How much insulation.

[Ferdinand]

@Russell griffiths

 

I have found the Vesma calculator to be the most useful of those available, as most of the others are from commercial companies as a semi-marketing device, and often require registration or are more detailed in the particular area.

http://www.vesma.com/tutorial/uvalue01/uvalue01.htm

 

If something is missing from the list, you can probably usefully substitute a similar material (ask here if you need advice).

 

Ferdinand

 

[Jeremy Harris]

4 minutes ago, Ferdinand said:

 

Ah. The immortal words of Emperor Hadrian President Trump :-) .

 

To add something useful @Russell griffiths, I think that a "typical" wall that you asked about will be referring to one built to meet basic Building Regs' standard or a little better on a "typical" new build house. Say with the u-value quoted of 0.25, whereas people here tend to build walls to a u-value significantly lower than that.

 

One of the design tools that should help you decide what is appropriate could be to model your long term etc costs over periods of 10 or 25 years against the extra cost of the higher-spec wall. Or you could use your intended occupation period if you know it.

 

Others (usually including me) would take a less pragmatic position and build it to the higher spec anyway. Many here are planning to stay for 20 years or often forever. I would argue that at some point the value of a high spec (or not) house will reflect the excess 20k in bills which will be paid over the next 15 years.

 

Hope that helps.

 

Ferdinand

 

 

Interestingly, there doesn't seem to be a direct correlation between build cost and thermal efficiency, as far as I could tell when going around getting quotes. One thing we did experience was companies quoting for their "standard" product when we'd specifically asked for an insulation and airtightness spec.  It did mean that we got to compare things like the price of a standard 140mm SIPs frame, that just met building regs, with a passive house spec frame that significantly exceeded them.  In one case (I won't name the company, but they were the most expensive of those we approached), their 140mm SIPs offering, on a passive slab foundation, was 20% more expensive than the passive house spec company we used in the end. 

 

I have a feeling that self-builders are treated a bit differently when it comes to pricing by some companies, but I've no real evidence to prove it.  There seemed to be an analogy, at times, between self-builders paying through the nose in the same way yacht owners do if they aren't careful.  When I owned a boat I always bought stuff from the "fishermens" chandlers, rather than the "yotty" places, as it was often half the price................

[Ferdinand]

9 minutes ago, JSHarris said:

 

Interestingly, there doesn't seem to be a direct correlation between build cost and thermal efficiency, as far as I could tell when going around getting quotes. One thing we did experience was companies quoting for their "standard" product when we'd specifically asked for an insulation and airtightness spec.  It did mean that we got to compare things like the price of a standard 140mm SIPs frame, that just met building regs, with a passive house spec frame that significantly exceeded them.  In one case (I won't name the company, but they were the most expensive of those we approached), their 140mm SIPs offering, on a passive slab foundation, was 20% more expensive than the passive house spec company we used in the end. 

 

I have a feeling that self-builders are treated a bit differently when it comes to pricing by some companies, but I've no real evidence to prove it.  There seemed to be an analogy, at times, between self-builders paying through the nose in the same way yacht owners do if they aren't careful.  When I owned a boat I always bought stuff from the "fishermens" chandlers, rather than the "yotty" places, as it was often half the price................

 

+1 A good deal of that is perhaps about fixed and variable costs, where the fixed element may be 75% (picking a number out of the air).

 

Ferdinand

 

Edited February 5, 2017 by Ferdinand

[Jeremy Harris]

I think some of it is to do with the design approach, too.  Taking a standard design and trying to improve the airtightness and overall thermal performance is probably going to be a fair bit more expensive than coming up with a new design that is specified from the start to meet higher performance standards.

 

My informal observations around building sites, and visiting houses being built by companies who were contenders for our build, indicated that the majority were taking a "sticking plaster" approach to getting better performance.  I'm certain this adds a fair bit to the cost, as, for example, trying to get a conventional trench foundation system and cavity wall house to  a spec much above building regs minimum levels requires a lot of work in detailing.

 

I'm pretty much convinced that the conventional block/brick cavity wall type house is right at the end of its development cycle, and that to take the next step towards improving energy efficiency builders really need to look "out of the box" at new methods of construction.  Unfortunately, there seems a fair bit of reticence amongst builders to build something they are unfamiliar with, and although I can understand that, I do think it's holding back performance improvements in our new housing stock.

