Insulation queries

skywalker_208

I see there are a few insulation threads with some good info. But what i need some advice on is insulation under the floor and in the ceiling.

Have 80mm (i think) of the black aeroboard stuff in the cavity and will also be drylining with the stick on slabs with insulation on the back of them.

I understand the ceiling in between the joists takes about 12" ? and will probably have room in the floor for about 4".

Not sure whether to go for fibre glass or spend an extra few quid and get rockwool etc.

any suggestions greatly appreciated

galwaytt

fwiw, I put Dow Floormate 2 x 50mm under my screed. Personally, I don't like fibreglass, and I always feel it 'packs down' over time. Rockwool should be better.

skywalker_208

thanks for the info there galwaytt

anon1

Drylining with the stick on slabs will eat into your room sizes, make sure your archtect is aware you are doing it as it may have unforeseen consequences.

Viking House

skywalker_208 wrote:

Have 80mm of the black aeroboard stuff in the cavity and will also be drylining with the stick on slabs with insulation on the back of them.

You need a ventilated cavity between the insulated slab and the wall to prevent condensation/fungus/mould between the insulated slab and the wall. This mess's up the U-values as the airflow removes heated air from between two layers of insulation. So I think drylining a cavity wall with insulated plasterboard is impossible to do correctly.

ardara1

Viking House wrote:

You need a ventilated cavity between the insulated slab and the wall to prevent condensation/fungus/mould between the insulated slab and the wall. This mess's up the U-values as the airflow removes heated air from between two layers of insulation. So I think drylining a cavity wall with insulated plasterboard is impossible to do correctly.

VH - show me a calc or evidence to prove your theories - you're constantly bringing this item to the boards and quoting some guru from Scandanavia who's written a paper on it. In the professional world we have work to European standards of measurement and acceditation - condensation risk for example to IS EN ISO 13788:2002 and BS54250 - we also set measurement standards of thermal bridging to IP1/06 - (before you jump on your next hobbie horse)

If you have EVIDENCE (or even calculations) that demonstrate that the specification mentioned are a load of tripe - then give it to us - there a many homes that, concrete block and timber frame that have recently used the spec.

wornout

here here,i am fed up listening to this crap! i have a house built with poroton blocks and paroc wool external insulation with no ventilation.if anybody is genuinely interested in this type of build,send me a pm i will gladly show it to you.

bakerbhoy

Well people .What are the facts.Can you insulate on both sides of the inner leaf of a cavity wall without risking '' condensation and mould'' and which types are compatable.
poly foil backed on both ?
rockwool in cavity foilbacked inner ?
do you vent the inner cavity?

muffler

There are underlying tones appearing in this thread. If I see this going in any way off topic or any comments made about other issues it will be locked and red cards issued if necessary.

Dont say you havent been warned

Mellor

Internal mould growth in a wall can happens due to interstital condensation. There ways to reduce the chances of this. Such as a vapour check. A cavity would severly affect the effectiveness of drylining.

The OPs question was in relation to insulation materials, there has been a few suggestions. My preference would to have all the insulation together in a new build. Half in cavity and half internal/external is more of a retrofit thing, Why not get it all the the same place.
When the OP gets back on he/she can answer the questions i suppose

ardara1

bakerbhoy wrote:

Well people .What are the facts.Can you insulate on both sides of the inner leaf of a cavity wall without risking '' condensation and mould'' and which types are compatable.
poly foil backed on both ?
rockwool in cavity foilbacked inner ?
do you vent the inner cavity?

Both the Accredited Details for Construction (Referred to in Part L) and the UKTFA give options for drylining block and TF walls - ensure that there is a seal behind the lining to avoid thermal looping and improve air permeability (as a fire break in any case) and a Vapour control layer to the inside.

skywalker_208

just to answer some of those questions - have allowed for the extra couple of inches that the drylining will take up - even in the corridor in the hall. rooms are all a good size anyway.

In relation to ventilation - left a hole in each room for a vent - i thought this was required as part of the regulations?

anyway what i was really asking about was the insulation in the ceilings and floors so if anyone has any advice on those that would be great!

ardara1

skywalker_208 wrote:

just to answer some of those questions - have allowed for the extra couple of inches that the drylining will take up - even in the corridor in the hall. rooms are all a good size anyway.

