Cavity wall insulation options

esox28

hey all

have a cavity wall construction with 150mm cavity and two 100mm block leaf,
the traditional method of cozy 80mm board on internals block and 100mm hdi in cavity securded to inside leaf and 50mm cavity etc.

there seem to be two other methods for insualting...
pump fill the entire cavity with insulation

or

insulate cavity on the outside leaf but still in cavity, this system seems to be designed to use the internal leaf as a thermal store ??

is there any opions or segestions

BryanF

esox28 wrote: »

hey all

have a cavity wall construction with 150mm cavity and two 100mm block leaf,
the traditional method of cozy 80mm board on internals block and 100mm hdi in cavity securded to inside leaf and 50mm cavity etc.

there seem to be two other methods for insualting...
pump fill the entire cavity with insulation

or

insulate cavity on the outside leaf but still in cavity, this system seems to be designed to use the internal leaf as a thermal store ??

is there any opions or segestions

1. can you clarify, is this 150 cavity wall built, or are you at design stage?
2. what has your architect recommended?
3. what % of glazing do you have? and
4. what wall U-value are you looking to achieve?

esox28

yea realise I wasent very clear

have had planning permission granted in september, basically ready to start with the right weather over head.

architech has designed in 300mm cavity wall construction and not much more construction detailing. House is to the rear (living/kitchen) is facing south with fairly large glass doors and windows.

has up untill recently been planning on constructing the cavity walls as fallows

9" stone cladding
100mm concrete block
50mm air
100mm hdi
100mm concrete block
38 - 80mm cozy board ( budget dependent)

im just worndering am I spending good money in the wrong way??

at the moment im pushing towards pumping the cavity with bonded beads but dont know wot u-value I'll will end up with. any thought's appericated

BryanF

esox28 wrote: »

yea realise I wasent very clear

have had planning permission granted in september, basically ready to start with the right weather over head.

architech has designed in 300mm cavity wall construction and not much more construction detailing. House is to the rear (living/kitchen) is facing south with fairly large glass doors and windows.

has up untill recently been planning on constructing the cavity walls as fallows

9" stone cladding
100mm concrete block
50mm air
100mm hdi
100mm concrete block
38 - 80mm cozy board ( budget dependent)

im just worndering am I spending good money in the wrong way??

at the moment im pushing towards pumping the cavity with bonded beads but dont know wot u-value I'll will end up with. any thought's appericated

this is entirely up to you, its not my preferred method, but there are loads of parameters to consider, like your windows, who's building it, thermal bridging issues etc
personally my view is if your building in block why would you dryline and remove the benefits of building in block?
if you going to dryline why not just build in timber frame?
also if your concerned that you cant budget for the extra insulation why are you putting on 150mm of stone on?
imo why not get an arch or arch tech to prepare a set of tender/construction dwgs with specification and get them to do provisional BER certificate. I promise you, if you get someone competent, they will save you time, grief and money in the long run.
there are several self-builders here building to near passive levels, why not read back through some of their posts.

kboc

BryanF wrote: »

this is entirely up to you, its not my preferred method, but there are loads of parameters to consider, like your windows, who's building it, thermal bridging issues etc
personally my view is if your building in block why would you dryline and remove the benefits of building in block?
if you going to dryline why not just build in timber frame?
also if your concerned that you cant budget for the extra insulation why are you putting on 150mm of stone on?
imo why not get an arch or arch tech to prepare a set of tender/construction dwgs with specification and get them to do provisional BER certificate. I promise you, if you get someone competent, they will save you time, grief and money in the long run.
there are several self-builders here building to near passive levels, why not read back through some of their posts.

defo, absolutely key!

fclauson

take a read of http://www.boards.ie/vbulletin/showthread.php?t=2056280674

esox28

this is entirely up to you, its not my preferred method, but there are loads of parameters to consider, like your windows, who's building it, thermal bridging issues etc

yea but by pumping the cavity arent you insuring that all areas are insulated, a block layer can leave unseen gaps in hdi, maybe the hdi isent fitted completely tighht to wall due to sloppy concrete 'snots', maybe some contractor starts drilling from inside to outside and pushes insulation away from inside leaf...??

personally my view is if your building in block why would you dryline and remove the benefits of building in block?
if you going to dryline why not just build in timber frame?

I know yea why dryline or cozy board but most new build iv seen have this done, but imo I think your removing the thermal storage aspect of the building in block.

