Old Cottage Restoration + Extension Project

[JulianB]

On ‎12‎/‎10‎/‎2019 at 09:49, scottishjohn said:

thats why when you doing a floor your plastic membrane  goes under the insulation and up to the walls so it cannot transfer moisture from walls to floor slab

Thanks John...I do see your point; I can understand the principles of completely sealing the walls and floor as one entity, and hence not being vunerable to any moisture external of this membrane. My only concern would be tthe need for greater internal insulation, as a result of the floor/walls having higher mositure contents as a result of the impermeable layers, and hence performing less efficiently (from a thermal point of view). I'm currently reading the old house eco handbook and the authors refer to this scenario in particular (I'll post a photo of it tonight...). Also, I had gone to see a barn a while back which had been tanked about a metre and a half up the walls together with the floor slab (not sure how well they were tied in...); what I did notice was that the tanking had actually blown off the walls in large sections, creating gaps of about 10mm...quite worrying (although potentially linked to some other problem I didn't spot...)

 

19 hours ago, Ferdinand said:

You need to consider your chimneys carefully.

 

The blocked off ones will be uninsulated spaces exposed to outside, depending on how you choose to block them.

 

Summary copied form here:
http://www.greenbuilding.co.uk/GBF_Forum/discussion/comment/213675/#Comment_213675
 

 

 

Thank you Ferdinand...I had briefly heard about the issues involved with de-commissioning fireplaces - will definitely give that a good read and take notes as I wouldn't want to create any more issues than I already have on my plate! One of the chimneys actually runs externally to the house, which I thought might be a bit easier to deal with from a thermal losses / maintaining ventilation within the stack POV. Could I ask what GBF stands for by the way?

 

On ‎12‎/‎10‎/‎2019 at 05:44, SteamyTea said:

Renovate it properly and any dampness should be a thing of the past.

 

I can't see how I'd ever get around the fact that the base of the solid walls are in direct contact with the earth, and would naturally draw moisture up them from time to time? Am I mising something? I can see why people find it a lot easier to flatten and start from scratch!

 

 

On ‎11‎/‎10‎/‎2019 at 23:54, scottishjohn said:

look at any of the real passiv house builder  guys and they will all tell you that PV is the last thing --even if it was suitable in your postion 

fabric of the house first --reduce energy requirements is primary goal --pv  etc are the frills 

 

Thanks John! The sole reason PV comes to mind is in order to heat the DHW to an adequate temperature without bankrupting me. I haven't had time to estimate the CH requirements of the proposed house / spec, but I've seemed to come across quite a few comments on ASHP and degraded COPs at DHW hot water temperatures (I haven't looked at the larger units and what their COP characteristics are like at high temperature demands / low temperatures & high relative humidity to get a worst case scenario). Any ideas for alternative methods of heating DHW? 

 

Thanks everyone!

[Ferdinand]

Green Building Forum ... long running forum ie 10 years plus.

 

BH seems to have largely taken over their self-build segment. GBF has for me generally been a bit more boffin-y and good for detailed howto questions where methods are not very widely established or accepted .. so eg for confirming by educated guesses.

 

Best way to navigate it is via Google.

 

(imo) 

Edited October 14, 2019 by Ferdinand

[scottishjohn]

1 hour ago, JulianB said:

what I did notice was that the tanking had actually blown off the walls in large sections, creating gaps of about 10mm...quite worrying (although potentially linked to some other problem I didn't spot...)

bad preparation-- not cleaned enough and loose surface not removed before application of tanking --very standard tactic for water proofing cellars --so it does work if done correctly.

closed cell foam ,not open cell,will do the same job --but not something that is DIY-- and it would ALL the the walls not just at bottom --not only does it waterproof ,but it insulates very well

you will have seen how well builders foam sticks to everything like shit to a blanket 

Edited October 14, 2019 by scottishjohn

[JulianB]

Evening All,

 

It’s been a while since my last post…

 

The good news is that our planning application has been granted against all odds, however it did require us to conjure up enough interest in the village to get it ‘called in’ and decided at committee level (6 in favour, 5 against!). They have placed a number of conditions in our path which are likely to drain more out of the budget and slow us down somewhat, but we’re still smiling!