In relation to ventilation - left a hole in each room for a vent - i thought this was required as part of the regulations?

anyway what i was really asking about was the insulation in the ceilings and floors so if anyone has any advice on those that would be great!

Throw as much fibre in the roof space as you can - between joists then another layer running across the way - normally 270mm to meet curret regs - 2 layers 6" pretty good (Take care with light fittings)

Floors - 1. suspended timber? or 2. solid?

1. Pea netting suspended over joists then packed with fibre 6" - seal under skirting board with silicone sealant and seal under floor boards/chipboard
2. Consider 'floating' floor - chipboard 18mm directly over polyiso insulation - watch your head height.

If you're doing walls - don't forget about in between joists at 1st floor level,

Viking House

Concealed/Interstitial Condensation

Interstitial condensation is condensation occurring within or between the layers of the building envelope. The migration of water vapour through the building envelope by diffusion or air leakage brings the moisture into contact with cold surfaces causing condensation. This gives rise to serious deterioration of materials.


If you blow up a regular "airtight" balloon and leave it in your kitchen overnight it goes down to half size.
If an airtight balloon looses half its air overnight how are you suppose to seal every pinhole in an airtight house.
Not possible! The Scandinavians realised this 50 years ago so they allow their houses to breathe/sweat like your skin leading to a healthier living envoirnment.

Before you "Dryline " a wall it is usually cold, when you dryline the moisture gets through the joints and condenses on the cold wall causing fungus and mould inside your house.

The extreme differences between the inside and outside temperatures in Scandinavia raises the risk of Condensation, making people more aware of the implications.

Viking House

ardara1 wrote:

Throw as much fibre in the roof space as you can - between joists then another layer running across the way - normally 270mm to meet curret regs - 2 layers 6" pretty good.

A layer of paper between every layer of 10cm insulation increases the effect of the insulation by 30% because it stops the trapped heated air being blown out of the insulation "Windchill-effect".
Heavier insulation materials let the heat/cold through slower because of their higher density, so Rockwool works better than Fibreglass in your roof but Cellulose is better again.

Polysterene for foundations
Rockwool for walls
Cellulose/Wood fibre for roofs

And insulate to Passive levels of 0.15

smashey

Okay Viking House, why is it that we have a member of boards who has used the poroton block and paroc wool external insulation, with no ventilation and no moisture can get out of his house. Are you saying the current regs/practices that Ardara1 mentioned are not good enough? As ardara1 said, show us some evidence.

muffler

smashey wrote:

Okay Viking House, why is it that we have a member of boards who has used the poroton block and paroc wool external insulation, with no ventilation and no moisture can get out of his house. Are you saying the current regs/practices that Ardara1 mentioned are not good enough? As ardara1 said, show us some evidence.

Give him time to get the Scandinavian slant on things.

Come to think of it Im just going to make it a bannable offense to quote from regulations that are not applicable to Ireland. I will have no problem with anyone saying that they do it this way and that way in some country or other but posts from Viking House are copied straight from a manual that has no relevance here.

Debate shall not be stifled but we have to be practical and stick to what applies in this wee country.

anon1

Surely you are just insulating the external walls and not the hallway as well.

BadCharlie

I have underfloor heating in my ground floor. And i used 70mm Extratherm insulation. But now a year later and reading alot more i wish i did 2 x 50 to give me 100.

Also its very very important when doing underfloor heating to insulate all around the room up the walls. I had to glue my insulation up the wall about 4inch high in each room. You dont want to be heating your concrete floor and it heating the walls and going stright down into your foundations that be a weaste of money. The insulation will help keep the heat in your concrete floor.

Mellor

anon1 wrote:

Surely you are just insulating the external walls and not the hallway as well.

I thought that too, but the hall way might be so shaped so that it has a significant proportion of external wall.

Mellor

Viking House wrote:

Concealed/Interstitial Condensation

Interstitial condensation is condensation occurring within or between the layers of the building envelope. The migration of water vapour through the building envelope by diffusion or air leakage brings the moisture into contact with cold surfaces causing condensation. This gives rise to serious deterioration of materials.


If you blow up a regular "airtight" balloon and leave it in your kitchen overnight it goes down to half size.
If an airtight balloon looses half its air overnight how are you suppose to seal every pinhole in an airtight house.


