Internal wall insulation and freeze thaw brick damage

[PaulBartSpears]

Hello!

We've recently moved into a Victorian house which is in need of some renovation. I'm 68 and my wife is 55 and we plan on staying here at least until I die. My calculations indicate that by insulating the solid brick walls to a U value of 0.3 I will roughly halve the heating energy consumption which currently runs at 22000 kWh per year. The house probably would not be suitable for a heat pump without the insulation, and I'm increasingly of the view that gas heating will not be available towards the end of my life, so I think insulating it now while I'm fit and sane is probably a good idea. 

 

So internal or external insulation? The house is big enough to take internal insulation and it would be cheaper as I can do the work myself and we wouldn't require scaffolding. My concerns are that the joist ends would rot or the brick would be damaged by freeze thaw action. The latter has already been a problem on some of the walls near ground level, and has been remedied by rendering up to about 1 metre above ground level. Presumably it has occurred here because the water content has been higher. How can I establish if the brick higher up is at risk through freeze thaw action after I insulate internally? Is this something architects know about? Are there specialists who know about this? Are there cheap treatments that keep the outside of the walls dry and hence reduce frost damage? It might not be acceptable to render the front of the house because we are in a conservation area.

Thanks

Paul

 

[saveasteading]

1 hour ago, PaulBartSpears said:

plan on staying here at least until I die.

I think she has to move you out after that.

 

Seriously...good on you, here are my immediate  thoughts.

External insulation would be expensive, need lots of thought and especially cause detailing issues at openings and the eaves. And planning issues.

Internal is easy and diy.

It shouldn't increase erosion of bricks. Instead check out why the walls are wet. Rendering requires caution too. Can you show photos of the wall in question?

[saveasteading]

Btw most of us stay anonymous, paranoid or sensibly? You could repost if you wanted.

[ProDave]

Our new house is the first house I have ever had, where the external wall surface is cold enough (due to so little heat loss) for frost to form on the render on a cold night (and on the outside of the 3G windows)

 

I do wonder if that is a contrubutor to the problems I have had (and probably not entirely fixed yet) with my thin coat render.  My suspicion that if any wind driven rain can find an opening to get in and not run off, then it will freeze and cause issues.

 

This is of course much more likely to happen in an exposed spot in the Highlands than in a sheltered spot somewhere less cold.

 

I notice around here, not one single garden wall that has been rendered has managed to keep it's render for more than about 2 years.

[Gone West]

3 hours ago, PaulBartSpears said:

Are there cheap treatments that keep the outside of the walls dry and hence reduce frost damage?

Welcome to the forum, good luck with the renovation. Stormdry is one type of treatment you could look at.

[PaulBartSpears]

23 minutes ago, saveasteading said:

I think she has to move you out after that.

 

 Very funny

23 minutes ago, saveasteading said:

 

External insulation would be expensive, need lots of thought and especially cause detailing issues at openings and the eaves. And planning issues.

Internal is easy and diy.

It shouldn't increase erosion of bricks. Instead check out why the walls are wet. Rendering requires caution too. Can you show photos of the wall in question?

I'm aware of the planning, detailing and cost issues of external insulation, which is why I want to avoid it if I can. I can't show the (supposed) historical frost damage because it's been covered up by render. Being 170 years old there is no DPC. The areas that are covered by render on the outside coincide with areas on the inside that have historically had damp problems, though that seems to have been cured by some specialist internal plastering done in the last 20 years and maybe a chemical DPC before that. I'm no expert but I guess the historic damp problems were due to https://en.wikipedia.org/wiki/Damp_(structural)#Rising_damp

 

My ideal outcome would be contact with some real expert who knows about this stuff, and who could, for example, measure the water content of the wall and test the strength of the brickwork, or come up with some mitigation scheme. I actually think the risk is quite small because I read somewhere that the wall has to be 90% saturated for it to be a problem. Most examples I've found were due to leaking pipes or are below DPC. Nevertheless I'd like to be sure because because the consequences of brick damage are fairly awful and would likely occur when I'm too senile to do anything about it.

[saveasteading]

2 hours ago, PaulBartSpears said:

The areas that are covered by render on the outside coincide with areas on the inside that have historically had damp problems, 

Its possible that the render is impermeable, and keeping the damp in.

[Gus Potter]

8 hours ago, PaulBartSpears said:

We've recently moved into a Victorian house which is in need of some renovation.

Hello Paul.

 

This is a good source of information and discussion.

 

https://www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html

 

Pete Ward has upset a lot of folk in the damp proofing industry so you can have a bit of fun reading around seeing what they are all saying. Main thing is if you spend a bit of time now you can inform yourself much more.. each house is different. 

 

When faced with this type of issue I always look at what is happening outside. For example, the roof details (eaves overhang and guttering) which way the building faces, the pevailing wind (the east, north and north north west walls get the coldest freezing winds that cool walls a lot and quickly which is important as they freeze before they can dry out a bit), overshaddowing trees, ground levels, any potential DPC.. be that slate or a less permeabile brick, say a good quality clay brick or an engineering brick and so on.

