Mon, 25 May 2026 21:29:39 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98956#Comment_98956 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98956#Comment_98956 Tue, 11 Jan 2011 18:49:55 +0000 DamonHD
Now, ignoring all my previous misgivings before about EWI and a partly-ventilated structure, I'm thinking of EWI (eg 100mm) on the windowless brick-faced north wall of our house, just up from the A in this pic:

http://maps.google.com/maps?oe=UTF-8&q=KT1+3JA&ie=UTF8&hq=&hnear=Kingston+Upon+Thames+KT1+3JA,+United+Kingdom&ll=51.406735,-0.288781&spn=0.000443,0.000848&t=h&z=20

I was previously concerned that:

a) EWI would be ineffective because the ventilation of the void would take heat away from inside the EWI

b) The EWI might retain moisture and encourage rot in the timber frame

Do either of those worries still hold water?

Running next to the north wall is a (barely used) footpath, so I'd have to get some sort of special permission I imagine. Our ground floor level is several feet above the path level, so if I could go right right down to path level I'd be usefully starting to trap some heat in the thermal mass on the warm side of the insulation.

I imagine I'd need planning permission anyway for EWI, yes? (IE no GPDOs apply.)

We're not in any sort of conservation area!

What flavour of EWI should I consider?

Note, BTW, that the bottom west quarter of that north wall is the one that we've drylined internally, so it would have a double dose!

Note also that some kind of tapering would be needed at the top since the gable/tiling hardly extends beyond the wall I think (I'd have to look again in daylight).

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98964#Comment_98964 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98964#Comment_98964 Tue, 11 Jan 2011 20:09:04 +0000 DamonHD I was expecting at least a dozen different opinions (from ST) and beautiful cutaway diagrams from VH already...

Rgds

Da,mon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98966#Comment_98966 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98966#Comment_98966 Tue, 11 Jan 2011 20:23:19 +0000 Viking House https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98967#Comment_98967 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98967#Comment_98967 Tue, 11 Jan 2011 20:39:40 +0000 DamonHD

What other than my opinions should I pump into that cavity, if you're being serious? I now think that rather than a cavity it may be 50mm of mineral wool with a plastic (VC presumably?) membrane on the warm side (from our explorations when dry-lining).

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98968#Comment_98968 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98968#Comment_98968 Tue, 11 Jan 2011 20:40:51 +0000 Timber
EWI is pointless on timber frame external cavity wall. Air movement in the cavity will reduce, if not eliminate any usefull contribution from the insulation,

DO NOT blow insulation into the external wall cavity. As much as anything else, if you try and sell in future, you might find trouble shifting it. I have seen this a few times recently. Home owners (unaware that thier property was timber frame) have cavity insulation installed. Come sale time a survey is conducted and this issue raised. The property then becomes un-saleable.

Moisture ingress might be minimal due to lack of windows on that elevation, but also, being a north facing wall the chances for it to dry out will also be minimal.

What insulation is between the studs currently?

In north america, a lot of the cladding systems are 'siding' (i.e weatherboarding (quite often vynal)) so it can be removed and insulation installed. E.g. installing 100 mm eps, new breather membrane and then battens (or strapping as they call it) and new cladding.

Timber]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98971#Comment_98971 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98971#Comment_98971 Tue, 11 Jan 2011 20:46:13 +0000 Paul in Montreal Posted By: TimberIn north america, a lot of the cladding systems are 'siding' (i.e weatherboarding (quite often vynal)) so it can be removed and insulation installed. E.g. installing 100 mm eps, new breather membrane and then battens (or strapping as they call it) and new cladding.

Exactly. Never, ever, fill the gap between the siding and the structure underneath. And, as Timber says, it's pointless putting EWI over the cladding. The gap between the cladding and the structure is essential for proper protection from the elements. Such a structure is often called "pressurized rainscreen construction" and works well as design. One can always remove the rainscreen, apply sprayfoam or whatever to the structure underneath and then re-apply the rainscreen. But this might compromise the timber frame as such frames are usually covered in a breathable air-barrier (e.g. Tvvek or Typar) and thus allow any moisture in the timber frame to escape. Sealing this up could be problematic. Vapour permeable foams such as Icynene could be OK, but closed-cell non-breathable foams (or too much thickness of EPS) may cause problems.