Before you "Dryline " a wall it is usually cold, when you dryline the moisture gets through the joints and condenses on the cold wall causing fungus and mould inside your house.

Some of this is correct. Interstitial condensation can be a terrible problem, and it does cause mould, and poor proformance in building materials.

But your example and interpitation is wrong.
First of all the balloon example is ridiculous. The reason the balloon has decrease in size has nothing to do with air leakage. In fact there is exactly the same amount of air in the balloon (as long as it was tied correctly).

At constant pressure the volume of a fixed mass of gas is directly proportional to its temperature.
The balloon was originally blown up with air by mouth. Warm air at body temp, a warm environment. But overnight, the heating is off, theres no people in the room so the room cools, add this to the fact that the air was at body temp and is not at the temp of the cold room. so the balloon is smaller,
This law has no relevance in building, but I said i'd clear up the issue as what you said made no sense.

And as for the moisture condensing on the cold wall. The point at which moisture condenses is the dew point. It can be calculated very easily, by know the inside temp, the outside temp and the build up. The higher the humidity, the closer the dew point will be to the inner leaf, as it has to cool less before it condenses.
Two ways to control this are controlling the humidity in the room with a extraction system, or controlling the humidity in the wall, with a vapour check that slows the passage of moisture into the wall keeping the RH down.

In a well designed cavity wall (cavity or internal insulation) the dew point will be in the cavity (or the outer leaf), so the moisture condense here and the wall or insulation isn't affected. This is fine.

In a wall with insulation externally, the dew point will in the insulation, or even before it. It will condense in the structure. It has to, it has nowhere else to. If there is a cavity it will condense in here and its not too bad a situation, insulationm will be wet which could reduce proformance. But if it is a solid wall, it could create serious problems. As the wall will be wet inside. A vapour check will improve the position of trhe dew point, but it will always be in the wall as it cant condense outside the wall.*


*Unless of course the humidity is so low, or the outside temperature is close enough to the inside so that the air isn't saturated at any point. This will be the case in summertime, condensation isnt an issue in that situation no matter what construction type.

ardara1

By Golly Mellor - you've thought about this one!

Another on the Balloon - what is the permeability of the rubber material used for balloons - 500g polythene in houses is around 250MN/sg. (Taped foil is highr)

Another thing - whats the air pressure in pascals WITHIN the balloon? houses are measured at 50 pascals.

Don't blame me Mellor - you started it!!:)

Mellor

ardara1 wrote:

By Golly Mellor - you've thought about this one!

Another on the Balloon - what is the permeability of the rubber material used for balloons - 500g polythene in houses is around 250MN/sg. (Taped foil is highr)
I don't know the peribility of the balloon, but the beauty of the statements about is that they hold true even if it is fully airtight, ie gaps between bonds are smaller than the smallest molecule in the gas mixture.
Going for 36 degrees body temp, to 12 degrees, say the kitchen in morning, it would be 1 third the size. It has no relevence in building, I was making a point that the agrument holds no weight


Another thing - whats the air pressure in pascals WITHIN the balloon? houses are measured at 50 pascals.
Depends on the surface tension , but it would be over 100,000 Pascals which is atmosphere pressure. In testing the reduce the pressure don't they. 50 inside, 100,000 outside and measure the time it takes to even out. A pressure difference like this will never be incountered in a house.


Don't blame me Mellor - you started it!!:)

Out of curiosity, are semi-detached houses tested as a whole unit?

ardara1

Single unit only - they should be sealed from each other

silhouette

What about sheep wool insulation? I'm thinking of using it as attic insulation because my house is old and I've heard sheepwool is good in the breathablity department as its a natural fibre. I'd also feel more confidant about installing it myself coz its supposed to be very clean. Has anyone here used it? Does anyone know how it compares with other kinds of insulation in terms of price?

silhouette

silhouette wrote:

What about sheep wool insulation?

I'd also feel more confidant about installing it myself coz its supposed to be very clean.

Having just laid 120m2 x 400mm of rockwool, I couldn't agree more, itch! scratch! scratch (still got another 70m2 to go...)

I looked into sheepwool a little while ago and it cost approx 4-6 times that of rockwool, may be cheaper now.

