Renovation/modernisation of former miner's cottages + 1970s extensions

[lookseehear]

On 01/02/2024 at 17:58, renovator123 said:

I'm wondering about your EWI options- do you have a price per sq m for Diathonite, and have you had difficulty finding an installer?

 

We are also looking at breathable EWI and options seem limited- although Diathonite looks excellent it's very expensive. I wondered your thoughts on CorkSol / SprayCork, or wood eg Gutex / Steico for EWI instead? I am not sure about durability of wood or about the ability to keep it dry when render over it will crack/decay sooner or later.

 

We had calculations done for EWI using Diathonite, giving approx 57-60mm thickness (evolution, agrathem, etc) over 500mm stone but have recently found some solid walls are not uniformly that thickness, which affects ability to reach EnerPHit U values.

 

Diathonite is similar in U value to rockwool and supasoft/thermafleece options which leaves me wondering about value.

 

Sorry - completely missed this! We have actually ditched the idea of EWI for now, so haven't pursued any installers or quotes but the difficulties in getting a trusted installer is one of the reasons we're leaving it for now. The main reason is that we are making a lot of other fabric upgrades, so we'll wait and see how that pans out before putting in any EWI which would be a big chunk of budget (I assume).

[lookseehear]

This is due an update I feel. We've commenced work under a building notice, after a builder that our architect has worked with many times before became free at relatively short notice. We've yet to finalise all the plans, but are getting started on the first discrete part of the build which is the single storey extension which will become the master bedroom and will have the roof terrace on top. We had planned to renovate the current utility room and excavate the floor to bring level with the neighbouring rooms but realised quickly that it has no foundation (built on clay) and was likely an external WC which was connected to the rest of the house at minimum cost. We've decided therefore to take it down and incorporate that into the new extension construction.

 

Here's the current state a couple of weeks in with the utility demolished and patio cleared ready to start digging the foundations. Our current quandries are about the flat roof buildup for the terrace due to limited thickness to work with, and what the larger plan for heating/insulation is going to be (I've posted topics on both of these recently).

 

Since I previously posted we've also had some structural calcs done, and we're going to put in a new roof with ridge beams so that we can vault the ceilings and insulate at rafter level, because the existing rafters are only 70mm deep unfortunately. As much as I'd like to have a 'full' plan to work off at this point, I can see this one is going to evolve over time, which is the benefit of working with our builder who charges a day rate and is happy to work to a changing set of plans.

 

[renovator123]

Just saw this and actually I also have an update: and lowering part of the ground floor is on the list for another year - there's no foundations here either. We got the EWI with Diathonite, great so far although not fully cured yet. Damp and mould were factors in the decision- Diathonite is very alkaline so inhibits mould, and with no floor insulation the internal solid walls have damp in a few places. We decided to go for MVHR in preference to heat pump and even just having the kitchen extractor recirculating with the wall insulation it's noticeably warmer and less drafty. The utility/downstairs loo extractor is gone in preparation for MVHR. Heating-wise it seems new builds and big renovations are going for heat pump and underfloor heating (at least for ground floor). That's not workable with low ceiling heights and low beams. 

 

We got an advice report drawn up from a charity that provides them and that's helped a lot with planning although the cost estimates are on the low side. The report broke it down into 3 stages and outlined risks eg condensation causing damp.

 

With windows and glazed doors trickle vents are heavily suggested but optional- going the MVHR unit satisfies the ventilation needs and allows you to look more at EnerPHit/Passive House standard triple glazing, which is much better than argon filled double glazing.

 

The "pink house" retrofit in Scotland is a mid terrace with real life figures on different combinations of options, and MVHR was particularly good value and was very good combined with ASHP, we have also discovered 2 further ceiling beams during the MVHR design process https://www.esru.strath.ac.uk//Documents/MSc_2015/MacLean.pdf

 

It's been pretty crazy this year for us, and part of last year so we have a break planned for at least a year, which should mean we get time to patch the numerous holes in walls and ceilings (and floors). The planning is actually more hassle than having the builders in and the endless small jobs and mess.

[Mr Punter]

I know you have already started work, but did you explore demolish and rebuild?  You save 20% VAT and do not need to compromise.  You could even reuse the stone.

