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Internal wall insulation using cork
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mikepepler
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Joined: 24 Nov 2005
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Location: Rye, UK

PostPosted: Sun Feb 19, 2017 10:37 am    Post subject: Internal wall insulation using cork Reply with quote

Although we've insulated most of our house, there's one problem area - the walls either side of our dormer windows. They are simply plasterboard on studwork, with hanging tiles on the outside. One day I hope to have all the tiles taken off and insulation put under them, but that could be some time away.

This week it was suggested to me that I could use up to 50mm cork insulation on the inside, as it's breathable. However, I have a few questions, if anyone here can help:
1. Can I fix the cork directly to the plasterboard? What adhesive is best if so?
2. Is there any risk of condensation forming between the cork and the plasterboard, or does the breathability deal with this?
3. What kind of paint or other decorative finish should be used, given it needs to be breathable?

Thanks in advance for any advice!
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adam2
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PostPosted: Sun Feb 19, 2017 10:59 am    Post subject: Reply with quote

If the plaster board reaches a temperature below the dew point, then I suspect that it will get damp or even wet and disintegrate.

The cork being porous will I fear allow a slow but steady stream of relatively warm and damp room air to come into contact with the now much colder plasterboard.
Calculations can be done to determine the dew point, and the temperature of the plasterboard, but I have limited faith in such. The very variable weather, varying temperature and humidity indoors make calculations a bit moot.

Would it be viable to remove the plasterboard, and then insulate the void thereby revealed, working from the inside. Plasterboard is reasonably cheap to reinstate, and the advantages of working from indoors and not disturbing the external tiles may make this worthwhile.

Alternatively, might it be worth permanently removing the plasterboard and fitting instead some rigid insulating foam board that is impervious and sealing the joints with tape.
The inside of such board will be very close to room temperature and condensation most unlikely.
The outside of such board will be cold and also not attract condensation, as it will not be exposed to warm and damp indoor air.
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mikepepler
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PostPosted: Sun Feb 19, 2017 11:23 am    Post subject: Reply with quote

Hmmm, I can see that would be easier that working from the outside, but it might be more than I can easily take on myself, with zero experience in doing stuff with plasterboard and walls... I don't to end up with a DIY disaster! Smile
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woodburner



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PostPosted: Sun Feb 19, 2017 2:56 pm    Post subject: Reply with quote

I've deleted the original post. I read the next two posts by K-L and LJ and consider mine rubbish. Must have suffered from excessive mould.

Last edited by woodburner on Mon Feb 20, 2017 8:52 pm; edited 1 time in total
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kenneal - lagger
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PostPosted: Mon Feb 20, 2017 4:12 pm    Post subject: Reply with quote

It is very difficult to get a fully vapour proof covering and in any case there will be moisture movement around the edges of your "vapour proof" perimeter into the cold area behind the insulation. This area comprises structural timber and it will get wet, very wet, on occasions so you shouldn't leave it too long before you insulate properly on the outside.

My daughter has just built an extension and put the insulation into the studwork on the inside before insulating the outside. It's been up for three or four months and the OSB sheathing is very wet inside. It will dry out but that gives you an idea of what to expect if you insulate the inside only. They are now thinking of finishing the external insulation before putting the plasterboard on the inside to give the OSB a chance to dry out.

I wouldn't have thought it worthwhile to insulate the inside rather than whipping the tiles off and insulating between and over the studwork of the dormer.
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Little John



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PostPosted: Mon Feb 20, 2017 4:58 pm    Post subject: Reply with quote

My general instinct when it comes to dealing with damp is to:

a) use materials that can get damp and then dry out without suffering too much.

b) have all areas well ventilated.

You can't beat damp unless you are prepared to spend a lot of money on high tech materials. And, even then, the damp will win in the end. High tech materials just cause the damp to win a bit later than it might otherwise have done.

To take one example - rising damp did not particularly exist before the widespread use of gypsum based plaster and renders and hermetically sealed houses. Prior to that, it was all lime and lime breathes moisture in and out.

If I had a wooden building, I would treat the outside with a wax based covering that would repel most water. On the inside, I would have a wooden skin such as match-board. The advantage of match-board is that if one of two of them get rotten they can be replaced easier than if it is one single big sheet of something like WBP plywood. In between I would have an air permeable insulator (such as straw) that still allowed moisture to pass through. And finally, all wooden structures should be several inches above ground level.

I have only ever broken the above principle once and that is on the current house I am renovating. I had to build a shower in an area where it was only possible to use stoothing walls and plasterboard. There is no underlying problem with damp (it's on the first floor). But, obviously, the area gets very wet once every few days. So, I have used a fancy high tech waterproofing covering on the shower walls prior to tiling them. It's been several months now and no problems thus far.

Time will tell.
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mikepepler
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PostPosted: Tue Feb 21, 2017 3:35 pm    Post subject: Reply with quote

Thanks for the advice. From what Ken and LJ say, it sounds like for now I should just increase ventilation a bit (after all, my heat source is logs and I have a *lot* of them, so a bit more heating is no big deal) to avoid damp in this spot.

Ken, when I then come to insulate from the outside, by removing tiles, it sounds like this should be a really thorough job, with membranes, insulation boards, etc.? The flat roof would be coming off at the same time, to be upgraded, as at present it has some temporary insulation I was able to slide in from the loft. My plan is to save up for this and pay someone to do a proper job.