Mellor

silhouette wrote:

What about sheep wool insulation? I'm thinking of using it as attic insulation because my house is old and I've heard sheepwool is good in the breathablity department as its a natural fibre. I'd also feel more confidant about installing it myself coz its supposed to be very clean. Has anyone here used it? Does anyone know how it compares with other kinds of insulation in terms of price?

Sheeps wool is more expensive, and it is ok from a thermal conductivity, not as good as the high spec quilt insulations, but sheeps wool has the benefit of being hygroscopic. This means that is regulates the moisture in the air. and it doesn't suffer from as much preformance dropping as other fibrous insulations.

silhouette

Thanks, Mellor and dolanbaker. I spoke to a builder today who reckons sheeps wool costs about 50% more than rockwool.
My attic is less than 30sqm so I won't be breaking the bank. So now all I need to do is work out how to teach the sheep to walk up the stira and close the hatch behind them

Viking House

Mellor wrote:

But your example and interpitation is wrong.
First of all the balloon example is ridiculous. The reason the balloon has decrease in size has nothing to do with air leakage. In fact there is exactly the same amount of air in the balloon (as long as it was tied correctly).

At constant pressure the volume of a fixed mass of gas is directly proportional to its temperature.
The balloon was originally blown up with air by mouth. Warm air at body temp, a warm environment. But overnight, the heating is off, theres no people in the room so the room cools, add this to the fact that the air was at body temp and is not at the temp of the cold room. so the balloon is smaller,
This law has no relevance in building, but I said i'd clear up the issue as what you said made no sense.

Hi Mellor

I was trying to provoke healthy debate here and I never called your posts ridiculous.

I blew up a balloon last night with a biycycle pump in the garden to test your theory, it was still reduced to half size this morning, try it yourself. If your theory is correct then the balloon should return to full size if I bring it inside, right!

I was trying to show that even a material as airtight as a balloon lets air through. Lots of moisture laden air gets into our walls/roofs even when you use a membrane and needs to get out.
The houses that Adara1 tested for airtightness were loosing the air volume of the house every 4 hours if my reading of the results is correct. Thats a lot of moist air getting through the walls and roof every day. If Polyeurethene backed plasterboard is used then this moisture is forced through the joints between sheets and onto the timber rafters/studs behind.

German results show that when a nonbreathable insulation was used externally, the U-value was 20% worse than expected because of the dampness built up in the wall because it could not breathe.
There are a number of claims into insurance companies in Sweden from people who bought timber frame houses with Polysterene insulation externally. There is a build up of moisture in the walls because they can't breathe causing decay.

Viking House

smashey wrote:

Okay Viking House, why is it that we have a member of boards who has used the poroton block and paroc wool external insulation, with no ventilation and no moisture can get out of his house. Are you saying the current regs/practices that Ardara1 mentioned are not good enough? As ardara1 said, show us some evidence.

Poroton pulls moisture through the walls hydroscopically without condensing like the old lime/stone walls in Irish houses.
You can open the top of the windows to let fresh air in. There is no vents in the walls of Most German and Scandinavian houses.
<SNIP>* but the house is really warm and needs little heating.
Xtratherm show details on page 6 of this document showing a cavity behind the drylining http://www.xtratherm.com/pdf/Xtratherm%20Specifiers%20Guide%20to%20Part%20L%20IRL.pdf
Interestingly enough they don't show the detail for drylining a cavity wall.
I don't agree with a lot of their details in this document like putting Polyeurethene in the roof, or drylining the inside of a timberframe house with Polyeurethene backed plasterboard.


* Edit by muffler: I have edited this post and I'm giving a yellow card but any further mention of personal matters here will lead to a substantial banning

2nd edit: This post contained a warning from a mod. It was deleted by the poster without consent. Red card offence. I dont want to see this happening again

mudz

wornout, i am having trouble trying to pm you. I am new to boards. Anyway, I am very interested in the Poroton blocks as a method of building. Can you tell me more. How did the blocklayers find them? How is the insulation value now that your house is built? Has anyone else any experience with these blocks? Anything you can tell me much appreciated. We are planning our self build at the moment.

Viking House

Mellor wrote:

In a wall with insulation externally, the dew point will in the insulation, or even before it.

I just checked the book I got from Weber and the "Dewpoint" with external insulation is on the outside 5mm of the insulation where any moisture build up easily dries.