[renovator123]

re solid wall insulation - wood boatds are a much less specialist option, Gutex or Lime Green Warm Shell for instance - level walls first though  - both can be used as IWI or EWI. EPS/XPS is the popular EWI option.

https://www.lime-green.co.uk/products/lime-systems/woodfibre

 

we currently have a bag of Lime Green Ultra which can be used as render but we are actually using for patching plaster and holes, using that instead of gypsum plaster gives breathable walls that are mould resistant (alkaline) and greatly improved U value compared to uninsulated solid walls. Diathonite Thermactive you can also hand mix and buy per bag for small repairs and leveling 

https://www.lime-green.co.uk/products/lime-render/ultra_render

 

re: EWI: with Diathonite (Evolution) at 55-60mm thick which is 0.60 U on rubble/sandstone (with original concrete render hacked off first, and a few mm lime green WP finish over the top), we did not need to extend the roof line at all. The walls were very uneven - especially thicker at the bottom and in places curving from one side to the other  (kind of concave) over the, so that was a nice surprise. You would also lose the stone look with EWI (what we found was missing stone and old blocked off doorways etc). Diathonite EWI case here sums up a lot of our issues  

 

With Diathonite if you go IWI you can use Thermactive which has a better U value, with our EWI we still have gypsum plaster internally so unless we replace that on external walls they won't "breathe" (though it may not matter with MVHR in soon). The reason we didn't do IWI was need for new render and lowering outside ground level (which is still higher than inside), as well as less mess to live with. Diathonite needs hose on water tap and electric if machine applied.

 

MVHR: you need an accessible room and unless sound proofed room (they are noisy), so under stairs, boot room, or shower room on left of stairs by bed 5/study. Central to the house is even better with air intake plus connecting to internal drain ie near plumbing - but the big issue we had was avoiding crossing the many exposed ceiling beams downstairs and ceilings way too low for false ceilings (under 2m in places). You would have to plan where the valves go for vaulted ceiling spaces - supply valves that are wall mounted are apparently really large. If you have a central chimney you can run ducting along it and box in and fit valve from there. You also need a recirculating cooker hood and to block/remove all bathroom extractors plus breather membrane in loft, and insulation on any loft ducting, and ideally avoid window vents in triple glazing. MVHR are extremely efficient and kitchen and bathrooms will always be warm and should dry laundry easily indoors.

 

MVHR planning resulted in finding 2 unknown and well hidden ceiling beams.

 

If you have never had oil before then it's really inconvenient - you end up having to buy over 1,500 litres at the (uncapped) Kerosene market rate at the time, in the month you need it, and it doesn't run without electrics anyway. Basically get fleeced once or twice a year, boilers are less efficient too. Skylights that aren't passive house standard will lose a load of heat especially with uninsulated floors - internal stone walls act as a cold bridge unless you de-couple walls from floor eg dry lining. Insulated lime based plaster is a good option for problem spots internally eg Lime Green or Aerogel ones (40% less heat loss compared to uninsulated solid walls). Weirdly we have internal damp at above electric socket height on 2 internal walls, one socket has been replaced multiple times from rust. Ground source heat pump is likely to be better than ASHP for the size of your house. If you do enough energy efficiency improvements eg towards EnerPHit standard then you probably won't need a central heating system.

 

Good luck with the rest of the plans 

[lookseehear]

On 23/10/2024 at 08:47, Mr Punter said:

I know you have already started work, but did you explore demolish and rebuild?  You save 20% VAT and do not need to compromise.  You could even reuse the stone.

Thanks for this, but we're way past that point! We looked at it, but a rebuild at the ~200 sqm would have been in the region of £500-600k. We may as well just be moving house at that point.

[lookseehear]

On 23/10/2024 at 00:40, renovator123 said:

Just saw this and actually I also have an update: and lowering part of the ground floor is on the list for another year - there's no foundations here either. We got the EWI with Diathonite, great so far although not fully cured yet. Damp and mould were factors in the decision- Diathonite is very alkaline so inhibits mould, and with no floor insulation the internal solid walls have damp in a few places. We decided to go for MVHR in preference to heat pump and even just having the kitchen extractor recirculating with the wall insulation it's noticeably warmer and less drafty. The utility/downstairs loo extractor is gone in preparation for MVHR. Heating-wise it seems new builds and big renovations are going for heat pump and underfloor heating (at least for ground floor). That's not workable with low ceiling heights and low beams. 