 

We’re now in the process of drawing up the necessary details to satisfy building control, and we really ought to be finalising our heat energy supply. I haven’t yet attempted to calculate the energy demand of the house (from JHarris’s spreadsheet), however I was under the impression that from a CH POV, ASHP should present us with a good improvement from our current oil fired boiler setup. We intend on integrating UFH in both the old and new part of the house. That said, the new part of the house is an upside house…i.e. upper level will be for living and lower for sleeping…I’ve seen UFH installed over floor joists (for the 1^st floor living), but am keen to get people’s opinion on it?

 

With regards to DHW, my wife and 2 children (& counting) enjoy their long showers/baths, and I’m aware that above ~45 degC, CoP plummets w.r.t. the majority of ASHPs? I have also read about people using the ASHP to supply the DHW tank with water @ 45degC, and then using an alternative source top up the remainder to get to say 65degC?

 

Solar seems to be a popular option, but given our proximity to mature trees, seems an unlikely candidate? Wind however is something we do have a great deal of (the good kind!); being situated on the top of a valley, we really do get fairly good gusts on most days, but I haven’t yet grasped whether this is a viable / realistic route for the domestic market, and particularly given that we are in quite a sensitive area in terms of focal points (& our pockets aren’t deep!).

 

Would using the grid to top up the remainder of the DHW needs be a viable option, or would we be better off scraping the whole idea and sticking with a more modern (& hopefully more efficient) oil fired system?

 

Any advice would be greatly appreciated!

[Cpd]

36 minutes ago, JulianB said:

Wind however is something we do have a great deal of (the good kind!); being situated on the top of a valley, we really do get fairly good gusts on most days, but I haven’t yet grasped whether this is a viable / realistic route for the domestic market, and particularly given that we are in quite a sensitive area in terms of focal points (& our pockets aren’t deep!).

you need good clean air for a turbine to be effective, meaning it has to be unhindered by buildings, trees and numerous other things. Just looking at your photos would suggest your site I not suitable IMHO. Also wind turbines on a domestic scale just don’t add up on instal and maintenance and everything I have read so far has put me off. I live on an elevated site with open frontage to the sea, facing south west where the prevailing wind comes from and so far nobody has said it’s a good idea! One day (a long time from now) I will instal a small turbine as an experiment to help provide heat and lighting to a proposed polly tunnel..... but it will be for novelty and fun and I won’t be heartbroken if it is not cost effective. I was just recently at a farm where they had a BIG turbine installed and the guy said it had just broken even on instal costs when it had a serious failure (also just out of warranty )and that it was going to cost serious money to get it fixed but felt he had to take the gamble and get it repaired with the hope that nothing else went horribly wrong again for a good long time otherwise he really would be loosing a lot of cash. 

[JulianB]

12 hours ago, Cpd said:

you need good clean air for a turbine to be effective, meaning it has to be unhindered by buildings, trees and numerous other things. Just looking at your photos would suggest your site I not suitable IMHO. Also wind turbines on a domestic scale just don’t add up on instal and maintenance and everything I have read so far has put me off. I live on an elevated site with open frontage to the sea, facing south west where the prevailing wind comes from and so far nobody has said it’s a good idea! One day (a long time from now) I will instal a small turbine as an experiment to help provide heat and lighting to a proposed polly tunnel..... but it will be for novelty and fun and I won’t be heartbroken if it is not cost effective. I was just recently at a farm where they had a BIG turbine installed and the guy said it had just broken even on instal costs when it had a serious failure (also just out of warranty )and that it was going to cost serious money to get it fixed but felt he had to take the gamble and get it repaired with the hope that nothing else went horribly wrong again for a good long time otherwise he really would be loosing a lot of cash. 

 

Thanks for the advice! Sounds like that may be off the list too then! Now just to find a suitable heat source for the DHW...

[Gone West]

@JulianB Just a couple of points. We heat our water with an EASHP and it is stored, 185l, at 45C although there are only two of us. Although it seems popular I wouldn't use UFH on the ground floor due to it's inefficiency, I would probably use some form of skirting heating.

[JulianB]

7 hours ago, PeterStarck said:

@JulianB Just a couple of points. We heat our water with an EASHP and it is stored, 185l, at 45C although there are only two of us. Although it seems popular I wouldn't use UFH on the ground floor due to it's inefficiency, I would probably use some form of skirting heating.

 

Thanks for the info... What sort of CoPs do EASHPs achieve relative to ASHPs? Am I right in assuming an EASHP would replace the role of an MVHR (I.e. EASHP would also provide some form of ventilation?).  Do you run your showers and baths at 45C??

