Benjseb

Advice or survey to help with insulating period house

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Hi all

 

We have an old period house c1750s. It’s been Renovated approx 15 years ago and it generally v good condition. Approx 250sqm and long and thin so most rooms have 2-3 external walls. 
 

We have realised that 1/3 of the house, which is our lounge and master bedroom has been insulated differently (kingspan behind dry lining rather than XPS backed plasterboard elsewhere). I think due to how that’s been done (it with big gaps!) these two rooms tend to take much longer to heat up and therefore cost more to keep cosy. 

I’ve done some work with a thermal camera which verifies our thoughts. 
 

We’d like a plan for improving the improving the wall and ceiling (master bed is in the eaves) insulation but I’m very aware that just whacking a load of kingspan in could lead to humidity issues in the house or interstitial consensation etc. Having a healthy interior is very important to us. 


I don’t trust getting this advice from a builder so would like the opinion of someone independent who can do the calculations etc then we can specify this to a builder. 
 

Who are we best to approach for this advice?

 

Thanks 

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I'd probably do some research before  engaging a builder as many poor practices prevail in the industry. Often not the fault of builders, but rather misunderstood problems and poorly thought out solutions, too often driven by the commercial interests of material manufacturers.

 

To feel comfortable you'll need a good levels of air-tightness but as you spotted it can lead to problems, even structural ones eventually.

 

Here are two good articles from passive house mag to get started with. 

 

https://passivehouseplus.ie/magazine/upgrade/victorian-passive-upgrade

https://passivehouseplus.ie/magazine/upgrade/radical-retrofit-transforms-pennines-historic-barn  

 

What is the current wall/roof buildup you plan to improve?

 

 

 

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Thanks @Iceverge. Will check those links out. 

 

Currently, from what we can tell it’s stone exterior with a cavity and brick interior. Then there’s 50mm of kingspan between studs and drywall over that. 
 

The issue is the kingspan has been added badly with no foam to seal it so there’s big chunks you can move about, so very poor fitting. 
 

It’s a pitched ceiling with, again, 50mm of badly fitted kingspan. 
 

Elsewhere in the house it’s the same structure but instead of the kingspan there’s 50mm of XPS backed plasterboard and it’s soo much better. The ceiling has had another 50mm of well fitted kingspan and that seems to be working nicely  


 

So I’m think long something like:

 

Remove kingspan, replace with 75mm and foam in place. Add 25mm insulation backed plasterboard on top of stud frame. 
 

or

 

Remove kingspan and use sheepswool, then 25mm insulated plasterboard on top. 

 

But what I’m not sure of is what depth I can go to without causing issues with interstitial condensation etc. I’ve had issues with mould in previous houses and really don’t want to go there again

 

our internal humidity can get to 70% in the summer so I was thinking using sheepswool might be better to allow it to breathe more, but again no idea how that works with the moisture risk etc. 

 

 

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Given its age i would tread very carefully.

 

It wont have a damp proof course, so the walls and floor will need to breathe or they will get wet (probably are now.)

 

Most insulation systems will prevent that from taking place, storing up future trouble.

 

Id suggest a peruse here would be a good idea. https://www.lime.org.uk/  Im just about to use their sublime insulated floor system.

 

Periodproperty forum is good too, though some of them can be a bit harrdcore!

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1 minute ago, Benjseb said:

Thanks @Iceverge. Will check those links out. 

 

Currently, from what we can tell it’s stone exterior with a cavity and brick interior. Then there’s 50mm of kingspan between studs and drywall over that. 
 

The issue is the kingspan has been added badly with no foam to seal it so there’s big chunks you can move about, so very poor fitting. 
 

It’s a pitched ceiling with, again, 50mm of badly fitted kingspan. 
 