 

We got an advice report drawn up from a charity that provides them and that's helped a lot with planning although the cost estimates are on the low side. The report broke it down into 3 stages and outlined risks eg condensation causing damp.

 

With windows and glazed doors trickle vents are heavily suggested but optional- going the MVHR unit satisfies the ventilation needs and allows you to look more at EnerPHit/Passive House standard triple glazing, which is much better than argon filled double glazing.

 

The "pink house" retrofit in Scotland is a mid terrace with real life figures on different combinations of options, and MVHR was particularly good value and was very good combined with ASHP, we have also discovered 2 further ceiling beams during the MVHR design process https://www.esru.strath.ac.uk//Documents/MSc_2015/MacLean.pdf

 

It's been pretty crazy this year for us, and part of last year so we have a break planned for at least a year, which should mean we get time to patch the numerous holes in walls and ceilings (and floors). The planning is actually more hassle than having the builders in and the endless small jobs and mess.

 

Thanks for the detail here. We've ruled out EWI, at least for now. There are just too many moving parts of this job, but the main ones being the roof and windows. If we wanted to do EWI we would need to factor that into the roof design, and we're enlarging quite a few of the window openings as we go through the refurb, so we already have the issue of when we order windows to ensure they fit, but not actually having physical openings to measure. Factor EWI detailing into this with an uncertain timeline and it just didn't feel like the right thing to do. Maybe if our builder or architect were experienced in this area that would have made a difference but that's not the case.

 

I would still consider diathonite internally, however finding a competent installer seems to be the bane of most 'eco tech' for buildings nowadays. My ideal solution for insulation and airtightness is something that is straightforwards enough for our builder to pick up, and using fairly common building materials, which is why I'm leaning towards a parge coat to the stone, with an insulated battened service void, using mineral wool or maybe wood fibre.

 

I'm really going to lean into airtightness and MVHR design will need to come relatively soon. We will likely switch out from our oil boiler to ASHP at some point, so all radiators will be sized to accommodate low flow temperatures. It's good to hear that you are seeing benefits of the MVHR already. Have you measured your airtightness at all?

[lookseehear]

14 hours ago, renovator123 said:

re solid wall insulation - wood boatds are a much less specialist option, Gutex or Lime Green Warm Shell for instance - level walls first though  - both can be used as IWI or EWI. EPS/XPS is the popular EWI option.

https://www.lime-green.co.uk/products/lime-systems/woodfibre

 

we currently have a bag of Lime Green Ultra which can be used as render but we are actually using for patching plaster and holes, using that instead of gypsum plaster gives breathable walls that are mould resistant (alkaline) and greatly improved U value compared to uninsulated solid walls. Diathonite Thermactive you can also hand mix and buy per bag for small repairs and leveling 

https://www.lime-green.co.uk/products/lime-render/ultra_render

 

re: EWI: with Diathonite (Evolution) at 55-60mm thick which is 0.60 U on rubble/sandstone (with original concrete render hacked off first, and a few mm lime green WP finish over the top), we did not need to extend the roof line at all. The walls were very uneven - especially thicker at the bottom and in places curving from one side to the other  (kind of concave) over the, so that was a nice surprise. You would also lose the stone look with EWI (what we found was missing stone and old blocked off doorways etc). Diathonite EWI case here sums up a lot of our issues  

 

With Diathonite if you go IWI you can use Thermactive which has a better U value, with our EWI we still have gypsum plaster internally so unless we replace that on external walls they won't "breathe" (though it may not matter with MVHR in soon). The reason we didn't do IWI was need for new render and lowering outside ground level (which is still higher than inside), as well as less mess to live with. Diathonite needs hose on water tap and electric if machine applied.