[TerryE]

23 hours ago, JSHarris said:

Taking a standard design and trying to improve the airtightness and overall thermal performance is probably going to be a fair bit more expensive than coming up with a new design that is specified from the start to meet higher performance standards.  ...  I'm pretty much convinced that the conventional block/brick cavity wall type house is right at the end of its development cycle ...

 

Tony's build (@tonyshouse) has demonstrated that you can achieve passive-class performance with a block/brick cavity wall construction, but it's a challenge.  As I've said elsewhere I feel that the root issue is total failure of innovation and true quality control in the major builders.  If you look at so many other sectors of business technology and innovation over the last 30 years have totally transformed how the products are mode and the services are delivered.  IMO, the building industry as a whole seems to have systemically resisted attempt and change and both the government and related professional bodies such as RIBA have miserably failed to perform their roles in legislating / advocating such change.  So we are left with a few small builders and specialist firms, and self-builders showing by example. 

 

@Sensus used the phrase anally retentive when discussing another post and Jan often refers to me as being anal to describe to sort of fine attention to detail that I sometimes adopt.  Yet we don't talk about Rolls-Royce being anally retentive about the design and manufacture of their jet engines or Apple being anal about the design of their iPhones, etc..  It seems to be almost a presumption that whilst attention to detail is essential (and expected) in some business areas, when it comes to building a house then this is just over-the-top.

 

However, I disagree.  Quite a few of the active members of this forum have demonstrated by personal example that you can build a top-quality passive-class home for the same sort of price as your average mediocre new-build of the same footprint, etc.  Where there are price premiums these are more to do with the overheads of building one-off rather building a high quality product.  But the devil is in the detail, and maintaining that quality, so maybe we should just use the "anal" description as a badge of recommendation.      If you are a self-builder who wants a highly efficient, high quality, low maintenance to live in then you need to get a bit of anality yourself or find a professional architect or project manager that you trust to do this for you.

 

[joe90]

I agree with all the above and I too am building to " passive house principles " ( I chose those words carefully) as with my location and weather patterns I believe my insulation levels to be adequate. Like Tony I am building in brick and block and not applying rocket science to make it airtight and fit for purpose.

 

i thought I was a bit anal about build quality and have wondered if my builder would not be on board but I could not be more wrong, they are very much on board and I cannot fault a thing they have done, sometimes without me asking because I took the time to explain my requirement before they even quoted. I do think I am very lucky with my builder.

[jamiehamy]

On 05/02/2017 at 14:38, JSHarris said:

 

I'm pretty much convinced that the conventional block/brick cavity wall type house is right at the end of its development cycle, and that to take the next step towards improving energy efficiency builders really need to look "out of the box" at new methods of construction.  

I was going to post earlier asking why more who want good insulation but also high airtightness don't go down the Icf route? 

 

I know you did consider it at one point - is it the cost factor? Aside it being very easy to build with airtightness is far easier to achieve,  you can almost completely eliminate cold bridging. It still seems to be very much a speciality from my perspective(having built with it). When we do another build it will be Icf,  no question. 

[TerryE]

@jamiehamy, ICF is an effective alternative to TF, but considering we passed the 0.6 ACH test first time through without any  leak hunting or the like, I am note sure that it is intrinsically more airtight than a properly designed and implemented timber frame.   Doesn't ICF rule out using a passive slab type construction because of the ground bearing pressure required?

[Jeremy Harris]

35 minutes ago, jamiehamy said:

I was going to post earlier asking why more who want good insulation but also high airtightness don't go down the Icf route? 

 

I know you did consider it at one point - is it the cost factor? Aside it being very easy to build with airtightness is far easier to achieve,  you can almost completely eliminate cold bridging. It still seems to be very much a speciality from my perspective(having built with it). When we do another build it will be Icf,  no question. 

 

 

TBH, we would have used ICF, I'm sure, if it wasn't for planning restrictions that pretty much forced us down the timber frame path.  Timber frame wasn't my number one choice of build method, but we had a choice where the only two external finishes that would have been acceptable (given that we're in an AONB, opposite a GII listed mill, in a CA etc) were local Chilmark stone (horrendously expensive - it comes from a closed quarry that has to be opened up specially for any order) or native timber, specifically larch or oak. With no real choice as to what the external finish could be, it then seemed to make more sense to use a timber frame with timber cladding rather than come up with a way to use rustic timber cladding on ICF (could be done, but not quite as straightforward to fix).