I'm not looking for passive house standards but as close as 'I' can manage, an air tight house and efficient heating system.

fclauson

esox28 wrote: »

......
architech has designed in 300mm cavity wall construction and not much more construction detailing

My advice do not turn a single sod until you have the detail much more specific than this - PM me for a very good detailing person

esox28 wrote: »

... dryline or cozy board but most new build iv seen have this done,

but its not the best method

for reference I have regular block/250mm bead cavity/regular block - Uvalue about 0.13

BryanF

esox28 wrote: »

yea but by pumping the cavity arent you insuring that all areas are insulated, a block layer can leave unseen gaps in hdi, maybe the hdi isent fitted completely tighht to wall due to sloppy concrete 'snots', maybe some contractor starts drilling from inside to outside and pushes insulation away from inside leaf...??

i wasn't disagreeing with you. dry-lining when you could just widen the cavity seems a bit odd to me.. AND

there are loads of parameters to consider, like your windows, who's building it, thermal bridging issues etc

that are not just a blanket solve using any method..

I know yea why dryline or cozy board but most new build iv seen have this done, but imo I think your removing the thermal storage aspect of the building in block.
I'm not looking for passive house standards but as close as 'I' can manage, an air tight house and efficient heating system.

you may not be looking for passive standards and you may not achieve them, but what were talking about here is the easy stuff, that you should get right and to passive spec - which in insulation terms is very close to what is required by the regs anyway.

just do it

esox28 wrote: »

hey all

have a cavity wall construction with 150mm cavity and two 100mm block leaf,
the traditional method of cozy 80mm board on internals block and 100mm hdi in cavity securded to inside leaf and 50mm cavity etc.

there seem to be two other methods for insualting...
pump fill the entire cavity with insulation

or

insulate cavity on the outside leaf but still in cavity, this system seems to be designed to use the internal leaf as a thermal store ??

is there any opions or segestions

Welcome to the early stages of decisions, decisions, decisions! I'll PM you a few posters on here who's posts are worth looking up. The replies you've got already are by good guys as well by the way;).

There is tons on boards on all this. It's well worth your while using the search facility and spending a few hours reading through various threads. BER is one thing, putting your design through PHPP is a more advanced step and well worth considering. Best to make as many, if not all, your decisions before you turn the sod. Best of luck.

Fracking Cylon

I'm in a similar position at the moment. Planning granted and now talking to builders. One suggestion was 100 mm cavity with pumped bead insulation and an insulation board on the inner leaf. I don't have specifics yet. My concern is that you have filled the cavity then and put insulation on the inside, so if you need any further insulation in the future you need to go to the external wall, which I don't fancy. I wonder is a board insulation inbetween the cavity the best solution? Or is the cost way more expensive vs first option outlined?

BryanF

Fracking Cylon wrote: »

I'm in a similar position at the moment. Planning granted and now talking to builders. One suggestion was 100 mm cavity with pumped bead insulation and an insulation board on the inner leaf. I don't have specifics yet. My concern is that you have filled the cavity then and put insulation on the inside, so if you need any further insulation in the future you need to go to the external wall, which I don't fancy. I wonder is a board insulation inbetween the cavity the best solution? Or is the cost way more expensive vs first option outlined?

this is the cheapest/easiest option and builders will always suit themselves. my preference would be for a wide cavity, pumped. this allows for better thermally broken window details and mean you can hang stuff of your walls internally. but it does require details!! as many builders are not comfortable with the wider cavity yet

Fracking Cylon

How wide is wide? Do you know what uValue's you get from this and a cost per sq m?

kboc

Fracking Cylon wrote: »

How wide is wide? Do you know what uValue's you get from this and a cost per sq m?

people are going for 300mm

It is not about u values. These on their own are no good.

It is a joined up picture starting with an energy assessment of your needs. then insulation, airtightness, MHRV closely follwed by excellent quality (workmanship) windows and doors.

Good luck, never accept second best, especially from some of those building contractors, unfortunately very very few of them accept (and want to accept) the need for these type of houses.

fealeranger

kboc wrote: »

people are going for 300mm

It is not about u values. These on their own are no good.

It is a joined up picture starting with an energy assessment of your needs. then insulation, airtightness, MHRV closely follwed by excellent quality (workmanship) windows and doors.

Good luck, never accept second best, especially from some of those building contractors, unfortunately very very few of them accept (and want to accept) the need for these type of houses.