 

I next look at the condition of the building; the gutters, the pointing, mastic around windows, weathering details and so on. I also look for signs of movement, normal cracking associated with an old building and for more significant structural cracking and lateral movement of the walls. All the time I'm thinking.. what can I see but try and avoid drawing any conclusion at this stage.

 

Lateral movement bulging of the walls is really important as you need to be careful later not to make the problem worse by say lowering or draining ground (to solve damp issues) and causing shrinkage of particularly clay soil under the found.

 

I try and identify where moisture can be penetrating from the outside.

 

Next is to go inside and look at the construction, if suspended floor what kind of solum, non or just earth or ash / blaze say with a bitumen layer. If stone flags what are they sitting on. Stone flags can be quite impermeable but can sometimes feel damp on top due to condensation.

 

I then move onto the condition of the structure. Are the structural members sound, are the signs of infestation or dry / wet rot. If so how is this happening? what conditions prevail that are promoting this behavoir?.. damp / warm and lack of ventilation.. a combination of the three particularly invite unwelcome guests (mice etc)and organic growths rot and moulds for example.

 

In summary I would do a bit more research before adopting any particular strategy. I can't make any more constructive comment at the moment until I know more.

 

Photos would be helpful if you feel able to post. Once you gain a deeper understanding of how the house behaves then you can plan a cost effective insulation strategy and get to the bottom of your concerns about freeze thaw of the bricks.

 

Remember that most common construction materials contain mosture to some degree. Often if not totally saturated and if a continuous flow of water is not present then ice crystal growth is limited.. I have this discussion from time to time about the NHBC /  BC min found depth of 450mm.. if there is no water supply to grow big ice crystals how is the found going to heave significantly?

 

Look forward to hearing more about what you are doing.

 

 

 

[PaulBartSpears]

17 hours ago, ProDave said:

Our new house is the first house I have ever had, where the external wall surface is cold enough (due to so little heat loss) for frost to form on the render on a cold night (and on the outside of the 3G windows)

 You have it good. When I was a kid in Scotland it was so cold that there was ice on the inside of the windows and you had to break the ice in the toilet even when the heating was on.

 

17 hours ago, ProDave said:

I do wonder if that is a contrubutor to the problems I have had (and probably not entirely fixed yet) with my thin coat render.  My suspicion that if any wind driven rain can find an opening to get in and not run off, then it will freeze and cause issues.

 

This is of course much more likely to happen in an exposed spot in the Highlands than in a sheltered spot somewhere less cold.

 

I notice around here, not one single garden wall that has been rendered has managed to keep it's render for more than about 2 years.

Yikes. My sister in law has just move into a super insulated new house in the Highlands, quite exposed, and rendered. Hope her render doesn't fall off. But I suspect there is something wrong with the local firm(s). I've seen houses in Northern Poland and Scandinavia with massive thicknesses of insulation and the render seems to stay on fine.

 

[PaulBartSpears]

12 hours ago, Gus Potter said:

Hello Paul.

 

This is a good source of information and discussion.

 

https://www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html

 

Pete Ward has upset a lot of folk in the damp proofing industry so you can have a bit of fun reading around seeing what they are all saying. Main thing is if you spend a bit of time now you can inform yourself much more.. each house is different. 

 

When faced with this type of issue I always look at what is happening outside. For example, the roof details (eaves overhang and guttering) which way the building faces, the pevailing wind (the east, north and north north west walls get the coldest freezing winds that cool walls a lot and quickly which is important as they freeze before they can dry out a bit), overshaddowing trees, ground levels, any potential DPC.. be that slate or a less permeabile brick, say a good quality clay brick or an engineering brick and so on.

 

...

 

Photos would be helpful if you feel able to post. Once you gain a deeper understanding of how the house behaves then you can plan a cost effective insulation strategy and get to the bottom of your concerns about freeze thaw of the bricks.

 

Remember that most common construction materials contain mosture to some degree. Often if not totally saturated and if a continuous flow of water is not present then ice crystal growth is limited.. I have this discussion from time to time about the NHBC /  BC min found depth of 450mm.. if there is no water supply to grow big ice crystals how is the found going to heave significantly?

 

Thanks for your comment and the link.Very interesting.

 

Apart from one isolated spot which I'm not too concerned about I don't currently have damp problems. They all occurred in the past before I owned the property and have been cured. There is render on the outside of some of the walls up to a height of about a metre which I think covers damaged brick.

 

I'm concerned that by lowering the wall temperature by installing internal insulation frost damage to brick higher up might occur. Is this something architects know about? Are there specialists who know about this? One solution might be to render the walls if they get frost damage, but that might not be acceptable because we are in a conservation area.

[PaulBartSpears]

14 hours ago, saveasteading said:

Its possible that the render is impermeable, and keeping the damp in.

I don't have damp problems. My concern is that by insulating the walls they will get colder and then may suffer frost damage.