 

I have thought about skirting heating, but struggle to see how there will be enough surface area in the rooms I am interested in as there will be a kitchen taking up a good portion fo wall area etc?

 

[Gone West]

@JulianB We have a Genvex Combi 185LS which has a MVHR unit and 585W EASHP built in which heats the DHW and provides supplementary warm air heating through the MVHR ducting. I don't know the CoP of our unit but IIRC it is supposed to average 4.0 in our climate.

The DHW is stored at 45C and the showers run at 38C.

The Genvex Combi 185LS is suitable for a small (130m2) very low energy house but would struggle in a larger house. There are other EASHP DHW heaters such as the ESP Ecocent.

Edited January 10, 2020 by PeterStarck

[JulianB]

Good bit of info re. 45degC being suitable for DHW...wouldn't that imply that the majority of ASHPs would still operate within their favorable COP for DHW needs? I've had a quick play with JHarris's Heat Loss Calculator and it does highlight the considerable amount of glazing we are incorporating! Due to the listing status and conservation area, we are constrained to certain heritage range aluminium windows, which don't seem to get much lower than 1.5W/m2.K. My U value break down, together with areas / volumes looks something like this:

 

Wall U value =	0.17	W/m2.K
Floor U value =	0.19	W/m2.K
Roof U value =	0.18	W/m2.K
Average window U value =	1.4	W/m2.K
Average door U value =	1.5	W/m2.K

 

Internal wall area =	94.40	m2
Internal roof area =	131.00	m2
Internal floor area =	92.00	m2
House total internal volume =	364	m³
Total wall and roof heat loss area =	225.40	m2
Total window area =	35.52	m2

 

As a result, the net heat loss power comes in at:

 

Heat loss versus outside air temperature
Difference between room and OAT (deg K) =	0	5	10	15	20	25	30
Ventilation heat loss energy (J) =	0	142042	284084	426126	568168	710210	852251
Ventilation heat loss power (W) =	0	39	79	118	158	197	237
Wall heat loss power (W) =	0	80	160	241	321	401	481
Window heat loss power (W) =	0	249	497	746	995	1243	1492
Door heat loss power (W) =	0	12	24	36	48	60	72
Roof heat loss power (W) =	0	118	236	354	472	590	707
Ground floor heat loss power (W) =	210	210	210	210	210	210	210
Fabric heat loss power (W) =	210	669	1127	1586	2045	2504	2963
Total heat loss power (W) =	210	708	1206	1705	2203	2701	3199

 

These calculations also assume that the old part of the house is consistent in construction with the new, which will naturally drag it down further! I will have to have a good look through a few ASHP specs to see which fits the bill together with MVHRs. Whilst the Genvex Combi does sound like a very good bit of kit, my better half has warned me against taking away her UFH! 

[scottishjohn]

On 14/10/2019 at 07:36, JulianB said:

My only concern would be tthe need for greater internal insulation, as a result of the floor/walls having higher mositure contents as a result of the impermeable layers, and hence performing less efficiently (from a thermal point of view

If the outside of the stone house is pointed with lime mortar,remove cement pointing  and any further painting or render is also permeable ,and remove any that is not 

then sealing inside will make all moisture go outwards 

so I do not see the worry with internal moisture if you seal walls and floor in one continuos unit .once sealed no more moisture will get in

more insulation will only help you heat loss calcs and  lower energy requirement 

I say again "fabric first "

Edited January 15, 2020 by scottishjohn

[JulianB]

On ‎15‎/‎01‎/‎2020 at 07:46, scottishjohn said:

If the outside of the stone house is pointed with lime mortar,remove cement pointing  and any further painting or render is also permeable ,and remove any that is not 

then sealing inside will make all moisture go outwards 

so I do not see the worry with internal moisture if you seal walls and floor in one continuos unit .once sealed no more moisture will get in

more insulation will only help you heat loss calcs and  lower energy requirement 

I say again "fabric first "

 

Thanks for the reply! I understand where you’re coming from, but in my mind I’m still thinking that this would be the wrong approach for the fabric of the house. Here’s my argument:

·        The bottom of the solid stone wall will still be sitting on wet ground which I can never get away from unless I unpin the entire lodge. The more you remove the ability for the internal floor and walls to breathe (with your proposed method) the greater the moisture levels within the walls

·        Lining the internal walls with a high level of insulation will pull the dew point inboard, potentially between the wall and insulation, which further raises the moisture content of the walls. Granted that you would not be directly impacted by this moisture as you’ve (hopefully) fully sealed the living space with the barrier, but I presume this would nonetheless reduce the thermal performance of the stone wall, not to mention structural integrity over time (granted a very long time)?