Paul in Montreal.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98975#Comment_98975 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98975#Comment_98975 Tue, 11 Jan 2011 20:57:42 +0000 DamonHD

We only did minimal exploration and we still don't know, but the construction (where we didn't dry-line) may be:

"Early on we made a couple of exploratory holes in the plasterboard of the exterior walls to check the construction, and rather than a void, behind the 12.5mm plaster is a ~0.5" fibre matt enclosed in a plastic lining, which seems in fairly good nick, eg no obvious sagging."

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98980#Comment_98980 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98980#Comment_98980 Tue, 11 Jan 2011 21:10:41 +0000 Megacycles
Can't see how EWI would achieve anything with the ventilated void and I doubt you would get sensible house insurance with the void filled as it would be a non-standard construction.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98990#Comment_98990 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98990#Comment_98990 Tue, 11 Jan 2011 21:43:17 +0000 Viking House
If you externally insulate, the brick now becomes bone dry, the risk of moisture ingress is eliminated, you can then pump the cavity to stop air movement between the 2 layers of insulation because the moisture that could jump the cavity has been eliminated.
The timber frame now becomes similar technically to a timber stud when drylining the inside of a partial filled cavity wall .

You'd better go with the guys advise above with regards house insurance and resale but I can see nothing wrong with it technically!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98992#Comment_98992 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98992#Comment_98992 Tue, 11 Jan 2011 21:49:36 +0000 DamonHD
Amongst others I could ask my insurers and the BCO...

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98993#Comment_98993 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98993#Comment_98993 Tue, 11 Jan 2011 22:03:34 +0000 Viking House
Water Vapour won't rot your timber frame, condensation will, by warming the timber frame you bring it away from the Dew Point risk zone and it then becomes similar to your wooden kitchen table, its then no longer subjected to condensation or temperature differences of minus 10 outside and plus 20 inside which makes it move constantly.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98994#Comment_98994 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98994#Comment_98994 Tue, 11 Jan 2011 22:25:47 +0000 SteamyTea I shall ponder this, but you could do a risk assessment on the temperature/humidity levels where you are. Easy enough to get the data.

Right done a minutes ponder, Have you thought of MVRH? could sort out the condensation issue.
Then you can do a heat transfer analysis on the expected temperature gradient and calculate the frequencies and period you could reasonably expect to get moisture build up. Just a starting point, no risk in doing sums,]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98996#Comment_98996 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98996#Comment_98996 Wed, 12 Jan 2011 06:51:53 +0000 DamonHD
I'd be slightly concerned now that we do have the aerogel in that corner of the house that the natural dew point would still be somewhere inside the wall because 40mm of aerogel inside beats 100mm EPS for example.

ST: where were you working? At the secret MI5 lair? Oh, wait...

And gimme a clue how to do that risk assessment: I'm game to try it. (Yes, the Bill people did ask if they could film in our house, but as I had a server room full of computers at the time I declined!)

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98997#Comment_98997 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98997#Comment_98997 Wed, 12 Jan 2011 07:14:03 +0000 SteamyTea It is really just a case of finding suitable weather station data and then working out the probability of the event happening. Roughly speaking, how often will the RH be at 100% over the range of temperatures that your house is at/in.

Arrow Plastics down Hampden Road, was a bit like a 1974 Bond film, there was a a cat and a strange man running it. Was the company that made me want to get out of engineering for ever, did not happen.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98999#Comment_98999 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=98999#Comment_98999 Wed, 12 Jan 2011 08:03:37 +0000 DamonHD
We use the nursery next to Arrow Plastics! B^>

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99000#Comment_99000 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99000#Comment_99000 Wed, 12 Jan 2011 08:26:48 +0000 SteamyTea
Just trying to tidy up that spreadsheet for you, shall have a look at the Airport data if I can Google it.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99001#Comment_99001 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99001#Comment_99001 Wed, 12 Jan 2011 08:35:51 +0000 Mike George https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99004#Comment_99004 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99004#Comment_99004 Wed, 12 Jan 2011 08:55:48 +0000 SteamyTea It is way too big to most on here with climate data included I think so may set up something on Google Docs or similar.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99009#Comment_99009 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99009#Comment_99009 Wed, 12 Jan 2011 09:27:04 +0000 Mike George https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99030#Comment_99030 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99030#Comment_99030 Wed, 12 Jan 2011 12:58:16 +0000 DamonHD
(I have no boards running across the joists, so the fibreglass is resting on the joists and what I assume to be the plasterboard nailed onto it.)