300mm cavity is definitly a good way to go from the advice I have received from a few modern engineers. I got quoted for the 100mm cavity and 63mm insulated slab inside too but decided on the 300mm cavity pumped. That does not mean this option is not good but choice is good too. Lets face fact if you seal your house and make it as airtight as possible with good quality finishing and insulation then if the 300mm pumped cavity does not keep the heat in or cold out you may as well throw your hat at it.:) You will get some quotes for big money and rubbish spec and you will get reasonable quotes with good spec just trying to balance the cost and figure out which is best is the problem:rolleyes:. Maybe self build is a good option!!:eek:

esox28

fclauson wrote: »

My advice do not turn a single sod until you have the detail much more specific than this - PM me for a very good detailing person



but its not the best method

for reference I have regular block/250mm bead cavity/regular block - Uvalue about 0.13

am up to sub-floor level and ready to in fill...very exciting:D

have been chatting to engineer, some builders and head buck cat @ high density insullation supplier with full fill cavity top of the ajenda
with 150mm cavity the direction at the moment is built in cavity insulation to achieve a 0.12 u - value. has any one used this product?

Put simply, the U-values achieved by placing CavityTherm into your standard 150mm cavity achieves 2016 standards - without the need to widen the cavity or incur all the additional cost of doing so. It's a very practical, affordable solution to low energy design.

fclauson

esox28 wrote: »

... CavityTherm into your standard 150mm cavity achieves 2016 standards ..

I looked at this product- the concern I had is if its not fitted correctly then it will not be a 0.12wall - that is in a perfect world only

The board must be snug against the inside wall (no cement snots whatsever) all the junctions and joins must be perfect - no gaps or spaces, the corners must be perfectly mitered, around windows you must not make any errors etc.

esox28

all the junctions and joins must be perfect - no gaps or space[/QUOTE

this is the very reason why i am moving towards full fill, the standard of workmanship has to be perfect. as you say the corners need alot of attention and i think my brickie will have issues with doing a mitred corner to any level of correctness. my own view is to leave the mitred joint for a butt joint with 600mm of dpc backing and a silcone sealant to the leading external joint.

I havent the option of putting 300mm cavity now, my foundations set out with 150mm cavity and even to pump the 150 wont give me near the uvalue.

just do it

fclauson wrote: »

I looked at this product- the concern I had is if its not fitted correctly then it will not be a 0.12wall - that is in a perfect world only

The board must be snug against the inside wall (no cement snots whatsever) all the junctions and joins must be perfect - no gaps or spaces, the corners must be perfectly mitered, around windows you must not make any errors etc.

Agree with fc, and this is one of my concerns with EWI. You need a perfectionist building the wall and even at that there will inevitably be slight gaps.

My intention is to go with pumped full fill wide cavity and ensure thermal imaging is done after. The contract will stipulate any gaps that show up at this stage will have to be re-pumped.

esox28

off the top of your head what is the uvalue with pumped full fill cavity @ 150mm?

BryanF

esox28 wrote: »

off the top of your head what is the uvalue with pumped full fill cavity @ 150mm?

between 0.18 - 0.22w/m2k depending on type of bead ( none really below .3wmk and imo you have to allow for actual conditions)

just looked back to post 3. are we to understand that your arch had specified 300mm - you went 150cavity and now you regret it and are looking for a solution? have you still retained the services of your arch?

esox28

again...wasent very clear 'sorry' always had spec. for a 150mm cavity I mistakely called the whole wall 300mm should have said 350mm.

no regrets at all love my 150mm its the biggest cavity in my area.:D

esox28

yea im getting back quotes for bonded beads of .18 to .20 for 150mm but just looking at a book beside me there is hdi @ .17w/m*k for 100mm

portwest

BryanF wrote: »

between 0.18 - 0.22w/m2k depending on type of bead ( none really below .3wmk and imo you have to allow for actual conditions)

just looked back to post 3. are we to understand that your arch had specified 300mm - you went 150cavity and now you regret it and are looking for a solution? have you still retained the services of your arch?

BryanF off the top of your head what would the u-value be for full-fill bonded bead @200mm and @300mm as my engineer and builder are of two different opinions on how wide the cavity should be to achieve a 0.6 ACH.

just do it

portwest wrote: »

BryanF wrote: »

between 0.18 - 0.22w/m2k depending on type of bead ( none really below .3wmk and imo you have to allow for actual conditions)

just looked back to post 3. are we to understand that your arch had specified 300mm - you went 150cavity and now you regret it and are looking for a solution? have you still retained the services of your arch?