I'm thinking of getting a professional assessment done on the house to look at these issues and other efficiency upgrades I could consider. I'm wondering whether a Passivhaus person with experience in retrofit is best, or someone else?
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kenneal - lagger
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PostPosted: Wed Feb 22, 2017 3:55 am    Post subject: Reply with quote

Mike, you need someone who can design the installation properly so that all the components join up to form a continuous layer in their various positions; the dormer insulation must be continuous with the roof insulation for example.

The flat roof would only need to come off if the timbers or, more likely, the skin need replacing because of damp damage. If the flat roof covering was shipboard it is quite likely to turn to dust after 5 to ten years. If the covering is solid insulate on top of the felt and then join the new felt to the old to encapsulate the insulation. Unless you are very lucky you are unlikely to find anyone locally who has more knowledge about building to modern insulation levels and methods than you do. It's not beyond the realms of the competent DIYer.

I would be looking at Enerfit, the Passivhaus renovation equivalent, levels of insulation to take you forward. You can then sell much of your wood to make you an income in the future. I would not go down the MVHR route as this is not, in my opinion, resilient enough. You have an ongoing 24/7 energy requirement and then you need the spares to be available indefinitely.

There is available a passive stack ventilation system with a heat exchanger on it called Ventive (in which I have no financial interest) which seems to work well. You could also just set up a manual passive stack system using either a Velux/Facro window in the roof above the staircase or some of the ducted systems together with trickle vents.

With the passive stack system you would take a hit of about a kilowatt on the heating requirement but as you get your wood virtually free/at low cost and you are using a small amount of a renewable resource I think that it is not a great problem. If you start adding the embodied energy of the MVHR system into the equation and the lack of long term resilience It's a no brainer from my point of view.
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mikepepler
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PostPosted: Sun Feb 26, 2017 7:57 pm    Post subject: Reply with quote

Thanks Ken, I'd been coming to the same conclusion myself on MVHR - and as you say, I can just burn a bit more wood and let some air through the house. I've come across Ventive at work, and like their design, though I'd need to think about where it could be installed, as our house is semi-detached. The chimney is already in use, so we'd need to use the version that has ducting, though I'm not sure where it would actually go. But I imagine they would advise on that.

When it comes to the flat roof, the plasterboard ceiling is fixed to the wooden joists, and the deck on top of the joists looks like treated softwood planks, not chipboard. There's something like a ventilated 70-80mm gap, into which I've slid 25mm polystyrene (chosen because I needed something flexible to be able to slide it in). On top is the usual felt and gravel. If I put insulation on the top, I'd still have ventilation in the gap under the existing roof - I was wary of blocking that up in case it caused condensation problems...

I know a local architect who is keen on energy saving, though not trained in Passivhaus, etc. It may be that he can recommend me some builders for stuff I'm hesitant to try myself - I'm not sure I'd call myself a competent DIYer yet. Not incompetent either, but somewhere between the two!
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vtsnowedin



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PostPosted: Mon Feb 27, 2017 2:06 am    Post subject: Reply with quote

mikepepler wrote:
- I'm not sure I'd call myself a competent DIYer yet. Not incompetent either, but somewhere between the two!
We DIYers never get to be fully competent. We just get the job done good enough for now and learn that we don't want to do that every day for a living. My rule of plumbing is you can do it wrong, then take it all apart and do it again still wrong, then go get a full new set of parts because you cut all the first set too short or otherwise ruined them and assemble those correctly using the lessons learned from attempts one and two and still be cheaper then having your local plumber do it for you. That is partly because he charges an arm and a leg and partly that he has a lot of help working for him that have less common sense then you do.
You do have to get it right by the third time though so you must have a learning curve.
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fuzzy



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PostPosted: Mon Feb 27, 2017 9:25 am    Post subject: Reply with quote

Agreeing with VTs thoughts, there are many ways to do construction work and the pro's only ever do it the fastest and cheapest. No reason you need to follow, especially if it is your final house and you can avoid building inspectors etc. It only has to be safe, efficient and last for your life or be repairable at any age.
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kenneal - lagger
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PostPosted: Mon Feb 27, 2017 3:35 pm    Post subject: Reply with quote

A reasonable DIYer is likely to do as good a job as most installation installers in the UK because most people installing insulation in the UK have never been trained to do the job and many regard it as an additional hassle imposed on their "normal" job.

Insulation needs to be fitted very carefully with very tight joints to ensure that air cannot move around so anyone who can cut a straight and square line can install insulation.
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Potemkin Villager



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PostPosted: Mon Feb 27, 2017 7:31 pm    Post subject: Reply with quote

kenneal - lagger wrote:


...... anyone who can cut a straight and square line can install insulation.


Very Happy It all depends how straight and square the building is! Costs can be greatly reduced by concentrating the insulation effort in the areas most used in the winter.
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kenneal - lagger
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PostPosted: Tue Feb 28, 2017 4:26 am    Post subject: Reply with quote

By all means do the most used areas first but leaving holes in insulation has a disproportionate effect on the efficiency of the system. You get cold bridges around the edges of the uninsulated areas which extend well into the insulated area rendering parts of the insulated area ineffective.
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vtsnowedin



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PostPosted: Tue Feb 28, 2017 8:45 am    Post subject: Reply with quote

How available are thermal imaging cameras? They used to be a specialty here but I wouldn't be surprised to find it is just an app for your smart phone now. A few pictures of the outside of your house on a cold morning while the heat is working will show you where the largest leaks are.
As an aside my youngest daughter just returned from a ten day visit to England and Ireland. A whirlwind tour with students in tow. The tour was not all that well managed with buses getting lost in the Cotswold for four hours etc. but the hospitality was excellent. She insists we will have to return with her for a more leisurely paced visit with time to actually look at what we came to see.
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