[saveasteading]

2 hours ago, PaulBartSpears said:

Is this something architects know about? Are there specialists who know about this

1. Not many

2. Some, and some on here know more than I do.

 

I say insulate internally. Presumably you have a solid 9" wall. The outside already gets very cold.

The main solution is to ensure that the wall sheds liquid  water. No drips, tidy pointing, drains or slopes taking water away frlm the walls.

[Gus Potter]

On 26/11/2023 at 11:12, PaulBartSpears said:

Thanks for your comment and the link.Very interesting.

 

Apart from one isolated spot which I'm not too concerned about I don't currently have damp problems. They all occurred in the past before I owned the property and have been cured. There is render on the outside of some of the walls up to a height of about a metre which I think covers damaged brick.

 

I'm concerned that by lowering the wall temperature by installing internal insulation frost damage to brick higher up might occur. Is this something architects know about? Are there specialists who know about this? One solution might be to render the walls if they get frost damage, but that might not be acceptable because we are in a conservation area

 

On 26/11/2023 at 10:04, PaulBartSpears said:

I've seen houses in Northern Poland and Scandinavia with massive thicknesses of insulation and the render seems to stay on fine.

Hi Paul.

 

Post a photo of typical wall if you can.

 

Appreciate you are not concerned about damp problems.

On 25/11/2023 at 13:23, PaulBartSpears said:

and has been remedied by rendering up to about 1 metre

Pity that as it is probably a cement based render, can easily trap water.

 

Ok going back to basics. For bricks to suffer frost damage they need to take in water which then freezes. My first real job after leaving college some 40 years ago was in a materials testing lab and one of my jobs was to take the bricks out the freezer in the morning and put them back in at night. Now for frost damage to occur you need sufficient mobile water for the ice crystals to grow big enough to spall the bricks.

 

Your comment about Poland / Scandinavia is interesting, add say parts of the USA and Canada to that list. I think there are a few reasons why their render stays on fine. One is that although it gets much colder the climate is different, they typically don't have the gulf steam blowing warm moist air for a few days and soaking everything followed by a rapid change in wind direction, for us in the UK that biting and chilling north east wind rapidly cools and freezes things quickly with rapid expansion. If the weather progressivly get colder then the external humidity tends to drop (Poland?) which drys the walls (even though it is cold) so less growth potential of the ice crystals.

 

Also as they know it gets very cold their tradesfolk understand the problem more. You'll have read about saying using SBR bond for render, but there are few trades folk that actually read and follow the instructions which are really important.. you need to let it get tacky so it bonds to the render which it does really well if done right. Let it (SBR) dry and you may have better luck getting render to stick to glass...  but funnily a lot of folk on BH will have found hard spashed render hard to get off their new windows.. some adhesion.. wrong place, but nowhere the levels of adhesion and mechanical key you need to keep render in place for a long time.

 

You're right in that if you insulate on the inside you tend to shift the dew point inwards. Also I can follow your thinking about causing a problem higher up the wall. It's rare that you see brick spalling high up in a wall due to frost damage as I think there is enough hot air / heat at the higher level to mitigate.

 

If it was my own house I would say. I'll first test by approximate calculation what happens if I turn this into a timber frame with 230mm old external masonry rendered leaf analysis. Ok you have thicker masonry on the outside but the principle is the same. Here we want the dew point to more often than not to (it shifts depending on season and internal / external conditions and can at times reverse) sit in the cavity, we then let any condensation drain down the cavity or evaporate later when conditions change.

 

Ideally we want to avoid hitting the dew point. But that often means creating more drafts / ventilation in the right place. You may need to sacrafice any meaningful insulation effect you get from the masonry, which won't be a lot anyway.

 

What would happen if I strapped and lined the walls, insulated all that with plenty air tape to stop the water gas getting to the problem area in the first place. Can I detail that at the bottom so water can drain into a solum space without rotting the ground floor joist ends (which you have recognised) and maybe get some cavity venting at the top of the ground floor walls. We are not talking a massive draft here, just enough to capture any water gas that gets past the air tape and stop the cavity from becoming musty. Ideally you want to remove the water gas (reduce air relative humidity) before it condenses.  In principle this works until you come to detail it so it actually works, the tricky bit will be at the bottom.

 

EWI shifts the dew point outwards, but it can look awful if not done correctly, not always work properly, particular when you come to sort out all the details and spoil the character of the house. I would explore all other options before going for EWI.

 

This all sounds a bit dramatic and technical. The most important thing is to stop the walls from getting wetted from the outside as much as possible; by checking gutters, pointing and ground levels and splash zones from say slabbing etc. Then making sure you get plenty draft round the house and (sun on the walls in the winter) if you can to dry them back out. The damage in the UK is often done by a North East wind, I would focus on any elevations facing that way first.

 

If you have big overhanging trees and / or  shrubs against the walls then you are starting a fight with one hand tied behind your back.

 

Keep us posted.., a photo or two would help generate more targeted comments. There are a lot of folk on BH that know a lot about this, more than I so a bit more visual info could encourage them to chip in with their ideas. Some are experts at insulation / thermal modelling so could maybe put more flesh on the bones of what I'm suggesting.