Elsewhere in the house it’s the same structure but instead of the kingspan there’s 50mm of XPS backed plasterboard and it’s soo much better. The ceiling has had another 50mm of well fitted kingspan and that seems to be working nicely  


 

So I’m think long something like:

 

Remove kingspan, replace with 75mm and foam in place. Add 25mm insulation backed plasterboard on top of stud frame. 
 

or

 

Remove kingspan and use sheepswool, then 25mm insulated plasterboard on top. 

 

But what I’m not sure of is what depth I can go to without causing issues with interstitial condensation etc. I’ve had issues with mould in previous houses and really don’t want to go there again

 

our internal humidity can get to 70% in the summer so I was thinking using sheepswool might be better to allow it to breathe more, but again no idea how that works with the moisture risk etc. 

 

 

 

Our posts overlapped.

 

Not much point using sheepswool if you slap plasterboard over it. Plasterboard will prevent moisture leaving the wall.

 

If you are allowing breathability, it has to be every layer, including the paint. One "waterproof" layer will render your efforts worthless.

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1 hour ago, Roger440 said:

 

Our posts overlapped.

 

Not much point using sheepswool if you slap plasterboard over it. Plasterboard will prevent moisture leaving the wall.

 

If you are allowing breathability, it has to be every layer, including the paint. One "waterproof" layer will render your efforts worthless.


Ah ok, makes sense. Thanks for that. 

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Just a thought.

 

One of the best ways to approach this is to start with the basics.

 

Always check, then double check the obvious to make absolutely sure, then you can proceed with confidence.

 

Have you looked under the floor if suspended? .. have you checked your roof, gutters, rain water pipes and drains to make sure all is in order. If you have neighbours in close proximity..have they been up to anything? If you have only done this once then do it a second time!

 

For older structures in particular drafts are good, that is partly why they last so long. What you are looking to do is to maintain ventilation while at the same time introduce insulation.. and as each house is different, like a vintage car you need to get a feel for your own home and work from there. Remember that often you won't be the first to have tinkered with the structure!

 

Look outside. Do you have a locally variable water table, have big trees been cut down? Big trees can also take a lot of water out the ground in the summer when it's warm so removal can result in a lifting of the water table locally thus in warm weather this may manifest as high humidity. And to state the obvious look at the ground levels and what the ground surface comprises, the falls away from the house and so on.

 

For all. Although Benjseb has a period house this applies to all investigation.

 

It's best to really get a handle on these basics before you start spending a fortune of ripping out walls / changing insulation and so on. If you don't, you run the risk of just transferring the problem somewhere else.

 

Benjseb.. Another key to this is to be patient with the old house.. the best way if you have time to is to make a change and see what happens..

 

 

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For later, I've been exploring clay plasters, eg by Clayworks.com they are breathable (and apparently easier to DIY). 

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Posted (edited)
10 hours ago, Gus Potter said:

Just a thought.

 

One of the best ways to approach this is to start with the basics.

 

Always check, then double check the obvious to make absolutely sure, then you can proceed with confidence.

 

Have you looked under the floor if suspended? .. have you checked your roof, gutters, rain water pipes and drains to make sure all is in order. If you have neighbours in close proximity..have they been up to anything? If you have only done this once then do it a second time!

 

For older structures in particular drafts are good, that is partly why they last so long. What you are looking to do is to maintain ventilation while at the same time introduce insulation.. and as each house is different, like a vintage car you need to get a feel for your own home and work from there. Remember that often you won't be the first to have tinkered with the structure!

 

Look outside. Do you have a locally variable water table, have big trees been cut down? Big trees can also take a lot of water out the ground in the summer when it's warm so removal can result in a lifting of the water table locally thus in warm weather this may manifest as high humidity. And to state the obvious look at the ground levels and what the ground surface comprises, the falls away from the house and so on.

 

For all. Although Benjseb has a period house this applies to all investigation.

 

It's best to really get a handle on these basics before you start spending a fortune of ripping out walls / changing insulation and so on. If you don't, you run the risk of just transferring the problem somewhere else.