I have the document in pdf from Weber but it is 310KB so too large for this forum. I can email it to anybody who is interested.

I just spoke to the Weber technical guy and he said that there are two areas of condensation risk with a drylined cavity wall with insulation in the cavity. Just inside the internal block and just inside the external block are the 2 risk areas.

Mellor

Viking House wrote:

I was trying to provoke healthy debate here and I never called your posts ridiculous.

I blew up a balloon last night with a biycycle pump in the garden to test your theory, it was still reduced to half size this morning, try it yourself. If your theory is correct then the balloon should return to full size if I bring it inside, right!

The houses that Adara1 tested for airtightness were loosing the air volume of the house every 4 hours if my reading of the results is correct. Thats a lot of moist air getting through the walls and roof every day.

I wrote a reply last night but my connection went, ill be keeping this brief (i hope)

First of all I am all for a healthy debate. My posts have always been "attacking the post" as smashey says. I made it clear which parts I agreed with, amd alot of what you say I agree with. But I disagreed with the balloon analogy. I always consider advice offer here on boards could be read by complete laypeople, and something taken up the wrong way could have severe affects.
The balloon comparisment was totally wrong imo. It loses volume due to temp change, this isn't a theory of mine. Its a scientific law, search for "Charles Law" if you still doubt me. After time the rubber degrades and air escapes, but all this does is highlights the need to use quaility materials as membranes. They have to be tested so that they wont degrade over a time.


As for the airchanges, I am not sure what units were posted so i dont know how long it takes for an airchange. But its not important at this time,
I 100% agree with you on this. That is alot of air passing through the fabric. There is alot of heat wasted this way. But you appear to ignore this factor when you talk about breathable walls. In walls were air can move through more freely, more air is lost, therefore more heat, and energy.
(It is very easy to calculate the heat lost this way, I did it a few hours ago for a small building)


The position of the dew point varies with RH% in the room, as well as temperature difference.
Saying it is in the 5mm of the external insulation is just wrong. There are unknown factors. The calculation to find it is very simple. The temperatures are junctions are calculated by multiplying resistance and thickess to get reduction in temp. As I said it is nearly always going to be in the insulation, but the colder it is outside the closer it is to warm side. This is one of the reasons for a cavity. To separate the source of moisture from the inner structure. In winter, moist external conditions will not allow this moisture to evaporate btw.
You said the dew point can evaporate from the external insulation without problem, this is connected to the internal structure. But you refer to a dew point in outer leaf of a cavity as a risk area. The dew point will be occur whereever it has to. There are no jumps in temperature between materials, it a a stead fall, the rate of which depends on the resistance. Most likely it will be inside a layer.

If I have time I will do up a drawing that shows dew point for a cavity wall with internal insulation and a solid wall with external.
With all the same resistances and thicknesses.



You claimed yesterday that poroton blocks allow moisture to pass through the walls without condensing. Could you provide a link, as I dont believe this is possible. Its a result of humidity and temperature, nothing else.



I actualy agree with alot of what you say, but very often something it applied to incorrectly, or to one situation and not to the other.

Viking House

Hi Mellor

I have a few documents I would like to send you for your consideration and debate. Can you send me an email so I can forward them to you. My email address is on my website. One of these documents explains and gives figures for the hydroscopic properties of different materials and their ability to handle/disperse water vapour.

And I will drop the balloon anology!!

wornout

christ,i have never heard so much bull**** in my life.a lot of people here seem to know what they are talking about.unfortunately there are others who know how to use these forums to tout for business,but cannot put what they are talking about into practice.i am thinking of having an open day on an eco friendly built house in south county dublin.anyone interested ?

muffler

Thats it. Viking House and wornout are both red carded.

sinnerboy

Tri iso super - had a stand at Plan Expo a couple of weeks back . Saw DS marvel at it on about the house recently too . Amazin'

Heard the news about it's losing its cert so I logged on to the BM Trada site 2 days back to check the status "from the horses mouth" .

http://www.bmtrada.com/site/html/home.html

To check the status of a product you have to enter your e mail address and the code of the product and wait for them "to get back to you" .... no reply yet

(042/0101 - is the Tri iso cert no by the way if any one else wants to "Tri" ):D