[NSS]

On 2/5/2017 at 13:12, TerryE said:

@NSS, Neil,  you can definitely get a single wall construction up to the same standard as a twinwall in terms of U-value, typically by adding extra layers of insulation such as a plasterboard/RUR composite over the service cavity.  I haven't done the numbers but a 50mm PUR or PIR layer would help a lot.  The quality issue is still problematic particularly if the inner skin has been incorporated in the factory.  At least if this is done on site, the home owner or project manager can inspect the fit of the internal block insulation and where necessary use injected foam to close up fitting gaps.  (A gap of 5mm top and bottom can more than double the effective U-value.)

 

As to the DDF, this is more down to the bulk properties of the main fill material.  PUR and PIR have excellent the thermal conductivity, but also very low the heat capacity, and its the ratio that largely dictates the DD. Any wall which uses these as its main filler (or any other low thermal capacity insulation) will usually end up with a low DD.  See this article which describes the concept and issue:  Greenspec: Decrement delay & Thermal buffering.

 

Hi Terry, I understand all that. The point of my query was that you infer in your previous post that twin wall construction such as yours is at least twice as good as single wall. As I'm sure you would agree, comparing the system you've chosen with what may be the norm for the big volume house builders is at best misleading in the context of this forum, where I doubt any of us would settle for insulation values that barely meet building regs. I just feel we have to be careful not to mislead new readers and/or budding self builders that single wall construction cannot be better than that, even if it may be difficult to replicate the levels of a twin wall construction. It is also, I believe, worth mentioning that the sheer breadth of a twin wall construction may make it less attractive to some, particularly where site constraints may restrict the footprint of the property that can be built and, hence, impact on the internal space that would result from its use.

[TerryE]

5 minutes ago, NSS said:

... you infer in your previous post that twin wall construction such as yours is at least twice as good as single wall .... I doubt any of us would settle for insulation values that barely meet building regs .... sheer breadth of a twin wall construction may make it less attractive to some ...

 

Neil, you are correct in the 0.24 U-value is typical of a 120 frame with 100mm PIR in it, but I did also say that you can improve this by using multiple layers.  So if you take ProDave's example of one way to do this, he has a 190mm frame, filled with Earthwool and then 100mm Wood fibre board on the outside, achieving a U value of 0.14 which is a good example of what I mean by a composite construction.  But note that this is only about 20mm less than my core frame.   

 

[Jeremy Harris]

23 minutes ago, NSS said:

Hi Terry, I understand all that. The point of my query was that you infer in your previous post that twin wall construction such as yours is at least twice as good as single wall. As I'm sure you would agree, comparing the system you've chosen with what may be the norm for the big volume house builders is at best misleading in the context of this forum, where I doubt any of us would settle for insulation values that barely meet building regs. I just feel we have to be careful not to mislead new readers and/or budding self builders that single wall construction cannot be better than that, even if it may be difficult to replicate the levels of a twin wall construction. It is also, I believe, worth mentioning that the sheer breadth of a twin wall construction may make it less attractive to some, particularly where site constraints may restrict the footprint of the property that can be built and, hence, impact on the internal space that would result from its use.

 

I'd agree with that.  There are many ways to skin this particular cat, but it's not easy if you want to stick with the build methods the big developers prefer.

 

I've long thought that a single masonry skin with EWI would be the best way to build, for people like the big developers.  The wall thickness's aren't massive, as the insulation doesn't need to have a particularly high decrement delay, so high performance, but low heat capacity, and relatively thin insulation can be used.  Running the external insulation down below the floor level (provided it's something like EPS that doesn't absorb water) effectively gets around the wall/floor thermal bridge problem.  The build method uses skills that already exist.  Construction time is probably less, because of the single internal masonry skin.  A quick parge coat over the masonry will get it pretty airtight, and the detailing needed to get thermal-bridge free window and door installation is easy, as they can be set out in the external insulation layer.  The downside is that a rendered outside finish may not be what everyone wants, and there is a significant cost in using something like brick or stone slips to get a more "traditional" look.