 

Benjseb.. Another key to this is to be patient with the old house.. the best way if you have time to is to make a change and see what happens..

 

 


Thanks, very wise words! I’m sure all our gutters and drains are OK as we had them all fixed. Funny story... we found them all draining into an old water pit under the house. Which was obviously now leaking so all the rainwater was just soaking the ground. So had it have it all dug out and drained properly. Anyway, that’s the other end of the house so doesn’t affect this room anyway but strange what you find!

 

We do have some flower beds against the walls so I’ve started digging a french drain between the house the soil to lower the levels. On one side we have a cobbled courtyard which is about 6” to high so will do the same there too but that requires a bit more than a spade so will have to wait until summer. 
 

I think in general our water table is quite high as we live on the bottom of a hill. Thanks fully very good working field drains which all head off away from us but any opportunity I get I add more acodrains to ensure any surface water is intercepted. 
 

The reason for looking at insulation is I did a thermal camera survey and from outside you see this section of the house is noticeably warmer externally (right 1/3 of pic attached). There’s also sections internally where you can see insulation is missing (see other pic, beside the bed)

7392DAC3-478E-436A-B24A-B508B692DE57.jpeg

4CBB01AB-3345-40B6-B955-892215B79F92.jpeg

01ACD767-7A23-4AD1-A21F-DA97F947AD22.jpeg

Edited by Benjseb
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+ 1 to @Roger440's suggestion re Ty Mawr (lime.org.uk), but I'd suggest you go one further and pick up the phone to talk to them. However, one word of advice about Ty Mawr is that whilst they all know their conservation stuff, they will present you with multiple options, sometimes too many. This is a really good thing in one way as they don't dictate a solution convenient to them and  it gives you the freedom to choose the best solution for you! But you need to know what you want first and have a good basis for making a decision. Either way, talk to them with pen and paper in hand and make notes! 😊

 

+ 1 to @Gus Potter's heads up about ventilation. If you're retrofitting insulation to an older property you must build into the designs a ventilation strategy. Don't leave this to the end as an afterthought.

 

As for insulation, there are various options available to you in terms of buildup but you need to look at the system as a whole rather than each component in isolation. For example, only looking at insulation material and forgetting about the whole wall from internal finish to external render. This essentially means using the same or similar materials that work together and in the same way.

 

As was suggested above this means that you'd undo all your good work by adding a layer of plastic paint to your plasterboard after spending vast amounts of money installing sheeps wool or wood fibre insulation (plasterboard in and of itself does function okay in terms of moisture buffering within this kind of wall system but not if it's backed with plastic insulation). Other options are available however where you could use wood wool board or lath & limeplaster (and as @Jilly suggests Clay plaster) but this all depends on how far you want to go with it, and your budget. @J

 

Beware there's lots of talk nowadays about breathability, but this is actually a bit of a meaningless term within the building industry. Within this you normally find discussion about vapour permeability and hygroscopicity, and then related airtightness. It's worth spending an evening or so doing some research about these terms and how they work within a building over a good glass of wine, if you're so inclined. Hygroscopicity is probably the most misunderstood term in terms of how it works and its value, but it relates to both the ability for a building material to buffer excess moisture produced within the building and then release that back into the atmosphere over time as well as a system's ability to pass moisture through the whole building fabric to equalise relative humidity levels with the outside. Research has shown that a well built hygroscopic building fabric can reduce relative humidity within the house by 10-25%. So important not just for the health of the building fabric (where the focus of this is most directed) but also for indoor air quality and comfort.  ☺️

 

Edited by SimonD

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Thanks all this has been very useful. 
 

We’ve got a few rooms to do so have picked up some recommendations for some low-energy retrofit architects who specialise in old houses to get in touch with for a while-house plan. Carbon.coop is up our way too so will be getting in touch with them. 
 

The plan is to get a full house plan so everything is considered then we can tackle each room with this plan in mind. 

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