 

My thoughts on the other hand are to dig the floor up and pour limecrete with integrated UFH (and breathable covering); I’m on the fence on whether to batten internal walls and use some form of permeable thermally efficient material, whilst also incorporating a ‘breathable’ airtight membrane… This would similarly pull the dew point inwards, however I’m hoping to manage this through only using breathable materials, together with the MVHR. It would be great if we had U values for solid stone walls in both a dry state and a sopping wet state (as a worst case) to begin to put some numbers to both methods?

[scottishjohn]

1 minute ago, JulianB said:

The bottom of the solid stone wall will still be sitting on wet ground which I can never get away from unless I unpin the entire lodge. The more you remove the ability for the internal floor and walls to breathe (with your proposed method) the greater the moisture levels within the walls

I,m not sure you have understood me 

you are digging out floor  of whole building  to fit new UFH concrete floor with insulation under it 

so here you fit full vapour barrier  under insulation which laps up onto wall and is sealed to tanked wall

 

plenty of choices of how to do it --closed cell foam is only one 

 

the only way damp can go is outwards  ,through your lime mortar walls --they are breathable 

there will be no damp from floor  as the new poured floor with UFH  is sealed by membrane from the ground under it- so no damp 

inside will not have any moisture because you have isolated it from damp with membrane 

[JulianB]

10 minutes ago, scottishjohn said:

I,m not sure you have understood me 

you are digging out floor  of whole building  to fit new UFH concrete floor with insulation under it 

so here you fit full vapour barrier  under insulation which laps up onto wall and is sealed to tanked wall

 

plenty of choices of how to do it --closed cell foam is only one 

 

the only way damp can go is outwards  ,through your lime mortar walls --they are breathable 

there will be no damp from floor  as the new poured floor with UFH  is sealed by membrane from the ground under it- so no damp 

inside will not have any moisture because you have isolated it from damp with membrane 

 

Yes I understand that…I’m referring to the bottom of the solid stone wall, not the internal floor. The fact that you’ve basically removed the ability for the floor/ internal walls to breathe to help regulate the moisture in the ground/earth would naturally result in the base of the wall having to do more work…which means a wetter wall…granted you can’t see that moisture because you’ve put up a barrier. Therefore thermal performance of the solid wall drops, and implies that you have to rely on more of the internal insulation you line the walls with to prevent heat loss? Essentially you sacrifice U value of the wall and rely on the box you’ve made within the box?

[scottishjohn]

54 minutes ago, JulianB said:

Therefore thermal performance of the solid wall drops, and implies that you have to rely on more of the internal insulation you line the walls with to prevent heat loss? Essentially you sacrifice U value of the wall and rely on the box you’ve made within the box?

YES

the thermal value of  a solid wall is next to nothing compared to insulation 

3ft of wall =150mm of PIR

all that thick walls do is slow down temp change --thats not the same as insulation

and a wet wall is even worse -

 

all you can do is isolate it from the livable part of house so you are not pumping heat into the ground or walls  at  great expense.

this is why you put insukation under your conrete slab so cold wet ground does not suck the heat out of your floor 

 

[Cpd]

So I have an old stone cottage with 700mm stone walls and 1000mm gables. I dug up the floor down to just above the footing base , dug in various land drainage systems to allow any water to escape should it get in there, filled the area with the stuff railways are build on (200mm) (golf ball sized stones.) compacted as I went but still allowing full drainage over the whole area. Capped it of with cement, but left a 50mm gap around the outside.  put two layers of DPM down, the first was semi sacrificial but in reality it will be fine. Laid 100mm of reinforced concrete (BIG MISTAKE) as I should have put insulation down...... again I left a 50mm gap round the edge and filled with pea gravel. Insulation will be 90mm  PIR, I am hoping to put WUNDA   - Wundatherm Premium+ Board – Underfloor Heating  boards down and then final floor coverings. The DPM will go up the wall and join up to whatever I have there. I will frame out the whole house and there will be a vented void between the stone wall and the framework. Insulation between and over stud-work, battens and plaster board. The building is bone dry with absolutely no sign of water coming up or into the walls even though there is no damp proof course. The 50mm drainage gap filled with pea gravel around the walls was a precaution as the exterior ground level is higher than my final floor height. However because it’s a 700mm double stone wall with a rubble middle it was not an issue as any water that does get in goes down the middle of the wall and then can exit through the huge drainage area. I regret not going deeper and if I knew then what I know now........ but hay ho. I don’t think 90mm of PUR is good but it will one day be a holiday rental and the losses in heat downwards will be compensated for by it making money. (limited head room means a MAX of 90mm PIR plus the WUNDA board)  I am hoping that UFH run from the ASHP will provide a really nice level of comfort. There will be a WBS for the caveman enthusiasts. Upstairs will be either fancy radiators run of the ASHP or just a couple of electric heaters on the wall for top up. 
 