BryanF off the top of your head what would the u-value be for full-fill bonded bead @200mm and @300mm as my engineer and builder are of two different opinions on how wide the cavity should be to achieve a 0.6 ACH.

Cavity width has nothing to do with airtightness?!

kboc

portwest wrote: »

BryanF off the top of your head what would the u-value be for full-fill bonded bead @200mm and @300mm as my engineer and builder are of two different opinions on how wide the cavity should be to achieve a 0.6 ACH.

a little bit of knowledge is a dangerous thing. I suspect when the 2 most crucial boys in the process are saying this they don't really know what they are talking about.

Be careful!

Good luck

BryanF

esox28 wrote: »

yea im getting back quotes for bonded beads of .18 to .20 for 150mm but just looking at a book beside me there is hdi @ .17w/m*k for 100mm

HDI? as in a board or pumped? remember that that manufacturers adjust the other wall build-up w/mk factors in their favour, thats why any arch worth their fee will check/calc the U-values themselves and not take the trade literature. also when you read the fine print some of these products also give a variable w/mk figure stating something like 'under test conditions' x can be achieved but y should be taken otherwise, so do check the lowest 'super' figures carefully and their actual application/ certified use.

portwest wrote: »

BryanF off the top of your head what would the u-value be for full-fill bonded bead @200mm and @300mm as my engineer and builder are of two different opinions on how wide the cavity should be to achieve a 0.6 ACH.

i'll just answer your question presuming you are confusing 'air-tightness' and 'wall U-value's' but ask yourself this: who are you paying to answer this question? the builder who is trying to save costs? or the Engineer who is putting his insurance and professionalism/reputation on the line?.. actually why haven't you an arch or tech employed? as last time I checked an engineer dealt with structure.. excuse the rant..

taking Esox28's issue above into consideration I'll take the full fill bead at an EPS board conductivity of 0.04wmk (this is the important factor) with two standard 1.33wmk blocks as per TGDL so at 200mm cavity thats circa .186w/m2k and at 300mm cavity that's circa .127w/m2k overall U-value.

so here's where you must feel confident about the products claims, especially imo where pumped bonded beads are concerned, but the same goes for all insulations - if for instance the product states a conductivity of 0.032wmk (assuming the same blocks and render as above) then that 200mm cavity could give a wall U-value of circa 0.1w/m2k...

fclauson

portwest wrote: »

...how wide the cavity should be to achieve a 0.6 ACH.

I am worried at this - a 1mm cavity is as airtight as a 300mm cavity if done right

portwest

fclauson wrote: »

I am worried at this - a 1mm cavity is as airtight as a 300mm cavity if done right

I am sorry guys I am new to all this passive lingo, the indication is that a 300mm full-fill bonded beaded cavity(block) will give 15kwh/m2 and a 200mm(ffbb) would give 20-24kwh/m2 with the appropriate 3g windows and a 0.6ach. My question is there a cost benefit analysis of going with a 300mm cavity (ffbb)?

BryanF

portwest wrote: »

I am sorry guys I am new to all this passive lingo, the indication is that a 300mm full-fill bonded beaded cavity(block) will give 15kwh/m2 and a 200mm(ffbb) would give 20-24kwh/m2 with the appropriate 3g windows and a 0.6ach. My question is there a cost benefit analysis of going with a 300mm cavity (ffbb)?

Company
€ cent
per Kwh

Bord Gais Std Rate 5.432

ESB DD 5.432

ESB Electric Ireland DD and ebilling 5.106

Flogas Standard 5.052

Flogas Direct Debit 4.617

http://www.moneyguideireland.com/category/electricity-charges

5.432(cent per kwh) x 9kwh (15-24kwh x ?msq (whats your meter msq of usable floor area calculated under phpp, ask your eng)

but will the 200mm pumped cavity will comply with TGDL 2011? has your engineer confirmed this?

fclauson

also check out

http://www.seai.ie/Publications/Statistics_Publications/Fuel_Cost_Comparison

portwest

BryanF wrote: »

Company
€ cent
per Kwh

Bord Gais Std Rate 5.432

ESB DD 5.432

ESB Electric Ireland DD and ebilling 5.106

Flogas Standard 5.052

Flogas Direct Debit 4.617

http://www.moneyguideireland.com/category/electricity-charges

5.432(cent per kwh) x 9kwh (15-24kwh x ?msq (whats your meter msq of usable floor area calculated under phpp, ask your eng)

but will the 200mm pumped cavity will comply with TGDL 2011? has your engineer confirmed this?

