Mundic Internal Wall Insulation

Scrimps

My House is built of mudic pot block - blooming cold! I have gas central heating and double glazing etc but can pretty much feel the cold walls sucking the heat out of the house. I also live in a frost pocket so although Im in rather mild cornwall, Its regularly below freezing in the mornings.

We moved in 3 years ago and had minimal funds to improve anything, that is beginning to change. I would like to make my home more comfortable, doing each room properly before we have children in the next couple of years. We only had time and money to get the woodchip off and paint the walls when we moved in.

External wall insulation is expensive, I am tempted at some point in the future as it will add a layer of weather resistance - important for mundic construction and it is aesthetically pleasing.

Do you know if there is anything inherently wrong with adding internal wall insulation to mundic pot block? It would have to be dot and dab method as the house doesnt have much room to give up for internal frames. Apparently mundic has to be allowed to breathe, I dont know if internal wall insulation would cause a problem there - though I know people tile their kitchens and bathrooms so not sure how much is really has to breathe? I have searched online but cant find the answer.

I would welcome your thoughts on this, Im keep changing my mind as to whether I should cut my losses on this good location/big garden house and spend the money moving somewhere else, or if I should make the improvements to make it a more comfortable home. (Or to not make any improvements, live with the discomfort and just massively overpay the mortgage)

Davesnave

Many people will not understand this post, so I will just add that mundic blocks were made with various concentrations of mining waste, and depending on composition, they are prone to decay over time, especially if subjected to large amounts of moisture.

Pot blocks are 9" thick, (the thickness of an old-fashioned solid brick wall) and have two air chambers inside which cannot be filled with insulation. They have poor insulation qualities and may make the house prone to condensation and damp. Mortgage providers don't like them.

Now read on.....:)

Davesnave

As you have a mortgage, the blocks have passed the mundic test and are deemed sound, so the house isn't about to fall down about your ears. All you have is a cold house, which is something many respondents will have had, especially when younger. It was no big deal.

Your kids wouldn't therefore be any worse off than we were if you stayed in the house, but they'd have the advantage of a good location, a large garden and possibly good schools too, as these often go with the location.

The future investment part of your question is harder to answer because few of us have the specialist knowledge to advise on methods of insulation in this scenario, or the likely benefits.

All we can be sure of is that the house will have a ceiling price which no amount of insulation will alter. Performing expensive remediation would be 'throwing good money after bad,' unless you commit to staying there a long time. After 3 years, you should know how you feel about the chances of that, bearing in mind what alternatives you could afford.

If another 10 years sounds too awful to contemplate, then overpaying and tarting-up, rather than spending out, might be the best route for you, but do be realistic about your alternative choices and what you'd lose. It's not cold in Cornwall for the majority of the time!

Furts

The above post is a well reasoned response. I will chip in with a building perspective to add some pointers.

Internal wall insulation would be a flawed concept. You want dot and dab and are short of space. Unfortunately this overlooks general principles of insulation. 25mm Celotex is good for preventing cold bridging, 50mm for providing some nominal insulation, and 100mm for providing something decent. Hence your dot and dab is unlikely to give anything worthwhile.

Add to this a key point. Introducing any internal insulation will create a risk of interstitial condensation within your structure. This is the vital thing to be avoided.

I came down this morning and my sun room was cold - it is exceptionally well insulated and well built. But cold temperatures are a fact of life, and one has to be realistic and accept some things cannot be changed.

brightontraveller

What was your home classified as a , b, c etc
If i remember surveys define mundic walls as "a" 1-2-3 ok made solely from "stable" aggregates. Mortgageable."a/b" ok 70 per cent stable still Mortgageable "b" more than 30% of aggregates is mundic (fits unstable category) hard to mortgage and "c" run for the hills

Although can be a problem for all walls when retro fitting/ adding insulation the potential affect of interstitial and reverse condensation etc are often worse more damaging for mundic walls and not only the damage done when fitting ? The cost is often prohibitive ( aside the potential for damage)unless your staying put 20 years I,d either crank the heating up a bit and live with it or move

FreeBear

Furts wrote: »

Internal wall insulation would be a flawed concept. You want dot and dab and are short of space. Unfortunately this overlooks general principles of insulation. 25mm Celotex is good for preventing cold bridging, 50mm for providing some nominal insulation, and 100mm for providing something decent. Hence your dot and dab is unlikely to give anything worthwhile.

Whilst I agree that dot & dab Celotex is probably not a good idea, there are alternatives. Cork or woodwool boards are breathable, and there are also cork & hemp insulating renders on the market. If space allowed, sheeps wool insulation batts between studwork would be an alternative. However, none of these have the same insulating ratings as the same thickness of Celotex.

Externally, cork, woodwool, and insulating renders might be a viable alternative - I'm guessing the OP is down in the west country, in which case, have a chat with a company by the name of Mike Wye.

phil24_7

I wouldn't consider internal insulation on your house. External would be the way to go so I would get saving and searching for a reputable installer/system with an insurance backed guarantee.

Alternatively someone on here a while ago built a second wall around their property, creating a cavity wall which was insulated with part fill celotex (you could use a full-fill breathable insulation instead). You would then have several layers of protection for your house but it would cost significantly more.

stator

If you're a competant DIYer then a thin layer of celotex or similar with plasterboard over the top wouldn't cost too much and would provide a little extra comfort.

Scrimps

Thank you all for your responses. Its been really helpful. I am glad I asked as you have helped settle my mind. I cant seem to work the multi quote button so will just answer various bits below. If you have any thoughts on my statements, I would welcome them but am aware I have a tendency to go on.....and on....