2 hours ago, scottishjohn said:

the thermal value of  a solid wall is next to nothing compared to insulation 

3ft of wall =150mm of PIR

Did not know this, I have assumed it was so poor I did not take it into consideration, however it really does help with stability of temperature as the house even unheated and with just the upstairs insulated stay very stable. I have no issues with glazing as the house faces east so only gets a bit of sun in the morning due to a hill. 
 

anyway a bit of a ramble but just another perspective. 

[jfb]

On 11/10/2019 at 15:19, scottishjohn said:

the walls you either seal them or you have to have an air gap and a draft up them to allow stone to dry out

 that is the way you make your old house into new close to passiv type house,

I don't think this is true. My stone walls have lime render (as flattening layer and airtight layer), wood fibre board, lime render, limewash. Breathable both ways and airtight.

 

I also went for a concrete floor with 200mm EPS below with a DPM under this. Also some French Drains around the perimeter. Initially I had looked at limecrete floor (and in fact did install a small limecrete floor in a small outbuilding) but was persuaded not to. Seems to have worked well.

[Cpd]

49 minutes ago, jfb said:

Breathable both ways and airtight.

This is probably the best way as it uses all the layers and they all work together, I made various mistakes along the way...... I repointed with a cement,  lime and sand mix but due to the really fissured / cracked stone I have and continue to paint the outside with white masonry paint as I live in an extremely wet environment in the hope of preventing rain ingress. The double wall and rubble fill is fully vented with vents low down and at wall head. Also living in a very windy location means I have plenty of ventilation. All the walls are bone dry. On another building I have a lime pointed solid gable wall and it is permanently saturated, there is just to much wet weather and the shite stone is so full of cracks that every time it rains the wall just fills up with water again. I will clad the whole gable to prevent water ingress...... 

[JulianB]

On ‎10‎/‎01‎/‎2020 at 16:53, PeterStarck said:

@JulianB We have a Genvex Combi 185LS which has a MVHR unit and 585W EASHP built in which heats the DHW and provides supplementary warm air heating through the MVHR ducting. I don't know the CoP of our unit but IIRC it is supposed to average 4.0 in our climate.

The DHW is stored at 45C and the showers run at 38C.

The Genvex Combi 185LS is suitable for a small (130m2) very low energy house but would struggle in a larger house. There are other EASHP DHW heaters such as the ESP Ecocent.

 

Could I ask if you do anything to tackle the risk of Legionnaires’ disease by storing your DHW @ 45degC. If I understand correctly this means showers and baths are still comfortable, but do flow rates take a hit as one typically is able to mix in more some cold water to hit the desired temperature when storing at say 60?

 

 

11 hours ago, Cpd said:

So I have an old stone cottage with 700mm stone walls and 1000mm gables. I dug up the floor down to just above the footing base , dug in various land drainage systems to allow any water to escape should it get in there, filled the area with the stuff railways are build on (200mm) (golf ball sized stones.) compacted as I went but still allowing full drainage over the whole area. Capped it of with cement, but left a 50mm gap around the outside.  put two layers of DPM down, the first was semi sacrificial but in reality it will be fine. Laid 100mm of reinforced concrete (BIG MISTAKE) as I should have put insulation down...... again I left a 50mm gap round the edge and filled with pea gravel. Insulation will be 90mm  PIR, I am hoping to put WUNDA   - Wundatherm Premium+ Board – Underfloor Heating  boards down and then final floor coverings. The DPM will go up the wall and join up to whatever I have there. I will frame out the whole house and there will be a vented void between the stone wall and the framework. Insulation between and over stud-work, battens and plaster board. The building is bone dry with absolutely no sign of water coming up or into the walls even though there is no damp proof course. The 50mm drainage gap filled with pea gravel around the walls was a precaution as the exterior ground level is higher than my final floor height. However because it’s a 700mm double stone wall with a rubble middle it was not an issue as any water that does get in goes down the middle of the wall and then can exit through the huge drainage area. I regret not going deeper and if I knew then what I know now........ but hay ho. I don’t think 90mm of PUR is good but it will one day be a holiday rental and the losses in heat downwards will be compensated for by it making money. (limited head room means a MAX of 90mm PIR plus the WUNDA board)  I am hoping that UFH run from the ASHP will provide a really nice level of comfort. There will be a WBS for the caveman enthusiasts. Upstairs will be either fancy radiators run of the ASHP or just a couple of electric heaters on the wall for top up. 
 

