as with a terraced house?

Builderfromhell

Briefly, I used Delta membrane on a new office building basement in London some years back. Great product in theory but I cannot emphasise enough the need to fit it properly. Especially at corners and where pipes etc. penetrate walls. Only needs one bad joint and you have water poring in.:(