Dry Lining - recommendations

voodoo

Hi all,

Just a quick query. I am going to dryline the external walls of my new build and wondered what is the best boards to go with. We have put 80mm in the cavity and I was thinking of a 52mm board inside.

Read somewhere on here about a new dry line board which is thinner but gives as good a U value but cannot find it...

Any advice?

beyondpassive

Dry lining is a bad idea it moves the dew point to the inside face of the blockwork. In other works the drylining will keep the inner leaf cold, therefore any humidity will condense behind the drylining and cause mould problems. This becomes a problem where floor or joists meet external walls as the drylining stops and is not continuous at the floor junction.

The 80mm of PIR in the cavity should help, if you have to dryline, you could consider doing it with vapour barrier and natural insulants like wood fibre.

heinbloed

Get the whole job calculated for the " Dynamic Dewpoint ", using a software lke ' wufi+ ' for example.
As beyond passivehouse said already drylining is a bad idea if done by incompetent people.
The likelyhood to lose more money in the long run than there will be saved in the short time is high. Once there are mould spores causing health trouble the hole building can be condemned, resulting in a financial total loss.
Consider as well that gas filled insulating foams will have lost their superior-but-expensive thermal insulation properties at the latest after 25 years when used in standard building aplications.

Look also at the contents of the insulant being used, there might be hazardous chemicals included like
flame retardents:
http://www.empa.ch/plugin/template/empa/*/54785/---/l=2
and other substances as well.
There seems to come up a surge of legal battles on the EU continent about some chemicals worked into technical foams.

YourAverageJoe

i am having a similar problem deciding on drylining thickness. I have decided it is the way i want to go but i am trying to decide on thickness.

Some posters say max 1/2 of the cavity insulation thickness is max of internal dryline thickness, as a rule of thumb.

I have spent the last 2 hours downloading and installing wufi. I have tried to the best of my abilities to run it for my scenario.

Does anyone here know how to interpret the results?

If so the results attached are for 70mm cavity and 40mm internal board (not including plaster board).

If not, can anyone tell me the details of someone whom i could get to run the calculation for me?

beyondpassive

have you set up a monitering position. you can collect the moisture content at the position using the moisture storage function or else set up a thin diagnostic layer. ....or something

http://www.wufi.de/index_e.html

there is a 'building life consultancy' type firm which specialises in Wufi, talk to joe as they say.

clint_eastman

heinbloed wrote: »

As beyond passivehouse said already drylining is a bad idea if done by incompetent people.

Hi Heinbloed,

I intend on using a 50mm dryining on my external walls which are 150mm cavity construction with fully pumped cavity insulation. I'm trying to understand yours (and beyondpassive's) stance on the whole idea of drylining. Is it good or bad, or good only when installed properly? Or is it the answer to that dependent on the results of a software analysis as disussed above?

I'm not intending on installing the boards myself but would have assumed the process to be quite straightforward for a trained professional, I mean how complicated could it be? Is there any obvious issue that should be looked out for?

voodoo

Clint,

I am of the same opinion... I have worked with my BER Assessor who said that if we go the way we are - 80mm cavity insulation with a 52.5mm insulated board this would give us a really good U value...

Are people suggesting that dry lining wont work, even if done by a competent person or are you saying that if done correctly, it's a very good system? Very confused and getting to the stage that I need to REALLY worry about this now as my trusses go up tomorrow and plastering is only around the corner...

Smcgie

Keep an eye on the kingspan kooltherm range. Its a phenolic foam based product that can have a thinner application than that of ordinary PIR rigid boards.

S.

heinbloed

@ clint_eastman:

"Drylining" can mean a lot of different materials and methods.

The main point for this exercise is to increase comfort, be it it particulary in this room or generally by having to spend less on fuel.

Both wishes should be served in the long term, a sustainable solution has to be looked for.
With many standard methods this can't be done in the long term. The systematic failures which might be build-in will hit back.
Either the insulant chosen will lose it's insulating qualities or mould would grow behind it or both - if the system fails.

Speculating on the one or the other insulation method could be done by looking at the worst case scenarios. Like buying an insurance policy someone has to fork out for the risks involved.
To reduce this financial risk wufi was developed. In the USA a different but propably as good method is used by responsible builders.

Ask your architect if he used wufi or the US method or if he used the Glaser method.
Get his/her calculation in full, showing the standard to which it was done.
Use the www for " Glaser method ", an internationally recogniced but outdated method. (Outdated when calculating differing circumstances like moisture and temperature in changing climates. But otherwise still the standard method.)
When looking for Glaser you'll find plenty of English pages offering calculation sheets, excel and the like, for free. Try them, include extreme values which might only occure once in 50 or 100 years. These programs are for free, play with them. Find the static limits of your insulation method.

And if these limits are somewhat going near to your planned insulation method stay away from this method. Use a different aproach.

This is the amateur's way. Step for step trying to eliminate the worst case scenario.

The professional would use a dynamic dew point analysis straight away. Because he/she would have to sign responsible for the recommendations given. Meaning he or she has to to show that '1+1=2' and not only that '1-1 is not 2'
If you have a particular recommendation from a professional and he/she is not willing to tell you how that was done then very likely the cheaper Glaser method had been used. Which is for free, tought on any university. But rather risky for external walls in our climate.

A proper dynamic calculation costs a few hundred €s, maybe the total enery saving of an entire year. But it will give peace of mind for the rest of the buillding's lifetime. No mould, bills slashed and a full guarantee for the materials used. And - important to be a professional building investor- a solid base to calculate the profit of the investment.

So - being in your position- I would go for the professional method.

An architect should advise you to do the same, if not then ask why...

Note that some insulation materials will partly lose their insulating properties over the years, namely the gas filled insulants as well as vacuum insulants. Note that some insulants are not suitable to cope with moisture, others might contain hazardous substances. The Queen's pot brand springs to my mind....gas filled and hazardous chemicals containing.
Recycling cost should be included. Asbestos was a formidable mateial for investors until... well, until it's capacity to last forever hit back.

It is important to look at corners, reveals, at floors and ceilings and partition walls when looking for potential mould risks with internal insulation. Glaser covers this detail only very limited. Wufi would give a much better, more accurate prediction for these detailed (but usually first-hit) places.

" ....good only when installed properly? Or is it the answer to that dependent on the results of a software analysis as disussed above? "

Yes and yes.

The temperature of the internal wall will be reduced, it won't get as much thermal energy in Winter time as it did before. If there where condensation problems they will increase. For example around doors and windows. If there wheren't any condensation problems so far these MIGHT turn up after installation.

With all internal insulation methods it is important to note that all organic material existing at and in the to-be-insulated walls would propably have to be removed: timber lintels/-plugs, wall papers, paints, glues, plasters containing organic materials. Maybe floor/ceiling joists as well.

Ask the one detailing the job why this work is not included in the pricing. If it is stated that this is not necessary ask for the dynamic dew point calculation to prove it. That's the way to eliminate the cowboys from the trade. If it isn't necessary the installer will have no problem to show evidence, a calculation sheet. It mightn't be necessary at all anyway- but ask why, ask for a written statement.

About wufi users:
There are only a few architects/engineers and other trade personel so far in Ireland who are actually using this software. Shop around, looking over to the USA/UK/EU continent per internet might be usefull for pricing and service.
You're on the right track once you start asking questions.