 

Ultimately, I think there needs to be a shift to build methods where there is better control over build quality, though, and the best way to achieve that would seem to be to move as much of the construction work away from the uncontrolled environment of a big building site, to controlled conditions in a factory.  It's a heck of a lot easier to ensure that factory-fabricated house major components, in any material you wish, are made to a consistently high standard.  For example, I was impressed by the wall panels for the big (900 people) office that was built as a part of my last job.  They were factory made, with two carbon-reinforced thin concrete skins and a foam insulation core.  They were non-structural, and were just hooked on to the structural frame and the joints foamed and then sealed externally.  They had pre-cast apertures for windows etc, set in the insulation layer.  The build time was dictated by how fast the cranes could lift the panels in place, and was remarkably quick.  The building ended up with the highest BREEM energy rating, too.

 

 

Edited February 6, 2017 by JSHarris

[NSS]

31 minutes ago, TerryE said:

 

Neil, you are correct in the 0.24 U-value is typical of a 120 frame with 100mm PIR in it, but I did also say that you can improve this by using multiple layers.  So if you take ProDave's example of one way to do this, he has a 190mm frame, filled with Earthwool and then 100mm Wood fibre board on the outside, achieving a U value of 0.14 which is a good example of what I mean by a composite construction.  But note that this is only about 20mm less than my core frame.   

 

Yes, but ProDave (please correct me if I'm wrong, Dave) chose his wall make up for reasons that were not solely to do with achieving that U-value, but also for cost, ease of self installation and the nature of the external finish desired (and he's hardly constrained by plot size). I was referring to a more typical 147mm stud frame and wall U-value circa to 0.16 such as (claimed for) mine - and no I'm not reopening the debate around the the insulation in my build - but also, I would guess, perfectly achievable with alternative insulation types/layers and a resulting overall wall thickness significantly thinner than yours. 

 

It goes back to something I mentioned months ago, and your self-admitted (earlier in this thread) attention to detail. I'm sure we all admire the forensic approach that you and Jeremy (for example) have applied to your builds, but it's unrealistic (and I'd contend unnecessary) to expect every self builder, never mind the volume builders, to adopt such targets anytime soon. Even if costs were comparable to the way the Persimmons of this world currently build, the skill base simply doesn't exist to execute the required attention to detail in their volumes.

 

My point is, we shouldn't lose sight of the fact that it would (I'd hope you would agree) be better to build many houses that are circa 35% more energy efficient than current regs dictate, than just a select few that are 50% better.

[NSS]

1 hour ago, JSHarris said:

 

I'd agree with that.  There are many ways to skin this particular cat, but it's not easy if you want to stick with the build methods the big developers prefer.

 

I've long thought that a single masonry skin with EWI would be the best way to build, for people like the big developers.  The wall thickness's aren't massive, as the insulation doesn't need to have a particularly high decrement delay, so high performance, but low heat capacity, and relatively thin insulation can be used.  Running the external insulation down below the floor level (provided it's something like EPS that doesn't absorb water) effectively gets around the wall/floor thermal bridge problem.  The build method uses skills that already exist.  Construction time is probably less, because of the single internal masonry skin.  A quick parge coat over the masonry will get it pretty airtight, and the detailing needed to get thermal-bridge free window and door installation is easy, as they can be set out in the external insulation layer.  The downside is that a rendered outside finish may not be what everyone wants, and there is a significant cost in using something like brick or stone slips to get a more "traditional" look.

 

Ultimately, I think there needs to be a shift to build methods where there is better control over build quality, though, and the best way to achieve that would seem to be to move as much of the construction work away from the uncontrolled environment of a big building site, to controlled conditions in a factory.  It's a heck of a lot easier to ensure that factory-fabricated house major components, in any material you wish, are made to a consistently high standard.  For example, I was impressed by the wall panels for the big (900 people) office that was built as a part of my last job.  They were factory made, with two carbon-reinforced thin concrete skins and a foam insulation core.  They were non-structural, and were just hooked on to the structural frame and the joints foamed and then sealed externally.  They had pre-cast apertures for windows etc, set in the insulation layer.  The build time was dictated by how fast the cranes could lift the panels in place, and was remarkably quick.  The building ended up with the highest BREEM energy rating, too.

 

 

I completely agree that controlled, factory conditions are the way forward, and the recently promised entry into the UK market of the Chinese may well force the volume builders to adapt or die, but a traditional brick skin and tiled roof can surely be wrapped around a factory built, energy efficient core just as easily as it can around what they currently construct.