If I *wanted* to put a whole metre's depth down, could I safely do so from that point of view and without so seriously impeding airflow that I risk causing rot up there?

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99032#Comment_99032 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99032#Comment_99032 Wed, 12 Jan 2011 13:07:40 +0000 SteamyTea So I would have though that you coudl just lay it down.

So where do you want the air to flow?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99038#Comment_99038 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99038#Comment_99038 Wed, 12 Jan 2011 13:47:25 +0000 DamonHD
Sealing the loft space seems to be a BadThing(TM), and this seems as if it might be a move in the same direction...

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99045#Comment_99045 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99045#Comment_99045 Wed, 12 Jan 2011 13:59:58 +0000 SteamyTea Seems that most people on here like is to leave an air gap below the roof that is also open to the atmosphere somewhere, allowing air movement.
I think, and I am not trying to be controversial here, that to stop condensation being a problem you have to look at the temperature gradient across each component of a wall or roof construction and calculate the risk at each interface.
Reducing RH within the insulated envelope is probably the best way to deal with it really though.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99065#Comment_99065 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99065#Comment_99065 Wed, 12 Jan 2011 20:52:53 +0000 Timber
If you want to upgrade the thermal peformance of the walls there are a few resources out there regarding this, giving advice and guidance. I can provide links if googling 'Improving the thermal performance of timber frame' doesn't point you in the right direction. As for the aerogel, condensation formation will depend on the presence of a vapour control layer, and where that is in relation to the insulation.

Viking - You said "Water Vapour coming from the inside the house can condense on the cold side of the timber frame, the ventilated cavity is necessary to dry this moisture."

That is sort of correct and wrong at the same time. Condensation shouldn't form on the sheathing on the outside of the timber frame. The vapour control layer on the warm side of the insulation is there to reduce the moisture vapour passage though the wall to a level where condensation won't form.

The cavity is not there to allow condensation to evaporate, it is there to allow moisture vapour that has safely made it though the wall dissipate to the outside world, rather than condensing on the brickwork cladding.

As for condensation in roofs, there should be eaves vents that provide ventillation air into the roof. This air transports moisture vapour away from the roof back to the outside. All roofs (except TRUE warm roofs) require ventillation between the insulation and roof covering.

Timber]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99345#Comment_99345 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99345#Comment_99345 Sun, 16 Jan 2011 12:09:06 +0000 DamonHD
Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99361#Comment_99361 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99361#Comment_99361 Sun, 16 Jan 2011 19:34:30 +0000 Timber
I think you can view it as an html document on the website if you navigate there.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99362#Comment_99362 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99362#Comment_99362 Sun, 16 Jan 2011 20:35:55 +0000 DamonHD
1) It says that I shouldn't have done my drylining quite the way I did it.

2) It says that I have to take down the brick outer leaf before cladding, and does note that retaining a drained and ventilated cavity to prevent rot will undermine the performance of any EWI.

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99479#Comment_99479 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99479#Comment_99479 Mon, 17 Jan 2011 23:13:02 +0000 Timber
As for the bit about cladding, I don't quite understand? Do you mean that for EWI you would need to remove the brickwork cladding. If so then yes, I can't see any other way to do EWI on brick clad timber frame!

Timber]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99486#Comment_99486 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99486#Comment_99486 Tue, 18 Jan 2011 07:08:40 +0000 DamonHD
As the EWI: well, I don't think we want that much fun! But I'll keep thinking about it.

Rgds

Damon]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99489#Comment_99489 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=6797&Focus=99489#Comment_99489 Tue, 18 Jan 2011 08:40:52 +0000 SteamyTea Purely out of academic interest and there being a number of threads along the same lines currently running. And it may be of interest to others. Here is another question:
"Do you have a problem with condensation or are you worried that condensation may be a problem in the future?"]]>