Did not know this, I have assumed it was so poor I did not take it into consideration, however it really does help with stability of temperature as the house even unheated and with just the upstairs insulated stay very stable. I have no issues with glazing as the house faces east so only gets a bit of sun in the morning due to a hill. 
 

anyway a bit of a ramble but just another perspective. 

 

That does make sense in my mind, as you have maintained the ventilation aspect and upped the drainage ability of the ground immediently underneath. Could I ask what you've done to the walls?

 

10 hours ago, jfb said:

I don't think this is true. My stone walls have lime render (as flattening layer and airtight layer), wood fibre board, lime render, limewash. Breathable both ways and airtight.

 

I also went for a concrete floor with 200mm EPS below with a DPM under this. Also some French Drains around the perimeter. Initially I had looked at limecrete floor (and in fact did install a small limecrete floor in a small outbuilding) but was persuaded not to. Seems to have worked well.

 

Your wall build up sounds very much like what I might be looking to do, together with french drains...Could I ask what persuaded you to steer clear of limecrete this time round? any pics of the project? 

[JulianB]

9 hours ago, Cpd said:

This is probably the best way as it uses all the layers and they all work together, I made various mistakes along the way...... I repointed with a cement,  lime and sand mix but due to the really fissured / cracked stone I have and continue to paint the outside with white masonry paint as I live in an extremely wet environment in the hope of preventing rain ingress. The double wall and rubble fill is fully vented with vents low down and at wall head. Also living in a very windy location means I have plenty of ventilation. All the walls are bone dry. On another building I have a lime pointed solid gable wall and it is permanently saturated, there is just to much wet weather and the shite stone is so full of cracks that every time it rains the wall just fills up with water again. I will clad the whole gable to prevent water ingress...... 

 

This same issue had crossed my mind and I thought about an external lime render, or potentially some breathable layer prior to this render, however I don't believe the conservation officer will let us touch the external walls on the lodge!

[scottishjohn]

I,m just wondering how you intend to get this draft up the wall

you going to put air bricks in bottom of walls and then leave a gap at head of wall to allow draft to eith go up into your cold roof  and out through ridge 

OR divert the draft out at eves?

 no air bricks --no air movement ,once you have done modern sealing of internal walls and skirting boards etc

 just making a void could cause mold orrotting of you timber frame if  no  draft to move it out and up and make space dry

you surely  still need a vapour barrier of some sort at the inside of the void to protect the wood frame  how ever you do it 

the old houses that just had studs +lathe plaster were never heated like modern houses ,so condensation was not a problem and yes moisture came into house from the plaster 

 

most large houses had cellars so the space between the  outside walls and  plaster walls got the draft from the cellar which went right up to roof 

this is why I say seal the outer walls from what ever you doing  to inside

 look at the detail in ANY type of new housebuild

there will be a vapour barrier (house wrap) between outside of house and inside and then an other air barrier  to stop air leaks 

 

 

 

[JulianB]

14 hours ago, scottishjohn said:

YES

the thermal value of  a solid wall is next to nothing compared to insulation 

3ft of wall =150mm of PIR

all that thick walls do is slow down temp change --thats not the same as insulation

and a wet wall is even worse -

 

all you can do is isolate it from the livable part of house so you are not pumping heat into the ground or walls  at  great expense.

this is why you put insukation under your conrete slab so cold wet ground does not suck the heat out of your floor 

 

 

Agreed solid walls doen't perform as well as modern superior materials, but the only point I was trying to make is that if taking your example of 3 ft wall is equivalent to 150mm of PIR  when dry...as soon as you've completed sealed up your internal living area and put a great demand on those walls to manage moisture, the wet solid stone wall will perform worse than the original 150mm PIR estimate (By what factor I don't know?), so depending on how much insulation you've added you might not be a lot better off? together with the potential acceleration of the rate of deterioration of the stone walls themselves from being saturated for a greater portion of time?