 

MVHR: you need an accessible room and unless sound proofed room (they are noisy), so under stairs, boot room, or shower room on left of stairs by bed 5/study. Central to the house is even better with air intake plus connecting to internal drain ie near plumbing - but the big issue we had was avoiding crossing the many exposed ceiling beams downstairs and ceilings way too low for false ceilings (under 2m in places). You would have to plan where the valves go for vaulted ceiling spaces - supply valves that are wall mounted are apparently really large. If you have a central chimney you can run ducting along it and box in and fit valve from there. You also need a recirculating cooker hood and to block/remove all bathroom extractors plus breather membrane in loft, and insulation on any loft ducting, and ideally avoid window vents in triple glazing. MVHR are extremely efficient and kitchen and bathrooms will always be warm and should dry laundry easily indoors.

 

MVHR planning resulted in finding 2 unknown and well hidden ceiling beams.

 

If you have never had oil before then it's really inconvenient - you end up having to buy over 1,500 litres at the (uncapped) Kerosene market rate at the time, in the month you need it, and it doesn't run without electrics anyway. Basically get fleeced once or twice a year, boilers are less efficient too. Skylights that aren't passive house standard will lose a load of heat especially with uninsulated floors - internal stone walls act as a cold bridge unless you de-couple walls from floor eg dry lining. Insulated lime based plaster is a good option for problem spots internally eg Lime Green or Aerogel ones (40% less heat loss compared to uninsulated solid walls). Weirdly we have internal damp at above electric socket height on 2 internal walls, one socket has been replaced multiple times from rust. Ground source heat pump is likely to be better than ASHP for the size of your house. If you do enough energy efficiency improvements eg towards EnerPHit standard then you probably won't need a central heating system.

 

Good luck with the rest of the plans 

 

Did you get a specialist installer for any of the diathonite products? Did you find it easy to find someone competent?

 

We're putting living space upstairs and have mostly vaulted ceilings, with the exception of one area which will house the MVHR system. It is above the utility room, so this shouldn't be too much of a problem noise-wise. I think we'll probably have 75% of the house connected to MVHR and the remainder will be hard to duct to, so will have decentralised systems installed.

 

We've always been on oil in this house and hate the process of buying oil twice a year. Our road is fairly narrow, so we've recently had two companies take our money then several weeks later say they can't deliver.

 

Our builder is fairly traditional and keeps talking about tanking stone walls, but I think I'm bringing him around to thinking about different possibilities, like lime based products.

[lookseehear]

Here's a couple of pictures showing the height of the chaos and where we're at now which is a lot more civilised. For a few weeks it felt like we were recreating a WW1 trench.

Edited November 16 by lookseehear

[lookseehear]

[saveasteading]

You do all that work and there is nothing to see.

[saveasteading]

Lime.

Builders and consultants often don't understand it. Have a read and then you will decide it is the right thing to do.

[lookseehear]

8 hours ago, saveasteading said:

Lime.

Builders and consultants often don't understand it. Have a read and then you will decide it is the right thing to do.

 

My problem is that not all lime is created the same. I know the difference between NHL 2, 3.5 and 5, and I know the difference between those and non-hydraulic lime. We had a survey of our house before we moved in by a historic buildings surveyor, who recommended all repointing etc be done with non-hydraulic lime mortar, and that any gypsum plaster be removed and replaced with a non-hydraulic lime based plaster. If you go anywhere near a 'historic buildings' or 'old homes' type community online you get shot for suggesting anything cementitious is used in an older house. The problem being that tradespeople willing to use these products that take many times longer to set than cement or gypsum based materials are rarer than hens teeth! It also means you're very limited in the types of finishes you can use - limewashes/distempers/clay paints.

 

What I always try to do in situations like this is understand the evidence, the science and the data and try and make a plan which balances convenience, cost and results. The problem with that is that not many people have experience of all of the options over a long term. It's either fine because they haven't seen problems with it yet, or it's terrible and to be avoided because it didn't work out for them.

[SteamyTea]

9 hours ago, lookseehear said:

What I always try to do in situations like this is understand the evidence, the science and the data and try and make a plan which balances convenience, cost and results

That is the right way to do it.

 

Why I did this with my limited chemical knowledge.