So Bryan is that 5.432 x 9kwh x 300msq = 14666.4= E146.60 ?

BryanF

portwest wrote: »

So Bryan is that 5.432 x 9kwh x 300msq = 14666.4= E146.60 ?

you pick the energy source and there you go

but don't forget

will the 200mm pumped cavity comply with TGDL 2011? has your engineer confirmed this?

+ take account of the other short-cuts that may be taken - thermal bridge free design planned?, windows below point .8wm2k installed, air-tightness expected etc

& is that 300msq the PHPP m2sq input or the area of the house as they are different

Fracking Cylon

I'm currently getting quotes for my house, and builders are coming back with a variety of insulation configurations. Configurations so far include: 1: 100mm pumped cavity with 50mm insulated plaster board internally.
2: 150 mm pumped cavity. 3: 150 mm pumped cavity with insulated board and 4: 100 cavity with 60mm insulated board and 50mm insulated plaster board internally. Any opinions gratefully accepted!

fclauson

Fracking Cylon wrote: »

I'm currently getting quotes for my house, and builders are coming back with a variety of insulation configurations. Configurations so far include: 1: 100mm pumped cavity with 50mm insulated plaster board internally.
2: 150 mm pumped cavity. 3: 150 mm pumped cavity with insulated board and 4: 100 cavity with 60mm insulated board and 50mm insulated plaster board internally. Any opinions gratefully accepted!

Fracking Cylon

one of the advantages of having a high mass on the internal surfaces is that if you can get the building warm and you insulate to keep it warm then it acts as a good thermal store and will balance you energy demand day/night

so

I would recommend
150mm or 200mm in the floor
200mm plus in the wall i.e. regular block/200mm or 250mm bead/regular block
400 or 500 mm in the roof
3G windows (and that is another mine field you will have to cross with U values and g% values )

get a BER done to make sure this all complies and remember you might fail to complie with the renewables element as you get towards super insulated (again thats another thread of discussion I have going on here somewhere)

BryanF

Fracking Cylon wrote: »

I'm currently getting quotes for my house, and builders are coming back with a variety of insulation configurations.

1. have you done a provisional BER and what wall, roof and floor U-value does that require?
2. what has your architect put in the drawings/specification?

Fracking Cylon

BryanF wrote: »

1. have you done a provisional BER and what wall, roof and floor U-value does that require?
2. what has your architect put in the drawings/specification?

No provisional BER done yet, and we got more of a draughtsman than am architect to do the house plans. I will ask the builder to calculate the BER ratings depending on what spec we go for.

BryanF

Fracking Cylon wrote: »

No provisional BER done yet, and we got more of a draughtsman than am architect to do the house plans. I will ask the builder to calculate the BER ratings depending on what spec we go for.

if your trusting your builder with all this, who is certifying the build?

sydthebeat

Fracking Cylon wrote: »

I will ask the builder to calculate the BER ratings depending on what spec we go for.

thats using the software backwards.

you should use the software to model the build in order to compile a specification for the builder to price.....

not getting the builder to input his specification to find out the rating....

New build in sight

esox28 wrote: »

fclauson wrote: »

My advice do not turn a single sod until you have the detail much more specific than this - PM me for a very good detailing person



but its not the best method

for reference I have regular block/250mm bead cavity/regular block - Uvalue about 0.13

am up to sub-floor level and ready to in fill...very exciting:D

have been chatting to engineer, some builders and head buck cat @ high density insullation supplier with full fill cavity top of the ajenda
with 150mm cavity the direction at the moment is built in cavity insulation to achieve a 0.12 u - value. has any one used this product?

Put simply, the U-values achieved by placing CavityTherm into your standard 150mm cavity achieves 2016 standards - without the need to widen the cavity or incur all the additional cost of doing so. It's a very practical, affordable solution to low energy design.

