Internal Insulation and Condensation in Kitchen

[andyrew1]

Hello

We have had some damp issues in our kitchen (standard victorian terrace). We had a damp survery done and got the usual reccomendations of sand and cement, dpc etc which I will be ignoring but he did convince me (or maybe confirm my thoughts) that the issues are mostly condensation related with maybe a bit of penetrating damp due to poor state of external pebbledash (I have couple of questions about replacing that which I will put in a separate thread), we also have a high concrete path that we will look to try to have removed down to a more appropriate height but is not the main cause. Note our damp problems are relatively mild compared to what I see in a lot of other posts!

On top of his other reccomendations he did suggest putting some internal insulation in the kitchen and a humidistat extractor fan both of which I am now considering.

I was looking at the options for breathable insulation (wood fibre board seems most appropriate) and lime plaster and have a number of concerns
1. how thick is the buildup of wood fibre board + lime plaster? The kitchen is not big and losing more than about 50-60mm will prevent us from fitting standard size units around in a U-shape
2. if the above is quite thick would insulating lime plaster be any thinner and does it really make any considerable difference?
3. being the kitchen I am concerned about the time needed to do lime plastering as we obviously want the room (and boiler) back in action as fast as possible, would the "modern" lime plasters like Lime Green Solo be a good option to speed up the work while maintaining the benefits?
4. can kitchen units and boiler be fixed to the wood fibre board or is a special approach required?
5. Is any special detail required where the wood fibre board will meet the solid floor? I have a doubt if the board risks either wicking moisture from the solild floor or if there is an increased risk of condensation in this area

Final question regarding the fan does anyone have any experience of this working? Moving a hygrometer around my house over the last few days the level of humidity is fairly constant outside of shower and cooking times, to me it seems the fan would just extract 70% RH air from the kitchen to draw 70% RH air from elsewhere in the house... I was planning on simply adding an extracting hood over the cooker rather than current recirculating one to remove the worst of the steam during cooking and manage the rest via heating, window opening etc.

Apologies for so many questions but it seems like there is wealth of knowledge in this community

 

[a twig]

1. how thick is the buildup of wood fibre board + lime plaster? The kitchen is not big and losing more than about 50-60mm will prevent us from fitting standard size units around in a U-shape
2. if the above is quite thick would insulating lime plaster be any thinner and does it really make any considerable difference?
3. being the kitchen I am concerned about the time needed to do lime plastering as we obviously want the room (and boiler) back in action as fast as possible, would the "modern" lime plasters like Lime Green Solo be a good option to speed up the work while maintaining the benefits?
4. can kitchen units and boiler be fixed to the wood fibre board or is a special approach required?
5. Is any special detail required where the wood fibre board will meet the solid floor? I have a doubt if the board risks either wicking moisture from the solild floor or if there is an increased risk of condensation in this area

6. ... I was planning on simply adding an extracting hood over the cooker rather than current recirculating one to remove the worst of the steam during cooking and manage the rest via heating, window opening

Hi

Lots of info on all your questions already on the forum via the search but v.quickly…

1) don’t use any thicker than 25mm board and you will be fine

2) to make a difference with the insulating plater it will be at least as thick and won’t perform as well

3) using an NHL based plaster will be fine, doesn’t have to be a “brand”

4) you’d need to fix through to the wall or leave a cut out in the board and use pattressing

5) I’ve never done any specific detailing. If you are worried leave the bottom inch or so uncovered and hide the gap with skirtinf

6) do your vented hood idea

 

[paulc]

From what I've seen of these insulating plasters, you have to put a really, really thick layer on to get any appreciable effect. A work colleague used some of the hemp plaster in her little cottage. She is somewhat disappointed...
I'd go for woodfibre or cork, and put as much as possible on the walls. Something in the region of 100mm will get you to the current building regs recommendation. If space is that much of a premium, go as thick as practical Anything attached to the walls will need fixing to something solid like brick. I wouldn't trust woodfibre/cork to take any weight. What you could do, is fix some sheets of ply over the insulation for things to be screwed to. Make sure any mechanical fixings go through the ply, insulation, and in to solid brick. Apply some grit bonding (eg DG27) to the ply, and then give a thin skim of lime. Mix plenty of fibres into the base coat, and it shouldn't crack.

 

[Zebra]

I would recommend using a strip of expanded polystyrene for the bottom 300mm or so if you're worried about moisture wicking. Not so breathable but it wouldn't matter just for that bit. Cheap and easily available, I think Wickes do it, for example. Having said that, I have a piece of leftover woodfibre insulation which I have left outside, stood up vertical, but on the ground by the bins, for ten years now, as I just wanted to see what would happen to it. Apart from having been used as a cat scratching post, it's fine. A bit bad at the bottom where it's in constant contact with the ground, as a piece of timber would be in those circumstances, but really not disintegrated like I would have expected, given what it is. So it may not be as susceptible to moisture as you might fear.
Regarding your question about whether you can fix to it - no, you can't. Either put a timber batten in the wall at the height your cabinets will be fixed, with the woodfibre butted up to it top and bottom, and plaster round it or over it, it won't be such good insulation but it won't matter just for that tiny bit. Or just do the wall with the woodfibre and then when you work out where you need to drill, do an extra big hole into the insulation and insert, say, a piece of 20mm plastic conduit (the stuff electricians use) the same length as the thickness of the insulation and plaster, resting against the brick, for the cabinet to sit against, with a washer on top if necessary. Then a plug and long screw all the way through into the brick. The screw will take the pulling force, the plastic conduit spacer the pushing force.

 

[Zebra]