[ProDave]

10 minutes ago, NSS said:

Yes, but ProDave (please correct me if I'm wrong, Dave) chose his wall make up for reasons that were not solely to do with achieving that U-value, but also for cost, ease of self installation and the nature of the external finish desired (and he's hardly constrained by plot size). I

I set out to build the best house I could for the money I had available (and yes not having unlimited funds probably forced a compromise)

 

I did try to get a quote from MBC for their twin wall system, but that never happened. I documented my search for a builder at the time on the other place.  I also looked at Touchwood (too expensive) and Beatie Passive (too big up front costs for the design).  So I ended up with the best I could find which was a local designer and a different local builder to build it.

 

One of my "design briefs" was I did not want a cavity and rendered blockwork skin. That is just an expensive rain shield adding virtually nothing to the insulation.  That's when I was offered the wood fibre and render option which seemed to tick all the boxes.

 

Yes I would have preferred that wood fibre and render finish on a twin stud frame, but that just wasn't to be I am afraid.
 

[SteamyTea]

12 minutes ago, NSS said:

but a traditional brick skin and tiled roof can surely be wrapped around a factory built, energy efficient core

I am sure with a bit of thought and planning, brick or stone slip panels could be made in a factory, transported to site, craned into place and fixed easily.

 

No good for a small builder as they would hate paying for a crane and will convince themselves that working in mud and rain they are 'doing the job cheaper'.

[NSS]

8 minutes ago, SteamyTea said:

I am sure with a bit of thought and planning, brick or stone slip panels could be made in a factory, transported to site, craned into place and fixed easily.

 

No good for a small builder as they would hate paying for a crane and will convince themselves that working in mud and rain they are 'doing the job cheaper'.

You're probably right, but is Joe Public ready for a brick/stone slip exterior rather than solid brick walls (even if, as Dave says, it's just a relatively expensive rain shield)?

[SteamyTea]

12 minutes ago, NSS said:

but is Joe Public ready

Probably not, many still remember the Barratt Homes fiasco back in the late 1980's.  (Edit: early 80's as this 2003 article shows: http://www.telegraph.co.uk/finance/property/3316998/On-the-level-timber-tommyrot.html)

 

I am not sure how the public can be convinced that a newer building method is better.  And you only have to have once serious failure to tarnish them all.

A friend of mine from the USA had never heard of the expression 'as safe as bricks and mortar', and she worked at an architects in New Hampshire (was bought up by a Texan and they all had to wear snake skin boots).

Edited February 6, 2017 by SteamyTea

[SteamyTea]

Thinking about 'different' construction methods, why don't we build the internal walls out block, they have good sound proofing, are good to hang things on and will not affect the thermal properties.

Then build the outside walls out of timber frame, clad in whatever you like.

And where you have two TF panels meet, why don't we glue and nail a strip of thin ply over the joints to make then airtight.

Edited February 6, 2017 by SteamyTea

[NSS]

3 minutes ago, SteamyTea said:

Probably not, many still remember the Barratt Homes fiasco back in the late 1980's.

 

I am not sure how the public can be convinced that a newer building method is better.  And you only have to have once serious failure to tarnish them all.

And the recent media hysteria about passiv houses suffering overheating issues has perhaps tainted that 'standard' in the eyes of the wider public too.

[SteamyTea]

Were they designed by an architect

[Declan52]

Mass developers will continue to use bricks and blocks because that's what people want. So it would take either a massive shift in taste or the building regs massively improved to sway towards alternate methods.

The first timber frame houses we built about 12 years ago were an obsolute disgrace. In the 24 bases we built the timber frame company didn't get the measurements correct once. Some were resting on the sub floor and some were already touching the outside skin at the base. Doors and window widths and head heights were wrong,by the time we reached the roof the frame was that much out of plumb that there was no cavity. My brother in law rented a brand new timber frame build 2 years ago that I am convinced had no insulation in between the studs. 

I think the best we can hope for is wider cavity builds with pumped insulation and more effort to improve airtightness to get it at least half of what is the minimum rate now. That would be a start. 

 

[SteamyTea]

Most of the new builds down here seem to be timber frame, so maybe it is a regional thing.

Or the Cornish are just a bit more advanced.

[Jeremy Harris]

Timber frame seems to have been the preferred build method in Scotland for the last couple of decades or more.  When we were living up there (in a timber framed house) every new build we saw was timber frame.  That was from 1992 to 1997.

[NSS]

Seems that Persimmon are at least building some of their homes with factory made timber frames (see http://corporate.persimmonhomes.com/corporate-responsibility/our-environment/space4). How good they are is another question.