Just wondering has anybody looked into these full file cavity products from cavitytherm 150 mm achieving. 12 u value would anybody recommend this or an alternative with same cavity width

BryanF

New build in sight wrote: »

Just wondering has anybody looked into these full file cavity products from cavitytherm 150 mm achieving. 12 u value would anybody recommend this or an alternative with same cavity width

my two cents - start at 200mm cavity (subject to BER and PHPP calcs) and full fill afterwards with bead insulation, it appears to be the cheapest option.

placing the insulation board as you go, is not a great option, mainly due to quality control, time taken + read the fine print on the certification regarding actual wmk under normal conditions- (there's been umpteen threads of a similar vein, if you care to go back and look)

HoofRocks

From our provisional ber we had two options to acheive .13 u.value

Meeting 2011 regulations

First was a 140 mm cavity with 100mm insulation and 75 mm internal

Second 160 mm cavity bead filled with 60mm internal

archtech

HoofRocks wrote: »

From our provisional ber we had two options to acheive .13 u.value

Meeting 2011 regulations

First was a 140 mm cavity with 100mm insulation and 75 mm internal

Second 160 mm cavity bead filled with 60mm internal

With all that internal insulation I would be seeking condensation risk analysis ( it is meant to be done under TGD L 2010 anyway) to be undertaken before going any further as there is a significant risk of problems down the road.

HoofRocks

archtech wrote: »

With all that internal insulation I would be seeking condensation risk analysis ( it is meant to be done under TGD L 2010 anyway) to be undertaken before going any further as there is a significant risk of problems down the road.

Would this not be taken into account with the deap analysis?

I don't want to have to start getting acccessments on accessments

archtech

HoofRocks wrote: »

Would this not be taken into account with the deap analysis?

No DEAP doesn't calculate u-values, its purpose is to determine a BER rating and is used to check compliance with Part L.

HoofRocks wrote: »

I don't want to have to start getting acccessments on accessments

Knowing what one proposes will work, is far better than hoping and then finding out it didn't and resulted in health problems.
Poorly designed insulation can lead to mould growth and health problems down the line. By way of poorly designed insulation I mean the selection of the material and where it is positioned within the wall build up and not the design of the material itself.

So of the insulation companies will do the analysis for you but bear in mind they will only used their products and they may not be the cheapest combinations.

HoofRocks

archtech wrote: »

With all that internal insulation I would be seeking condensation risk analysis ( it is meant to be done under TGD L 2010 anyway) to be undertaken before going any further as there is a significant risk of problems down the road.

Would deap not take that into account. I don't want to be doing accessments on accessments

archtech

HoofRocks wrote: »

Would deap not take that into account. I don't want to be doing accessments on accessments

Nope.

DEAP is a free piece of basic software designed for a specific purpose.
Assessing condensation risk in building construction is a fairly complex process and well outside the scope of DEAP.

just do it

HoofRocks wrote: »

From our provisional ber we had two options to acheive .13 u.value

Meeting 2011 regulations

First was a 140 mm cavity with 100mm insulation and 75 mm internal

Second 160 mm cavity bead filled with 60mm internal

You've a lot more options than that. The general consensus on here is a full full wide cavity (220-250mm) is better than either of above.

HoofRocks

just do it wrote: »

You've a lot more options than that. The general consensus on here is a full full wide cavity (220-250mm) is better than either of above.

Why is it better?
We have already submitted for planning would we have to re submit for a wider cavity. Also what u value would that give you?
Thanks

Casati

esox28 wrote: »

yea but by pumping the cavity arent you insuring that all areas are insulated, a block layer can leave unseen gaps in hdi, maybe the hdi isent fitted completely tighht to wall due to sloppy concrete 'snots', maybe some contractor starts drilling from inside to outside and pushes insulation away from inside leaf...??



I know yea why dryline or cozy board but most new build iv seen have this done, but imo I think your removing the thermal storage aspect of the building in block.

I'm not looking for passive house standards but as close as 'I' can manage, an air tight house and efficient heating system.

Lads- this is v interesting - I made that very mistake, thinking with the mentality that more insulation the better, I decided to stick on a cozy board to the inside leaf, having already stuck in insulation in the cavity. As a result the thermal storage is gone- the house heats ups v quickly, but as its not airtight, it tends to cool down faster than expected, meaning on cold evenings I am sticking the heat on and off. Next time round I will maximize thermal storage and go with external insulation only I think

Casati

HoofRocks wrote: »

Why is it better?
We have already submitted for planning would we have to re submit for a wider cavity. Also what u value would that give you?
Thanks

I don't think making the cavity wider would result in a new planning application, it would just mean the rooms are slightly smaller?