 

On the other hand if you go with something like a wood fibre board which has a lambda of 0.038W/m.K, you can continue to build on that thermal efficiency, without loosing any of that theoretical 130mm PIR equivalence, whilst also keeping everything pearmable? 

Edited January 17, 2020 by JulianB
Too keen to press send!

[scottishjohn]

2 minutes ago, JulianB said:

 

Agreed solid walls doen't perform as well as modern superior materials, but the only point I was trying to make is that if taking your example of 3 ft wall is equivalent to 150mm of PIR  when dry...as soon as you've completed sealed up your internal living area and put a great demand on those walls to manage moisture, the wet solid stone wall will perform worse than the original 150mm PIR estimate (By what factor I don't know?), so depending on how much insulation you've added you might not be a lot better off? together with the potential acceleration of the rate of deterioration of the stone walls themselves from being saturated for a greater portion of time?

have you looked at thickness of sip panelled houses where there is nothing  but render on outside of the them. and the wall vlaues 

you stone wall is really no vlaue at all 

look at the ICF houses like the ISOTEX which  has only 120mm of concrete inthe wallanbd then insulation --no need for thick heavy walls for insulation vlaues

build another house fully sealed inside your stone shell  that is the correct way . 

I am wrestling with same problem on a larger scale and every time I look at it  or get professionalk advice the answer comes back the same.

the problem is biuilding an airtight and vapour proof shell inside a bulding that is already there as you cannot easily get at the outisde of the new intewrnal walls to apply a properly sealed layer.

and  every builder or kit suppler or ICF suppplier has said the same 

you need to tank the walls and let any moisture go back outwards .

30-40mm of closed cell foam and well cleaned wall is simplest way -do it after you  build your internal timber frame and have it encompassing the back of the studs and it wil lock it all together as well as making it water and air tight..

often used for  barn conversons  for this reason or for stable roofs from inside --its is insulation and holds all the old slates in postion --so water proofs roof as well

 

 

 

 

 

 

[Gone West]

38 minutes ago, JulianB said:

Could I ask if you do anything to tackle the risk of Legionnaires’ disease by storing your DHW @ 45degC. If I understand correctly this means showers and baths are still comfortable, but do flow rates take a hit as one typically is able to mix in more some cold water to hit the desired temperature when storing at say 60?

I haven't increased the DHW temperature above 45C in the, nearly, two years we've lived here. The flow rates seem fine but we do have aerating showers and taps so I don't know whether the aerating effect masks anything.

[jfb]

8 hours ago, JulianB said:

 

Could I ask what persuaded you to steer clear of limecrete this time round? any pics of the project? 

 

I think it was a few things. I had a few architects come around at the beginning and one who had some experience of renovations of this type suggested a concrete floor for cost reasons and after a general assessment of the house not being too damp as it was. He also pointed me in the direction of cheaper woodfibre boards than I was considering. (he was Charlie Luxton from a programe called 'Building the dream' if that means anything).

I think it is undeniably cheaper to use a concrete floor as it uses more conventional materials (I was comparing limecrete and expanded glass sub base against concrete slab and type 1). Also I had quite a large area to do so used a pump for the pour which might be possible with limecrete but not as straightforward.

It did also leave the floor finish more open as you don't have to think about permeability of tile/floor finish. In fact for a new extension to the house I ground the concrete slab down for a polished finish which wouldn't have been possible with  a limecrete slab.

I also read up on some issues with UFH and limecrete floors.

 

I would say that my place isn't in an exposed situation so that is to my advantage.

 

I ended up with 60mm steico woodfibre board and 20mm on window reveals. In theory the 60mm of woodfibre board doesn't meet building regs but my thinking is that the more insulation the higher the risk of interstital condensation. I suspect this wall buildup performs much better in practice than theory might suggest. Room size is also a consideration when using IWI.

 

MVHR is another thing that I wasn't 100% I was going to install but the more I read the more I decided to go with it. Also I think the architect had the assumption that it would be necessary. I did go pretty overboard with airtightness detailing in the end and got a reading of 1 ACH/hour so I am glad I went with MVHR. Overall I have been very happy with the results - house temperature remains very stable without much heating needed and we have barely used the radiators upstairs.