I think saving a bit up and keeping our fingers crossed for some more subsidies being paid for external wall insulation being forthcoming. I always seem to be on the trailing edge for taking advantage of subsidies, good deals and tax breaks....missed the old 6k grant for external wall insulation, bought just before the stamp duties were reduced, fixed the mortgage rate for 5 years just before the interest rates plummeted (previous/1st property)...you catch my drift :eek: I will try and push the over worrying from my mind and just ensure that next time the deals come up I am in a good position - if they dont, I will pay out the 'additional' funds and get it done for full cost to myself.

The mundic was grade A with A/B footings, the house is not about to fall down around us....though there is a non-structural (still I hope) crack on the gable end. I will get this looked at again before I have external wall insulation fitted.

We really cant afford to lose the internal space. We had wall panels fitted rather than tiles in our (2 external wall, cold bathroom) and it made a perceptible difference to the heat, it became the warmest room in the house with 2cm depth of wall paneling around the bath area, which got me thinking...but external is the way to go for us.

interstitial condensation this is what I was worried about so queried the internal insulation -
question - in your opinion; would the wall paneling cause more of an issue over regular bathroom tiles?
would this issue be enough to not go for external wall insulation as well as using the 2.5cm celotex to help prevent cold the cold bridge effect?
should i use a specific type of paint? Ive heard conflicting stories
We would only do this as we renovated each room so the disruption wouldnt be an issue

I do get that children grew up in colder houses to no ill effect, we also have an external toilet next to the coal bunker but I wouldnt consider using that as our only toilet just because it didnt harm the people before us. I just want a comfortable home but I am needlessly miserly with my heating and will turn it all the way up to 19.5 from 18.5 Its the sitting room that gets cold, our boiler has more than enough capacity to add another radiator and I will do that next time the boiler is serviced.

Cornwall isnt cold. However, I am genuinely very surprised by how much living in a frost pocket (by a river, at the bottom of a valley) makes to the temperature. There is sheet ice on the roads and shrubs are fully hard-frosted in the garden in the mornings, by the time I cycle or drive up the hill, its usually 3-4 C warmer and there is just a little dew and no ice.

Ive never lived further oop north than north dorset, I make no apologies for being spoilt by a warm climate :rotfl: (though, I lived in a panel van for 3 months in a snowy (even in cornwall) mid-winter before we moved, im not a wimp myself but wouldnt want to raise a family in those conditions)

Re the ceiling price, that's a big concern. I dont think we're that far off it already to be honest so want to keep any works done at a reasonable cost and not go nuts just because I can, though we have no major desire to move currently. We've just stopped feeling genuinely poor/over debted and dont want to go back to it. It was horrible.

Which brings me on to the moving. We do have a good location, its a bit noisier than I would like (including hearing next doors living - thank you pot block construction, the neighbours are nice and have lived there for years so not a huge deal - currently) but living in the middle of nowhere is very expensive and I dont want to have to drive our future children everywhere. Happily, there is quite a lot on the doorstep here and we have a short <20 min, pleasurable cycle commute to work. I do count my blessings but when I found out the building society would lend us enough to buy a new build close to the beach, I was very tempted.....its nice to have the smaller mortgage payments though and new build developments seem so congested externally.

Thanks again for all your responses:T

Edited for typos

jackomdj

Personally I would be concerned with ceiling prices and selling on, so I wouldn't spend too much.

My reasoning.... I bought a lovely terrace house in my home town in 1997, 3 years later (so when house prices had increased substantially) we were relocating, mortgage companies had brought in mundic tests (not even mentioned when we bought) and our property was grade c.

My worry would be that they can change their lending criteria and what is currently mortgeable can suddenly become unmortgegable, meaning the pool of people you can sell to suddenly becomes very limited.

phil24_7

Scrimps wrote: »

I think saving a bit up and keeping our fingers crossed for some more subsidies being paid for external wall insulation being forthcoming. I always seem to be on the trailing edge for taking advantage of subsidies, good deals and tax breaks....missed the old 6k grant for external wall insulation, bought just before the stamp duties were reduced, fixed the mortgage rate for 5 years just before the interest rates plummeted (previous/1st property)...you catch my drift :eek: I will try and push the over worrying from my mind and just ensure that next time the deals come up I am in a good position - if they dont, I will pay out the 'additional' funds and get it done for full cost to myself.

Don't stress to much about this. I had the insulation fitted by British Gas/ECL Contracts and I got the £3.5k local grant plus a further 3K ECO funding for external insulation. They bump the price right up and then subcontract all the work to the cheapest available company (this probably covers the ECO funding)...who then subcontract to the cheapest possible Romanian crews. The work done on my house was a negligent/sub-standard/a right pain and had I not spent a considerable amount of time/effort/energy/stress on keeping things in line I would have so many problems its unreal. As it is I just have damage to many bits of property that still need to be resolved and an area of damp that crops up each winter. On the plus side I haven't paid them yet!

With my first mortgage I fixed for 5 years just before the rates dropped. I have just fixed for 10 years and the rates have started creeping up!

The mundic was grade A with A/B footings, the house is not about to fall down around us....though there is a non-structural (still I hope) crack on the gable end. I will get this looked at again before I have external wall insulation fitted.

I would get the outside sorted as soon as you can so that you can be sure everything is fine before you have the insulation fitted. Don't go crazy just make sure everything is sound and doesn't leak.

Re the ceiling price, that's a big concern. I dont think we're that far off it already to be honest so want to keep any works done at a reasonable cost and not go nuts just because I can, though we have no major desire to move currently. We've just stopped feeling genuinely poor/over debted and dont want to go back to it. It was horrible.

If you are planning to stay a while don't worry to much about the ceiling price. You need to make the house comfortable and also suit you. Don't go stupid like a full remodel, but things like external insulation will be a plus point when you come to sell and may even attract a premium

Replied in red.